700R92011
DETERMINATION OF RATES OF REACTION
IN THE GAS-PHASE IN THE TROPOSPHERE
THEORY AND PRACTICE
3. Rate of Indirect Photoreaction: Technical Support
Document for Test Guideline § 796.3900. Structure/Reactivity
Relationships for Estimating the Second-Order Rate
Constant for the Reaction of an Organic
\s Chemical with Hydroxyl Radicals
by
Asa Leifer
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF TOXIC SUBSTANCES
WASHINGTON, DC 20460
CJ
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Table of Contents
Abstract
I.
II.
II. A.
II. B.
III.
III. A.
III. A.I.
III. A. 2.
III. A. 2. a.
III. A. 2. a. i.
III. A. 2. a. ii.
III. A. 2. a. ill.
III. A. 2. b.
III. A. 2. c.
III. A. 2. d.
III. A. 2. e.
Introduction
Kinetics of the Reaction of a Chemical with
Hydroxyl Radicals in the Gas-Phase in the
Troposphere
Rate Laws
Effect of Temperature on Rate
Structure/Reactivity Relationships for
Estimating the Second-Order Rate Constant
(kOH) for the Reaction of Hydroxyl Radicals
with Organic Chemicals in the Gas-Phase
H-Atom Abstraction from C-H and 0-H Groups
and the Estimation of k0jj
Formulation of the Structure/Reactivity
Relationships
Estimation of kOH for Several Classes
of Organic Chemicals at 298 K and a
Comparison of These Results with the
Experimental Data
Alkanes
Acyclic Alkanes
Cyclic Alkanes
All Alkanes (Acyclic and Cyclic)
Haloalkanes
Carbonyl Compounds: Aldehydes, Ketones,
a-Dicarbonyls, Acid Chlorides, and Esters
Alcohols, Glycols, and Ethers
Nitrates and Nitriles
xii
1
5
5
7
9
10
10
24
24
24
28
30
30
34
41
49
III.A.2.f. Olefins, Diolefins, Alkynes, and Aromatic
Compounds 5 3
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Table of Contents (cont.)
III.A.3. Summary 54
III.B. Addition of Hydroxyl Radicals to Olefinic,
Conjugated Diolefinic, 1,2-Diolefinic
Compounds and Alkynes and the Estimation
of kOH 58
III.B.I. Formulation of the Structure/Reactivity
Relationships 58
III.B.2. Estimation of kOH for Several Classes of
Chemicals at 298 K and a Comparison of
These Results with the Experimental Data 67
III.B.2.a. Unsubstituted Alkenes 67
IZI.B.2.b. Substituted Alkenes 73
III.B.2.C. Conjugated Dialkenes 76
III.B.2.d. Alkynes. and 1,2-Dialkenes (Allenes) 79
III.B.3. Summary 81
III.C. Reaction of Hydroxyl Radicals with
Organic Chemicals Containing Sulfur,
Nitrogen, and Phosphorus Functional
Groups and the Estimation of kOH 83
III.C.I. Reaction of Hydroxyl Radicals with Thiols,
Sulfides, and Oisulfides 83
III.C.I.a. Formulation of the Structure/Reactivity
Relationships 83
Ill.C.l.b. Estimation of kOH at 298 K and a Comparison
of These Results with the Experimental Data 85
III.C.2. Reaction of Hydroxyl Radicals with Aliphatic
Amines, Hydrazines, N-Nitrosamines,
N-Hydroxylamines, and N-Nitramines 89
III.C.2.a. Formulation of the Structure/Reactivity
Relationships 89
III.C.2.b. Estimation of kOH at 298 K and the
Comparison of these Results with
Experimental Data 92
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Table of Contents (cont.)
III.C.3. Reaction of Hydroxyl Radicals with
Organophosphorus Compounds 95
III.C.3. a. Formulation of the Structure/Reactivity
Relationships 95
III.C.3.b. Estimation of kOH at 298 K and the
Comparison of These Results with
Experimental Data 98
III.C.4. Summary 102
III.D. Reaction of Hydroxyl Radicals with Aromatic
Compounds and the Estimation of XQJJ 105
III. D.I. Formulation of the Structure/Reactivity
Relationships 105
III.D. 2. Estimation of kOH for Several Classes of
Aromatic Compounds at 298 K and the
Comparison of These Results with the
Experimental Data 113
III.D. 2. a. Benzene and Biphenyl 113
III.D.2.b. Alkylbenzenes 122
III.D.2.C Alkenylbenzenes 123
III.D.2.d. Halogenated Benzenes 124
III.D.2.e. Haloalkylbenzenes 125
III.D.2.f. Monochlorobiphenyls 126
III.D.2.g. Hydroxybenzenes 127
III.D.2.h. Nitrobenzenes 128
III.D.2.i. Aminobenzenes 123
III.D.2.J. Additional Substituted Benzenes 129
1 1 1 . D . 2 . k . Po lyar omat ic Hydrocarbons 1 3 o
III.D. 3. Summary 132
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Table of Contents (cont.)
III.E. Summary of Results for the Estimation of
kon for All Chemicals in a Number of Classes
of Chemicals by the Structure/Reactivity
Relationships of Atkinson of the University
of California/Riverside 137
IV. Illustrative Examples: Use of the Structure/
Reactivity Relationships of Atkinson to
Estimate the Second-Order Rate Constant
(kOH) for the Reaction of Hydroxyl Radicals
with Organic Chemicals in the Gas-Phase
at 298 K in Air at Atmospheric Pressure 139
IV.A. Alkanes (Acyclic and Cyclic) 144
IV.A.I. 2-Methylpentane 144
IV.A.2. Bicyclof3.3.0]octane 145
IV.A.3. Isopropylcyclopropane 145
IV.B. Haloalkanes 146
IV.B.I. Difluoromethane 146
IV.B.2. 1,1-Difluoroethane 147
IV.C. Carbony1 Compounds 147
IV.C.I. Butanal 147
IV.C.2. Trichloroacetaldehyde 148
IV.C.3. 2-Pentanone 148
IV.C.4. Cyclobutanone 149
IV.C.5. Methyl Glyoxal 149
IV.C.6. Acetyl Chloride 150
IV.C.7. n-Propyl Acetate 150
IV.D. Alcohols and Glycols 150
IV.D.I. 2-Propanol 150
IV.D.2. 1,2-Ethanediol 151
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Table of Contents (cont.)
IV. E.
IV. E.I.
IV. E. 2.
IV. E. 3.
IV. E. 4.
IV. F.
IV. F.I.
IV. G.
IV. G.I.
IV. H.
IV. H.I.
IV. H. 2.
IV. H. 3.
IV. I.
IV. I.I.
IV. I. 2.
IV. I. 3.
IV. I. 4.
IV. I. 5.
IV. I. 6.
IV. J.
IV. J.I.
IV. J. 2.
IV. J. 3.
Ethers (Acyclic and Cyclic)
2-Ethoxyethanol
Diethoxymethane
1 , 2-Epoxybutane
Oxepane (Hexamethylene Oxide)
Nitrates
3-Methyl-2-pentyl Nitrate
Nitriles
Propionitrile
Unsubstituted Alkenes (Acyclic and Cyclic)
1-Pentene
1,4-Pentadiene
Bicyclo [2.2.1] -2-heptene
Substituted Alkenes
Vinyl Bromide
trans-2-Butenal ( trans-Crotonaldehyde )
cis-3 -Hexene-2 , 5-dione
fcis-1.2-Diacetylethylene)
Tetrachloroethene
Acrylonitrile
Methyl Ketene
Conjugated Diolefins
cis-1 . 3-Pentadiene
1, 3-Cyclohexadiene
2 , 5-Dimethyl-2 , 4-hexadiene
152
152
153
153
154
154
154
155
155
156
156
157
158
159
159
159
160
161
162
162
163
163
164
165
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Table of Contents (cont.)
IV.J.4. 4-Methyl-l,3-pentadiene 166
IV.K. Alkynes 166
IV.K.I. 1-Butyne 166
IV.L. Allenes 167
IV.L.I. 1,2-Pentadiene 167
IV.M. Thiols, Sulfides, and Bisulfides 168
IV.M.I. 2-Methyl-l-propanethiol 168
IV.M.2. Tetrahydrothiophene 169
IV.M.3. Dimethyl Disulfide 170
IV.N. Compounds Containing Nitrogen Functional
Groups 170
IV.N.I. Dimethylhydroxyethylamine 170
IV.N.2. Dimethyl-N-nitrosamine 171
IV.N.3. Methyl Hydrazine 172
IV.N.4. Diethyl-N-hydroxylamine 172
IV.0. Compounds Containing Phosphorus
Functional Groups 173
IV.0.1. Triethyl Phosphate 173
IV.0.2. 0,0-Dimethyl Chlorophosphorothioate 174
IV.0.3. O,0,N-Trimethylphosphoroamidothioate 174
IV.P. Aromatic Compounds 175
IV.P.I. Toluene 175
IV.P.2. trans-1-Phenyl-l-propene 177
IV.P.3. 4-Chlorobenzotrifluoride 178
IV.P.4. 1,2,4-Trichlorobenzene 179
IV.P.5. o-Cresol 181
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Table of Contents (cont.)
IV.P.6. Aniline 182
IV.P.7. Hexafluorobenzene 183
IV.P.8. 2,3-Dihydrobenzofuran 185
IV.P.9. 3-Chlorobiphenyl 186
IV.P.10. 1-Methylnaphthalene 188
IV.P.11. 1,4-Dichloronaphthalene 190
V. Tropospheric Half-Life 190
VI. Screening-Level Test Guideline: Estimation
of kOH and ^(i/2\E for a Chemical (S)
Produced by Chemical Company X via the
Estimation Techniques of Atkinson 193
VII. Mathematical Synopsis of the Structure/
Reactivity Relationships of Atkinson 198
VIII. References 205
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List of Tables
Table 1.
Table 2.
Table 3.A.
Table 3.B.
Table 4.
Table 5.
Table 6.
Table 7.
Table 8.
Table 9.
Table 10.
Table 11.
Group Rate Constants k° and k at 298 K and the
Parameters A" and E'[=E(X)] in Equation 26 17
Substituent Factors F(X) at 298 K and E(X) in
Equation 26 for Various Substituents X 19
Comparison of Experimental and Estimated
Values of k0n for Acyclic Alkanes
at 298 K and the Percent Error 25
Comparison of Experimental and Estimated
Values of k0H for Cyclic Alkanes at 298 K
and the Percent Error 29
Comparison of Experimental and Estimated
Values of kOH for Haloalkanes at 298 K and
the Percent Error 31
Comparison of Experimental and Estimated
Values of k0H for Carbonyl Compounds at
298 K and the Percent Error 36
Comparison of Experimental and Estimated
Values of kOH at 298 K for Alcohols, Glycols,
and Ethers and the Percent Error 43
Comparison of Experimental and Estimated
Values of kOH at 298 K for Nitrates and
Nitriles and the Percent Error 50
Summary of the Average Percent Error in kOH
for H-Atom Abstraction from C-H and OH
Groups at 298 K for Chemicals within Several
Classes of Chemicals and for All Chemicals
in These Classes 55
1S
Group Rate Constants ko in Equation 91
for Hydroxyl Radical Addition to Isolated
Olefinic Groups at 298 K 63
Substituent Factors C(X) in Equations 91,
92, and 93 for Substituent X on Nonaromatic
Unsaturated Carbon-Carbon Groups at 298 K 64
CO
Group Rate Constants ko in Equation 92
for Hydroxyl Radical Addition to Conjugated
Nonaromatic Functional Groups at 298 K 65
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Table 12.
Table 13.
Table 14.
Table 15.
Table 16.
Table 17.
Table 18.
Table 19.
Table 20.
Table 21.
Table 22.
Group Rate Constants k°,u in Equation 93
for Hydroxyl Radical Addition to Alkynes and
Allenes at 298 K 68
Comparison of Experimental and Estimated
Values of kOH for Unsubstituted Alkenes
and the Percent Error 69
Comparison of Experimental and Estimated
Values of kOH for Substituted Alkenes at
298 K and the Percent Error 74
Comparison of Experimental and Estimated
Values of kOH for Conjugated Acyclic and
Cyclic Dialkenes at 298 K and the Percent
Error 77
Comparison of Experimental and Estimated
Values of k0jj f°r Alkynes and Allenes 80
at 298 K and the Percent Error
Summary of the Average Percent Error in
kpH for the Reaction of Hydroxyl Radicals
with a Number of Olefins, Conjugated
Diolefins, Allenes, and Alkynes and for
All Chemicals in These Classes 82
Comparison of Experimental and Estimated
Values of kOH for Alkyl Thiols, Sulfides,
and Disulfides at 298 K and the Percent
Error 86
Comparison of Experimental and Estimated
Values of kOH at 298 K for Alkyl Amines,
Hydrazines, and N-Substituted Amines and
the Percent Error 93
(
Comparison of Experimental and Estimated
Values of k0H at 298 K for Aliphatic
Compounds Containing Phosphorus Functional
Groups and the Percent Error 99
Summary of the Average Percent Error on kpH
at 298 K for the Reaction of Hydroxyl Radicals
with a Number of Chemicals in Several Classes
of Chemicals Containing Sulfur, Nitrogen, and
Phosphorous Functional Groups and for All
Chemicals in These Classes of Chemicals 103
Electrophilic Substituent Constants
(a"1" and a+) for a Number of Substituents
*" p
m
108
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Table 23. Comparison of Experimental and Estimated
Values of KQH for Chemicals in Various
Classes of Aromatic Chemicals at 298 K
and the Percent Error 114
Table 24. Comparison of Experimental and Estimated
Values of kOH for Fused Ring Polyaromatic
Hydrocarbons 133
Table 25. Summary of the Average Percent Error in kOH
at 298 K for a Number of Chemicals in Several
Classes of Aromatic and Polyaromatic
Compounds and for All Chemicals in These
Classes 134
Table 26. Summary of the Statistical Data for All the .
Compounds Used in the Analysis of the S/R
Relationships of Atkinson 140
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Abstract
In support of the Exposure Assessment Branch's (EAB)
environmental fate programs (U.S. Environmental Protection
Agency, Office of Toxic Substances), Atkinson [1986, 1986a,
1987, 1987b, 1988, 1988a, and Atkinson et al. (1985)] of the
University of California/Riverside, developed structure/
reactivity (S/R) relationships for estimating the second-order
rate constant (k0H) for tne reaction of an organic chemical
with hydroxyl radicals (OH) in the gas-phase in the
troposphere. These S/R relationships are based on the premise
that several separate OH radical reaction pathways occur and
they can be treated individually. These reaction pathways are:
(1) H-atom abstraction by OH radicals from C-H groups in
alkanes, ethers, carbonyls, and other saturated
organics; and from C-H groups in unsaturated carbon-
carbon groups such as in alkenes, dialkenes, alkynes,
and aromatic compounds;
(2) H-atom abstraction by OH radicals from hydroxyl
functional groups;
(3) OH radical addition to nonaromatic unsaturated
carbon-carbon functional groups;
(4) OH radical interaction with nitrogen, sulfur, and
phosphorus functional groups; and
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(5) OH radical addition to aromatic and polyaromatic
rings.
The total OH radical rate constant, kOH (cm3molecule""1s~1) , is
then the sum of the rate constants for each of these reaction
pathways.
This report gives a detailed discussion of the development
of the S/R relationships of Atkinson. All pertinent parameters
for estimating k0n are summarized in several tables in this
report. For the reader's convenience, a mathematical synopsis of
the S/R relationships of Atkinson is given at the end of the
report (Section VII).
These S/R relationships were used to estimate kOH at 298 K
of 405 organic chemicals covering a wide variety of chemical
classes. These chemical classes were: alkanes (acyclic and
cyclic); haloalkanes; carbonyl compounds such as aldehydes,
ketones, esters, etc.; ot-dicarbonyls; alcohols and glycols;
ethers (acyclic and cyclic); nitrates; nitriles; alkenes and
dialkenes (both conjugated and unconjugated); ketenes; alkynes;
1,2-dienes (allenes); thiols; sulfides (acyclic and cyclic);
disulfides; amines; hydrazines; N-substituted amines (such as
N-nitroso, N-hydroxyl, and N-nitro); alkyl phosphates/
thiophosphates; dialkyl chlorophosphorothionates; alkyl
phosphoroamidates/phosphorothioamidates; benzene, biphenyl, alkyl
and alkenyl benzenes; halogenated benzenes and haloalkyl
benzenes; monochlorobiphenyls; hydroxy-, niro-, amino-, methoxy-,
and cyanobenzenes; aromatic aldehydes; polyaromatic hydrocarbons;
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and other aromatic compounds. This report lists the experimental
kOH data for each of the 405 compounds and compares the estimated
values with the experimental values (Percent Error). Of the 405
chemicals, 20 had a percent error greater than +100 and were
omitted in the analyses. For the remaining 385 chemicals, the
average percent error ranged from +21 to -19 which is very good
to excellent. One hundred fifty-four chemicals were not used by
Atkinson to derive the parameters in the S/R relationships and,
therefore, were good candidates to test the validity of these
relationships. The average percent error of these 154 chemicals
ranged from +24 to -20 which ranged from very good to excellent,
thereby confirming these S/R relationships. However, a few of
the classes had a minimum number of chemicals so that more
experimental kOH data are needed for additional chemicals in
these classes to corroborate the S/R relationships of Atkinson.
In addition, more experimental kOH data are needed for the 20
chemicals having a percent error greater than +100 to determine
why the percent error was so high.
A detailed discussion is given in Section III.E. on all the
estimated kOH data including a summary of the statistical data
(Table 26).
Since the S/R relationships of Atkinson are excellent, these
methods have been computerized for use in Sections 4, 5, and 6 of
the Toxic Substances Control Act (TSCA) by Syracuse Research
Corporation (called the Atmospheric Oxidation Program or AOP).
Since this report lists the validated kOH data for a large number
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of chemicals, these kOH data have been entered into the data base
in the Syracuse Computer Program.
This report represents the technical support document for
the "First-Tier Screening-Level Test Guideline § 796.3900.
Structure/Reactivity Relationships for Estimating the Second-
Order Rate Constant and Half-Life for the Reaction of Hydroxyl
Radicals with Organic Chemicals in the Troposphere."
Fifty-six illustrative examples are given in Section IV to
show how to use the S/R relationships of Atkinson to estimate
kOH. In addition, in order to illustrate the use of the S/R
relationships of Atkinson under Section 4 of TSCA, a hypothetical
scenario has been postulated in which Chemical Company X, located
on Cross Lake near Shreveport, LA, manufactures 2 million kg per
year of the chemical 2,3-difluoro-4-[l-methylpropyl]nitrobenzene
(S). This chemical is used as a solvent to solubilize some of
the disperse dyes which they manufacture for the textile and
carpet industries. During the manufacture and use of S, vapors
escape into the atmosphere. Hence, it is important to determine
the fate of this chemical in the troposphere. Since S can react
with OH radicals, the S/R relationships of Atkinson were used to
estimate kOjj and the half-life [t^^JEl "* tne troposphere. A
detailed description of these calculations are given in Section
VI of this report. Since k0H and ^(i/2)E we^e estimated to be
4.07 x 10~12cm3molecule~1s~1 and 2.6 d, respectively, so that OH
radical reaction represents an important mode of transformation
in the troposphere, it is recommended that S 796.3950 [described
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in the hierarchal test scheme of Leifer (1989)] be carried out
using the relative rate technique in Teflon bags to measure kOH
for S.
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I . introduction
Numerous chemicals, both natural and anthropogenic, are
emitted to the troposphere from a variety of sources and may be
removed by wet or dry deposition or by three important
transformation processes. These three transformation processes
are:
(1) direct photoreaction which involves the absorption of
sunlight followed by transformation;
(2) indirect photoreaction which involves the reaction of
a chemical with hydroxyl radicals (OH) ; and
(3) oxidation which involves the reaction of a chemical
with ozone (03) .
There is another indirect photoreaction process which involves
the reaction of a chemical with nitrate radicals (NO3) during
the night. However, this transformation process only occurs
for a few types of chemicals (e.g., olefins, phenols, and
cresols) ; hence, it will not be considered when determining the
rate of transformation in the troposphere.
A quantitative measure of the three important
transformation processes is given by the rate constants
kOH, and kg . The rate constant k^g represents the first-order
rate constant for direct photoreaction, while kQjj and k0
represent second-order rate constants for indirect
photoreaction and oxidation with OH and 03, respectively.
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The first report in a series titled "DETERMINATION OF
RATES OF REACTION IN THE GAS-PHASE IN THE TROPOSPHERE. THEORY
AND PRACTICE" describes a hierarchal test scheme for
determining the rate constants JcdE/ kOH, and k0 and the half-
lives [t(!/2)E] for each transformation process and the net
half-life in the troposphere {Leifer [USEPA (1989a)]}. The
second report describes a screening-level test guideline for
determining the maximum rate of direct photoreaction [k
-------
In parallel with the research program of SRI, OTS
sponsored work with Heicklen of Penn. State University, through
a Battelle subcontract, to review the literature on gas-phase
transformations in the troposphere [Heicklen (1980)]. A report
was issued after the completion of this project [Heicklen
(1980)]. As a result of this work, Heicklen (1981) published
an S/R method for estimating kOH for hydroxyl radical H-atom
abstraction from C-H bonds from enthalpy data.
Another parallel extramural research program was initiated
by the Atmospheric Sciences Research Laboratory (ORD)/Research
Triangle Park, NC, with Atkinson and Pitts (1981) of the
University of California/Riverside, in support of OTS programs.
This research program was extremely productive and more than 23
research papers and several EPA reports were published. For
the complete details of the accomplishments of this 3-year
cooperative agreement, the reader is referred to the EPA report
by Atkinson et al. (1985).
With respect to the reaction of OH radicals with organic
chemicals in the gas-phase, Atkinson and his coworkers:
(1) developed a relative rate method for measuring k_u in
Un
Teflon bags at approximately one atmosphere pressure in air at
298 K [Atkinson et al. (1981); Atkinson in Pitts et al.
(1982)]; (2) experimentally measured kOH for a large number of
chemicals in the relative rate/Teflon bag method [Atkinson et
al. (1985)]; (3) critically analyzed all the rate data (kOH)
published through 1987 and developed and refined S/R
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relationships for estimating kOH [Atkinson (1986, 1986a, 1987,
1987b, 1988, 1988a)].
Recently, Atkinson (1989) had a monograph "Kinetics and
Mechanisms of the Gas-Phase Reactions of the Hydroxyl Radical
with Organic Compounds" published by the American Chemical
Society which lists all the experimental kOH data as a function
of the temperature. The book covers the literature through
1988 and in a number of cases, the temperature range covered
was 220-2000 K. Atkinson critically analyzed all the
experimental kOH data and recommended rate expressions as a
function of the temperature wherever possible. In addition,
the rate dependence on pressure was included where data was
available. He also listed the recommended value of kOH for
each chemical at 298 K, the rationale behind each
recommendation, and the estimated uncertainty for each
recommendation. Recently, a few of the S/R relationships have
been modified [Atkinson (1989a)].
In addition, the Atmospheric Sciences Research Laboratory
(ORD)/Research Triangle Park, NC, funded work with Cohen at the
Aerophysics Laboratory/Aerospace Corporation/Los Angeles, CA,
and Benson of the University of Southern California/Los
Angeles, CA, to develop methods of calculating kOH strictly
from theory [Cohen (1985)]. Cohen and Benson (1985, 1985a,
1987) used transition state theory to calculate kOH for
haloalkanes.
Leifer critically analyzed all the S/R relationships
described above for estimating kOH and found that the S/R
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relationships of Atkinson were by far: (1) the most accurate
of all the methods; (2) were applicable to a considerably wider
number of classes of organic chemicals; and (3) were applicable
to a considerably larger number of chemicals. In addition, the
S/R relationships of Atkinson were adopted by OECD and were
published in a "derestricted OECD document" in 1988 to be used
as guidance to those who decide to carry out gas-phase trans-
formation tests [Atkinson (1987b, 1988a) in an OECD Report].
As a result, this report will describe in detail the S/R
relationships of Atkinson and these methods will be used as a
test guideline for estimating kOH under Sections 4 and 5 of the
Toxic Substances Control Act.
II. Kinetics of the Reaction of a Chemical with Hydroxyl
Radicals in the Gas-Phase in the Troposphere
II.A. Rate Laws
The kinetics of the reaction of a chemical with OH
radicals in the gas phase, at a constant temperature T (the
absolute temperature in the units K), can be treated
mathematically in the following manner:
kOH
C + OH » Products (l)
-(dC/dt) = kOH C(OH) (2)
where kOH is the second-order rate constant in the units
cm3 molecule"1^"1 and C and (OH) represent the concentration of
the chemical and hydroxyl radicals, respectively. In gas-phase
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chemistry, the OH radical and chemical concentrations are
usually expressed in the units molecules cm""3.
Since a chemical is usually present in the troposphere at
a very low concentration at a given time t and a steady-state
concentration of OH radicals is produced by sunlight, the
hydroxyl radical concentration can be treated as a constant so
that equation 2 becomes a pseudo first-order equation
-(dC/dt) - kC . (3)
where
k = kOH(OH) (4)
The pseudo first-order rate constant k is in the units
reciprocal time, usually s"1. Integrating equation 3 under the
boundary conditions (t = 0, C0) and (t, Ct) yields
ln(C0/Ct) = kt (5)
The half-life t^^JE ^n tne troposphere is defined as the
time for the chemical concentration to reach one-half its
initial concentration. Therefore, under the boundary condition
tct " G0/2' t = t(l/2)£]' equation 5 yields
t(l/2)E = ln 2/k = 0.693/k (6)
and substituting equation 4 in equation 6 yields
" 0.693/kQH(OH) (7)
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Thus, with the value of kOH, either measured in the laboratory
or estimated by S/R relationships, and the average OH
concentration in the troposphere, the half-life of a chemical
in the gas-phase in the troposphere can be estimated using
equation 7.
II.B. Effect of Temperature on Rate
The effect of temperature on the rate constant KOH can be
expressed mathematically in several ways. A widely used
empirical equation was developed by Arrhenius (1887) in the
following way. Arrhenius indicated that the variation of a
rate constant with temperature can be represented by an
equation similar to one used for equilibrium constants, namely
d[ln k{T}]/dt = AE*/RT2 (8)
where k{T} is the specific rate constant for a given reaction,
T is the absolute temperature in the units K, R is the gas
constant which is equal to 1.987 x 10"3 kcal/K/mol or 8.314 x
10~3 kJ/K/mol, and AE* represents the energy of activation for
the reaction in kcal/mol or kJ/mol. Replacing AE* with E and
integrating equation 8, assuming that E is independent of the
temperature, yields
In k{T} = In A' - E/RT x .. (9)
k{T} = A'exp(-E/RT) (,10)
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-------
where A' is a constant of integration and is called a frequency
factor, or a preexponential factor. Equation 10 is usually
valid over a limited temperature range.
For a number of reactions, A' is not a constant but is a
function of the temperature. Therefore, a more accurate
empirical equation is
k{T} = ATnexp(-E/RT) (11)
where A and n are constants. Equation 11 has been used by
Kassel (1932) as an empirical relationship to analyze
experimental kinetic data. Equation 11 has theoretical
justification, the exponent n having a specific value depending
upon the theory used and the nature of the reaction [Frost and
Pearson (1961); Finlayson-Pitts and Pitts (1986)].
Collision theory has been used to derive an equation
describing how the rate constant k can vary with temperature
[Frost and Pearson (1961); Finlayson-Pitts and Pitts (1986)].
Collision theory is based on the concept that molecules can be
represented by hard spheres and reaction takes place as a
result of collisions between these spheres. From this theory,
it can be readily shown that equation 11 is applicable with the
exponent n equal to 1/2 [Frost and Pearson (1961); Benson
(1960); Finlayson-Pitts and Pitts (1986)].
Transition state theory has also been used to describe the
kinetics of chemical reactions. In this theory, the reaction
between two molecules A and B proceeds via the formation of an
activated complex [A-••-B]$ which then falls apart to form
-8-
-------
products. Using thermodynamics in this theory, it can be
readily shown that a form of equation 11 is applicable with n
equal to 1 [Finlayson-Pitts and Pitts (1986)]. Using quantum
mechanics in this theory, it can also be shown that a form of
equation 11 is applicable with n also equal to 1 [Eyring (1935)]
III. Structure/Reactivity Relationships for Estimating the
Second-Order Rate Constant (kQH) for the Reaction of
Hydroxyl Radicals with Organic Chemicals in the Gas-Phase
Atkinson (1986, 1986a, 1987, 1987b, 1988, 1988a)
critically analyzed the hydroxyl radical rate data (kOH) for a
large number of organic chemicals and developed a number of S/R
relationships based solely on the molecular structure of these
chemicals. In developing these S/R relationships, he assumed
that a number of OH radical reaction pathways exist and the
various OH radical reaction pathways could be separated and
treated individually. Therefore, he calculated rate constants
for each of these reaction pathways. The reaction pathways and
rate constants for each of these pathways were:
k(l) = k
H-atom abstraction from acyclic
saturated, cyclic saturated, and
unsaturated C-H groups by OH radicals.
(12)
k(2) = k [H-atom abstraction from 0-H groups'] (13)
[by
OH radicals J
;]
k(3) = k [OH radical addition to >C=C<,~] (14)
>C=C-C=C<, -CsC-, and >C=C=C<[
[.groups
k(4) = k [OH radical interaction with -SH,] (15)
L-s-,
and -S-S- groups
idical interact]
L>NH, and >N- groups
k(5) = k [OH radical interaction with -NH2,~] (16)
-9-
-------
k(6) = k [OH radical interaction with] (17)
[phosphorus groups J
k(7) = k [OH radical addition to aromatic rings] (18)
k(8) = k
OH radical addition to fused ring
polyaromatic compounds (i.e.,
jpolyaromatic hydrocarbons)
(19)
Atkinson postulated that the overall OH radical rate constant
k-.., is equal to the sum of the rate constants for each of these
On
reaction pathways. Therefore, the OH radical rate constant is
given by the equation
8
KOH = E
i = 1
and the individual rate constants [k(l), k(2), , k(8)] and
kOH are all in the units cm3 molecule""1 s"1. In a few cases,
the estimation of the rate constants are applicable in the
temperature range 220-1,000 K or 250-500 K; all the estimations
of the rate constants are applicable at T = 298 K.
Structure/reactivity relationships will be described for each
of these reaction pathways in detail in the following sections.
For convenience, a mathematical synopsis of the S/R
relationships is given in Section VII.
III.A. H-Atom Abstraction from C-H and 0-H Groups and the
Estimation of kOH
III.A.I. Formulation of the Structure/Reactivity Relationships
Under an OTS extramural contract, Hendry and Kenley
(1979), of SRI International, developed S/R relationships for
-10-
-------
estimating the second-order rate constant kOH for tne reaction
of hydroxyl radicals with organic chemicals in the gas-phase.
Based on a detailed analysis of the available kOH data for a
number of organic chemicals, these researchers postulated that
for H-atom abstraction from C-H groups, there is an intrinsic
rate constant for each C-H reaction center. These intrinsic
reactivity rate constants are modified by various substituents
at the reaction center ( a position) and adjacent to the
reaction center ( j8 position) . The total rate constant kOH f°r
H-atom abstraction from C-H groups is equal to the sum of the
rate constants for each reactive hydrogen. Following similar
procedures, they developed S/R relationships for the addition
of OH radicals to olefinic groups and aromatic groups. The
total rate constant for an organic chemical (kOH) is the sum of
the individual rate constants for H-atom abstraction from C-H
groups, addition to olefinic groups, and addition to aromatic
rings, where appropriate.
Atkinson (1986, 1986a, 1987, 1987b, 1988, 1988a), in
support of EAB programs, elaborated on and expanded the S/R
relationships of Hendry and Kenley. Atkinson's S/R
relationships were also based on the premise that CH3-, -CH2-/
and >CH- group rate constants were also dependent on the
identity of the a and 0 substituents. For the n-alkanes, which
represents the simplest case, Atkinson observed that the -CH2-
group rate constant at approximately 298 K was dependent on the
neighboring groups, increasing from a -CH2- bonded to two CH3-
groups (CH3-CH2-CH3) through a -CH2- group bonded to one -CH2-
-11-
-------
group and one CH3- group (CH3-CH2-CH2-)/ to a -CH2- group
bonded to two -CH2- groups (-CH2-CH2-CH2-).
For a number of classes of organic chemicals (e.g., the
alkanes, haloalkanes, aldehydes, ketones, esters, nitriles, and
nitrates, etc.), Atkinson formulated the generalized S/R
relationships for H-atom abstraction from CH3-, -CH2-, and >CH-
groups at 298 K by defining the following mathematical
relationships:
k(CH3-X) = k° F(X) (21)
k(X-CH2-Y) - k° F(X) F(Y) (22)
/Y
k(X-CH ) = kg F(X) F(Y) F(Z) (23)
\Z
where: k°, k°- and k? represent the group rate constants for
primary OH groups (CH3-), secondary C-H groups (-CH2-), and
tertiary C-H groups (>CH-), respectively, for a standard
substituent X; F(X), F(Y), and F(Z) represent factors for the
substituents X, Y, and Z, respectively; and the standard
substituent, for practical reasons, was postulated as X = Y = Z
= CH3-, and F(CH3-) = 1.00.
In addition, for organic compounds containing hydroxyl
groups (-OH), H-atom abstraction from this group was included
as a reaction pathway and this group rate constant was
designated as k(-OH). It should be noted that the group rate
constant for H-atom abstraction from the OH functional group is
-12-
-------
written as k(-OH) to distinguish it from the total OH rate
constant koH*
Atkinson then used the following approach for H-atom
abstraction from a number of classes of organic compounds:
e.g., acyclic and cyclic alkanes, haloalkanes, aldehydes,
ketones, alcohols, etc. Most of the available kOH data were
for compounds containing single functional groups, with very
little data available for compounds containing difunctional and
polyfunctional groups. Furthermore, the alkanes (acyclic and
cyclic) had the largest number of chemicals with kOn data. As
a result, Atkinson analyzed the kinetic data sequentially in
the following order: alkanes (acyclic), alkanes (cyclic);
haloalkanes; carbonyl compounds such as aldehydes, ketones,
ot-dicarbonyls, acid chlorides, and esters; alcohols, glycols,
and ethers; nitrates; and nitriles. Using the available kOH
data for alkanes, he formulated S/R relationships for this
class of compounds. Then, using the S/R relationships for
alkanes and the kOH data for haloalkanes, he developed S/R
relationships for the haloalkanes. This process was repeated
sequentially for the other classes of compounds listed above.
For the purposes of validation, Atkinson compared the
experimental values of k0jj with the estimated values. This
validation procedure was also used for the other classes of
chemicals discussed in this report.
First, let us consider the acyclic alkanes with a general
structure RCH2CH(CH3)2« This molecule contains primary,
secondary, and tertiary carbon-hydrogen groups (CH3-, -CH2-,
-13-
-------
and >CH-, respectively) and R is an alkyl group. The hydroxyl
radical reacts with each of these C-H groups by abstracting a
hydrogen as follows:
CH3
—» RCH2-£-CH3 + HOH (24a)
3 RCH2CH(CH3)2 + 3(»OH)
13
» RCH-CH-CH3 + HOH (24b)
9H3
—* RCH2-CH-CH2«+ HOH (24c)
The rate of H-atom abstraction from these three groups is in
the order: tertiary C-H > secondary C-H > primary C-H [i.e.,
>CH- > -CH2-, > CH3-]. For the acyclic alkanes, equation 20
reduces to
k(la) = k [H-atom abstraction from C-HJ (25)
[bonds in acyclic alkanes J
Atkinson made a detailed study of the temperature
dependence of the group rate constants (kp, kg, k°) in the
range 220 - 1,000 K. For this temperature range, the modified
Arrhenius equation (equation 11), with n = 2, in the form
k{T} - A'T2 exp(-E'/T) (26)
was found to be applicable. In equation 26, the energy of
activation E' is equal to E/R and the preexponential factor A
is equal to A'. For the narrower temperature range 250-500 K,
the simple Arrhenius equation (equation 10) was found to be
applicable.
-14-
-------
Equation 26 was used to obtain the group rate constants
*p, *!/ *t (defined by equations 21, 22, and 23) in the
temperature range 220 - 1,000 K. Making the assumption that
the effects of the substituent X are only on the activation
energy E" and not on the preexponential factor A', then, from
equation 26, the substituent factor F(X) is given by the
equation
F(X) =
exp E(X)/T (27)
where E' = E(X) . To a good approximation, this assumption is
valid since any deviations in the data will be small and within
the uncertainties of the experimental rate data.
Using the extensive set of kOH data for the acyclic
alkanes, Atkinson (1986, 1986a) carried out a nonlinear, least-
squares fit of the data to the equation
kOH = k(la)
° F(X) + J>! F(X) F(Y) + £kg F(X) F(Y) F(Z) (28)
and calculated k2, kg, and kg as a function of the temperature
Using these results in the modified Arrhenius equation 26, he
found that
kp = 4.47 x 10~18T2exp(-303/T) (29)
k2 = 4.32 X 10"18T2exp(233/T) (30)
-15-
-------
kf = 1.89 x 10~18T2exp(711/T) (31)
and
F(-CH2-) - F(>CH-) - F(>C<) = exp(76/T) (32)
The first term in equation 28 represents the sum of the
contributions from each primary group (CH3-) in an alkane; the
second term represents the sum of the contributions from each
secondary group (-CH2-) in the alkane; and finally, the third
term represents the sum of the contributions from each tertiary
group ( >CH-) in an alkane.
Using equations 29 through 32, the group rate constants
kg, kj, kg, and the factors F(X) at 298 K are given by
kg = 0.144 x 10~12 cm3 molecule'1^"1 (33)
kg = 0.838 x 10~12 cm3 molecule~1s">1 (34)
kg - 1.83 x 10~12 cm3 molecule' 1s~1 (35)
F(-CH2-) = F(>CH-) = F(>C<) - 1.29 (36)
and by definition
F(CH3-) = 1.00 (37)
The group rate constants kg, k§, and k° at 298 K, the
preexponential factors A', and the energies of activation E'[=
E(X)] are all summarized in Table l. For the substituent
-16-
-------
Table 1. Group Rate Constants k° and k at 298 K and the
Parameters A' and E' [ = E(X)] in Equation 26
Group Rate 1012k° 1018A' E(X) = E'
Constant (cm3 molecule"3^"1) (cm3molecule~1s~1) (K)
k°
KP
k°
Ks
kt
k(-OH)
k(l,UNS CH)a
k(-NH2)
k(>NH)
k(>N-)
k(-SH)
k(-s-)
k(-S-S-)
k(>N-NO)
k(>N-N02)
k[P(0)]
k(PCl)c
k[P(S)]
0.144
0.838
1.83
0.036
0
20
60
60
31d
2.0b
200
0
0
0
0
55
4.47 303
4.32 -233
1.89 -711
1.89 460
- -
-
-
- -
-
- -
-
- -
-
- -
-
-
a k(l, UNS CH) represents the group rate constant for
abstraction of a hydrogen from an unsaturated carbon-carbon
functional group. Even at elevated temperatures up to 500 K,
k(l,UNS CH) is approximately zero [Atkinson (1987)].
b Applicable at 298 K and at a total pressure of 1 atmosphere
in air (and thus in the presence of oxygen). In the absence
of oxygen, k(-S-) = 0.
c Applicable to PCI in the compounds (RiO)2P(S)Cl, where R^ is
an alkyl group.
^ Applicable only to aliphatic group; connection to aromatic
rings is not included based on the experimental rate constant
of thiophenol [Meylan (1990)].
-17-
-------
groups X, the data for F(X) at 298 K, and E(X) (where avail-
able) are listed in Table 2.
To illustrate Atkinson's method of calculating k... at
Urt
298 K, consider the acyclic alkane
CH3
i
H
CH3-C-CH2-CH2-CH3 (38)
Using equation 28, and starting at the first carbon at the left
and then proceeding from carbon to carbon to the right, one
obtains
kOH - k(la)
- k°, F(>CH-) + kg F(CH3-) F(CH3-) F(-CH2-)
+ kg F(>CH-) + k§ F(>CH-) F(-CH2-) (39)
+ k| F(-CH2-) F(CH3-) + k° F(-CH2-)
Atkinson [1986, 1986a, 1987, 1987b, 1988, 1988a] indicated
that for strained cyclic alkanes, energies greater than 5
kcal/mol lead to a decrease in H-atom abstraction rate
constants. Therefore, the effects of ring strain must be taken
into account when estimating kOH for cyclic alkanes. Since the
decrease in the rate constant kOH is related exponentially to
the ring strain energy, the decrease in kOH will be evident in
the activation energy term F(X) = exp[E(X)/T], equation 27, and
not in the preexponential factor A' in equation 26. Based on a
detailed analysis of the kOH data for the strained cyclic rings
cyclopropane, cyclobutane, and cyclopentane, and unstrained
-18-
-------
Table 2. Substituent Factors F(X) at 298 K and E(X) in
Equation 26 for Various Substituents X
Substituent Grouo X
CH3-
-CH2-, >CH-, >C<
F-
Cl-
Br-
-CH2C1, -CHC12, -CH2Br, >CHCla
C13C-
FCH2-
F2CH-
F2C1C-
F3C-
=0 or (0)
-C(0)C1
-CH(0), -C(0)-
-CH2C(0)- , >CH-C(0)- , »C-C(0)-
2nd-CH2C(0)-, 2M>CHC(0)-/ 2nd^CC(0)-
C6H5-
>C=C< , -CsC-
-OH
-0-
2M -o-
-CH2-0-
*C-0-
FfX)
1.00
1.29
0.099
0.38
0.30
0.57
0.090
0.85
0.10
0.025
0.075
8.8
0.50
0.76
4.4
1.0
1.0
1.0
3.4
6.1
1.0
4.5
4.5*
E(X)
m
0
76
-689
-288
-359
-168
-718
-48
-686
-1099
-771
648
-207
-82
442
0
0
0
365
539
___
-19-
-------
Table 2. Substituent Factors F(X) at 298 K and E(X) in
Equation 26 for Various Substituents X (Continued)
E(X)
Substituent Group X Fm m
-OC(0)R 1.5 121
-OC(0)CF3 0.36°
-C(0)-0-R 0
-SH , -S- , -S-S- 9.0
-NH2/ >NH-, >N- 10
>N-NO , >N-N02 10
>NOH, -NHOH 10d
-CH2-ONO2/ >CH-ON02, »C-ON02
-ON02
-CN
-CH2CN
-0-P< , -S-P<
F(3)
F(4)
F(5)
F(6)
F(7), F(8), etc.
0.30
0.10
0.14
0.50
20
0.017
0.22
0.80
1.00
1.0
a Estimated bv A. Leifer using the experimental value of :
0.96 x 1O~" cm^molecule'^s"1 for 2,3-dichlorobutane at
— — —
-686
-586
-207
-1214
-451
-66
0
0
298 K
[from Mill et al. (1982)].
b Given the same value as for -CH2-O- [Meylan (1990)].
c Estimated by Leifer using the experimental value of
0.052 x 10~^ cm^molecule~1s~1 from the experimental data of
Wallington et al. (1988) of CF3C(0)OCH3.
^ Estimated by Leifer based on the experimental data of
diethy1-N-hydroxylamine.
-20-
-------
rings such as cylohexane, etc., Atkinson indicated that
F(3) = 0.017; F(4) = 0.22; F(5) = 0.80 (40)
F(6) = 1.00; F(7) = F(8) = 1.0 (41)
All these substituent factors F(X) for cyclic alkanes at 298 K
are listed in Table 2.
From equations 20 and 12 for unsubstituted cyclic alkanes
kOH = k(lc) (42)
and modifying equation 28 for cyclic alkanes, one obtains
kOH = k(lc)
= |E kg F(X)F(Y) + E kg F(X)F(Y)F(Z)j F(i) (43)
where F(i) is the ring strain factor corresponding to a ring
with i carbons.
As an example, consider cyclopropane
H2C— CH2 (44)
Using equation 43 in the same manner as described previously,
and the ring strain factor F(3) for the cyclopropane ring, one
obtains
kOH = k(lc) = [3k° F2(-CH2-)
F(3) (45)
with the short-hand notation
-21-
-------
F2(-CH2-) = F(-CH2-) F(-CH2-) (46)
When calculating JcOH [Jc(lc)] for alkyl substituted cyclo-
alkanes, the ring substituents are unaffected by ring strain
while the various C-H groups within the ring are affected by
strain. As a result, equation 43 is valid for the cyclic
alkane while equation 28 is valid for the acyclic component.
As an example, consider the compound isopropylcyclopropane
CH-CH(CH3)2
(47)
CH2 CH2
The ring C-H groups must be separated from the substituted
acyclic C-H components. Thus, from equations 20, 28, and 43,
one obtains
kOH - k(lc) + k(la)
= jkt F2(-CH2-) F(>CH-) + 2k°;F(-CH2-) F(>CH-)j F(3)
(48)
+ kg F2(CH3-) F(>CH-) + 2kpF(>CH-)
Atkinson, in Atkinson and Aschmann (1988), measured k0n
for this compound at 298 K and found that kOn [Experimental]
was equal to 2.83 x 10~12cm3 molecule"3^"1. Atkinson (1989)
revised this value slightly to 2.84 x 10"12cm3 molecule~1s"1.
The estimation of JCQH for this compound is given as an
illustrative example [See Section IV.A.3.]. Using equation 48,
[Estimated] = 2.85 x 10~12cm3 molecule'^-s'1. Clearly, the
-22-
-------
estimated XQH value is in excellent agreement with the
experimental value indicating that the ring strain has no
effect on the reactivity of the isopropyl substituent group.
For polycyclic rings, the ring strain factors are
multiplicative. For example, for bicyclo[2.2.1]heptane
CH,
H-
H2C
*CT2
' (49)
k
2k? F3(-CH2-) + kg F2(>CH-)
+ 4k§ F(>CH-) F(-CH2-)j F2(5) F(6) (50)
Again, it should be noted that for alkyl substituted polycyclic
compounds, the ring correction factor F(i) is only applied to
the -CH2- and >CH- groups within the ring and not to
substituted alkyl groups.
As an illustration, consider the compound bicyclo[3.3.0]
octane: th» experimental value of kO}] is 11.0 x 10~12
cm3 molecule^s""1 [Table 3.B./Atkinson, Aschmann, Carter
(1983a)]; the estimated value of kOH is 10.4 x 10~12cm3
molecule~1s~1 (see illustrative example IV.A.2); again, in this
case, the experimental value is in excellent agreement with th«
-23-
-------
estimated value and clearly confirms the S/R relationships for
strained polycyclic alkanes. [See also the data for other
bicyclic and tricydie alkanes in Table 3.B.]
Furthermore, since strain energies for rings containing
heteroatoms O, S, N are similar to the corresponding
cycloalkanes, the ring factors F(3), F(4), and F(5) are also
applicable to strained heterocyclic rings such as cycloethers,
cycloamines, and cyclosulfides.
The formulation of S/R relationships for classes of
compounds containing hydroxyl groups (-OH) will be discussed in
Section III.A.2.d. Alcohols, Glycols, and Ethers.
III.A.2. Estimation of kOH for Several Classes of Organic
Chemicals at 298 K and a Comparison of These Results
with the Experimental Data
III.A.2.a. Alkanes
III.A.2.a.i. Acyclic Alkanes
Table 3.A. summarizes the pertinent !CQH data at 298 K for
the reaction of OH radicals with acyclic alkanes as obtained
from the literature. The first column lists the name of each
acyclic alkane. The second column, labeled Experimental/(a),
lists the experimental values of kOH as obtained from Atkinson
(1986). These kQH data represented the best available values
at that time. The underlined values of kOH in this column
(i.e., those values above the dashed line in Table 3.A.) were
used by Atkinson (1986, 1986a) to derive the S/R relationships
for acyclic alkanes. In a monograph published recently,
Atkinson (1989) critically reviewed all the available kOH data
-24-
-------
Table 3.A. Comparison of Experimental and Estimated Values of k0H
Acyclic Alkanes at 298 K and the Percent Error [Underlined
Values of Rate Constants Were Used by Atkinson (1986, I986a)
to Derive the Group Rate Constants and Substituent Factors
Listed in Tables 1 and 2, Respectively, for the Acyclic
Alkanes.]
Chemical
Ethane
Propane
n- Butane
2 -Methy Ipropane
n-Pentane
2-Methylbutane
2 , 2 -Dime thy Ipropane
n-Hexane
2 -Methy Ipent ane
3 -Methy Ipentane
2 , 2-Dimethylbutane
n-Heptane
2 , 4 -Dimethy Ipentane
2,2, 3-Trimethylbutane
n-Octane
2,2, 4-Trimethylpentane
2,2,3, 3-Tetramethylbutane
n-Nonane
1012 kOH (cm3molecule~1s~1)
Experin
(a)
0.274
1.18
3r53
2.37
4_^0
3.9
0.852
5.58
5_^
1^6.
2^1
lil
5^1
4^
8.72
3.66
1.06
10.0
lent a 1
(b)
0.268*
1.15*
2.54*
2.34*
3.94*
3.9*
0.849*
5.61*
5.6*
5.7*
2.32*
7.15*
5.16
4.23*
8.68*
3.68*
1.08*
10.2
Estimated
0.288
1.21
2.53
2.39
3.92
4.00
0.743
5.32
5.39
5.77
1.83
6.71
6.85
3.30
8.11
4.68
1.11
9.50
Percent
Error*-
+7
+ 5
0
+2
-1
+3
-12
-5
-4
-t-1
-21
-6
+ 33
-22
-7
*27
» 3
-25-
-------
Table 3.A. Continued
Chemical
n-Decane
H-Undecane
n-Dodecane
n-Tridecane
2 , 3-Dimethylbutane
2 , 2-Dimethylpentane
2 , 2-Dimethylhexane
2,3, 4-Trimethylpentane
2 -Methy loctane
4 -Methy 1 octane
2,3, 5-Trimethylhexane
n-Tetradecane
H-Pentadecane
n-Hexadecane
1012 kOH (cm3molecule"1s~1)
Exoerimental
(a)
11,3
13.3
13.9
15.5
6.2
(b)
11.6*
13.2*
14.2*
16*
6.2*
3.37°
4.83°
6.97d
10. lc
9.72°
7.78C
19. 2e
22. 2e
24. 9e
Estimated
10.9
12.3
13.7
15.0
5.46
3.22
4.61
8.70
9.58
9.95
10.1
16.5
17.9
19.3
Percent
Errorf
-6
-7
-4
-6
-12
-4
-5
+25
-5
+ 2
+30
-14
-19
-22
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989) and the literature.
c Experimental data is from Behnke et al. (1988).
" Experimental data is from Harris and Kerr (1988).
3 Experimental data is from Nolting et al. (1988).
f Based on the experimental data given in the third column,
Experimental/(b).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-26-
-------
published in the literature up to 1988 and listed the recommended
values at 298 K, the rationale behind each recommendation, and
the uncertainty for each recommendation. These values have an
asterisk after the value and are listed in the third column
labeled Experimental/(b). The values of kOH without an asterisk
were not recommended by Atkinson either because of the limited
temperature dependence data or the limited data from a single
source. These data, however, represent the best available kOH
values at 298 K up to 1989. The fourth column lists the
estimated values of kOH using the S/R relationships of Atkinson;
and finally, the fifth and last column lists the percent error
of the estimated value of kOH relative to the experimental values
listed in the column labeled Experimental/(b).
The underlined values of k0n in tne second column, repre-
senting the first 19 alkanes listed above the dashed line, were
used by Atkinson (1986, 1986a) to derive the group rate constants
and substituent factors for the alkanes. These group rate
constants and substituent factors are given in equations 33, 34,
35, 36, and 37, respectively, and are listed in Tables 1 and 2.
One of the best ways of testing Atkinson's S/R relationships
for the acyclic alkanes is to apply them to the calculation of
kOH for compounds which were not used to derive the group rate
constants and substituent factors. This was carried out for the
13 acyclic alkanes listed below the dashed line in Table 3.A.
Thus, using equation 28, for H-atom abstraction from C-H bonds in
these alkanes, kOH [= k(la)] was estimated at 298 K. The average
percent error for these 13 compounds, based on the kOH data in
-27-
-------
the column Experimental/(b), was +19(1) to -10. These results
ranged from excellent to superb(2) , thereby confirming the S/R
relationships of Atkinson for the acyclic alkanes.
The average percent error for all 32 acyclic alkanes listed
in Table 3.A. ranged from +12 to -9. These results, therefore,
ranged from excellent to superb.
III.A.2.a.ii. Cyclic Alkanes
Table 3.B. lists the pertinent kOH data at 298 K for 18
cyclic alkanes as obtained from the literature. This table is in
exactly the same format as Table 3.A. as described in the first
paragraph of Section III.A.2.a.i.
The underlined values of kOH in the second column,
representing the first 14 cycloalkanes above the dashed line,
were used by Atkinson (1986, 1986a), along with the knowledge of
the strain energies in these rings, to derive the substituent
factors F(3), F(4), F(5), F(6), etc. These substituent factors
are given by equations 40 and 41 and are listed in Table 2.
To test the validity of the S/R relationships of Atkinson,
the estimated values of kOH were compared to the experimental
values of those compounds not used to derive the substituent
1 The average positive error was calculated based on the total
number of chemicals with a positive error plus those with a
zero error.
2 The descriptive ratings for this class of chemicals and those
in later sections are based on the following scale: superb
<10%; excellent >10% and <20%; very good >20% and <35%; good
>35% and <55%; relatively poor >55% and <100%.
-28-
-------
Table 3.B. Comparison of Experimental and Estimated Values of kOH for
Cyclic Alkanes at 298 K and the Percent Error [Underlined
Values of Rate Constants Were Used by Atkinson (1986, I986a)
to Derive the Substituerit Constants for the Cycloalkanes
Listed in Table 2.]
chemical
Cyclopropane
Cyclobutane
Cyclopentane
Cyclohexane
Cy c lohept ane
B icy c lo [2.2.1] heptane
Bicyclo [2.2.2] octane
Bicyclo [ 3 . 3 . 0 ] octane
cis.-Bicyclo [4.3.0] nonane
trans-Bicvclo [4.3.0] nonane
cis-Bicvclo [4.4.0] decane
trans -Bicyclo [4.4.0] decane
Tr icyclo [ 5 . 2 . 1 . O2 • 6 ] decane
Tricyclo [ 3 . 3 . 1 . I3 • 7 ] decane
Me thy 1 cy c 1 ohexane
i-Propylcyclopropane
Cyclooctane
1,1, 3-Trimethylcyclohexane
1012 k0jj (cm^molecule'^s"1)
Experimental
(a)
0.07
5*2.
7.38
13.1
5.42
14.5
10.9
17.0
17.4
19.6
20.2
11.2
22.7
10.3
__..
(b)
0.071°
1.2h
5.16*
7.49*
12. 5d
5.49e
14. 7e
11.0®
17. 2e
17. 6e
19. 9e
20. 4e
11. 3e
22. 6f
10. 41
2.84J
13. 7k
8.73k
Estimated
0.0711
1.23
5.58
8.37
9.77
9.49
16.2
10.4
14.1
14.1
19.0
19.0
12.3
24.1
10.2
2.85
11.2
9.18
Percent
Error?
+1
+3
+8
+ 12
-22
+73
+ 10
-5
-18
-20
-5
-7
+9
+9
-2
0
-18
+5
a Experimental Data from Atkinson (1986).
b Experimental Data from Atkinson (1989).
C At7Av>arra walna fvmrn t-he ovnoyi mont-a 1 Ha-ha nf 7o^-y«!r'H MQQn\ ariH .Toller
d
e
et al. (1985) .
Average value of the experimental data from Jolly et al. (1985) and
Behnke et al. (1988) as reported by Atkinson.
Experimental data from Atkinson, Aschmann, and Carter (1983a) .
Average value from the experimental data of Atkinson, Aschmann, and
Carter (1983a) and Behnke et al. (1988).
Based on the experimental data given in the third column,
Experimental/ (b) .
Experimental value from Gorse and Volman (1974).
Experimental value from Atkinson et al. (1984) .
Experimental value from Atkinson and Aschmann (1988) .
Experimental value from Behnke et al. (1988) as reported in Atkinson
(1989).
Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-29-
-------
factors for the cyclic alkanes. Therefore, for the four
compounds listed below the dashed line, kOH was estimated using
equations 28 and 43, where appropriate; and these results are
listed in the fourth column of Table 3.B. The average percent
error, based on the experimental kOH values listed in the third
column, ranged from +3 to -10 and these results are superb,
confirming the S/R relationships for cyclic and acyclic
alkanes.
The average percent error for all 18 cyclic compounds
ranged from +13 to -12 and these results are excellent.
III.A.2.a.iii. All Alkanes (Acyclic and Cyclic)
Of the 50 alkanes analyzed, 17 compounds were not used to
derive the group rate constants and substituent factors. The
average error for these 17 compounds ranged from +12 to -10
which ranged from excellent to superb, thereby confirming the
S/R relationships of Atkinson for the alkanes.
For all 50 alkanes (acyclic and cyclic) listed in Tables
3.A. and 3.B., the average percent error ranged from +12 to
-10. These results, therefore, ranged from excellent to
superb.
III.A.2.b. Haloalkanes
Table 4 lists the pertinent kOH data at 298 K for 32
haloalkanes as obtained from the literature. This table is in
exactly the same format as Table 3.A. and the column headings
are exactly the same as those described in the first paragraph
of Section III.A.2.a.i. It should be noted that the
-30-
-------
Table 4. Comparison of Experimental and Estimated Values of kOH for
Haloalkanes at 298 K and the Percent Error [Underlined
Values of Rate Constants Were Used by Atkinson (1986, 1986a)
to Derive the Substituent Factors Listed in Table 2 for the
Haloalkanes]
Chemical
Fluor ome thane
Chloromethane
Bromomethane
Dif luor ome thane
F luor och lor ome thane
Dichloromethane
Tr i f luor ome thane
Dif luorochloromethane
Fluorodichloromethane
Chloroethane
1, 1-Dif luoroethane
1, 1-Dif luoro-1-chloroethane
1,1, 1-Trichloroethane
1,1,1, 2 -Tetraf luoroethane
l-Chloro-2 , 2 , 2 -tr if luoroethane
2 , 3-Dichlorobutane
Trichlorometharie
F luoroethane
1 , 2 -Dif luoroethane
1 , 1-Dichloroethane
1 , 2-Dibromoethane
1,1, 1-Tr if luoroethane
1,1, 2 -Tr if luoroethane
1,1, 2-Trichloroethane
1 , 2-Dichloro-2 , 2-dif luoroethane
1014 kOH (cm3molecule~1s~1)
Experimental
(a)
1.68
4.36
3.93
1.09
4.41
14.2
0.020°
0.468
3.03
40.0
3.4
0.358
1.19
0.854
1.62
96d'h
10.3
23.0
11
26
25
-0.20
1.8
32.8
<1.9
(b)
1.68*
4.36*
4.02*
1.09*
4.41*
14.2*
0.024°
0.468*
3.03*
39*
3.4*
0.358*
1.19*
0.854*
1.62*
10.3*
23. 2e
11. 2f
26.09
25.09
0.171f
1.83f
32.43
2.61*
Estimated
1.43
5.47
4.32
0.821
3.15" .
12.1
0.682
2.62
40.0
3.23
0.360
1.30
0.622
2.39
95.7
10.0
20.5
14.1
34.6
28.7
1.08
2.35
33.3
0.796
Percent
Error1
-15
+25
+7
-25
-29
-15
+46
-14
+3
-5
+1
+9
-27
+48
0
-3
-12
+26
+33
+15
+440
+23
+2
-70
-31-
-------
Table 4. Continued
Chemical
Pentaf luoroethane
1-Chloro-l ,2,2, 2 -tetraf luoro-
ethane
1 , l-Dichloro-2 , 2 , 2-trif luoro-
ethane
2 -Chlorobutane
1, 2-Dichloroethane
1,1,2, 2 -Tetraf luoroethane
1 , 2-Dibromo-3-chloropropane
1014 kOH (cm3molecule~1s~1)
Experiment a 1
(a)
0.25
1.02
3.35
230d
(b)
0.249f
1.02*
3.35*
22.09
0.67*
43. 51
Estimated
0.135
0.516
1.98
164
36.3
0.359
50.3
Percent
Error1
-46
-49
-41
-29
+65
-46
+16
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989).
C cinr>a +h«» ovneiri mental rls» + s» uaCHC1) =0.57 which is listed in Table 2.
Based on the Experimental data given in the third column,
Experimental/ (b) .
Extrapolated from the experimental data of Jeong and Kaufman (1979)
and Jeong et al. (1984) .
Extrapolated from the experimental data of Clyne and Holt (1979) .
Experimental data from Tuazon et al. (1986) .
Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-32-
-------
experimental JCQH data for trifluoromethane was not included in
the analysis given below. That is, the data at 298 K was
obtained from the extrapolation of the experimental data at
>387 K and, therefore, must be used with caution at
temperatures <300 K [Atkinson (1989)].
Using the appropriate group rate constants (k°) and
substituent factors F(X) for the alkanes from Tables 1 and 2,
respectively, Atkinson (1986) carried out a nonlinear least-
squares fit of the underlined experimental kOH data of the
haloalkanes (i.e., the 14 underlined compounds listed above the
dashed line) to equation 28 and derived the following
substituent factors F(X) for the haloalkanes:
F(F-) = 0.099; F(Cl-) = 0.38; F(Br-) = 0.30 (51)
F(C1CH2-) - F(C12CH-) = F(BrCH2-) = 0.57 (52)
F(C13C-) = 0.090; F(FCH2-) = 0.85; F(F2CH-) = 0.10 (53)
F(C1F2C-) » 0.025; F(F30) = 0.075 (54)
The values of these substituent factors [F(X)], along with the
corresponding values of E(X), are listed in Table 2. It should
be noted that the substituent factor F(C13C-) was adjusted
slightly from a value of 0.083 [Atkinson (1986)] to 0.090
[Atkinson (1987)] to optimize the fit of the 298 K rate
constants (kOH) for CH3CC13 and C13CCHO.
The rate constants kOH for 2,3-dichlorobutane and
2-chlorobutane were measured by Mill et al. (1982) at 298 K.
/
Using the measured value of kOH for 2,3-dichlorobutane, Leifer
-33-
-------
estimated that the substituent factor F(>CHC1) was equal to
0.57 and this value is listed in Table 2. Since this compound
was used to derive this substituent factor it is listed above
the dashed line in Table 4.
Using the group rate constants k° for the alkanes from
Table 1 and the appropriate substituent factors F(X) from
Table 2, kOH was estimated using equation 28 for the remaining
16 haloalkanes listed in Table 4 (i.e., those compounds listed
below the dashed line which were not used to derive the substi-
tuent constants for the haloalkanes) along with the percent
error. Only 1,1,1-trifluoroethane had an error greater than
+100 percent (+440) and was dropped in subsequent analyses.3
Excluding the value for this compound, the average percent
error of the remaining 15 compounds ranged from +26 to -37.
These results ranged from very good to good, confirming the S/R
relationships of Atkinson for the haloalkanes.
The average percent error for all 30 compounds (which
excluded 1,1,1-trifluoroethane and trifluoromethane) ranged
from +21 to -28 so that these results are very good.
III.A.2.c. Carbonyl Compounds: Aldehydes, Ketones,
o-Dicarbonyls, Acid Chlorides, and Esters
The experimental values of kOH at 298 K for 52 carbonyl
compounds: aldehydes (11 compounds); ketones [19 compounds
3 The value of +100 was chosen so that only a minimum number of
chemicals would be dropped from the total number of chemicals
used to obtain the average percent error. See Sections
III.A.2.b. and III.A.3.; Summary Tables 8, 17, 21, 25 and 26;
and Section III.E.
-34-
-------
(comprised of 16 acyclic and 3 cyclic compounds) ]; ot-dicarbonyls
(3 compounds); acyl chlorides (l compound); and esters (18
compounds) are listed in Table 5 as obtained from the
literature. Using the appropriate group rate constants and
substituent factors from Tables 1 and 2, Atkinson carried out a
nonlinear least-squares fit of the experimental KOH data of 13
of the aldehydes and ketones (i.e., the underlined values of
k0H above the dashed lines in Table 5.A. and B.) to equation 28
and derived the following substituent factors [Atkinson
(1986)]:
F(=0) = 8.8; F[-CH(0)] = F[-C(0)-] = 0.76 (55)
F[-CH2C(0)-] = F[>CHC(0)-] = F^CC(O)-] = 4.4 (56)
Atkinson (1989a) reevaluated the k0n data for the
aldehydes and ketones and indicated that for compounds
containing a second aIkyl-(CO)-group, the substituent factor is
F [ 2^ R-C(O)- ] = 1.00 (57)
Similarly, for the esters, Atkinson (1987) carried out a
nonlinear least-squares fit of the experimental data of 5 of
these compounds (i.e., those underlined values of kOH above the
dashed line in Table 5.F.) and derived the substituent factors
F [ -OC(0)R ] = 1.5; F [ -C(0)OR ] = 0 (58)
Furthermore, Atkinson (1987) estimated the substituent
factor for the acyl chlorides from the experimental kQjj data of
-35-
-------
Table 5. Comparison of Experimental and Estimated Values of kOH for
Carbonyl Compounds at 298 K and the Percent Error (Underlie
Values of k0H Were Used by Atkinson (1986, 1987) to Derive
Substituent Factors for the Carbonyl Compounds)
Chemical Class/Chemical
A. ALDEHYDES
Formal
Ethanal
Propanal
Trichloroacetaldehyde
Butanal
2 -Methy Ipr opana 1
Pentanal
3 -Methy Ibutanal
2 , 2-Dimethylpropanal
Pentane-1 , 5-dial
Hydr oxy ethana 1
(Glycolaldehyde)
B. ACYCLIC KETONES
Propanone
2 -Butanone
2-Pentanone
3-Pentanone
2-Hexanone
3-Hexanone
1012 kOH (cm-^molecule'^-s'1)
Exoerin
(a)
9_L£
16.2
19.6
1.95°
23
27
27
27
27
0.23
1^0
4.64
1.82
8.97
6.81
lent a 1
(b)
9.77*
15.8*
19.6*
1.73
23.5*
26.3*
28.5*
27.4*
26.5*
23. 8d
9.9e
0.226*
1.15*
4.9*
2.0*
9.1*
6.90°
Estimated
7.37
16.2
22.0
1.45
25.5
23.4
27.6
30.0
22.7
46.9
23.0
0.219
1.38
4.81
2.56
6.96
5.97
Percent
Error"
-25
-1-3
+12
-16
+9
-11
-3 (
+9
-14
+110
+132
-3
+20
-2
+28
-24
-13
-36-
-------
Table 5. Continued
Chemical Class/Chemical
2 , 4-Dimethyl-3-pentanone
4 -Me thy 1-2 -pentanone
2 , 6-Dimethyl-4-heptanone
3 , 3-Dimethyl-2-butanone
2-Heptanone
2-Octanone
2-Nonanone
2-Decanone
2 , 4-Pentanedione
2 , 5-Hexanedione
C. CYCLIC KETONES
Cyclobutanone
Cyclopentanone
Cyclohexanone
D. a-DICARBONYLS
Glyoxal
Methylglyoxal
Biacetyl
E. ACYL CHLORIDES
Acetyl chloride
1012 kOH (cm3molecule~1s"1)
Experimental
(a)
5.31
14.1
27.1
—
11.2
16.9
0.24
0<068h,i
(b)
5.38°
14.1*
27.5*
1.21*
8.67f
11.0*
12. 2f
13. 2f
1.159
7.139
0.879
2.949
6.399
11.4*
17.2*
0.238*
0.068
Estimated
5.31
9.35
18.5
2.01
8.35
9.74
11.1
12.5
0.703
5.82
1.17
8.92
12.6
24.5
12.3
0.219
0.0720
Percent
Errorn
-1
-34
-33
+66
-4
-11
-9
-5
-39
-18
+34
+203
+97
+115
-28
-8
.+6
-37-
-------
Table 5. Continued
Chemical Class/Chemical
F . ESTERS
Ethyl acetate
n-Propyl acetate
i-Propyl acetate
n-Butyl acetate
Ethoxy ethyl acetate
Methyl trifluoroacetate
Methyl formate
Ethyl formate
n-Propyl formate
n-Butyl formate
Methyl acetate
s -Butyl acetate
Ethyl propionate
n-Propyl propionate
Methyl butyrate
Ethyl butyrata
n-Propyl butyrate
n-Butyl butyrate
1012 kOH (cm3molecule~1s"1)
Exper iment a 1
(a)
1.7h'3
ao5h'i
3.09h' 3
4.3h'3
i3>J
— -
(b)
1.6*
3.4*
3.4*
4.2*
13
0.052k'1
0.227k
1.02k
2.38k
3.12k
0.34m
5.5*
2.1m
4.02k
3.04k
4.94k
7.41k
10. 6k
Estimated
1.44
2.89
3.12.
4.28
14.0
0.0518
0.216
1.44
2.89
4.28
0.216
4.99
1.63
3.07
1.48
2.71
4.16
5.55
Percent
Error11
-10
-15
-8
+2
+8
-17
-5
+41 '
+21
+37
-36
-9
-22
-24
-51
-45
-44
-48
-38-
-------
Table 5. Continued
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989) .
c Atkinson (1987) used this value of kOH to derive the substituent
constant for F[F3C(0)-].
d Experimental data from Rogers (1989). This value of k0H represents
the average value of 25.2 and 22.4 x 10~12cm3 molecule'^-s"1 as
measured with the reference compounds propene and trans-2-butener
respectively.
e Experimental data from Niki et al. (1987).
f Experimental data from Wallington and Kurylo (1987).
9 Experimental data from Dagaut et al. (1988).
h Experimental data from Atkinson (1987).
i Used by Atkinson (1987) to derive the substituent factor for acid
chlorides F[-C(O)C1].
J Used by Atkinson (1987) to derive the substituent factors for
esters F[-OC(0)R and F[-C(0)OR].
k Experimental data from Wallington et al. (1988).
1 Used by Leifer to derive the substituent factor F[-OC(0)CF3].
m Experimental value from Wallington et al. (1988). The experimental
data of Campbell and Parkinson (1978) was not used since the
experimental method used was probably not valid [Atkinson (1989)].
n Based on the experimental data given in the third column,
Experimental/(b).
0 Experimental data from Atkinson et al. (1982).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-39-
-------
acetyl chloride and Leifer estimated the substituent factor
F[F3C(O)O-] from the kOH data for methyl trifluoroacetate.
These results are
F[-C(0)C1 ] = 0.50; F[-OC(0)CF3 ] = 0.36 (59)
These substituent factors, along with the corresponding E(X)
data, are listed in Table 2.
Consider the 32 compounds not used to derive the
substituent factors for the carbonyl compounds (i.e., all those
compounds whose values of k0H are not underlined and/or are
below the dashed line). Four of these compounds had a percent
error greater than +100 [i.e., pentane 1,5-dial (+110);
hydroxyethanal (+132); cyclopentanone (+203); glyoxal (+115)]
and were not used in the calculation of the average percent
error. Therefore, for the remaining 28 compounds, the average
percent error ranged from +39 to -22 and, thus, ranged from
good to very good. These results, therefore, confirm the S/R
relationships of Atkinson. It should be noted that of the four
compounds dropped, three had kOH values which were not
recommended by Atkinson since they only had experimental data
from one literature source. More experimental kOH data are
needed for these three compounds.
For the 48 carbonyl compounds remaining (after dropping
the 4 compounds with a percent error greater than +100), the
average percent error ranged from +26 to -19 and, therefore,
ranged from very good to excellent.
-40-
-------
III.A.2.d. Alcohols, Glycols, and Ethers
For methanol, the simplest member of the aliphatic
alcohols, the hydroxyl radical can react via two pathways:
(1) hydrogen abstraction from the CH3- group; and (2) hydrogen
abstraction from the -OH group. Therefore, the reaction of OH
radicals with methanol can be described by the following two
reactions:
ka
—- CH30- + HOH (60a)
2 CH3OH + 2(-OH)
-> 'CH2OH + HOH (60b)
where ka is the rate constant for H-atom abstraction from the
hydroxyl group and kj, is the rate constant for H-atom
abstraction from the CH3- group. The branching ratio (BR) for
this reaction scheme is given by the equation
BR = ka/(ka + kb) (61)
The branching ratio was measured at 298 K recently and it was
found that it was equal to 0.038 [McCaulley et al. (1986)].
Using this branching ratio, Atkinson (1987) found that the
group rate constant for H-atom abstraction from the OH group at
298 K was
k(-OH) = 0.036 x 10~12 CTO^molecule'is'1 (62)
This value of k(-OH) is lower by a factor of approximately 4
from the value 0.13 obtained previously [Atkinson (1986)].
However, the value of k(-OH) given in equation 62 is more
-41-
-------
consistent with the C-H and OH bond dissociation energies in
CH3OH. Therefore, the value given in equation 62 is listed in
Table 1.
For the general case for a saturated alcohol,
R-CH(CH3)CH2OH, which contains primary, secondary, and tertiary
C-H groups [i.e., CH3-, -CH2-, and >CH- groups, respectively]
and R is a saturated alkyl group, the hydroxyl radical
reactions can be written as follows:
4 RCHCH2OH
I 2
CH3
9H3
R-C-CH2OH
HOH
>- R-6HCHOH + HOH
CH2
l-CH<
R-CHCH2OH + HOH
CH3
R-CHCH2O« + HOH
(63a)
(63b)
(63c)
(63d)
From equation 20, for the two reaction pathways, the total rate
constant for OH radical reaction with acyclic alcohols is given
by
kOH = k(la) + k(2)
(64)
Using equation 11 and the preexponential factor given in
equation 31, Atkinson (1987) found that
kOH - 1.89 X 10"18 T2exp(-460/T) (65)
where k0n is in the units c
The experimental values of k0n at 298 K for a number of
alcohols (16) and glycols (2) are listed in Table 6 as obtained
-42-
-------
Table 6. Comparison of Experimental and Estimated Values of XOH
at 298 K for Alcohols, Glycols, and Ethers and the Percent
Error [Underlined Values of kOH Were Used by Atkinson
(1986, 1987) to Derive the Substituent Factors for These
Classes of Chemicals]
Chemical Class/Chemical
A. ALCOHOLS
Methanol
Ethanol
1-Propanol
2-Propanol
2-Methyl-2-Propanol
1-Butanol
1-Pentanol
2-Pentanol
3-Pentanol
3 -Me thy 1-2 -but ano 1
1-Hexanol
2-Hexanol
1-Heptanol
2 -Chloroethanol
l-Hydroxy-2 -propanone
Cyclopentanol
1012 kOH (cm3molecule"1s~1)
Experimental
(a)
0.90
1^1
Sol
6.2
1.09
7.3
1.4
— _
(b)
0.932*
3.27*
5.34*
5.21*
1.12*
8.31C
10.8°
11. 8d
12. 2d
12. 4d
12. 4d
12. ld
13. 6d
1.4
3.02e
10. 7d
Estimated
0.526-
3.08
4.99
6.63
0.593
6.38
7.77
10.9
12.9
11.0
9.17
12.3
10.6
2.07
2.32
12.7
Percent
Error^
-44
-6
-7
-1-27
-47
-23
-28
-8
+6
-11
-26
+2
-22
-1-48
-23
+ 19
-43-
-------
Table 6. Continued
Chemical Class/Chemical
B. GLYCOLS
1,2-Ethanediol
1 , 2-Propanediol
C. ACYCLIC ETHERS
Dimethyl ether
Di ethyl ether
Di-n-propyl ether
Methyl-t-butyl-ether
Methyl-n-butyl ether
Ethyl-n-butyl ether
Ethyl-t-butyl ether
Methyl -t-amyl ether
Di-n-butyl ether
Di-i-butyl ether
Di-n-pentyl ether
1,1, -Dime thy oxy ethane
D i ethoxymethane
1 , 2-Dimethoxypropane
2 , 2-Dimethoxypropane
2 , 2-Diethoxypropane
2-Methoxyethyl ether
1012 KOH (cm3molecule~1s~1)
Experin
(a)
7.7
12
2.98
13.4
16.8
2.64
Cental
(b)
7.7
12
2.98*
13.3*
17.2*
2.83*
16. 4d
18. lf
6.9f
7.91d
22. 4f
26.09
34. 7d
8.89e
16.8s
14. 3e
3.92e
11. 7e
17. 5e
Estimated
7.42
11.9
1.76
11.5
21.1
2.82
13.6
18.5
7.7
6.13
25.5
30.4
28.2
13.1
16.6
22.9
3.05
12.8
28.1
Percent
Errork
-4
-1
-41
-14
+23
0
-17
+2
+12
-23
+14
+17
-19
+47
-1
+60
-22
+9 '
+ 61
-44-
-------
Table 6. Continued
Chemical Class/ Chemical
1,1, 3 -Tr imethoxypropane
2-Ethoxyethyl ether
Methoxyacetone
2 -Methoxyethanol
2 -Ethoxyethanol
3-Ethoxy-l-propanol
3 -Methoxy-1-butanol
2 -Butoxyethanol
2-Hydroxyethyl ether
D. CYCLIC ETHERS
Ethylene Oxide
1 , 2 -Epoxypropane
1, 2-Epoxybutane
l-Chloro-2 , 3-epoxypropane
Trimethylene oxide
Tetrahydrofuran
1,3-Dioxane
1,4-Dioxane
1,3,5-Trioxane
Oxepane (Hexamethylene oxide)
1012 kOH (cm3molecule~1s"1)
Experimental
(a)
30
0.07
0.52
2.1
0.44
— _
15
(b)
19. 2e
26. 8e
6.77e
12. 5e
15. 4h
22. Oe
23. 6e
18. 6h
30
0.076*
0.52*
2.1
O.SQi
10. 3e
16.1*
9.15e
10. 9e
6.23
15. 4e
Estimated
28.5
37.8
4.87
11.2
16.1
20.9
20.6
23.0
20.6
0.224
0.543
1.70
0.662
3.73
18.3
22.1
26.4
15.3
25.7
Percent
Error*
+48
+41
-28
-10
+ 5
-5
-13
+24
-31
+ 190
+ 4
-19
+ 32
-64
+ 14
1-140
*140
+ 15D
•*•'
-45-
-------
Table 6. Continued
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989) .
c Experimental data from Wallington and Kurylo (1987a). The data from
Campbell et al. (1976) was not used since the validity of the
experimental method is questionable [Atkinson (1989)].
d Experimental data from Wallington et al. (1988b).
e Experimental data from Dagaut et al. (1988a)
f Average value from the experimental data of Wallington et al. (1988b)
and Bennett and Kerr (1989).
9 Experimental data from Bennett and Kerr (1989).
n Average value from the experimental data of Hartmann et al. (1987)
and Dagaut et al. (1988a).
i Average value from the experimental data of Zetzsch (1980) and Edney
et al. (1986) assuming kOH = 0.55 x 10~12cm3 molecule~1s~^- of Edney.
J Extrapolated from the experimental data of Zabarnick et al. (1988).
^ Based on experimental data given in the third column,
Experimental/(b).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-46-
-------
from the literature. In addition, Table 6 lists the
experimental values of kOH for a number of acyclic (26) and
cyclic ethers (10), including hydroxy and chloro substituted
ethers, as obtained from the literature.
Using the group rate constants for alkanes and k(-OH) for
alcohols from Table 1 and the appropriate substituent factors
F(X) from Table 2, Atkinson carried out a nonlinear least-
squares fit of the experimental k0n data of the alcohols (i.e.,
the 5 compounds above the line in Table 6.A.) and at 298 K to
equation 28 and found that
F(-OH) = 3.4 (66)
This substituent factor is listed in Table 2.
Thirteen compounds were not used by Atkinson (1986, 1987)
to derive the substituent factor for the alcohols (i.e., the 11
alcohols listed below the dashed line in Table 6.A. and the 2
glycols in Table 6.B.). The second-order rate constant k0jj was
estimated using equation 64 (and, therefore, using equations 28
and using 62) and these results are summarized in Tables 6.A.
and B. The average value of k0H ranged from +19 to -16; and
these results are excellent, thereby confirming the S/R
relationships of Atkinson.
The average value of kOH for all 18 alcohols ranged from
+20 to -19 so that these results are also excellent.
Using the appropriate group rate constants and substituent
factors, Atkinson (1986) carried out a nonlinear least-squares
fit of the experimental data at 298 K for the first four
-47-
-------
ethers listed in Table 6.C. and found that
F(-O-) = 6.1 (67)
Atkinson (1987) reevaluated the S/R relationships of the
ethers. For 1,3,5-trioxane, Atkinson indicated that the ring
strain energy is approximately 6 kcal/mol, the same as the ring
strain energy of cyclopentane. Therefore, kOH was estimated
for this cyclic ether using the ring strain factor F(5) =0.80
(Table 2) and Atkinson found that kOH = 75 x 10~12
cm3molecule~1s~1. Even with this ring strain factor, the
percent error was too high (+850). It appears that 1,3,5-
trioxane is much less reactive than implied by the presence of
the two substituent ether groups (-0-) per methylene group
(-CH2-). Based on these results and a reevaluation of the k0H
data for all the ethers listed in Tables 6.C. and D., Atkinson
(1989a) indicated that for the ethers
F(-O-) = 6.1 (68)
-0-) = 1.0 (69)
F(-CH2-0-) =4.5 (70)
F(»C-0-) = 4.5 (71)
and these results are summarized in Table 2.
Using the appropriate substituent factors and group rate
constants, kOH was estimated for all 36 ethers listed in Tables
6.C. and D. and these results are summarized in the fourth
column of this table. The percent error for each compound is
-48-
-------
listed in the s£Jl column of this table. Inspection of all
these data indicated that 4 compounds had an error greater than
+100 [ethylene oxide (+190); 1,3-dioxane (+140); 1,4-dioxane
(+140); 1,3,5-trioxane (+150)]. Excluding these 4 compounds,
the remaining 32 compounds had a percent error which ranged
from +27 to -22. These results are very good, indicating that
the S/R relationships for the ethers are very good. However,
it should be noted that all these compounds were used to derive
the substituent factors for the ethers. Therefore,
considerably more experimental kOH data are needed on
additional ethers to confirm the S/R relationships of Atkinson.
In addition, more experimental data is needed for the 4
compounds with percent error > +100 to determine why they had
such a large percent error.
III.A.2.e. Nitrates and Nitriles
The experimental values of kOH at 298 K for 17 alkyl and
cycloalkyl nitrates and 2 alkyl nitriles are listed in Table 7
as obtained from the literature. The experimental values of
kOH listed in the third column represent the best available
values for these compounds as obtained from Atkinson (1989) and
the literature. Atkinson (1987, 1989) indicated that the
experimental JCQH data for methyl and ethyl nitrate from Kerr
and Stocker (1986) were systematically high and should be used
with caution. Only for acetonitrile did Atkinson (1989) list a
recommended value of kOH at 298 K with the rationale and
uncertainty for this recommendation.
~49~
-------
Table 7. Comparison of Experimental and Estimated Values of
koH at 298 K for Nitrates and Nitriles and the
Percent Error [Underlined Values of kOH Were Used
by Atkinson (1986, 1987) to Derive the Substituent
Factors for the Nitrates and Nitriles]
Chemical Class/Chemical
A. NITRATES (ACYCLIC)
2-Propyl nitrate
1-Butyl nitrate
2 -Butyl nitrate
2-Pentyl nitrate
3-Pentyl nitrate
2-Methyl-3-butyl nitrate
2,2-Dimethyl-l-propyl nitrate
2-Hexyl nitrate
3-Hexyl nitrate
2-Methyl-2-pentyl nitrate
3-Methyl-2-pentyl nitrate
3-Heptyl nitrate
3-Octyl nitrate
Methyl nitrate
Ethyl nitrate
1-Propyl nitrate
1012 kOH (cm3molecule~1s~1)
Excerimental
(a)
0.18
1.39
0.67
1.83
1.10
1.72
0.85
3.13
2.66
1.71
3.01
3.64
3.82
(b)
0.41C
1.78°
0.92°
1.85d
1.12d
1.72e
0.85e
3.17d
2.70d
1.72e
3.02e
3.69e
3.88d
0.034f
0.499
0.67h
Estimated
0.416
1.79
0.905
2.06
1.42
1.39
0.752
3.45
2.58
1.68
2.63
3.97
5.37
0.0259
0.632
Percent
ErrorJ
+1
-i-l
-2
+ 11
+27
-19
|
1
-12
+ 9
-4
-2
-13
+ 8
+ 38
-24
-6
-50-
-------
Table 7. Continued
Chemical Class/Chemical
B. NITRATES (CYCLIC)
Cyclohexyl nitrate
C . NITRILES
Acetonitrile
Propionitrile
1012 kOH (cm3molecule"1s~1)
Exper iment a 1
(a)
3.29
0.021
0.19
(b)
3.30e
0.0214*
0.1941
Estimated
5.38
0.0202
0.189
Percent
ErrorJ
+63
-6
-3
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989).
c Experimental data from Atkinson and Aschmann (1989).
d Experimental data from Atkinson et al. (1982a).
e Experimental data from Atkinson et al. (1984b).
f Atkinson (1987) reported a value of kOK = 0.034 x 10"12 and 0.38 x
10~12cm3 molecule'is""1 from Gaffney et al. (1986) and Kerr and Stocker
(1986), respectively. Atkinson (1987) used the value of 0.034 x 10~12
since it was more consistent with the entire set of k_H data used to
develop the S/R relationships and the value from Kerr and Stocker was
systematically too high. Atkinson (1989) also tentatively preferred
the value of kOH from Gaffney et al. (1986) since the value from
Kerr and Stocker was systematically too high.
9 Experimental data from Kerr and Stocker (1986). Atkinson (1987, 1989)
did not accept this data since the results were systematically too
high.
n This value of kOH represents the average value from the experimental
data of Kerr and Stocker (1986) and Atkinson and Aschmann (1989).
i Experimental data from Harris et al. (1981).
J Based on the experimental data given in the third column,
Experimental/(b).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-51-
-------
Atkinson (1986) analyzed the k0n data at 298 K for the
first 13 alkyl nitrates listed above the dashed line in Table
7.A. (i.e., the underlined values of kOH in column 2) and for
cyclohexyl nitrate in Table 7.B. Using the appropriate group
rate constants and substituent factors from Tables 1 and 2,
respectively, Atkinson carried a nonlinear least-squares fit of
the experimental kOH data of the nitrates to equations 28 and
43 (for the acyclic and cyclic nitrates, respectively) and
derived substituent factors for the nitrates. Atkinson (1987)
repeated the analysis of the kOH data (excluding the data of
Kerr and Stocker (1986) for methyl and ethyl nitrate) and found
that the substituent factors for the alkyl nitrates were
F(-CH2ON02) » F(>CHON02) = F(>CON02) = 0.21 (72)
F(-ON02) = 0.10 (72a)
Recently, Atkinson (1989a) repeated the analysis of the kOH
data for the alkyl nitrates (excluding only the data for ethyl
nitrate) and obtained refined values of the substituent factors
given by
F(-CH2ON02) = F(>CHON02) = F(»CON02) = 0.30 (73)
••—. F(-ON02) = 0.18 (73a)
The second-order rate constant kOH for all 16 alkyl
nitrates (excluding ethyl nitrate) was estimated in the
standard manner and these results are summarized in Table 7
along with the percent error. The average percent error ranged
-52-
-------
from +20 to -10 and these results ranged from excellent to
superb.
The only compound not used to derive these substituent
factors was 1-propyl nitrate. The estimated value of KOH
this compound was 0.632 x 10~12cm3 molecule~1s~1 and the
percent error was -6 which was excellent. However/ more
experimental kOH data are needed for other alkyl nitrates to
confirm the S/R relationships of Atkinson.
In a similar manner, Atkinson (1986) analyzed the k0H data
at 298 K for two nitriles listed in Table 7.C. and derived the
following substituent factors for this class of compounds:
F(-CN) = 0.14 (74)
F(-CH2CN) = 0.50 (75)
and these results are summarized in Table 2. The rate constant
kOH was then estimated in the standard manner for the two
nitriles using equation 28 and these results are listed in
Table 7 along with the percent error. The average percent
error for these two nitriles is -5 which is superb. More
experimental k^H data are needed for additional alkyl nitriles
to confirm the S/R relationships of Atkinson.
III.A.2.f. Olefins, Diolefins, Alkynes, and Aromatic
Compounds
Atkinson (1986, 1987) analyzed the kinetic data at 298 K
for H-atom abstraction from compounds containing the following
carbon-carbon unsaturated groups: (1) olefins such as -?CH=CH2,
-CH=CH-, etc.; (2) conjugated diolefins such as -CH=CH-CH=CH-,
-53-
-------
-CH=CH-C=CH2/ etc.; (3) alkynes such as -CsC-H; allenes such as
>C=C=C<; and (4) aromatic compounds such as C6H5-, etc. For
all practical purposes, Atkinson (1986, 1987) concluded that
the rate constant for H-atom abstraction from the above
functional groups was essentially zero. Therefore, from
equation 20, one obtains
vn TTOQ rm - vfH~atom abstraction from carbon-carbon] _ .....
k(l,UNS CH) - "Lunsaturated functional groups J ~ ° (76)
Even at elevated temperature up to 500 K, k(l,UNS CH) was
essentially zero [Atkinson (1987)]. In addition, Atkinson
(1987) concluded that the substituent factors for carbon-carbon
unsaturated groups were approximately 1.0; therefore
F(>C=C<) = F(-CsC-) = F(C6H5-) =1.0
All the above results are summarized in Tables 1 and 2.
III.A.3. Summary
Table 8 summarizes the average percent error in the
estimation of kOH for H-atom abstraction from C-H and -OH
groups by hydroxyl radicals at 298 K for chemicals within each
of several classes of organic chemicals and for all chemicals
within all the classes of chemicals as obtained from Tables
3-7. The total rate constant for H-atom abstraction kQjj was
estimated for a total of 207 chemicals and these results are
compared to the experimental values. Only 9 chemicals had a
percent error greater than +100 [pentane 1,5-dial (+110);
hydroxyethanol (+132); cyclopentanone (+203); 1,1,1-
-54-
-------
Table 8. Summary of the Average Percent Error in kOH f°r
H-Atom Abstraction From C-H and OH Groups at 298 K
for Chemicals Within Several Classes of Chemicals and
for All Chemicals in These Classes
Chemical Class3
Alkanes [Acyclic (32)
and Cyclic (18) ]
Haloalkanes, Acyclic
(32)c
Carbonyls (52)d
[Aldehydes (11) ; Ketones
(19); a-Dicarbonyls
(3) ; Acyl Halides (1) ;
Esters (18)]
Alcohols (16); Glycols
(2);
Ethers [Acyclic (26) ;
and Cyclic (10)®]
Nitrates [Acyclic (16) f
and Cyclic (1)]
Nitriles, Acyclic (2)
All chemicals not used
to derive the substi-
tuent constants and
group rate constants
All Chemicals (207)
No. of
Chemicals*3
50
30
48
18
32
16
2
74
196
Average Percent Error
From
+12
+21
+26
+20
+27
+20
— .
+26
+21
TO
-10
-28
-19
-19
-22
-10
-5
-20
-18
a The numbers in parentheses represent the total number of
chemicals in which k,™ was estimated.
UH
b These numbers represent the number of chemicals used to
calculate the average percent error.
-55-
-------
Table 8. Continued
c One of these chemicals had a percent error greater than 100
1,1,1-trifluoroethane (+440)] and was not used to determine
the average percent error. The second chemical, trifluoro-
methane, did not have a reliable experimental value of kOH
and therefore was not used to determine the average percent
error.
d Four chemicals had a percent error greater than 100 [pentane-
1,5-dial (+110); hydroxyethanal (+132); cyclopentanone
(+203); glyoxal (+115)] and were not used to determine the
average percent error.
e Four chemicals had a percent error greater than 100 [1., 3-
dioxane (+(140); 1,4-dioxane (+140); ethylene oxide (+220);
1,3,5-trioxane (+150)] and were not used to determine the
average percent error.
f One chemical, ethyl nitrate, had unreliable kOH data and was
not used to determine the average percent error.
-56-
-------
trifluoroethane (+440); glyoxal (+115); 1,3-dioxane (+140);
1,4-dioxane (+140); 1,3,5-trioxane (+150) and ethylene oxide
(+220)]. Two chemicals (trifluoromethane and ethyl nitrate)
had unreliable experimental kOH data. Therefore, the kOH data
for these 11 chemicals were not included in the determination
of the average percent error for certain classes of chemicals
and for all chemicals. It should be noted that the value of
+100 was chosen so that only a minimum number of chemicals
would be dropped from the total number of chemicals used to
obtain the average percent error. See Summary Tables 8, 17,
21, 25, 26, and Section III.E. The range in the average
percent error for each class ranged from superb to very good.
The average percent error for the 74 chemicals not used by
Atkinson to derive the group rate constants and substituent
factors ranged from +26 to -20. These results, therefore,
ranged from very good to excellent and confirm most of the S/R
relationships of Atkinson. For all 196 chemicals, the average
percent error ranged from +21 to -18; and these results ranged
from very good to excellent. More experimental kOH data,
however, are needed to determine why the nine chemicals listed
above had a large percent error (> +100 percent) and to confirm
the S/R relationships for ethers, nitriles, a-dicarbonyls, acid
chlorides, and glycols. In addition, more reliable
experimental kOH data are needed for trifluoromethane and ethyl
nitrate.
-57-
-------
III.B. Addition of Hydroxyl Radicals to Olefinic, Conjugated
Diolefinic, 1,2-Diolefinic Compounds and Alkynes and
the Estimation of kOH
III. B.I. Formulation of the Structure/Reactivity Relationships
Atkinson (1986, 1987) analyzed the kinetic data for OH
radical reaction with olefins and acetylenes. For these two
classes of compounds with the following general structures
R1R2C=CR3R4 (78)
R5C5CR6 (79)
(where R^ is an alkyl group or H) , the total rate of hydroxyl
radical reaction, kQjj , is: (1) a function of H-atom
abstraction by OH radicals from C-H groups in the alkyl groups
R^, from the groups =CH2, =CH-, etc. in olefins and from the
groups sc-H; and (2) the addition of OH radicals to the
isolated unsaturated carbon-carbon groups.
H-atom abstraction by hydroxyl radicals from C-H groups
has already been described in Section III. A. The addition of
OH radicals to the unsaturated carbon-carbon groups in alkenes
and alkynes can be represented by the following reactions:
?H
2 R1CH=CH2 + 2('OH) - * RiCHCH^ + R1CHCH2OH + 2 HOH (80)
OH OH
2 R2CH=CHR3 + 2 (-OH) - »• R2CHCHR3 + R2CHCHR3 + 2 HOH
9H
2 R4C=CH + 2 (-OH) - * R4C=CH + R4C=CHOH + 2 HOH (82)
2H • 2H
2 R5C3CR6 + 2 (-OH) - » R5C=CR6 + R5C=CR6 + 2 HOH (83)
-58-
-------
where R^ are all alkyl substituents. Similar reactions can be
written for conjugated diolefins.
To a good approximation, the addition of OH radicals to
unsaturated carbon-carbon groups can be described by the simple
Arrhenius equation (equation 10) at temperatures £ 500 K
[Atkinson (1987a)]. The energy of activation for these systems
is on the order of -1 kcal/mol [Atkinson (1986, 1987)].
Atkinson developed S/R relationships at 298 K which are based
on the number of unconjugated unsaturated carbon-carbon groups
or on the number of nonaromatic conjugated unsaturated carbon-
carbon groups in a molecule and on the degree, identity, and
configuration of substitution around these groups [Atkinson
(1986, 1987, 1987b, 1988, 1988a)]. For example, cis-2,5-
hexadiene, with molecular structure
CH2=CH-CH2 /CH3
">=C (84)
H H
contains a cis-dialkyl substituted alkene and a monosubstituted
alkene. To a good approximation, Atkinson indicated that the
overall rate constant for OH addition to these two isolated
double bond groups is the sum of the rate constants for cis-2-
butene and propene.
For dialkenes with conjugated carbon-carbon double bond
groups, there is a strong interaction between the two double
bonds (i.e., resonance). Therefore, for conjugated dialkenes,
Atkinson considered the entire conjugated system
I i
>C=C-C=C< (85)
-59-
-------
as a single unit. For example, 3-methylene-l, 6-octadiene, with
molecular structure
CH2 CH3
U '
CH2=CH-C-CH2CH2CH=C-CH3 (86)
CH2
II
contains the conjugated diene system CH2=CH-C- and an isolated
double bond group R1CH=CR2R3 (where R^ is an alkyl group) .
Thus, to a good approximation, the overall rate of OH radical
addition to the carbon-carbon double bonds is the sum of the
rate constants for 2-methylbutadiene and trimethylethene.
Alkynes and 1,2-dialkenes are treated as separate carbon-
carbon unsaturated bond groups.
For the total rate of hydroxyl radicals with alkenes,
dienes, alkynes, etc., k0jj , from equation 20, is given by the
equations
kOH = k(l) + k(3) (87)
kOH = Ml) + *add,nar (88)
where: k(l) represents the rate constant for the H-atom
abstraction from C-H groups (equation 12); k(3) is given by the
equation
M3) = kadd,nar (89)
and kadd nar represents the rate constant for OH radical
addition to nonaromatic unsaturated carbon-carbon groups
(equation 14) . It should be noted that H-atom abstraction f rc^i
-60-
-------
the unsaturated groups =CH2/ =CH-, etc. is essentially zero up
to 500 K {i.e., k(l, UNS CH) = 0, Table 1} [Atkinson (1986,
1987) ].
Atkinson (1986, 1987, 1987b, 1988a), based on a detailed
study of the kinetic data for OH radical reaction with
compounds containing nonaromatic unsaturated carbon-carbon
groups at 298 K, formulated S/R methods for estimating ka(jd nar
according to the relationship
kadd,nar = E kadd,nar + E kadd,nar + E kadd,nar (90)
where: the first term represents the contribution from OH
radical addition to isolated olefinic systems and is described
by the subscript add,nar and the superscript is on the rate
constant k; the second term represents the contribution from OH
radical addition to nonaromatic conjugated olefinic groups and
is described by the subscript add,nar and the superscript co on
the rate constant k; and the last term represents the
contribution from other unsaturated carbon-carbon groups such
as -CaC- and >C=C=C< and is described by the subscript add,nar
and the superscript ou on the rate constant k.
The first term in equation 90, for isolated carbon-carbon
double bond groups, can be represented by the equation
E "idd.nar = E *? OD
i Q
where: kg represents the group rate constants at 298 K for OH
-61-
-------
radical addition to isolated >C=C< groups and the numerical
values for the various types of unsaturated carbon-carbon
groups are listed in Table 9 (derived from the experimental kOH
data of specific alkenes as listed in the footnotes of this
table); the terms C(X) and C(Y) represent the substituent
factors on the unsaturated groups for the substituents X and Y
and the numerical values for these factors are listed in Table
10 (derived from the experimental KQH data of specific alkenes
as listed in the footnotes of this table) .
In a similar manner, the second term in equation 90, which
represents OH radical addition to nonaromatic conjugated
carbon-carbon double bond groups, is given by the equation
02)
where: kg° represents the group rate constants at 298 K for OH
radical addition to nonaromatic conjugated carbon-carbon double
bond groups such as -CH=CH-CH=CH- . The numerical values of kQO
for these groups are listed in Table 11 (derived from the
experimental kOH data of specific conjugated dienes at 298 K as
indicated in the footnotes of this table) ; and the substituent
factors C(.X) and C(Y) , for substituents X and Y, are listed in
Table 10. Conjugated aryl-alkene systems are treated by
-62-
-------
Table 9. Group Rate Constants kg3 in Equation 91 for Hydroxyl
Radical Addition to Isolated Olefinic Groups at 298 K
1012kjs
Structure3 (cm3 molecule~1s~1)
CH2=CH-R 26.3b
C 51.4C
se.i
,. _e
trans 63.7«
-CH-C'* 86.9f
5X5
a R in these structures represent alkyl groups
b Derived from the experimental data of propene with k0H ~ 26.3
x 10~12cm3 molecule"^"1 at 298 K [Atkinson (1986)].
c Derived from the experimental data of 2-methylpropene with
kOH = 51.4 x 10~12cm3 molecule~1s~1 at 298 K [Atkinson
(1986)].
d Derived from the experimental data of cis-2-butene with
kOH = 56.1 x 10~12cm3 molecule"1s~1 at 298 K [Atkinson
(1986)].
e Derived from the experimental data of trans-2-butene with
kOH = 63.7 x 10~12cm3 molecule~1s"1 at 298 K [Atkinson
(1986)].
f Derived from the experimental data of 2-methyl-2-butene with
kOH = 86.9 x 10~12cm3 molecule~1s"1 at 298 K [Atkinson
(1986)].
9 Derived from the experimental data of 2,3-Dimethyl-2-butene
with kOH = 110 x 10"12cm3 molecule"^"1 at 298 K [Atkinson
(1986)].
-63-
-------
Table 10. Substituent Factors C(X) in Equations 91, 92, and 93
for Substituent X on Nonaromatic Unsaturated Carbon-
Carbon Groups at 298 K
Substituent
Group
-Ra
-F
-Cl
-Br
-CH2C1
-CN
-CH(O)
-C(0)CH3
-OCH3
=0 (0)
a R is alkyl group. If R is a phenyl
is also equal to 1.00 [see Table 23,
Factors cm
1.00
0.4b
0.20b
0.26b
0.76°
0.15d
0.26e
0.91f
1.39
1.0n
group, then C(C6H5-)
C. ALKENYLBENZENES] .
b Derived from the best available k0n data for CH2*=CHF,
CH2=CHC1, CH2=CHBr, CH2=CF2 , CHC1=CC12, CC12=CC12, and
CFC1=CF2 [Atkinson (1986, 1987)].
c Derived from fitting the best available experimental kOH data
and calculated rate constants for cis- and trans- 1,3-
dichloro-1-propene and 2-chloromethyl-3-chloro-l-propene
[Atkinson (1986, 1987)].
Derived from the best available k0H data of CH3CsN [Atkinson
(1986)].
e Derived from the best available k0jj data for CH2=CHCHO,
CH3CH=CHCHO, and CH2=C(CH3)CHO [Atkinson (1986)].
f Derived from the best available kpH data for CH2=CHC(0)CH3
and cis- and trans-3-hexene-2.5-dione [Atkinson (1986)].
9 Derived from the best available kOH data for CH2=CHCOCH3
[Atkinson (1986)].
n Derived from the best available kOH data for a series of
ketenes [Atkinson (1987)].
-64-
-------
Table 11. Group Rate Constants kg° in Equation 92 for
Hydroxyl Radical Addition to Conjugated Nonaromatic
Functional Groups at 298 K
Set
No.
No. of
Alfcyl
Groups
(R)
Structure3
10
12
(cm3molecule~1 s-
CH2=CH-CH=CH-R
CH2=CH-C=CH2
1051
II
CH2=CH-C=CHR
CH2=C-CH=CHR
R-CH=CH-CH=CH-R
135°
III
CH2=C-p=CHR
R R
R-CH=CH-C=CHR
180C
IV
R-CH=p-9=CHR
R R
230d
-65-
-------
Table 11. Continued
a R is an alkyl Group.
b Derived from the average value of kOH for cis-1,3-pentadiene,
2-methyl-1,3-butadiene and t£ans-l,3-hexadiene [Atkinson
(1986)].
c Derived from the average value of kOH for cis-, trans-2f4-
hexadiene, 2-methy1-1,3-pentadiene, 4-methyl-l,3-pentadiene,
2,3-dimethyl-1,3-butadiene, 1,3-cyclohexadiene and 1,3-
cycloheptadiene [Atkinson (1986)].
d Derived by multiplying the rate constant for the two
substituent structures by a factor of 1.3 and (1.3)(1.3)
(i.e., Ill = (1.3)(135) - 176 = 180; IV - (1.3)(1.3)(135) =
176 - 180) [Atkinson (1986)].
-66-
-------
considering OH radical addition to the >C=C< and aryl groups
separately. See Section III. 0.2. a. and Table 23, C. ALKENYL-
BENZENES .
Finally, the third term in equation 90, for other
nonaromatic unsaturated carbon-carbon groups, is given by the
equation
(93)
where: k°,u represents the group rate constants at 298 K for OH
radical addition to nonaromatic unsaturated groups such as
-esc-, >c=C=C< , etc. and the numerical values for various
types of these groups are listed in Table 12 (derived from the
experimental kOH data of specific 1,2-dienes and alkynes at
298 K as indicated in the footnotes of this table) ; and the
substituent factors C(X) and C(Y), for the substituents X and
Y, are listed in Table 10.
III.B.2. Estimation of kOH for Several Classes of Chemicals at
298 K and a Comparison of These Results with the
Experimental Data
III.B.2. a. Unsubstituted Alkenes
Table 13 lists the pertinent kOH data at 298 K for the
unsubs.tituted alkenes as obtained from the literature. This
table is in exactly the same format as Table 3. A. and the data
in each column is the same as that described in the first
paragraph of Section III. A. 2. a. i.
-67-
-------
Table 12. Group Rate Constants k2u in Equation 93 for
Hydroxyl Radical Addition to Alkynes and Allenes
at 298 K
10-12kou
*J ^, 1 «, 1
Structure3 (cm3molecule s )
CH2=C=CHR 31b
H-CSC-R 6.4d
R-CsC-R 29e
a R in these molecular structures represent alkyl groups.
b Derived from the average value of the kOH data of 1,2-
butadiene and 1,2-pentadiene [Atkinson (1986)].
c Derived from the experimental kOH data of 3-methyl-l,2-
butadiene [Atkinson (1986)].
d Revised from Atkinson (1986) using the kOH data of Atkinson
and Aschmann (1984) for propyne and 1-butyne [Atkinson
(1987)].
e Derived from the kOH data of Hatakeyama et al. (1986) for 2-
butyne [Atkinson (1987)].
-68-
-------
Table 13. Comparison of Experimental and Estimated Values of
kgu for Unsubstituted Alkenes and the Percent Error
[Underlined Values of kOH Were Used by Atkinson (1986)
to Derive the Group Rate Constants for Alkenes]
Chemical Class/Chemical
A. ACYCLIC ALKENES
Propene
cis-2-Butene
trans- 2 -Butene
2 -Methy Ipropene
2-Methyl-2-butene
2 , 3-Dimethyl-2-butene
1 -Butene
1-Pentene
cis-2-Pentene
trans-2 -Pentene
2-Methyl-l-butene
3 -Methy 1-1-butene
1-Hexene
2 -Methy 1- l-p«ntene
2-Methyl-2-pentene
trans-4-Methyl-2-pentene
3 , 3-Dimethyl-l-butene
1012 )COH (cm3molecule"1s~1)
Experimental
(a)
26.3
56.1
63.7
51.4
86.9
110.
31.4
31.4
65.1
67
31.8
37
62.6
88.8
60.8
28.4
(b)
26.3*
56.4*
64.0*
51.4*
86.9*
110*
31.4*
31.4*
65. 7C
66. 9d
60.6°
31.8*
35. 2e
62. 6f
89. lf
60. 5f
28.59
Estimated
26.4
56.4
64.0
51.7
87.3
111
27.3
28.6
57.3
64.9
52.6
28.5
30.0
53.9
88.2
66.0
26.9
Percent
Error0
0
0
0
+1
0
+1
-13
-9
-13
-3
-13
-10
-15
-14
-1
+9
-6
-69-
-------
Table 13. Continued
Chemical Class/Chemical
1-Heptene
2 , 3-Dimethyl-2-pentene
trans-4 , 4-Dimethyl-2-pentene
1 , 4-Pentadiene
trans-1 , 4-Hexadiene
1,5-Hexadiene
2-Methyl-l , 4-pentadiene
2-Methyl-l , 5-hexadiene
2 , 5-Dimethyl-l , 5-hexadiene
B. CYCLIC ALKENES
Cyclopentene
Cyclohexene
1 , 4-Cyclohexadiene
Cycloheptene
1-Methyl-cyclohexene
Bicyclo [2.2.1] -2-heptene
Bicyclo [ 2 . 2 . 1 ] -2 , 5-heptadiene
Bicyclo [2.2.2] -2-octene
ot-Pinene
0-Pinene
1012 KOH (cm3molecule~1s"1)
Experimental
(a)
40
108
54.8
53.3
91.0
62.0
79
96
120
67
67.4
99
74.1
95
49.1
120
40.6
53.2
(b)
38. 3h
103f
54. 5f
53.3d
90. 6d
62. Od
78. 8d
96. ld
120d
65. 51
67.7*
99. 5J
74. 4k
94. 41
49. 3k
120k
40. 8k
53.7*
78.9*
Estimated
31.4
111
64.4
53.4
91.0
54.8
78.7
80.0
105
58.9
61.1
114
62.5
92.0
62.7
116
67.8
96.9
54.2
Percent
Error0
-18
+8
+18
0
0
-12
0
-17
-13
I
-10
-10
+ 15
-16
-3
*27
-3
.66
»30
- J 1
-70-
-------
Table 13. Continued
Chemical Class/ Chemical
<|-Limonene
A3-Carene
•y-Terpinene
1012 KQH (cm3molecule~1s~1)
Experimental
(a)
169
87.0
176
(b)
160m
87. 8n
177n
Estimated
145
87.5
178
Percent
Error0
-9
0
+1
a
b
c
e
f
1
m
n
o
Experimental data from Atkinson (1986).
Experimental data from Atkinson (1989).
Average value of the experimental data of Ohta (1984) and Wu et al.
(1976).
Experimental data from Ohta (1983).
Average value from the experimental data of Wu et al. (1976) and
Atkinson and Aschmann (1984).
Experimental data from Ohta (1984).
Experimental data from Wu et al. (1976).
Average value from the experimental data of Darnall et al. (1976) and
Atkinson and Aschmann (1984).
Average value from the experimental data of Atkinson, Aschmann, Carter
(1983) and the relative rate data with cyclohexene of Rogers (1989).
Average value from the experimental data of Atkinson, Aschmann, Carter
(1983) and Ohta (1983).
Experimental data from Atkinson, Aschmann, Carter (1983).
Experimental data from Darnall et al. (1976).
Average valu* from the experimental data of Winer et al. (1976) and
Atkinson, Aschmann, Pitts (1986).
Experimental: data from Atkinson, Aschmann, Pitts (1986).
Based on th» experimental data given in the third column,
Experimental/(b).
Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-71-
-------
The underlined values of kOH in the second column,
representing the first 6 alkenes above the dashed line, were
used by Atkinson (1986, 1987) to derive the group rate
constants for these compounds (Table 9). The substituent
factors C(R) for alkyl and phenyl groups were set equal to 1.00
(Table 10).
The experimental values of kOn at 298 K are listed in
Table 13 for 39 unsubstituted alkenes (26 acyclic and 13
cyclic) as obtained from Atkinson (1986). Using equation 91,
the appropriate group rate constants k£s from Table 9 and
the substituent factors C(R) = 1.00, Table 10, ki|^ nar was
calculated for each alkene. This result is substituted in
equation 90 to obtain *add,nar' Ifc should be noted that for
these alkenes, k^dd nar and kadd nar are zer°* Tne H-atom
abstraction rate constants for C-H groups in each
alkene,[k(l)], were estimated by the methods described in
Section III.A. The total rate constant kOH for each alkene is
then the sum of k(l) and kad(j nar, equation 88. These results
are listed in Table 13 along with the percent error. For the
34 acyclic and cyclic alkenes listed below the dashed line, the
average percent error ranged from +16 to -11; and these results
therefore,, are excellent, confirming the S/R relationships of
Atkinson. For all 39 alkenes, the percent error was +13 to -11
which is excellent.
-72-
-------
III.B.2.b. Substituted Alkenes
The experimental values of kOH at 298 K for 24 substituted
acyclic alkenes are listed in Table 14 as obtained from the
literature.
This group of 24 compounds can be divided into the
following categories: 12 halogenated alkenes; 10 carbonyl
substituted alkenes; aeryIonitrile; and methyl vinyl ether.
Using equation 91 and the appropriate group rate constants and
substituent factors from Tables 9 and 10, respectively,
*add nar was estimated for each substituted alkene.
Substituting equation 91 in 90 yields kadd nar* Again, it
CO
should be noted that for these substituted alkenes, kadd nar
and kad
-------
Table 14. Comparison of Experimental and Estimated Values of kOH
for Substituted Alkenes at 298 K and the Percent Error
[Underlined Values of kOH Were Used by Atkinson (1986,
1987) to Derive the Substituent Factors for these
Chemicals]
Chemical Class/ Chemical
A. HALOALKENES
Vinyl fluoride
Vinyl chloride
Vinyl bromide
1, 1-Dif luoroethene
Trichloroethene
Tetrachloroethene
cis-1 , 3-Dichloro-l-propene
trans-1 . 3-Dichloro-l-propene
3 -Chloro-l-propene
2- (Chloromethyl) -3-chloro-l-
propene
cis-1 , 2-Dichloroethene
trans-1 , 2-Dichloroethene
B. a,/3-UNSATURATED CARBONYLS
Acrolein (2-Propenal)
trans-Crotonaldehyde ftrans-
2-ButenalX
Methacrolein (2-Methyl-2-
propenal)
Methyl vinyl ketone
Ketene
1012 JCQH (cm3molecule~1s~1)
Experimental
(a)
5.56
6.60
6.81
8.10
2.36
0.167
8.45
14.4
11
33,5
2.38
1.80
19.6
M
30.7
18.5
(b)
5.56°
6.60°
6.81C
-d-
2.36*
0.167*
8.41e
14. 3e
17*
33. 5e
2.38e
1.80e
19.9*
36*
33.5*
18.8*
17.3f'
-------
Table 14. Continued
Chemical Class /Chemical
Methyl ketene
Ethyl ketene
Dimethyl ketene
c isT- 3 -Hexene- 2 , 5-dione
trans-3-Hexene-2 , 5-dione
C. NITRILO ALKENES
Aery Ion itrile (Cyanoethene)
D. ALKOXY ALKENES
Methyl vinyl ether
1012 kOH (cm3molecule~1s""1)
Experimental
(a)
63
53
-1
33t5
(b)
70f 'n
118*'9
107f<9
63. 11
53. 11
4.13
33.5°
Estimated
87.0
87.9
110
46.7
53.0
3.95
35.1
Percent
Errork
+24
-26
+3
-26
0
-4
+5
c
d
e
Experimental data from Atkinson (1986) .
Experimental data from Atkinson (1989).
Experimental data from Perry, Atkinson, Pitts (1977a) .
Experimental data is probably not reliable [Atkinson (1989)].
Experimental data from Tuazon et al. (1988). This data is preferred
since the experiments avoided or have taken into account the side
reactions of the Cl atom with the reference compounds [Atkinson
(1989)].
Used by Atkinson (1987) to derive the substituent constant C(=O),
Table 2.
Experimental data from Hatakeyama et al. (1985) .
Average value from the data of Hatakeyama et al. (1985).
Experimental data from Tuazon et al. (1985).
Average value from the experimental data of Harris et al. (1981) and
Zetsch (1983) as reported in Atkinson (1989).
Based on the experimental data given in the third column,
Experimental/ (b) .
Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-75-
-------
2,5-dione were not used to derive the substituent factors.
The average percent error for these 4 compounds ranged from +21
to -16 which ranged from very good to excellent. More
experimental kOH data are needed for a number of additional
compounds to confirm the S/R relationships of Atkinson.
Excluding the chemicals 1,1-dichloroethene and ketene from this
group of substituted alkenes, the average percent error for the
remaining 22 chemicals ranged from +20 to -21, which ranges
from excellent to very good.
III.B.2.C. Conjugated Dialkenes
The experimental values of kOH at 298 K for 13 conjugated
acyclic and cyclic dialkenes are listed in Table 15 as obtained
from the literature. For 11 compounds (excluding the compounds
3-methylene-7-methyl-l,6-octadiene and 3,7-dimethyl-l,3,6-
octatriene), kOH was estimated as follows. Using equation 92
and the appropriate group rate constants k0,0 from Table 11 and
CO
C(R) =1.00 from Table 10, kad(j nar was estimated for each
conjugated diene. These results are substituted in equation 90
to obtain kaddfnar. For these compounds, fcj§dfnar and kadd,nar
are zero. The H-atom abstraction rate constants for the C-H
groups in each conjugated dialkene [k(l)] were obtained by the
methods described in Section III.A. The total rate constant
k0j] for each compound is then the sum of k(l) and kadd>nar,
equation 88.
The compounds 3-methylene-7-methyl-l,6-octadiene and 3,7-
dimethyl-l,3,6-octatriene contain one conjugated diene group
and one isolated alkene group. Hence, for these two compounds,
-76-
-------
Table 15. Comparison of Experimental and Estimated Values of
XQU for Conjugated Acyclic and Cyclic Dialkenes at
298 K and the Percent Error [Underlined Values of
kOH Were Used by Atkinson (1986) to Derive the
Substituent Factors for These Compounds]
Chemical Class/Chemical
A. ACYCLIC DIALKENES
cis-1 , 3-Pentadiene
2 -Methyl-1, 3 -butadiene
trans- 1. 3-Hexadiene
3-Methyl-l, 3-pentadiene
4 -Methyl-1, 3 -pentadiene
2 , 3-Dimethyl-l , 3-butadiene
2 , 5-Dimethyl-2 , 4-hexadiene
3-Methylene-7-methyl-l, 6-
octadiene
3 , 7-Dimethyl-l , 3 , 6-octatriene
B. CYCLIC DIALKENES
l , 3-Cyclohexadiene
1 , 3-Cycloheptadiene
a-Phellandrene
a-Terpinene
lO1^ XQJJ (cm^molecule~1s~1)
Experimental
(a)
101
101
ill
137
131
121
211
213
161
139
310
360
(b)
101c'e
101*
112°' e
136c'e
131c'e
122c'e
210c'e
215f
252*
164d
139e
313*
363f
Estimated
105
105
106
135
135
135
231
194
223
137
139
187
235
Percent
Error1?
+4
+4
-5
-1
+3
+ 11
+10
-10
-12
-16
0
-40
-35
-77-
-------
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989).
c Experimental data from Ohta (1983).
d Experimental data from Atkinson, Aschmann, Carter (1983).
6 Experimental data from Atkinson, Aschmann, Carter (1984a).
f Experimental data from Atkinson, Aschmann, Pitts (1986).
9 Based on the experimental data given in the third column,
Experimental/b).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-78-
-------
equations 92 and 91 were used to estimate k° and
nar
kadd,nar, respectively, as described above while k^d/nar is
zero. The sum of these results is fcadd,nar' equation 90. The
H-atom abstraction rate constants for the C-H groups [k(l) ]
were obtained by the methods described in Section III. A. The
total rate constant k0n is then equal to the sum of k(l)
and kadd,nar' equation 88.
All the estimated values for each compound are listed in
Table 15 along with the percent error. For the 5 compounds
below the dashed lines, the average percent error ranged from
-HO to -24 which ranged from superb to very good. The average
percent error for the 13 compounds ranged from +5 to -17, which
is superb to excellent. More experimental kgjj data are needed
for a number of conjugated dienes to confirm the S/R
relationships of Atkinson.
III.B.2.d. Alkynes and 1,2-Dialkenes (Allenes)
The experimental values of kOH at 298 K are listed in
Table 16 for five alkynes and three 1,2-dienes (allenes) as
obtained from Atkinson (1986). Using equation 93, the
appropriate group rate constants k°,u from Table 12, and the
substituent factors C(R) = 1.00 from Table 10, kadd nar was
calculated for each compound. For these two classes of
compounds, kadd,nar and kadd,nar are zero. These results are
then substituted in equation 90 to obtain kadd nar* Tne H-atom
abstraction rate constants for the C-H groups in each alkyne or
allene [k(l) ] were obtained by the methods described in Section
-79-
-------
Table 16. Comparison of Experimental and Estimated Values of kOH
for Alkynes and Allenes at 298 K and the Percent Error
[Underlined Values of kQH Were Used by Atkinson (1986,
1987) to Derive the Substituent Factors for these
Classes of Compounds]
Chemical Class/ Chemical
A. ALKYNES
Propyne
l-Butyne
2-Butyne
1-Pentyne
1-Hexyne
B. 1,2-DIENES (ALLENES)
1 , 2 -Butadiene
1,2-Pentadiene
3-Methyl-l, 2-butadiene
1012 k0H (cm3molecule"1s"1)
Experimental
(a)
1^1
8.0
27.4°
26.0
35.6
57.1,
(b)
5.9*
8.0*
27.4*
11. 2d
12. 6d
26. le
35. 5e
56. 9e
Estimated
6.54 .
7.42
29.3
8.75
10.1
31.1
32.0
57.3
Percent
Errorf
+11
-7
+7
-22
-20
j
\
+19
-10
+1
a Experimental data from Atkinson (1986).
b Experimental data from Atkinson (1989).
c Experimental data used by Atkinson (1987) to derive the substituent
factors for the alkynes.
d Experimental data from Boodaghians et al. (1987).
e Experimental data from Ohta (1983).
f Based on the experimental data given in the third column,
Experimental/(b).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-80-
-------
III.A. The total rate constant kOH for each compound is then the
sum of k(l) *n
-------
Table 17. Summary of the Average Percent Error in kOH for the
Reaction of Hydroxyl Radicals with a Number of
Olefins, Conjugated Diolefins, Allenes, and Alkynes
and for All Chemicals in These Classes
Chemical Class
Unsubstituted Alkenes and
Conjugated Dienes
Substituted Alkenes and
Nonconjugated Dienes
Conjugated Dialkenes
Alkynes
1,2-Dienes (Allenes)
All compounds not used to
derive the substituent
constants and group rate
constants
All Compounds
Number of
Chemicals
39
22a
13
5
3
45
82
Average Percent
Error
From
+13
+20
+5
+9
+10
+16
+13
To
-11
-21
-17
-16
-10
-14
-15
a A total of 22 compounds were used in the estimation of kOH.
However, 1,1-difluoroethene did not have reliable kOH data
and was not used in the analysis of the percent error. The
compound ketene had a percent error greater than 100 (i.e.,
the percent error was +200) and was not used in the analysis
of the average percent error.
-82-
-------
compounds were used. To corroborate the S/R relationships for
these two classes of chemicals, more experimental kOH data are
needed for additional compounds.
III.C. Reaction of Hydroxyl Radicals with Organic Chemicals
containing Sulfur, Nitrogen, and Phosphorus Functional
Groups and the Estimation of kOH
III.C.I. Reaction of Hydroxyl Radicals with Thiols, Sulfides,
and Disulfides
III.C.I.a. Formulation of the Structure/Reactivity
Relationships
Atkinson (1987) made a detailed study of the kinetic data
for the reaction of hydroxyl radicals with thiols, sulfides, and
disulfides. In air at a total pressure of approximately 1
atmosphere, and thus in the presence of oxygen, the total rate
of reaction, kOjj, is a function of H-atom abstraction by OH
radicals from the alkyl groups Ri in Ri-SH, Ri-S-Ri, and
Ri~S-S-Ri and by the interaction of OH radicals with the sulfur
functional groups to form the adduct [>S---tOH]. The adduct
reacts rapidly with oxygen in a series of complex reactions to
form the products. Therefore, the reaction of hydroxyl radicals
with thiols (Ri-SH), sulfides (Ri-S-Ri), and disulfides
can be described by the following reactions
OH
•
•
•
+ -OH » Ri-SH » Products (94)
-83-
-------
+ -OH
OH
Ri~s~Ri
•* Products
(95)
+ -OH
OH
/:
Ri-5-S-Ri
•* Products
(96)
and by the reactions 24a, b, c for H-atom abstraction by. OH
radicals from alkyl groups R^. In the absence of oxygen, for the
sulfides, Atkinson (1987) indicated that OH radicals only reacted
via H-atom abstraction from the alXyl groups Rj^.
Based on a critical analysis of the kinetic data for OH
radical reaction with thiols, sulfides, and disulfides in air at
a total pressure of approximately 1 atmosphere (and therefore in
the presence of oxygen), Atkinson indicated that the group rate
constants for these three classes of compounds were
k(^SH) = 31 x 10~12 cm3 molecule'^-s"1
k(-S-) = 2.0 x 1CT12 cm3molecule~1s"1
k(-S-S-) = 200 x 10~12 cm3molecule~1s"1
(97)
(98)
(99)
and the substituent factors were
F(-SH) = F(-S-) = F(-S-S-) = 9.0
(100)
-84-
-------
These results are summarized in Tables 1 and 2, respectively, for
the group rate constants and the substituent factors for these
sulfur functional groups.
Using equation 20, the overall rate of OH radical reaction
with thiols, sulfides, and disulfides in air at a total pressure
of approximately 1 atmosphere, and thus in the presence of
oxygen, is given by the relationship
COH
k(4) . (101)
where: k(l) is the contribution to kOH from H-atom abstraction
from an alkyl group R^ (equation 12): and k(4) represents the
contribution to k0n from the interaction of OH radicals with the
sulfur functional groups (equation 15) , which is the group rate
constant for these sulfur compounds.
For sulfides, in the absence of oxygen, k(4) = 0 so that
equation 101 becomes
kOH = k(l) (102)
and only H-atom abstraction from the alkyl groups in R^ is
observed. The group rate constant k(-S-) = 0, in the absence of
oxygen, is listed in Table 1.
Ill.C.l.b. Estimation of kOH at 298 K and a Comparison of
These Results with the Experimental Data
The experimental values of kOH at 298 K in air at a pressure
of approximately 1 atmosphere (and therefore in the presence of
oxygen) are listed in Table 18 for nine thiols and
-85-
-------
Table 18. Comparison of Experimental and Estimated Values of
kOH for Alkyl Thiols, Sulfides, and Disulfides at
298 K and the Percent Error [Underlined Values of
kop Were Used by Atkinson (1987) to Derive the
Substituent Factors for These Classes of Compounds]
Chemical Class/Chemical
A. THIOLS
Methanethiol
Ethanethiol
l-Propanethiol
2 -Propanethiol
1-Butanethiol
2-Methyl-l-propanethiol
2-Butanethiol
2-Methyl-2-propanethiol
2 -Methy 1-1-butanethiol
B.I. ACYCLIC SULFIDES0
Dimethyl sulfide
Methyl ethyl sulfide
Diethyl sulfide
Di-n-Propyl Sulfide
1012 koH |
Exoerii
(a)
33.1
46.5
45.9
42.4
43.8
41.8
39.8
35.1
51n
4.28
JLJi
15.5
[cm3molec
lent a 1
(b)
32.9*
46.8*
48.3*
42.0*
51*
45*
40*
33.1*
54.3d
4.56*
8.50e
15*
20. Of
:ule~1s~1)
Estimated
32.3
38.7
42.0
47.8
43.4
43.5
53.7
31.6
44.9
2.59
9.02
15.5
22.0
Percent
Error^
-2
-17
-13
+14
-15
-3
+34 '
-5
-17
-43
+6
+3
+ 10
-86-
-------
Table 18. Continued
Chemical Class/Chemical
B.2. CYCLIC SULFIDES0
Tetrahydrothiophene
C. DISULFIDES
Dimethyl disulfide
1012 kOH (cm3molecule"1s"1)
Exoerimental
(a)
19.1
205
(b)
19.7*
211*
Estimated
17.8
203
Percent
Error9
-10
-4
a Data were obtained from Table VII of the paper by Atkinson
(1987) . It should be noted that the second column of Table VII
represents the estimated value of kOH while the third column
represents the experimental value.
b Experimental data from Atkinson (1989) .
c For these compounds,
was measured in tne absence of oxygen.
d Experimental data from Barnes et al. (1986).
e Experimental data from Hynes et al. (1986) .
f Experimental data from Barnes et al. (1986). The experimental data
of Nielsen et al. (1987) appear to be erroneous [Atkinson (1989)].
9 Based on the experimental data given in the third column,
Experimental/ (b) .
n In Table VIII of the paper by Atkinson (1987), the molecular structure
of the compound corresponding to this value of kOH was
CH3CH(CH3)CH2CH2SH (3-methyl-l-butanethiol) as obtained from Barnes et
al. (1986). However, from the paper by Barnes et al. (1986), the
compound was 2-methyl-l-butanethiol. This has been corrected in the
book by Atkinson (1989).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty for the recommendation.
-87-
-------
one disulfide as obtained from the literature.4 For the five
sulfides, the experimental values of kOH, measured in the
absence of oxygen, were obtained from the literature.4
For the estimation of kOH for the five sulfides, in the
absence of oxygen, equation 102 is applicable. Thus, only
H-atom abstraction from the alkyl groups R^ is needed. Using
equation 28 for H-atom abstraction and the appropriate group
rate constants and substituent factors from Tables 1 and 2,
respectively, kOH was estimated for the four acyclic sulfides
and these results are listed in Table 18. For tetrahydrothio-
phene, which is a cyclic sulfide, equation 43 is valid; and
using the appropriate group rate constants and substituent
factors, kOH was estimated in the standard manner for this
cyclic compound. This result is listed in Table 18. In
addition, the percent error in kOH for each sulfide is also
listed in this table. The average percent error for the five
sulfides ranged from +6 to -27 so that these results ranged
from superb to very good. Only the rate constants kOH for di~
n-propyl sulfide and tetrahydrothiophene were not used to
derive the substituent factors for the sulfides. The percent
errors for these two compounds were +10 and -10, respectively,
tentatively confirming the S/R relationships. However, more
experimental k^jj data is needed for additional alkyl sulfides
(both cyclic and acyclic) to confirm these S/R relationships.
4 Data were obtained from Table VII of the paper by Atkinson
(1987). It should be noted that the second column in Table vn
represents the estimated value of k0jj while the third column
represents the experimental value of kOH.
-88-
-------
For the estimation of kOH in the presence of oxygen for
the nine thiols, equation 101 is applicable. Using the
appropriate group rate constants and substituent factors for
the alkyl groups from Tables 1 and 2, respectively, k(l) was
estimated for each chemical using equation 28. The group rate
constant for the thiols [k(-SH)] was obtained from Table 1.
The sum of k(l) and k(4) is equal to kOH and these results are
listed in Table 18 along with the corresponding percent error.
The average percent error for these 9 thiols ranged from +24 to
-10 so that these results ranged from very good to superb. All
nine compounds were used to derive the group rate constants and
substituent factors for the thiols. Hence, more experimental
kOH data is needed for additional alkyl thiols to confirm these
S/R relationships.
In a similar manner as described above, k0H was estimated
for one disulfide along with the percent error. These results
are listed in Table 18. The percent error for dimethyl
disulfide is -4, which is superb; however, more experimental
k-., data are needed for additional alkyl disulfides to confirm
un
the S/R relationships of Atkinson for this class of compounds.
III.C.2. Reaction of Hydroxyl Radicals with Aliphatic Amines,
Hydrazines, N-Nitrosamines, N-Hydroxylamines, and
N-Nitramines
III.C.2.a. Formulation of the Structure/Reactivity
Relationships
Atkinson (1987) indicated that in air at a total pressure
of approximately one atmosphere, OH radicals can react with
aliphatic amines via H-atom abstraction from the alkyl group
-89-
-------
and by OH radical interaction with the nitrogen atom in an
analogous manner to those described for the thiols, sulfides,
and disulfides. Therefore, OH radicals can interact with the
nitrogen in the amines to form the adduct
H
Ri— N •••• OH (103)
H
which then decomposes rapidly in the presence of oxygen to form
the products. Thus, the reaction of OH radicals with primary
aliphatic amines can be described by the reaction
Ri-NH2 + 'OH
H
°2
N •••-OH
H
•* Products (104)
while H-atom abstraction from the alkyl group R^ is given by
reactions 24a,b,c. Similar reactions can be written for
secondary amines (R^)2NH and tertiary amines (R^)3N.
From equation 20, OH radical reaction with amines can be
described by the relationship
+ k(5) (105)
where k(l) represents the contribution to kOH from H-atom
abstraction from the alkyl group R^ while k(5) represents the
contribution to JCQH from OH radical interaction with the
nitrogen atom in the amine group.
-90-
-------
Based on a critical analysis of the kOH data for the
amines including diethyl-N-hydroxylamine, Atkinson (1987) found
that for this class of chemicals the group rate constants were
k(-NH2) = 20 x 10~12 cm3molecule"1s"1 (106)
k(>NH) = k(>N-) = 60 x 10~12 cm3molecule""1s"1 (107)
and the substituent factors were
F(-NH2) = F(>NH) = F(>N-) = 10 (108)
These results are summarized in Tables 1 and 2.
For hydrazine (H2N-NH2) and alkyl substituted hydrazines
(Ri~NH-NH2, RiNH-NHRi, etc.)/ the reaction pathways for the
.reaction of OH radicals are similar to those described above
for the amines. Thus, OH radicals can react with the nitrogen
functional groups similar to reaction 104 and can abstract a
hydrogen atom from the alkyl group R^ similar to those
described in reactions 24a,b,c. For hydrazine, Atkinson (1987)
assumed that the neighboring -NH2 group had essentially no
effect on the OH radical interaction group rate constant so
that
koH = 2k(-NH2) (109)
and the substituent factor F(X) for -NH2 bonded to another -NH2
group was equal to 1.0. From the very limited k-.. data from
vJn
the alkyl substituted hydrazines, Atkinson found that the group
rate constants and substituent factors listed in 106, 107, and
108 were applicable.
-91-
-------
In exactly the same manner as described above, and on the
very limited kinetic data for N-nitrosamines and N-nitroamines,
Atkinson (1987) indicated that the group rate constants for
these compounds were
k(>NNO) = k(>NN02) = 0 (110)
and the substituent factors F(X) were
F(>NNO) = F(>NN02) . (Ill)
Although Atkinson (1987) did not explicitly define group
rate constants and substituent factors for the N-substituted
hydroxy lamines , from the experimental k0n data in Table 19B,
k(>NOH) = 0 (Ilia)
F(-NHOH) = F(>NOH) » 0
The group rate constants from equations 110 and Ilia are listed
in Table 1 while the substituent factors from equations 111 and
lllb are listed in Table 2.
III.C.2.b. Estimation of kpH at 298 K and the Comparison of
these Results with Experimental Data
The experimental values of kOH for six amines, one each
for N-hydroxylamine, N-nitrosamine, N-nitramine, and for two
hydrazines at 298 K and in air at a total pressure of
approximately 1 atmosphere are listed in Table 19 as obtained
from the literature. Using equations 28 and 105 and the
appropriate group rate constants and substituent factors for
these compounds from Tables 1 and 2, kOH was estimated for the
-92-
-------
Table 19. Comparison of Experimental and Estimated Values of
kgH at 298 K for Alkyl Amines, Hydrazines, and
N-substituted Amines and the Percent Error [Underlined
Values of kOH Were Used by Atkinson (1987) to Derive the
Group Rate Constants and Substituent Constants for
These Compounds]
Chemical Class/Chemical
A. AMINES
Methylamine
Ethylamine
Dimethylamine
Trimethylamine
D imethy Ihydr oxy ethy 1 amine
2-Methyl-2-amino-l-propanol
B. N-HYDROXYLAMINES
Diethyl-N-hydroxylamine
C. N-NITROSAMINES
Dimethyl-N-nitrosamine
D. N-NITRAMINES
D imethy 1-N-nitr amine
E. HYDRAZINES
Hydrazine
Me thy Ihydr a z ine
1012 kOn (cm3molecule~1s~1)
Experimental
(a)
22.0
27.7
65.4
60.9
80
28
101
2.53
3.84
61
65
(b)
22.0°
27. 7d
65. 4d
60. 9d
90e
28f
1019
2.53h
3.84h
611
651
Estimated
21.4
28.6
62.9
64.3
77.4
24.1
77.2
2.88
2.88
40.0
81.4
Percent
ErrorJ
-3
+ 3
-4
+6
-14
-14
-24
+ 14
-25
-34
*25
-93-
-------
Table 19. Continued
a Experimental data from Table VII of the paper by Atkinson (1987).
It should be noted that the second column in Table VII represents
the estimated value of kOH while the third column represents the
experimental value.
b Experimental data from Atkinson (1989) and the literature.
c Experimental data from Atkinson, Perry, Pitts (1977).
d Experimental data from Atkinson, Perry, Pitts (1978).
e Original experimental data is from Anderson and Stephens (1988) which
represents the most reliable data [Atkinson (1989)].
f Experimental data from Harris and Pitts (1983).
9 Experimental data from Gorse et al. (1977).
11 Experimental data from Tuazon et al. (1984).
1 Experimental data from Harris et al. (1979) as reported by Atkinson
(1987).
J Based on the experimental data given in the third column
Experimental/(b).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty in the recommendation.
-94-
-------
amines in the standard manner. These results are summarized in
Table 19 along with the percent error. For the six amines, the
average percent error ranged from +5 to -9 indicating that the
S/R relationships of Atkinson for the aliphatic amines are
superb. However, considerably more experimental kOH data are
needed for additional alkyl amines to confirm the S/R
relationships of Atkinson.
The total rate constant k0n f°r diethyl-N-hydroxylamine,
dimethyl-N-nitrosamine, dimethyl-N-nitroamine, hydrazine, and
methyl hydrazine was estimated in the standard manner as
described above and these results are listed in Table 19 along
with the percent error. The percent errors for these compounds
ranged from excellent to very good. However, considerably more
experimental kOH data are needed for chemicals in these classes
of compounds to confirm the S/R relationships of Atkinson.
III.C.3. Reaction of Hydroxyl Radicals with Organophosphorus
Compounds
III.C.3.a. Formulation of the Structure/Reactivity
Relationships
Atkinson made a detailed study of the kinetic data for the
reaction of hydroxyl radicals with several classes of
organophosphorus compounds [Atkinson (1988); Atkinson et al.
(1987b, 1988a); Atkinson in Goodman et al. (1988, 1988a); and
in Tuazon et al. (1986)]. For compounds with molecular
structure
-95-
-------
(112)
where X is 0, or X = 0 and S, and R^ is an alkyl group,
hydroxyl radicals can react with them via two pathways. One
pathway involves the formation of a phosphorous complex with OH
radicals followed by rapid decomposition to products in the
presence of oxygen
(— P=X + -OH
•p=:x
r \
bH
Products (113)
The second pathway involves H-atom abstraction from the alkyl
groups (reactions 24a,b,c). Similar reaction pathways can be
written for dialkyl chlorophosphorothioates. In addition,
similar reaction pathways can be written for the classes of
compounds with molecular structure
X
II
P—XR2
NR3R4
(114)
where X = O, or X = O and S, P.1 and R2 are alkyl groups, and R3
and R4 are H and/or alkyl. Furthermore, OH radicals can react
with the functional group NR3R4 as described in Section
III.C.2.
-96-
-------
From equation 20, OH radical reaction with the phosphorus
compounds given by molecular structure 112 can be described by
the following relationship
kOH - k(l) + k(6) (115)
where k(l) represents the contribution to kOH from H-atora
abstraction from the alkyl groups and k(6) represents the
contribution to kOH from the OH radical interaction with the
phosphorus groups.
For the phosphorus compounds given by molecular structure
114, OH radical reaction can be described by the following
relationship
kOH = k(l) + k(5) + k(6) (lie)
where k(l) represents the contribution to k_« from H-atom
un
abstraction from the alkyl group R^, k(5) represents the
contribution to kOH from OH radical interaction with the
nitrogen group, while k(6) represents OH radical interaction
with the phosphorus group.
Atkinson [Atkinson (1988); Atkinson et al. (1988);
Atkinson in Goodman et al. (1988, 1988a) ; and Atkinson in
Tuazon et al. (1986)] analyzed the kinetic data for these
organophosphorus compounds in the standard manner and found
that the group rate constants were
k[P(0)] = 0 (117)
k[PCl in (CH30)2P(S)C1] = 0 (118)
-97-
-------
k[P(S)] = 55 x 10-12 cn^molecule-is-1 (119)
k(-S-) = 2.0 x 10~12 cm3molecule~1s~1 (120)
and the substituent factors were
F(-0-P<) = F(-S-P<) = 20 (121)
F(-S-) - 9.0 (122)
These data are listed in Tables 1 and 2. For those organophos-
phorus compounds containing nitrogen functional groups, the
group rate constants and substituent factors defined in
equations 106, 107, and 108 are applicable.
III.C.3.b. Estimation of kpH at 298 K and the Comparison of
These Results with Experimental Data
The experimental kOH data in the second column of Table 20
were taken from the literature as follows: the experimental KQ^
data for trimethyl phosphate was taken from Atkinson (1988) and
Atkinson in Tuazon et al. (1986); triethyl phosphate from
Atkinson et al. (1988) and from Atkinson (1988). The
experimental kOn data for the next four alkyl thiophosphates
were taken from Atkinson in Goodman et al. (1988) and Atkinson
(1988). Similarly, the experimental kOH data for one chloro-
phosphorothioate was obtained from Atkinson et al. (1988); and
the experimental kOH for the three alkyl phosphoroamidothioates
and the single alkyl phosphoroamidate were obtained from
Goodman et al. (1988a). The best available kOH data for these
compounds are listed in the third column, Experimental/(g), as
-98-
-------
Table 20. Comparison of Experimental and Estimated Values of
KQH at 298 K for Aliphatic Compounds Containing
Phosphorus Functional Groups and the Percent Error
Chemical Class/Chemical
A. ALKYL PHOSPHATES/
THIOPHOSPHATES
Trimethyl phosphate
(CH30)3P=0
Tri ethyl phosphate
(CH3CH20)3P=O
0,0,0-Tr imethyl
phosphorothioate
(CH30)3P=S
o,0, S-Tr imethyl
phosphorodithioate
(CH30)2P(S)SCH3
0,0, S-Tr imethyl
phosphorothioate
(CH30)2P(0)SCH3
0 , S , S-Tr imethyl
phosphor od ith ioat e
(CH3S)2P(0)OCH3
B. DIALKYL CHLORO-
PHOSPHOROTHIOATES
0,0-Dimethyl chloro-
phosphorothioate
(CH30)2P(S)C1
1012 k0n (cm3molecule"1s~1)
Experimental
7.4a
55. 3b
69.7°
56.0°
9.15°
9.45°
59. 6b
(g)
7.37
55.3
69.7
56.0
9.29
9.59
59.0
Estimated
8.64
52.2
63.6
65.6
10.6
12.6
60.8
Percent
Errorf
-1-17
-6
-9
+ 17
+ 14
+31
+3
-99-
-------
Table 20. Continued
Chemical Class/Chemical
C. ALKYL PHOSPHOROAMIDATES
AND ALKYL PHOSPHOROTHIO-
AMIDATES
0,O-Dimethyl
phosphoroamidothioate
(CH30)2P(S)NH2
0,0,N-Trimethyl
phosphoroamidothioate
(CH30)2P(S)NHCH3
0 , 0 , N , N-Tetramethy 1
phosphoroamidothioate
(CH30)2P(S)N(CH3)2
0 , O , N , N-Tetramethy 1
phosphoroamidate
(CH30)2P(0)N(CH3)2
1012 kOH (cm3molecule~1s~1)
Experiment a 1
244d
232d
46. 8d
31. 9d
(g)
244
233e
46.8
31.9
Estimated
80.8
122
124
68.6
Percent
Errorf
-67
-48
+160
+ 115
a Experimental data from Atkinson in Tuazon et al. (1986) and Atkinson
(1988) .
b Experimental data from Atkinson et al. (1988) and Atkinson (1988).
c Experimental data from Atkinson in Goodman et al. (1988) and Atkinson
(1988).
d Experimental data from Atkinson in Goodman et al. (1988a).
e Average value of kOH using the reference compounds propene and
2,3-dimethyl-2-butene from Goodman et al. (1988a).
f Based on the experimental kOH data given in the third column,
Experimental/(b).
9 Best available data from Atkinson (1989). It should be noted that
these data are not recommended by Atkinson (1989) since the
experimental data for each compound is only from one source.
-100-
-------
obtained from Atkinson (1989). It should be noted that these
data are not recommended by Atkinson (1989) since the
experimental data for each compound was obtained from a single
source.
Using equations 20, 28, 115, or 116 and the appropriate
group rate constants and substituent factors from Tables 1 and
2, kOH was estimated for six phosphates/thiophosphates, one
chlorophosphorothioate and four alkyl phosphoroamidates/
phosphorothioamidates. These values of kOH are listed in
Table 20 along with the percent error.
For the six phosphates and thiophosphates, the average
error ranged from +20 to -8 indicating that the S/R
relationships developed by Atkinson ranged from excellent to
superb. The single chlorophosphorothioate had an estimated
value of kOH =* 60.8 x 10~12 cm3molecule~1s~1 with a percent
error of +3 which is superb. These results are expected since
Atkinson (1987) used all the kOH data for the compounds listed
in Table 20.A. and B. to derive the group rate constants and
substituent factors for these compounds. Therefore, kOH data
for several more compounds in these classes of compounds must
be obtained to confirm the S/R relationships of Atkinson.
Inspection of the kOH data for four alkyl phosphoroami-
dates /phosphorothioamidates indicates that two of the compounds
had percent errors greater than +100. Therefore, neglecting
these two compounds, the average percent error is -58 which is
relatively poor. It appears that for these compounds, which
contain both nitrogen and phosphorus functional groups, OH
-101-
-------
radical interaction is more complex. Therefore, more experi-
mental KQH data are needed on a number of compounds in these
two classes of chemicals to evaluate and refine the S/R
relationships of Atkinson.
III.C.4. Summary
Table 21 summarizes the average percent error in kOH for
the reaction of OH radicals with organosulfur, organonitrogen,
and organophosphorus compounds. The second-order rate constant
KOH was estimated for a total of 37 compounds, Tables 18-20,
and these results are compared to the experimental values.
Only two of these compounds had a percent error greater than
+100 [(CH30)2P(S)N(CH3)2 (+160); (CH3O)2P(O)N(CH3)2 (+115)] and
the results for these two compounds were omitted in the
analysis. For the remaining 35 compounds, the average percent
error ranged from +14 to -18 which is excellent. Only two
compounds were not used in the derivation of the group rate
constants and substituent factors for these classes of
compounds. These were: di-n-propyl sulfide (+10 percent
error) and tetrahydrothiophene (-10 percent error). These
results were superb, tentatively confirming the S/R
relationships for the sulfides. However, very limited data
were available for most of these classes of compounds so that
considerably more experimental kOH data are needed for these
classes to confirm some of the S/R relationships of Atkinson.
-102-
-------
Table 21. Summary of the Average Percent Error in kOH at 298 K
for the Reaction of Hydroxyl Radicals with a Number of
Chemicals in Several Classes of Chemicals Containing
Sulfur, Nitrogen, and Phosphorus Functional Groups and
for All Chemicals in These Classes of Chemicals
Chemical Class
A. SULFUR COMPOUNDS
Thiols
Sulfides
Disulfides
B. NITROGEN COMPOUNDS
Alkyl amines
Alkyl N-hydroxylamines
Alkyl N-nitrosamines
Alkyl N-nitramines
Alkyl hydrazines
C. PHOSPHORUS COMPOUNDS
Alkylphosphates/
thiophosphates
Dialkylchlorophos-
phorothioates
Alky Iphosphoroamidates /
phosphorothioamidatesa
Chemicals not used to
derive the substituent
constants and rate
constants
ALL COMPOUNDS
Number of
Chemicals
9
5
1
6
1
1
1
2
6
1
2
2
35
Average Percent
Error
From
+24
+6
—
+5
—
+14
—
+25
+20
+3
—
+10
+14
To
-10
-27
-4
-9
-24
--
-25
-34
-8
--
-53
-10
- 1 3
-103-
-------
Table 21. Continued
Estimates of kOH were made for four compounds in these two
classes of compounds. Two of the chemicals had percentage errors
greater than +100 [(CH3O)2P(S)N(CH3)2(+160); (CH3O)2P(0)N(CH3)2
(+115)]. These two results were excluded in estimating the
average percent error for all chemicals in these classes.
-104-
-------
III.D. Reaction of Hydroxyl Radicals with Aromatic Compounds
and the Estimation of kOH
III.D.I. Formulation of the Structure/Reactivity Relationships
Atkinson (1986, 1987, 1987a,b, 1988, 1988a) made a
detailed study of the kinetic data for the reaction of hydroxyl
radicals with aromatic compounds. This reaction involves the
addition of OH radicals to the aromatic ring and the reaction
of OH radicals with the substituents on the aromatic ring. For
example, for toluene in air at a total pressure of
approximately one atmosphere at a constant temperature, OH
radicals add to the aromatic ring and abstract a hydrogen from
the CH3 substituent on the ring. Thus, the reaction of toluene
with OH radicals can be described by the following two reaction
pathways
•OH
+ HOH
(123)
•OH
-1- HOH
(124)
Atkinson indicated that the rate constant for the
addition of OH radicals to an aromatic ring, k(7) [from
equation 18], is a function of the sum of the electrophilic
-105-
-------
substituent constants, J^ of Brown and Okamoto (1958) .
Based on a least-squares correlation of the room-temperature
rate constants for OH addition to the aromatic ring [kadd ar]
with the £ff+ values for 34 aromatic compounds (i.e., those
compounds whose names are marked with the superscript ** in the
first column in Table 23), Atkinson (1987) found that
Io9io[*add,ar] = -H-69 - 1-35 £a+ (125)
For convenience, the rate constant for the addition of OH
radicals to an aromatic ring is expressed as 1012kadd ar as
shown in Table 23 and in all calculations. Thus, equation 125
has been modified by adding +12 to both sides of this equation.
As a result, one obtains
Iog10[l012kadd/ar] = 0.31 - 1.35 £
-------
of a+ for the ortho position will be discussed in the next
paragraph. The substituents are listed in Table 22 in the
order of increasing value of a+. The values of a"*" and a~j" were
obtained from Brown and Okamota (1958) for a large number of
substituents. In addition, the a+ values for a number of
additional substituents were obtained from Meylan (1990).
Meylan derived these a+ values by analogy with similar
structures. Leifer also derived the a+ values for a few
substituents by analogy with similar structures. The values of
aj" and a+ for the polychlorobiphenyl ring [i.e., -C6H4C1,
-C6H3Cl2, -C6H2C13, -C6HC14, and -C6C15] were originally
calculated by Atkinson (1987a) and were revised slightly
[Atkinson (1987)]. The revised values are listed in Table 22.
The values of ]Pff+ for various substituents on the
aromatic ring can be calculated using the following rules:
(1) steric hindrance is neglected;
(2) aj = a£ ;
(3) ^ a+ represents the sum of all the substituent
constants on the aromatic ring;
(4) the hydroxyl radical adds to the position with the
most negative value of £ a+ (preferably a free
position); and
-107-
-------
Table 22. Electrophilic Substituent Constants (a* and a"1")
for a Number of Substituents m P
Substituent
Dimethylamino
Dialkylamino
(assume dimethyl
amino)
Anilino
Sulfoxide
Amino
Secondary Amine
Hydroxy
Methoxy
H-Alkoxy (assume
methoxy)
Oxide (assume
methoxy)
Thiol (assume
methylthio)
Methylthio
n-Alkylthio (assume
methylthio)
Sulfide (assume
methylthio)
Disulfide (assume
methylthio)
Acetylamino
Benzoylamino
Structure
-N(CH3)2
-N(R)3
-NHC6H5
-S(0)-
-NH2
-NH-
-OH
-OCH3
-OR
-0-
-SH-
-SCH3
-SR
-S-
-S-S-
-NHC(0)CH3
-NHC(0)C6H5
<<>a
-0.16b
-0.16°
-0.16b
-0.16b
-0.16
-0.16b
0.121b
0.047
0.047b
0.047b
0.158b
0.158
0.158°
0.158b
0.158°
0.21b
0.21b
«#a
-1.7
-1.7C
-1.3
-1.3b
-1.3
-1.0b
-0.92
-0.778
-0.778b
-0.778b
-0.604b
-0.604
-0.604C
-0.604b
-0.604°
-0.6 \
-0.6
-108-
-------
Table 22. Continued
Substituent
Phenoxy
Ethenoxy (assume
phenoxy)
Methyl
Ethyl
n-Alkyl
Methylene (assume
ethyl)
Hydr oxymethy 1
(assume ethyl)
i-Propyl
Methine (assume
i-propyl)
t-Butyl
Oxyphosphorous
Phenyl
Carboethoxymethyl
0-Naphthyl
Aromatic (other
than phenyl)
Hypohalous (e.g.,
hypochlorous)
Car boxy lie Ester
(aliphatic)
Structure
-OC6H5
-OCH=CH2
-CH3
-CH2CH3
-R
-CH2-
-CH2OH
-CH(CH3)2
>CH-
-C(CH3)3
-O-P
-C6H5
-CH2C(0)OCH2CH3
-C10H7(/3)
-Aromatic
-OX
-OC(0)R
«•;)•
0.10b
0.10°
-0.066
-0.064
-0.064C
-0.064b
-0.064°
-0.060
-0.060b
-0.059
0.10b
0.109
-0.10
0.10C
0.10°
0.15b
0.10b
(^)a
-0.5
-0.5C
-0.311
-0.295
-0.295°
-0.295b
-0.295°
-0.280
-0.280b
-0.256
-0.20b
-0.179
-0.164
-0.135
-0.135°
-0.10b
-0.10b
-109-
-------
Table 22. Continued
Substituent
Car boxy lie Ester
(aromatic)
Fluoro
Fluoromethyl
Carboxylate
Chloromethyl
Bromomethyl
(assume
Chloromethyl)
lodomethyl
(assume
Chloromethyl )
Ha lome thine
( assume
Chloromethyl)
Hydrogen
Undefined
Phosphoro
Cyanomethyl
Olefinic
Chlorophenyl
Trimethylsilyl
Structure
-OC(0)C6H5
-F
-CH2F
-C(0)0e
-CH2C1
-CH2Br
-CH2I
-CH-Halogen
-H
-P
-CH2CN
-C=C-
-C6H4C1
-Si(CH3)3
<*m>a
0.10b
0.352
0.10b
-0.028
0.14
0.14b
0.14b
0.14b
0.000
Ob,c
0.0b
0.17
0.02b
0.25d
0.011
«£)*
-0.10b
-0.073
-0.05b
-0.023
-0.01
-0.01b
-0.01b
-0.01b
0.000
Ob,c
0.0b
0.01b
0.02b
0.02d
0.021
-110-
-------
Table 22. Continued
Substituent
Chloro
lodo
Bromo
Sulfocarbonyl
Imino
Aldehyde
D i ch 1 or opheny 1
Acetylenic
Thiocyanate
Car bony 1
Tr ime t hy 1 ammon ium
Tr ia Iky lammonium
Triaryl ammonium
Trichlorophenyl
Carboxy
Carboethoxy
Carboalkoxy
Carbomethoxy
Sulfonic Acid
Esters
Trifluoromethyl
Tetrachlorophenyl
Azo
Structure
-Cl
-I
-Br
-SC(0)-
-N=
-CH(0)
-C6H3C12
-C3C-
-SCN
-C(0)-
©
-N(CH3)3
-N(R)3
-N(Ar)3
-C6H2C13
-C(0)OH
-C(0)OCH2CH3
-C(0)OR
-C(0)OCH3
-S(0) (0)OR
-CF3
-C6HC14
-N=N-
<°:>a
0.399
0.359
0.405
0.20b
-0.03b
0.36b
0.39d
0.21b
0.30b
0.10b
0.359
0.359°
0.359C
0.53d
0.322
0.366
0.366°
0.368
0.50b
0.52
0.67d
0.30b
<ȣ>a
0.114
0.135
0.150
0.15b
0.15b
0.22b
0.22d
0.23b
0.25b
0.35b
0.408
0.408°
0.408°
0.42d
0.421
0.481
0.481°
0.489
0.50b
0.612
0.62d
0.64b
-111-
-------
Table 22. Continued
Substituent
Trichloromethyl
(similar to -CF3)
Tribromomethyl
(similar to -CF3)
Tr i i odome thy 1
(similar to-CF3)
Cyano
Nitro
Nitrate
(assume nitro)
Pentachlorophenyl
Structure
-CC13
-CBr3
-CI3
-CN
-N02
-ONO2
-c6ci5
(<>*
0.55b
0.55b
0.55b
0.562
0.674
0.674b
0.81d
«#a
0.65b
0.65b
0.65b
0.659
0.790
0.790b
0.82d
a Data from Brown and Okamota (1958).
b Data from Meylan (1990) based on similar structures.
c Data from Leifer (1990) based on similar structures.
d Data from Atkinson (1987).
-112-
-------
(5) if all the positions on the ring are occupied, the
ipso position (i.e., the position on the ring
being evaluated) is treated as the meta position.
This rule will become clearer when a specific
example will be used to illustrate the method for
estimating kadd,ar • See Section IV. P. 7.
Hexaf luorobenzene .
III.D.2. Estimation of )CQH for Several Classes of Aromatic
Compounds at 298 K and the Comparison of These.
Results with the Experimental Data
Table 23 lists the pertinent kOH data at 298 K for a
number of aromatic compounds as obtained from the literature.
This table is in a similar format to Table 3. A. and, in
addition, contains the column £a+ for each compound. As
mentioned in Section III. D.I, the chemicals with the
superscript ** after the name were used by Atkinson (1987) to
derive equation 125. The chemicals below the dashed line in
Table 23 were not used by Atkinson to derive equation 125.
III.D.2. a. Benzene and Biphenyl
The recommended experimental value of k_.u for benzene is
-------
Table 23. Comparison of Experimental and Estimated Values of kOH for
Chemicals in Various Classes of Aromatic Chemicals at 298 K
and the Percent Error [The Chemicals Whose Names are Marked
with a Superscript ** Were Used by Atkinson (1987) to
Derive Equation 125]
Chemical Class/Chemical
A. UNSUBSTITUTED AROMATIC
COMPOUNDS
Benzene**
Biphenyl**
B. ALKYLBENZENES
Methylbenzene (Toluene) **
Ethylbenzene**
n-Propylbenzene**
i-Propylbenzene**
o-Xylene**
m-Xylene**
g-Xylene**
o-Ethyltoluene**
m-Ethyltoluene**
j>-Ethyltoluene**
1,2, 3-Trimethylbenzene**
1,2, 4-Trimethylbenzene**
1,3, 5-Trimethylbenzene**
£-Buty Ibenzene
E«+
0.000
-0.179
-0.311
-0.295
-0.295
-0.280
-0.377
-0.622
-0.377
-0.375
-0.606
-0.375
-0.688
-0.688
-0.933
-0.256
10 KOH (cm3molecule~1s~1)
Experimental
(a)
1.28
7.5c'd
6.19
7.5
5.7
6.6
14.7
24.5
15.2
12.0
17.1
11.4
33.3
40.0
62.4
(b)
1.23*
7.2*
5.96*
7.1*
6.0*
6.5*
13.7*
23.6*
14.3*
12.3*
19.2*
12.1*
32.7*
32.5*
57.5*
4.60d
Estimated
2.04
7.12
5.51
6.13
7.46
7.08
6.88
14.4
6.88
7.72
14.6
7.72
17.8
17.8
37.5
5.08
Percent
Errorcc
+66
-1
-8
-14
+24
+9
-50
-39
-52
-37
-24
-36
-46
-45
-35
+ 10
-114-
-------
Table 23. Continued
Polemical Class/Chemical
C. ALKENYLBENZENES
Phenylethene (Styrene)
2-Phenyl-l-propene
(o-Methylstyrene)
trans- 1 -Pheny 1-1 -pr opene
(/3-Methylstyrene)
l-Phenyl-2-methyl-l-propene
(j3-Dimethylstyrene)
D . HALOBENZENES
Fluorobenzene**
Chlorobenzene**
Bomobenzene* *
lodobenzene**
o-Dichlorobenzene**
in-Dichlorobenzene**
g-Dichlorobenzene**
1,2, 4-Trichlorobenzene**
Hexaf luorobenzene* *
n-Propylpentafluorobenzene
E. HALOALKYLBENZENES
Benzotrifluoride**
£«*
0.02
0.02
0.02
0.02
-0.073
0.114
0.150
0.135
0.513
0.228
0.513
0.627
0.837
0.421
0.520
10 kOH (cm3molecule~1s~1)
Experimental
(a)
52
52
59
32
0.54
0.94
0.71
0.93
0.42
0.72
0.32
0.532
0.219
3.06
0.48
(b)
58*
52*
59*
339
0.69*
0.77*
0.77*
1.1*
0.42n
0.72h
0.32h
0.5321
0.172*
3.06J
0.46k
Estimated
28. 2e
53. 5e
65. 7e.
89. le
2.56
1.42
1.28
1.34
0.414
1.01
0.414
0.291
0.151
2.90
0.406
Percent
Errorcc
-51
+3
+11
+170
+270
+84
+66
+22
-1
+40
+29
-45
-12
-5
-12
-115-
-------
Table 23. Continued
Chemical Class/ Chemical
4-Chlorobenzotrifluoride**
Benzyl chloride
F. MONOCHLOROBIPHENYLS
2 -Chlorobipheny 1
3 -Chlorobipheny 1
4 -Chlorobipheny 1
G. HYDROXYBENZENES
Phenol**
o-Cresol**
m-Cresol**
g-Cresol**
2 , 3-Dimethylphenol
2 , 4-Dimethylphenol
2 , 5-Dimethylphenol
2 , 6-Dimethylphenol
r.
0.634
-0.010
Ring A:
0.021
Ring B:
0.2201
Ring A:
0.021
Ring B:
-0.0651
Ring A:
0.021
Ring B:
0.2201
-0.920
-0.986
-1.231
-0.986
-1.297
-1.052
-1.297
-1.052
10 kOH (cm3molecule"1s~1)
Experimental
(a)
0.25
2.9
2.9°
5.4C
3.9C
28.3
40
57
44
(b)
0.24k
2.9*
2.82
5.28
3.86
26.3*
42*
64*
47*
80. 2m
71. 5m
80. Om
65. 9m
Estimated
0.285
2.43
2.95
4.42
2.95
35.6
44.0
93.9
44.0
115
54.1
115
54.1
Percent
Errorcc
+19
-16
+5
-16
-24
+35
+5
+48
-6
+44
-24
+44
-18
-116-
-------
Table 23. Continued
•Chemical Class/Chemical
3 , 4-Dimethylphenol
3 , 5-Dimethylphenol
2 , 3-Dichlorophenol
2 , 4-Dichlorophenol
H. NITROBENZENES
Nitrobenzene**
p,-Nitrophenol
p.-Nitrotoluene
g^Nitrotoluene
W I . AMINOBENZENES
N, N-Dimethylaniline**
Aniline
g-Chloroaniline
2 , 4-Toluenediamine
J. ADDITIONAL SUBSTITUTED
BENZENES
Me thoxy benzene**
Benzonitrile**
Benz aldehyde
E°+
-1.297
-1.542
-0.407
-0.122
0.674
-0.246
0.363
0.479
-1.7
-1.3
-0.901
-2.666
-0.778
0.562
0.22
1012 kOH (cm3molecule~1s~1)
Exper:
(a)
0.14
0.90
**•
148
117
19.6
0.333
13
mental
(b)
81. 4m
113m
1.66n
1.06n
0.149°
0.90
0.70
0.95
148P
111*
83. Or
192s
17.3*
0.33
12.9*
Estimated
115
200^
7.27
3.02
0.251
4.42
0.805
0.605
200U
136
53.6
200t
23.8
0.356
17.1
Percent
Error00
+41
+77
+340
+ 190
+68
+390
+15
-36
+35
+23
-35
+4
+38
+8
+33
-117-
-------
Table 23. Continued
Chemical class/Chemical
Acetophenone
Thiophenol
(Mercaptobenzene)
Benzyl alcohol
Tetralin (1,2,3,4-Tetra-
hydronaphthalene)
Indan (2,3-Dihydro-lH-
indene)
Fluorene
1 , 4-Benzodioxin
2 , 3-Dihydrobenzofuran
2 , 3-Benzofuran
E°+
0.10
-0.604
-0.295
-0.359
-0.359
Ring A:
-0.243dd
Ring B:
-0.243dd
-0.731
-0.842
-0.48bb
lO^ kOH (cm3molecule"~1s~1)
Experii
(a)
___
25
37
dent a 1
(b)
2.74n
11. 2V
22.9
34.3*
9. ay
13. Oz
25.2aa
36.6aa
37.3aa
Estimated
1.61
13. 3W
7.99
11.2
9.09
9.37
33.0
36.3
65.2
Percent
Errorcc
-41
+19
-65
-67
-1
-28
+ 31
-1
+75
a Experimental data from Atkinson (1987).
b Experimental data from Atkinson (1989).
c Experimental data from Atkinson and Aschmann (1985).
d For biphenyl. kpu was reported as 8.5, 8.06, and 5.8 x 10~12
Therefore, the average value is 7.5 x 10~12cm3molecule"1s~1.
d/ Experimental data from Ohta and Ohyama (1985).
e In the estimation of kpjj / it was assumed that the OH radicals add
separately to the olefinic group and the aromatic ring. Thus,
k(3) [=ka(}ci nar] was calculated for the olefinic group using equations
90 and 91 and with C[C6H5-] = 1.00; k(7) [ = kj^ ar ] was calculated for
the aromatic ring using equations 127, 128a, 129'and ^T,a+ Caa'
Illustrative Example IV.P.2. trans-1-phenyl-l-propene.
See
-118-
-------
Table 23. Continued
• Experimental data from Bignozzi et al. (1981).
3 Experimental data from Chiorboli et al. (1983).
h Experimental data from Wanner and Zetzsch (1983).
1 Experimental data from Rinke and Zetzsch (1984).
3 Experimental data from Ravishankara et al. (1978a).
k Experimental data from Atkinson et al. (1985a).
1 Calculated from the structure: Cl
RING A RING B
m Experimental data from Atkinson and Aschmann (1989).
n Experimental data from Nolting et al. (1987) and Atkinson (1989).
I
Average of the experimental data of Witte et al. (1986) and Zetzsch
(1982) as reported in Atkinson (1989).
P Experimental data from Atkinson et al. (1987).
9 The estimated kgg was 247 x 10~12 cm3molecule~1s"1. However, this
exceeds the collision rate so that the value of kOH was set equal to
200 x 10~12 cm3molecule~1s"1 [Atkinson (1987)].
r Experimental data from Wanner and Zetzsch (1983).
3 Experimental data from Becker et al. (1988) .
t The estimated value of )CQH was 8150 x 10~12 cm3molecule~1s~1. This
exceeds the collision rate so that the value of kOH was set at
200 x 10~12 cm^molecule^s"1 [Atkinson (1987)].
u The estimated value of kQH was 466 x 10~12 cm3molecule"1s"1. However,
this exceeds the collision rate so that the value of kOH was set at
200 x 10~12 cB^molecule^s"1 [Atkinson (1987)].
v Experimental data from Barnes et al. (1986).
-119-
-------
Table 23. Continued
w For the thiol group on an aromatic ring, it was assumed that Jc(4) =
k(-SH) = o [Meylan(1990)].
x Experimental data from Atkinson and Aschmann (1988a).
Y Experimental data from Baulch et al. (1986) as reported by
Atkinson (1989).
2 Experimental data of Klopffer et al. (1986) and Becker et al.
(1984) as reported by Atkinson (1989).
aa Experimental data from Atkinson et al. (1989).
bb In calculating k(7), it was assumed that the molecular structure of
2,3-benzofuran can be approximated by the molecular structure of
l-vinyl-2-vinyloxybenzene. (It should be noted that this compound is
a polynuclear aromatic hydrocarbon and should probably be considered
in Section III.D.2.k. However, since no ionization potential is
available, it cannot be calculated using equation 138.)
cc Based on the experimental kOH data given in the third column,
Experimental/(b).
dd Calculated from the molecular structure
Ring A Ring B
* Recommended value by Atkinson (1989) with the rationale for the
recommendation and the uncertainty in the recommendation.
-120-
-------
and this result is listed in the second column of Table 23. For
benzene, C-H abstraction is given by k(l) = k(l,UNS CH) = 0
(Table 1); OH addition to the aromatic ring can be estimated
using equations 127, 128, 129, and 130 so that k(7) = ka(jd ar =
2.04 x 10~12 cm3molecule~1s~1. From equation 20, kOH = Ml) +
k(7). Therefore, using the above data in this equation yields
kOH = 2.04 x 10"12 cm3molecule~1s"1 (131)
This result is listed in the fifth column of Table 23. Based
on the recommended value of kOH from Atkinson (1989) listed in
the fourth column, the percent error for benzene is +66 which
is relatively poor.
The experimental value of kOH for biphenyl is listed in
the third column of Table 23 as obtained from Atkinson and
Aschmann (1985) while the recommended value is given in Column
4 as obtained from Atkinson (1989). For biphenyl, kOH can be
calculated as follows. From equation 20, for each phenyl ring
kOH = k'(l) + k'(7) (132)
where k'(l) represents the H-atom abstraction rate constant for
the aromatic ring while k'(7) represents the OH addition to the
aromatic ring. Therefore, for biphenyl, which contains two
aromatic rings,
2kOH = Z
-121-
-------
For C-H abstraction from the aromatic ring, k'(l) = k(l,UNS CH)
= 0. For OH addition to the aromatic ring, ^o+ was
calculated according to the rules listed in Section III.D. and
was estimated to be
f = -0.179 (134)
and this result is listed in the second column of Table 23.
Using equations 127, 128, 129, and 134, k'(7) was estimated to
be 3.56 x 10~12 ca^molecule'^-s'1. Using the above results of
k'(l) and k'(7) in equation 133 gives
7.12 x 10~12 cm3molecule~1s~1 (135)
and this result is listed in the fifth column of Table 23. The
percent error is -1 which is superb.
III.D.2.b. Alkylbenzenes
Experimental kOH data is available for 14 alkylbenzenes,
Table 23.B. The rate constant k_« for each alkylbenzene was
calculated as follows. The rate constant for H-atom
abstraction from the alkyl group [k(la)] was calculated using
equation 28; for H-atom abstraction from the phenyl ring,
k(l,UNS CHV - 0. Therefore, k(l) = k(la). The rate constant
for OH addition to the aromatic ring [k(7)] was calculated
using equations 127, 128, and 129 and the value of
obtained using the rules listed in Section III.D. The value of
kOH was then calculated from equation 20, which is the sum of
-122-
-------
k(l) and k(7); and these results are listed in Table 23.B. for
each compound along with the values of ^Tff* and the percent
error. For £-butylbenzene, which was not used to derive
equation 125, the percent error is +10 which is excellent
tentativley confirming this equation for the alkylbenzenes.
For all 14 alkylbenzenes, the average percent error ranged from
+14 to -35 which ranged from excellent to very good. More
experimental kQH data are needed on a number of additional
alkylbenzenes to confirm the S/R relationships of Atkinson.
III.D.2.C. Alkenylbenzenes
Experimental k0H data is available for four alkenyl-
benzenes, Table 23.C. These experimental kOH data were not
used by Atkinson (1987) to derive equation 125. The rate
constant JCQH for each alkenylbenzene was calculated as follows.
The rate constant for H-atom abstraction was calculated in the
same manner as described in Section III.D.2.b. For OH addition
to the unsaturated carbon-carbon functional groups, it was
assumed that OH added to the olefinic group and the aromatic
ring separately as postulated by Atkinson (1987). For the
olefinic group, k(3) C=fcadd,narJ was calculated using equations
is ou
90 and 91 (for these compounds ka(j£ nar and ka(j(j nar are zero);
for the aromatic ring, k(7) [= kad(j ar] was calculated using
equations 127, 128, and 129 and the value of J^a+ was
calculated from the rules listed in Section III.D. The value*
of kOH were then calculated from the sum of k(l), k(3), and
k(7) [equation 20], where applicable, and these results are
-123-
-------
listed in Table 23.C. along with the values of £a+ and the
percent error.
For th« four alkenylbenzenes, only l-phenyl-2-methyl-l-
propene had a percent error greater than +100 (+170). For the
remaining three alkenylbenzenes, the average percent error
ranged from +7 to -51. Overall, these results ranged from
superb to good, tentatively confirming equation 125; but more
experimental data on a number of additional alkenylbenzenes are
needed to confirm the S/R relationships of Atkinson for this
class of aromatic compounds. Perhaps these S/R relationships
should be modified using the fact that there is strong
interaction between the unsaturated carbon-carbon bonds in the
olefinic groups and the phenyl rings (i.e., resonance) so that
there should be unique group rate constants for these
conjugated groups (e.g., as described in Section III.B.I. for
conjugated diolefins).
III.D.2.d. Halogenated Benzenes
Experimental kQK data is available for 10 halogenated
benzenes, Table 23.D. Nine of these compounds were used by
Atkinson to derive equation 125. The values of J^"1"/ kOH' and
the percent error were calculated as.described previously and
these results are listed in Table 23 for each halobenzene. For
these chemicals, only fluorobenzene had a percent error greater
than +100 (+270); and this compound was omitted in calculating
the average percent error for all the halogenated benzenes.
-124-
-------
Only n-propyl pentafluorobenzene was not used by Atkinson to
derive equation 125. The percent error for this compound was
-5 which ia excellent, tentatively confirming this equation.
However, more experimental )CQH data are needed for additional
halobenzenes to confirm this equation. For all 9 halogenated
benzenes, the averaqe percent error ranged from +48 to -16.
Overall, these results ranged from good to excellent. More
experimental kOH data is needed for fluorobenzene to determine
why this compound had such a large percent error.
III.D.2.e. Haloalkylbenzenes
Experimental kQH data is available for 3 haloalkyl-
benzenes, Table 23.E. The experimental )CQH data for the first
two compounds were used by Atkinson (1987) to derive equation
125. The values of $^a+ ' ^H' and tne percent error were
calculated as described previously and these results are listed
in Table 23 for each compound. For benzyl chloride, which was
not used by Atkinson (1987) to derive equation 125, the percent
error was -16 which was excellent, tentatively confirming this
equation for the haloalkylbenzenes. For these 3 compounds, the
average percent error ranged from +19 to -14 which is
excellent. However, more experimental kOH data for additional
compounds in this class are needed to confirm the S/R
relationships of Atkinson.
-125-
-------
III.D.2.f. Monochlorobiphenyls
At the request of Leifer, Atkinson {under a (1981) ORD
cooperative agreement} measured kOH for three monochloro-
biphenyls. The experimental values of k0H for three
monochlorobiphenyls are listed in Table 23 as obtained from
Atkinson and Aschmann (1985). These experimental kOH data were
not used by Atkinson to derive equation 125. To calculate k^u
Orl
for the three monochlorobiphenyls, each ring was considered
separately {i.e., C6H5[Ring A] C6H4Cl[Ring B]}. The values
of ]P<*+ were then calculated for each ring in the standard
manner and k'(l) and k'(7) were calculated as described
previously. The overall rate constant is the sum of the rate
constants for each ring. Therefore, for each monochloro-
biphenyl
kOH = 2k'(l,UNS CH) + kadd,ar,(Ring A) + kadd/ar (Ring B) (136)
The estimated values of kOH for each monochlorobiphenyl are
listed in Table 23.F. along with the values of $^ff+ for each
ring, and the percent error. The estimation of kOM for
3-chlorobiphenyl is given in Illustrative Example IV.P.9.
The average percent error for all three monochloro-
biphenyls ranged from +5 to -20 which ranged from superb to
excellent. All these results indicate that equation 125 is
valid for this class of compounds. However, more experimental
k0H data are needed for this class of compounds to confirm
equation 125.
-126-
-------
III.D.2.g. Hydroxybenzenes
Experimental kOH data is available for phenol and 11
substituted phenols, Table 23.G. The values of ^2°+ >
estimated kQH/ and the percent error were calculated for these
compounds as described previously and these results are
summarized in Table 23.G. For 3,5-dimethylphenol, the
calculated value of £a+ was -1.542 and the estimated value of
kadd ar was e(3Ual to 246.4 x 10~12 cm3molecule~1s~1. The
second-order rate constant kOH [=k(la) + k(-OH) + k(l,UNS CH)
+ ka(jd arl was tnen equal to 247 x 10~12 cm3molecule~1s"1. In
this case, the estimated value of kOH exceeded the collision
rate so that an upper limit must apply. Therefore, Atkinson
(1987) recommended that kOH be set at 200 x 10~12
cm3molecule~1s~1 and this is the value entered into the fifth
column of Table 23.G.
Inspection of the percent error data in the last column
indicated that two of the phenolic compounds had a percent
error greater than +100 [2,3-dichlorophenol (+340); 2,4-
dichlorophenol (+190)] and these values were omitted in the
estimation of the average percent error. For the six chemicals
below the dashed line which were not used to derive equation
125, the average percent error ranged from +52 to -21 and,
therefore, ranged from good to very good, tentatively
confirming the validity of equation 125 for the phenolic
compounds. The average percent error for the 10 remaining
compounds was +42 to -16 and, therefore, ranged from good to
-127-
-------
excellent. However, more experimental data is needed for
2,3-dichlorophenol and 2,4-dichlorophenol to see why these two
compounds had a large percent error.
III.D.2.h. Nitrobenzenes
Experimental JCQH data is available for nitrobenzene and
three substituted nitrobenzenes, Table 23.H. The values
of ^,a+ i *OH» an<* tne Percent error were calculated for
these four compounds as described previously and these results
are summarized in Table 23.H. For the three compounds below
the dashed line in Table 23.H. o-nitrophenol had a percent
error of +390 and was omitted in calculating the average
percent error. The percent error for the other two compounds
was +15 and -36 which is excellent and good, respectively. The
average percent error for the three remaining compounds ranged
from +42 to -36 which is very good. More experimental kOH data
are needed for o-nitrophenol and for other substituted nitro-
benzenes to confirm equation 125 for this class of compounds.
III.D.2.i. Aminobenzenes
Experimental KQJJ data is available for aniline and three
substituted anilines, Table 23.1. For the compound
N,N-dimethylaniline, the calculated value of ^a+ was -1.7.
The second-order rate constant kOH t= Mia) + k(l,UNS CH) +
k(5) + kaaci ar] was then equal to 466 x 10~12 cm3molecule~1s~1.
In this case, kOH exceeded the collision rate so that it is set
at 200 x 10~12 cm3molecule"1s"1 [Atkinson (1987)] and this
-128-
-------
value was entered into the fifth column of Table 23.1. In a
similar manner for 2,4-toluenediamine, ^o+ = -2.666, k(7) =
8110 x 10~12, and k0H was 8150 x 10~12 cm3molecule"1s~1. Since
this exceeds the collision rate, k0n was set a^ 200 x 10~12
cm3molecule~1s~1 [Atkinson (1987)] and this value was entered
in the fifth column of 23.1.
For the three amino compounds below the dashed line, the
average percent error was +14 to -35 and therefore ranged from
excellent to very good. These results tentatively confirm
equation 125 for the substituted aniline compounds. For all 4
compounds, the average percent error ranged from +21 to -35 and
are very good. More experimental data is need for additional
chemicals in this class to confirm equation 125.
III.D.2.J. Additional Substituted Benzenes
The experimental kOH data at 298 K for twelve additional
substituted benzenes [methoxybenzene, benzonitrile,
benzaldehyde, acetophenone, thiophenol, benzyl alcohol,
tetralin (1,2,3,4-tetrahydronaphthalene), Indan (2,3-dihydro-
IH-indene), fluorene, 1,4-benzodioxan, 2,3-dihydrobenzofuran,
and 2,3-benzofuran] are summarized in Table 23.J. The values
of ]5^tf+» *OH' an^ **ne Percent error were calculated as
described previously and these results are listed in Table 23
for each compound. For 2,3-benzofuran, ^o+ was calculated
assuming that this chemical can be represented by the molecular
-129-
-------
structure of l-vinyl-2-vinyloxybenzene5. For 2,3-
dihydrobenzofuran, Atkinson (1987) estimated kQH but did not
include a ring strain factor F(5) [for the five membered ring]
in calculating k(lc). To be consistent with the S/R
relationships in this report, the ring strain factor was
included in the estimation of k(lc). The same comments apply
to indan and fluorene.
For thiophenol, as an approximation, it has been assumed
that there is no interaction of OH radicals with the -SH group
on the aromatic ring; hence, k(4) = k(-SH) = 0 [Meylan(1990)].
Ten of these compounds were not used by Atkinson to derive
equation 125. The average percent error ranged from +40 to
-34 which is very good to good, tentatively confirming
equation 125. However, more experimental kOH data are needed
for additional compounds of these types to confirm this
equation. For all 12 additional aromatic compounds, the
average percent error was ±34 which was very good.
III.D.2.k. Polyaromatic Hydrocarbons
Table 24 summarizes the experimental k.u data for nine
-------
Table 24. Comparison of Experimental and Estimated Values of kOH for
Fused Ring Polyaromatic Hydrocarbons [Underlined Values of
KQJJ Were Used by Atkinson (1987) and Atkinson in Biermann
et al. (1985) to Derive Equation 137]
Chemical
Naphthalene
1-Methyl-
naphthalene
2 -Methyl -
naphthalene
2, 3 -Dimethyl-
naphthalene
Anthracene
Phenanthrene
flitro-
naphthalene
2-Nitro-
naphthalene
1,4-Dichloro-
naphthalene
lonization
Potential3
(eV)
8.13
8.13
8.13
8.13
7.55
8.1
8.13
8.13
8.13
E*+
0.000
-0.311
-0.311
0.377
0.000
0.000
0.674
0.674
0.513
10 12 kOH (cm3mo:
Experimental
21.6*
53. Ob
52.3^
s
76. 8b
112°
31*
5.4d
5.6*
5.8e
Lecule~1s~1)
Estimated
21.4
56.3
56.3
69.5
91.2
22.9
2.63
2.63
4.37
Percent
Error
-1
+6
+8
-10
-19
-26
-51
-53
-25
a lonization potential (IP) in electron Volts (eV) of the parent chemical
as obtained from Atkinson (1987) and Weast (1976-1977).
k Experimental data from Atkinson and Aschmann (1987).
. •*
D Experimental data from Atkinson and Aschmann (1986).
c Experimental data from Biermann et al. (1985).
d Experimental data from Atkinson et al. (1989d).
e Experimental data from Klopffer et al. (1986) and Becker et al. (1984)
as reported in Atkinson (1989).
-131-
-------
methylnaphthalenes, and 2,3-dimethylnaphthalene, Atkinson
(1987) and Atkinson in Biermann et al. (1985) formulated the
equation
lo9lOkadd,PAH = -1-89 - 1-08(IP) - 1.35 £a+ (137)
where kadd PAM represents the second-order rate constant for
the addition of OH radicals to the fused polyaromatic ring in
the units cm3molecule~1s~1, IP represents the ionization
potential of the unsubstituted polyaromatic ring in electron-
volts (eV) , and ^T^"1" represents the sum of the electrophilic
substituent constants of Brown and Okamota (1958) derived for
the monocyclic substituted portion of the molecule to allow for
the effects of substituted groups on the reactivity.
Conversion of equation 137 to the more useful form by adding
+12 to both sides of the equation yields
lo9lOk'add,PAH = I-0-11 - 1.08(IP) - 1.35 a (138)
1012kadd/PAH = kadd/PAH
Thus, when kadd/PAH is computed using equations 138 and 139,
then kadd PAH is multiplied by 10~12 to obtain kadd PAH*
From equation 19, it is seen that
M«) = *add, PAH
Using equations 20, 138, 139, and 140, along with the
appropriate group rate constants and substituent factors from
-132-
-------
Tables 1 and 2, the appropriate electrophilic substituent
factors from Table 22, the ionization potential of the parent PAH
from Weast (1976-1977), and the appropriate experimental values
of kOH from the literature, the values of J^cr+ , kOH, and the
percent error were calculated for nine PAH compounds in the
standard manner. These results are summarized in Table 24.
For the three compounds below the dashed line, which were
not used to derive equation 137, the average percent error was
-43 which was good, tentatively confirming equation 137.. For all
nine PAH compounds, the average percent error ranged from +7 to
-26 which ranged from superb to very good. More experimental k0n
data, however, are needed for additional PAH compounds to confirm
equation 137.
III.D.3. Summary
Table 25 summarizes the average percent error in kOH
for the reaction of OH radicals with aromatic and polyaromatic
compounds as obtained from Tables 23 and 24. kOH was estimated
for a total of 77 aromatic and polyaromatic compounds and these
results were compared to the experimental values. Only five of
these compounds had a percent error greater than +100 [1-phenyl-
2-methyl-l-propene(+170); fluorobenzene (+270); 2,3-dichloro-
phenol (+340); 2,4-dichlorophenol (+190); o-nitrophenol (+390)];
and these compounds were omitted in the estimation of the average
percent error. Of the 72 remaining aromatic compounds, kOH was
-133-
-------
Table 25. Summary of the Average Percent Error in kOH at 298 K
for a Number of Chemicals in Several Classes of
Aromatic and Polyaromatic Compounds and for All
Chemicals in These Classes
Chemical Class/Chemical
Benzene
Biphenyl
Alkylbenzenes
Alkenylbenzenes
Halobenzenes
Haloalkylbenzenes
Monochlorobiphenyls
Hydroxybenz enes
Nitrobenzenes
Aminobenzenes
Polyaromatic Hydrocarbons
ADDITIONAL SUBSTITUTED
BENZENES
Methoxy benzene
Benzonitrile
Benz aldehyde
Acetophenone
Thiophenol
( Her captobenz ene )
Benzyl Alcohol
Number of
Chemicals
1
1
14
3a
9b
3
3
10°
3d
4
9
1
1
1
1
1
1
Average Percent
Error
From
+66
+14
+7
+48
+19
+5
+42
+42
+21
+7
+38
+8
+33
+19
To
-1
.-35
-51
-16
-14
-20
-16
-36
-35
-26
-41
-65
-134-
-------
Table 25. Continued
Chemical Class/Chemical
Tetralin (1,2,3,4-Tetra-
hydr onaph tha 1 ene )
Indan (2,3-Dihydro-lH-
Indene)
Fluorene
1 , 4-Benzodioxin
2 , 3-Dihydrobenzof uran
2 , 3-Benzofuran
All Compounds Not Used to
Derive Equation 125
All Compounds Not Used to
Derive Equation 137
All Compounds
Number of
Chemicals
1
1
1
1
1
1
30
3
72
Average Percent
Error
From
_ ——
-1
+31
+75
+29
+32
To
-67
-28
-1
-29
-43
-28
a Estimates of kOH were made for four alkenylbenzenes.
However, the percent error for l-phenyl-2-methyl-l-propene
was greater than +100 (+170) and was not used in the
estimation of the average percent error for this class of
compounds.
b Estimates of kOH were made for ten halobenzenes.
However, the percent error for fluorobenzene was greater
than +100 (+270) and was not used in the estimation of the
average percent error for this class of compounds.
c Estimates of kpK were made for twelve hydroxybenzenes.
However, 2,3-dichlorophenol and 2,4-dichlorophenol had
errors greater than +100 [+340 and +190] and were
omitted in the calculating the percent error for this
class of compounds.
d Estimates of KQH were made for four nitrobenzenes and the
percent error for o-nitrophenol was greater than +100 (+390),
This result was omitted in calculating the percent error for
this class of compounds.
-135-
-------
estimated for 63 chemicals using equation 125; kOH was
estimated for 9 polyaromatic compounds using equation 137.
Thirty of the 63 aromatic chemicals were not used by Atkinson
to derive equation 125. The average percent error of these 30
compounds was ± 29 which is very good, thereby tentatively
confirming equation 125. Three of the 9 polyaromatic compounds
were not used by Atkinson to derive equation 137. The
average percent error of these three compounds is -43 which is
good, tentatively confirming equation 137. The average percent
error for all 72 aromatic and polyaromatic compounds ranged
from +32 to -28 which is very good. However, more experimental
kOH data are needed in several classes of aromatic and
polyaromatic compounds to confirm the S/R relationships of
Atkinson (i.e., equations 125 and 137).
It should be noted that for substituent groups which
result in large negative values of £a+» the estimated rate
constants from equations 125 and 137 can exceed the collision
rate so that an upper limit must apply. This was probably the
case for N,N-dimethylaniline, 2,3-dimethylphenol, and
2,4-toluenediamine which had estimated values of kOH greater
than 200 x 10~12cm3molecule~1s~'1 (the upper limit collision
rate). Therefore, Atkinson (1987) recommended that for
aromatic and polyaromatic compounds in which the estimated rate
constant kOH at 298 K exceeds 200 x 10~12cm3molecule~1s~1/ the
estimated rate constant kOH should be set equal to 200 x
10~12cm3molecule~1s""1.
-136-
-------
If one compares the average percent error for all the
specific classes of compounds, it is evident that the aromatic
and polyaromatic compounds have the largest percent error.
[See Tables 8, 17, 21, 23 and 24.] From equations 125 and 137,
it is seen that the estimated value of kadd ar is an
exponential function of ^o+ which is in turn related to the
individual values of a£ and a£ for specific functional groups.
Thus, any small error in these a"1" values will have a large
effect on the estimated value of kOH and this is probably the
reason why aromatic and polyaromatic compounds have the largest
relative average percent error.
III.E. Summary of the Results for the Estimation of kOH
for All Chemicals in a Number of Classes of Chemicals
by the Structure/Reactivity Relationships of Atkinson
of the University of California/Riverside.
The second-order rate constant kOH at 298 K was estimated
by the S/R relationships developed by Atkinson at the
University of California/Riverside for 405 organic chemicals
covering a wide variety of chemical classes and these results
were compared to the experimental values. These chemical
classes were: alkanes (acyclic and cyclic); haloalkanes;
carbonyl compounds such as aldehydes, ketones, esters, etc.;
ct-dicarbonyls such as glyoxal, etc.; alcohols and glycols;
ethers (acyclic and cyclic); nitrates; nitriles; alkenes,
conjugated and nonconjugated; ketenes; alkynes; 1,2-dienes
(allenes); thiols; sulfides; disulfides; N-hydroxylamines;
N-nitrosamines; N-nitroamines; hydrazines; alkyl
-137-
-------
phosphates/thiophosphates; dialkylchlorophosphorothionates;
alkyl phosphoroamidates/ phosphorothioamidates; benzene and
biphenyl; alkyl benzenes; alkenyl benzenes; halogenated
benzenes; haloalkylbenzenes; monochlorobiphenyls; hydroxy-,
nitro-, and aminobenzenes; methoxy and cyanobenzenes; aromatic
aldehydes; polyaromatic hydrocarbons; and other aromatic
compounds. Of the 405 chemicals, 20 had percent errors greater
than +100. The value of +100 was chosen so that only a minimum
number of chemicals would be dropped from the total number of
chemicals used to obtain the average percent error. For the
remaining 385 chemicals in a number of chemical classes, the
average percent error ranged from +21 to -19 which is
excellent. One hundred fifty-four chemicals were not used by
Atkinson to derive all the parameters in the S/R relationships
and, therefore, were good candidates to test the validity of
these S/R relationships. The average percent error of these
154 chemicals ranged from +24 to -20 which ranged from very
good to excellent, thereby confirming the S/R relationships of
Atkinson. However, a few of the classes of chemicals had a
minimum number of chemicals so that more experimental kOH data
are needed for additional chemicals in these classes to
corroborate and/or refine some of the S/R relationships
developed by Atkinson. In addition, more experimental kgjj data
are needed for the 20 chemicals with errors greater than +100
to get a better estimate of the percent error for each chemical
and for all chemicals. It should be noted- that, in general,
-138-
-------
the estimated values of kOH for the first member of a given
class of chemicals has the greatest deviation from the
experimental value (i.e., it had the largest percent error).
Therefore, more experimental kOH data are needed for the first
member of a given class of chemicals. Table 26 summarizes the
statistical data for all the compounds used in the analysis of
the S/R relationships of Atkinson.
IV. Illustrative Examples: Use of the Structure/Reactivity
Relationships of Atkinson to Estimate the Second-Order
Rate Constant (kOH) f°r tne Reaction of Hydroxyl
Radicals with Organic Chemicals in the Gas-Phase at
298 K in Air at Atmospheric Pressure
(1) A large number of examples (56) are given in this
section to illustrate the methods of estimating k-..
Uii
with the S/R relationships of Atkinson and to cover
most of the classes of organic chemicals evaluated in
this report.
(2) The group rate constants listed in Tables l, 9, 11,
and 12 are reported with a numerical value of
1012kOH • *n calculating OH radical addition to the
aromatic and polyaromatic rings, equations 127 and
138 were used where k'add/ar = 1012*add ar (equations
128 and 139) . Thus, kOH was calculated for all
examples without the factor 10~12. The final value of
kOH (Estimated) was then reported with the factor
10~12 and the units cm3molecule~1s~^-.
-139-
-------
Table 26. Summary of the Statistical Data for All the Compounds Used
in the Analysis of the S/R Relationships of Atkinson
Chemical
Class/
Chemical
Alkanes
Saturated
Haloalkanes
Saturated
Carbonyl
Compounds
Saturated
Alcohols
and Glycols
Saturated
Ethers
Saturated
Nitrates
Saturated
Nitriles
Unsubsti-
tuted
Alkenes
Substituted
Alkenes
Conjugated
Dienes
Alkynes
Allenes
Saturated
Thiols
Total
No. of
Chemicals
50
32
52
18
36
17
2
39
24
13
5
3
9
Number3
Dropped
0
2
4
0
4
1
0
0
2
0
0
0
0
Phpmi nal a Poma i rH nrr
NO.
50
30
48
18
32
16
2
39
22
13
5
3
9
No.b With
(+) and
(Ave %)
Error
22(+12)
15(+21)
15(+26)
5(+20)
18 (+27)
8 (+20)
18 (+11)
12(+20)
6(+5)
2(+9)
2 (+10)
2 (+24)
No. With
(-) and
(Ave.%)
Error
28(-10)
15(-28)
33(-19)
13(-19)
14(-22)
8 (-10)
2 (-5)
21(-11)
10(-21)
7 (-17)
3(-16)
K-io)
7(-10)
Chemical Below
DachoH T,i npO
No.
17
15
28
13
0
1
0
34
4
5
2
0
0
No.b With
(+) and
(Ave. %)
Error
5(+12)
7(+26)
8(+39)
4(+19)
13 (+16)
2(+21)
1(+10)
No. With
(-) and
(Ave.%)
Error
12(-10)
8(-37)
20(-22)
9(-16)
1(-6J
21(-11)
2(-16)
4(-24)
2(-21)
-140-
-------
Table 26. Continued
Chemical
Class/
Chemical
Saturated
Sulfides
Saturated
Disulf ides
Saturated
Amines
N-Hydroxyl-
araines
N-Nitros-
amines
Ll-Nitra-
Hines
Hydrazines
Alkyl
Phosphates/
Thiophos-
phates
Dialkyl
Chloro-
Phosphoro-
thioates
Alkyl
Phosphoro-
amidates/
Phosphoro-
thio-
amidates
Benzene
Total
No. of
Chemicals
5
1
6
1
1
1
2
6
1
4
1
Numbera
Dropped
0
0
0
0
0
0
0
0
0
2
0
Phemirals R^m^-ininrf
No.
5
1
6
1
1
1
2
6
1
2
1
No.b With
(+) and
(Ave %)
Error
3 (+6)
2(+5)
1(+14)
l(+25)
4(+20)
-l(+3)
l(+66)
No. With
(-) and
(Ave.%)
Error
2(-27)
l(-4)
4(-9)
l(-24)
l(-25)
l(-34)
2(-8)
2(-58)
Chemical Below
nash*>rt T.in*»C
NO.
2
0
0
0
0
0
0
0
0
0
0
No.b With
(+) and
(Ave. %)
Error
1(+10)
_. — .„
No. With
(-) and
(Ave.%)
Error
1(-10)
-141-
-------
Table 26. Continued
Chemical
Class/
Chemical
Biphenyl
Alkyl-
benzenes
Alkenyl-
benzenes
Halo-
benzenes
Haloalkyl-
benzenes
Monochloro-
biphenyls
Hydroxy-
benzenes
Nitro
benzenes
Amino-
benzenes
Poly-
aromatic
Hydro-
carbons
Additional
Substituted
Aromatic
Compounds
All
Compounds
Total
No. of
Chemicals
1
14
4
10
3
3
12
4
4
9
12
405
Number3
Dropped
0
0
1
1
0
0
2
1
0
0
0
20
rhptrn rials Pevma i ni net
NO.
1
14
3
9
3
3
10
3
4
9
12
385
No.b With
(+) and
(Ave %)
Error
3 (+14)
2 (+7)
5(+48)
K+19)
l(+5)
7(+42)
2(+42)
3 (+21)
2 (+7)
6(+34)
170(+21)
NO. With
(-) and
(Ave.%)
Error
1(-1)
ll(-35)
1(-51)
4(-16)
2(-14)
2(-20)
3(-16)
l(-36)
l(-35)
7(-26)
6(-34)
215(-19)
Chemical Below
DasVieri T.i nf»G
NO.
0
1
3
1
1
3
6
2
3
3
10
154
No.b With
(+) and
(Ave. %)
Error
1(+10)
2(+7)
l(+5)
4(+52)
1(+15)
2 (+14)
4 (+40)
56(+24)
NO. With
(-) and
(Ave.%)
Error
'
K-51)
K-5)
1(-16)
a
2(-21)
K-36)
l(-35)
3(-43)
6(-34)
98(-20)
-142-
-------
Table 26. Continued
Chemicals with percent error greater than +100. The value of +100 was
chosen so that a minimum number of chemicals would be dropped from the
total number of chemicals used to obtain the average percent error.
b The number of chemicals which had an average (+) percent error including
those with zero error.
c The number of chemicals not used by Atkinson to derive the parameters
in the S/R relationships. These data represent the best test for the
reliability of the S/R relationships of Atkinson.
-143-
-------
(3) In calculating the percent error, the factor 10~12
was omitted since this factor cancels out.
IV.A. Alkanes (Acyclic and Cyclic)
IV.A.I. 2-METHYLPENTANE (CH3) 2CHCH2CH2CH3
Using equations 20 and 28 and going from carbon to carbon
sequentially from left to right yields
kOH = k(l) = k(la) = 2k° F(>CH-) + kg F2(CH3-)F(-CH2-)
+ k| F(>CH-)F(-CH2-) + k| F(-CH2-)F(CH3-)
+ kg F(-CH2-)
Using the appropriate group rate constants from Table 1 and the
appropriate substituent factors from Table 2 yields
kOH = 2(0.144)(1.29) + 1.83(1.00)2(1.29) + 0.838(1.29)(1.29)
+ 0.838(1.29)(1.00) + 0.144(1.29)
kOH =5.39
kOH(Estimated) = 5.39 x 10~12cm3molecule~1s~1
From Table 3.A., the experimental value of k-.. is 5.6 x 10~12
VJtl
cm3molecule""^s~1.
Percent Error = [ (5.39-5.6)/5.6 ](100) = -4
-144-
-------
IV.A.2. BICYCLO[3.3.0]OCTANE
CH2-CH-CH2
H2C
\
:CH-
CH2-CH-CH2
Since this is a bicyclic compound, equations 20 and 43 are
used; and using the appropriate group rate constants and
substituent factors listed in Tables 1 and 2, respectively,
gives
kOH = Jc(l) = k(lc) = [ 2k°F2(-CH2-)F(>CH-) + 2kfF2(-CH2-)
+4k|F(-CH2-)F(>CH-)] F2(5) F(8)
2(1.83) (1.29)3 + 2(0.838) (1.29)2
+ 4(0.838)(1.29)2
(0.80)2(1.0)
kOH = 10.4
kOH(Estimated) = 10.4 x 10~12cm3molecule~1s~1
kOH(Experimental) = 11.0 x 10~12cm3molecule~1s~1 (Table 3.B.)
Percent Error = f (10.4-11.0) /li.o 1(100) = -5
IV.A.3. ISOPROPYLCYCLOPROPANE
CH-CH(CH3)2
CH2 CH2
-145-
-------
Since this is a substituted cyclic compound, equations 20, 28,
and 43 are applicable; and using the appropriate group rate
constants and substituent factors listed in Tables 1 and 2,
respectively, gives
kOH = k(l) = k(la) + k(lc)
k(la) = k°.F2(CH3-)F(>CH-) + 2kgF(>CH-)
k(la) = 1.83 (1.00)2(1.29) + 2 (0. 144) (1.29)
k(la) = 2.73
k(lc) = {k°F2(-CH2-)F(>CH-) + 2k§F(-CH2-)F(>CH-)}F(3)
k(lc) = {1.83 (1.29)3 -I- 2(0.838) (1.29)2}(0. 017)
k(lc) = 0.12
kOH = 2.73 + 0.12 = 2.85
k0n[ Estimated] = 2.85 x 10~12cm3molecule~1s~1
kOK[ Experimental] = 2.84 x 10~12 cm3molecule~1s~1 (Table 3.B.)
(100) = 0
Percent Error = (2.85 - 2. 84) /2. 84
IV . B . Haloalkanes
IV . B . 1 . DIPLUOROMETHANB CH2 F2
kOH = k(l) = k(la) = k| F2(F-) = 0.838 (0.099)2
-146-
-------
kOH = 0.821 x 10~2
kOH( Estimated) = 0.821 x I0~14cm3molecule~1s~1
kOH( Experimental) = 1.09 x 10"14cm3molecule~1s~1 (Table 4)
Percent Error = f (0.821-1.09) /1. 09 ](100) = -25
IV. B. 2. 1,1-DIFLUOROETHANE F2CHCH3
kOH = k(l) = k(la) = kg F2(F-) F(CH3-) + k° F(-CHF2)
= 1.83(0.099)2(1.00) + 0.144(0.10)
kOH = 3.23 X 10~2
kOH (Estimated) = 3.23 x 10~14cm3molecule"1s~1
kOH( Experimental) = 3.4 x 10"14cm3molecule~1s~1 (Table 4)
Percent Error = [ (3.23-3.4) /3. 4 ](100) = -5
IV. C. Car bony 1 Compounds
IV. C.I. BUTMIAL CH3CH2CH2CHO
kOH - k(l) = k(la) = k°F(-CH2-) + k§F(CH3-) F[-CH2CH(0)]
+ k|F(-CH2-)F[-CH(0)] + kg F[(0)] F(-CH2-)
kOH = 0.144(1.29) + 0.838(1.00)(4.4)
+ 0.838(1.29)(0.76) + 1.83(8.8)(1.29)
kOH =25.5
kOH(Estimated) = 25.5 x 10~12cm3molecule"1s"1
-147-
-------
kOH( Experimental) = 23.5 x 10~12cm3molecule~1s~1 (Table 5. A.)
Percent Error = [ (25.5-23.5) /23. 5] (100) - +9
IV. C. 2. TRICHLOROACETALDEHYDE C13CCHO
kOH - k(l) = k(la) = kg F[(0)] F(C13C-)
kOH - 1.83 (8.8) (0.09)
kOH = 1.45
kOH( Estimated) = 1.45 x 10"12cm3molecule~1s~1
kOH( Experimental) = 1.73 x 10~12cm3molecule~1s~1 (Table 5. A.)
Percent Error - [ (1.45-1.73) /1. 73 ](100) = -16
IV. C. 3. 2-PENTANONE 0
CH3CCH2CH2CH3
kOH = k(l) = k(la) = k°,F[-C(0)-] + k|F(-CH2-)
k°F(CH3-) F[-CH2C(0)-] 4- k°,F(-CH2-)
kOH = 0.144(0.76) + 0.838(1.29) (0.76)
+ 0.838(1.00) (4.4) + 0.144(1.29)
kOH = 4.81
kOH( Estimated) = 4.81 x 10"12cm3molecule~1s~1
kOH( Experimental) = 4.9 x 10"12cm3molecule~1s1 (Table 5.B.)
Percent Error = [ (4.81-4.9) /4.9J (100) = -2
-148-
-------
IV. C. 4 . CYCLOBUTANONB CH2 CH
CH2 - C=:0
kOH = k(lc) - {k°F[-CH2C(0)-][F(2nd-CH2C(0)-)]
+ 2k°F(-CH2-) P[-C(0)-]>F(4)
kOH - {0.838(4.4) (1.0) + 2(0.838) (1.29) (0.76)}(0. 22)
kOH =1.17
kOH[ Estimated] = 1.17 x 10~12cm3molecule~1s""1
kOH[ Experimental] = 0.87 x 10~12cm3molecule"1s~1 (Table 5.C.)
Percent Error - [(1.17 - 0.87) /O. 87] (100) = +34
0 0
It II
IV.C.5. METHYL GLYOXAL CH3C-C-H
kOH = k(l) = k(la) = k°F[-C(0)-] + k?F(0)F[-C(0) -]
kOH = (0.144) (0.76) + 1.83(8.8) (0.76)
kOH =12.3
kOH (Estimated) = 12.3 x 10"12cm3molecule""1s""1
kOH (Experimental) = 17.2 x 10"12cm3molecule~1s~1 (Table 5.D.)
Percent Error - [ (12.3-17.2) /17. 2] (100) = -28
-149-
-------
0
IV. C. 6. ACBTYL CHLORIDE CH3C-C1
kOH = k(l) = k(la) = k°,F[-C(0)Cl] = 0.144(0.50)
kOH = 0.0720
k0H (Estimated) = 0.0720 x 10~12cm3molecule~1s~1
kOH (Experimental) = 0.068 x 10~12cm3molecule~"1s~1 (Table 5.E.)
Percent Error = [ (0.0720-0.068) / 0.068] (100) = +6
0
il
IV. C. 7. a-PROPYL ACETATE CH3C-OCH2CH2CH3
kOH = k(l) = k(la) = kpF[-C(0)OR] + k|F[-OC(0)R]F(-CH2-)
+ kgF(-CH2-)F(CH3-) + k°F(-CH2-)
kOH = 0.144(0) + 0.838(1.5) (1.29) + 0. 838 (1. 29) (1. 00)
+ 0.144(1.29)
kOH = 2.89
kOH (Estimated) = 2.89 x 10~12cm3molecule"1s~1
kOH (Experimental) = 3.4 x 10~12cm3molecule~1s~1 (Table 5.F.)
Percent Error - [ (2.89-3.4) /3. 4] (100) = -15
IV. D. Alcohols and Glycols
OH
I
IV . D . 1 . 2 -PROPANOL CH3 CHCH3
-150-
-------
Using equation 20
kOH = k(l) + k(2) = k(la) + k(-OH)
k(la) = 2k°)F(>CH-) + k°.F2(CH3-)F(-OH)
k(la) = 2(0.144)(1.29) + 1.83(1.00)2(3.4)
k(la) = 6.59
k(-OH) = 0.036 (Table 1)
kOH = 6.59 + 0.036 =6.63
(Estimated) = 6.63 x 10~12cm^molecule~1s~3-
kOH (Experimental) = 5.21 x 10"12cm3molecule~1s~1 (Table 6.A.)
Percent Error = f (6.63-5.21)/5.21] (100) = +27
IV.D.2. 1,2-ETHANEDIOL HOCH2CH2OH
kOH = k(l) + k(2) = k(la) + 2k(-OH)
k(la) = 2 k|F(-OH)F(-CH2-) = 2(0.838)(3.4)(1.29)
k(la) a 7.35
k(-OH) = 0.036 (Table 1)
kOH = 7'35 + 2(0.036) = 7.42
k0H (Estimated) = 7.42 x 10~12cin3Inoiecu^e-ls-l
-151-
-------
kOH (Experimental) = 7.7 x 10-12CB3molecule-ls-l (Table 6.B.)
Percent Error » [ (7.42 - 7.7J/7.7] (100) = -4
IV . E . Ethers (Acyclic and Cyclic)
IV. E.I. 2-ETHOXYETHANOL
Using equation 20
kOH = k(l) + k(2) = k(la) + k(-OH)
k(la) = k°,F(-CH2-0) + k|F(CH3-)F(-0-)
+ k|F(-CH2-)F(-0-) + k|F(-CH2-)F(-OH)
k(la) = 0.144(4.5) + 0.838(1.00) (6.1)
+ 0.838(1.29) (6.1) + 0.838(1.29) (3.4)
k(la) = 16.03
k(-OH) = 0.036 (Table 1)
kOH = 16.03 + 0.04 = 16.07
(Estimated) = 16.1 x 10~12cm3molecule""1s~1
(Experimental) = 15.4 x 10~12cm3molecule~1s~1 (Table 6.C.)
Percent Error = [ (16.1-15.4) /is. 4] (100) = +5
-152-
-------
IV. E. 2. DIBTHOXYMETHANE CH3CH2OCH2OCH2CH3
kOH = k(la) - 2k°,F(-CH2-0-) + 2k°F(CH3-) F(-O-)
kOH = 2(0.144) (4.5) + 2(0.838(1.00) (6.1) -I- 0. 838 (6. 1) (1. 0)
kOH = 16.6
kOH[ Estimated] = 16.6 x 10~12cm3molecule~1s~1
kOH[ Experimental] = 16.8 x 10~12cm3molecule~1s~1 (Table 6.C.)
(100) = -1
Percent Error = (16.6 - 16.8)/16.8
IV.E.3. 1,2-EPOXYBUTANE CH2—CHCH2CH3
kOH = k(l) = k(la) + k(lc)
Using equation 28 for the CH3CH2- group
k(la) = k°F(-CH2-) + k§F(CH3-)F(>CH-)
k(la) = 0.144(1.29) + 0.838 (1.00)(1.29) = 1.27
Using equation 43 for the three membered epoxide ring
k(lc) = [ k°,F(-0-)F(>CH-) + kgF(-0-)F2(-CH2-)l F(3)
k(lc) =[ 0.838(6.1) (1.29) + 1.83(6.1) (1.29)2 ](0. 017)
k(lc) = 0.43
-153-
-------
= 1.27 + 0.43 = 1.70
kOH (Estimated) = 1.70 x 10~12cm3molecule"1s~1
k0H (Experimental) = 2.1 x 10~12cm3molecule~1s"1 (Table 6.D.)
Percent Error = [ (1.70-2.1)/2.1 ](100) = -19
IV.E.4. OXEPANE (HEXAMETHYLENE OXIDE)
CH2 CH2
Using equation 43 CH2—CHf^
kOH = k(lc) = {2k|F(-CH2-)F(-0-) + 2k|F(-CH2-)F(-CH20-)
+ 2k|F2(-CH2-)}F(7)
*OH = {2(0.838)(1.29)(6.1) + 2(0.838)(1.29)(4.5)
+ 2(0.838)(1.29)2}(1.0)
kOH = 25.7
kOH[Estimated] = 25.7 x 10"12cm3molecule"1s~1
fcoH[ExPer^men^al] ~ !5'4 x 10~12cm3molecule"1s~1 [Table 6.D.]
Percent Error = I (25.7-15.4)/15.4] (100) = +67
IV.F. Nitrates
IV.F.I. 3-METHYL-2-PBNTYL NITRATE ON02
CH3CHCHCH2CH3
CH3
-154-
-------
kOH = k(l) = k(la) = kgF(>CH-ON02) + kgF(-ON02)F(CH3-)F(>CH-)
+ kgF(CH3-)F(-CH2-)F(>CHON02)
+ k°,F(>CH-) + k|F(CH3-)F(>CH-) + k°,F(-CH2-)
= 0.144(0.30) + 1.83(0.18)(1.00)(1.29)
+ 1.83(1.00) (1.29) (0.30) + 0.144(1.29)
+ 0.838(1.00)(1.29) + 0.144(1.29)
kOH = 2.63
kOH (Estimated) = 2.63 x 10~12cm3molecule~1s"1
k0H (Experimental) = 3.02 x 10~12cm3molecule~1s~1 (Table 7.A.)
Percent Error = f (2.63-3.02)/3.02 1(100) = -13
IV.G. Nitriles
IV.G.1. PROPIONITRILE CH3CH2CsN
kOH = k(l) = k(la) = kgF(-CH2CN) + k|F(CH3-)F(-CN)
kOH = 0.144 (0.5) + 0.838(1.00)(0.14)
kQH ~ 0.189
kOH (Estimated) = 0.189 x 10~12cm3molecule"1s~1
kOH (Experimental) = 0.194 x 10~12cm3molecule~1s~1
(Table 7.C.)
Percent Error = [ (0.189-0.194)/O.194)] (100) = -3
-155-
-------
IV.H. Unsubstituted Alkenes (Acyclic and Cyclic)
IV.H.I. l-PBHTENE CH3CH2CH2CH=CH2
Using equation 20 yields
kOH = k(l) + k(3)
where k(l) represents the rate constant for hydrogen
abstraction from a C-H group and k(3) represents the rate of OH
radical addition to the >C=C< group. The rate constant k(l) is
given by the equation
k(l) = k(la) + k(l,UNS CH)
Using equation 28 and the appropriate group rate constants and
substituent factors from Tables 1 and 2 yields
k(la) = k°F(-CH2-) + ks(CH3-)F(-CH2-)
+ k|F(-CH2-)F(>C=C<)
k(la) = 0.144(1.29) + 0.838(1.00)(1.29) + 0.838(1.29)(1.0)
k(la) = 2.3
k(l,UNS CH) = O (Table 1)
k(l) = 2.3 + 0 = 2.3
Using equations 89, 90, and 91 and the appropriate group
rate constant and substituent factors from Tables 9 and 10,
respectively, yields
= kis[RCH=CH2] [C(CH3CH2CH2-)]
-156-
-------
k(3) = 26.3(1.00) = 26.3
kOH = 2.3 + 26.3 = 28.6
(Estimated) = 28.6 x 10~12cm3molecule"1s~1
kOH (Experimental) = 31.4 x 10~12cm3molecule~1s~1 (Table 13.A.)
Percent Error = [ (28.6-31.4)/31.4 ](100) - -9
IV.H.2. 1,4-PENTADIENE CH2=CH-CH2-CH=CH2
kOH = k(l) + k(3)
k(l) = k(la) + 2k(l,UNS CH)
k(la) = k|F2(>C=C<) = 0.838(1.0)2 = 0.8
k(l,UNS CH) = 0
k(l) = 0.8 -I- 2(0) = 0.8
Using equations 89, 90, and 91 and the appropriate group rate
constants and substituent factors from Tables 9 and 10,
respectively, yields
*add,nar = 2kos [CH2=CH-R] [C(-CH2-)] = 2(26.3)(1.00)
k(3) = kadd/nar = 52.6
kOH = 0.8 + 52.6 = 53.4
(Estimated) = 53.4 x 10~12cm3molecule"1s~1
-157-
-------
kOH (Experimental) = 53.3 x 10-12cm3molecule-ls-l (Table 13.A.)
Percent Error = [ (53.4-53.3)/53.3 ](100) = 0
IV.H.3. BICYCLO[2.2.1]-2-HEPTENE
*OH = Ml) •+ *(3)
= k(lc) + k(l,UNS CH)
k(lc) =
k§F2(>CH-) + 2k|F2(-CH2-)F(>C=C<)
2 k|F(>CH-)F(-CH2-)
F2(5)F(6)
k(lc) =
0.838(1.29)2 + 2(1.83)(1.29)2(1.0)
+2(0.838)(1.29)2
(0.80)2(1.0)
k(lc) = (10.3)(0.64) = 6.6
k(l,UNS CH) - 0
= 6.6
6.6
kadd,
nar
RCH=CHR
cis
[C2(cycloalkyl)] = 56.1(1.00)2
k(3) = 56.1
-158-
-------
kOH = 6.6 + 56.1 = 62.7
kOH (Estimated) = 62.7 x 10~12cm3molecule~1s~1
kOH (Experimental) = 49.3 x 10~12cm3molecule~1s~1 (Table 13.B.)
Percent Error = [ (62.7-49.3)/49.3 ](100) = +27
IV.I. Substituted Alkenes
IV.I.I. VINYL BROMIDE CH2=CHBr
^OH = ^ (1) + M 3)
k(l) = k(l,UNS CH) = 0
k(3) = kadd,nar - kis [CH2=CH-R][C(Br-)]
k(3) = 26.3(0.26) = 6.84
kOH = ° + 6.84 = 6.84
(Estimated) = 6.84 x 10~12cm3molecule~1s~1
(Experimental) = 6.81 x 10~12cm3molecule~1s~1 (Table 14)
Percent Error - [ (6.84-6.81)/6.81 1(100) = 0
IV.I.2. trana-2-BUTENAL (trans-CROTONALDEHYDE)
CH3 XH
N,
"CHO
kOH = k(l) + k(3)
-159-
-------
='k(la) + k(l,UNS CH)
k(la) = kg F(>C=C<) + kg F(0) F(>C=C<)
k(la) = 0.144(1.0) + 1.83(8.8) (1.0) = 16.2
k(l,UNS CH) - 0
k(l) = 16.2 + 0 = 16.2
k(3) = kadd/nar =
trans
63.7(1.00)(0.26)
[C(CH3-)] [C(-CHO)]
k(3) - 16.6
kOH = 16.2 +16.6 = 32.8
(Estimated) = 32.8 x 10"12cm3molecule~1s~1
kOH (Experimental) = 36 x 10~12cm3molecule~1s~1 (Table 14)
Percent Error = [ (32.8 - 36)/36 ](100) = -9
IV.I.3. cis-3-HEXENE-2,5-DIONB fcis-1.2-DIACETYLETHYLENE]
V
=9
CH-
OH = k(l) + k(3)
= k(la) + k(l,UNS CH)
-160-
-------
k(la) = 2kgF[-C(0)-] = 2(0.144)(0.76) = 0.22
k(l,UNS CH) = 0
k(l) = 0.2 + 0 = 0.2
M3) = kadd/nar =
kis (RCH=CH-R)
C2[CH3C(0)-]
CIS
k(3) = 56.1(0.91)2 = 46.5
kOH = 0.2 + 46.5 =46.7
kOH (Estimated) = 46.7 x 10~12cm3molecule~1s~1
kOjj (Experimental) = 63.1 x 10~12cm3molecule~1s""1 (Table 14)
Percent Error = [ (46.7-63.1)/63.1 ](100) = -26
IV.I.4. TETRACHLOROETHENE
Cl /Cl
C1X SC1
kOH = k(l) + k(3)
k(i) = o
JV I J J ~" •**a/^*^ n Sk 1* "™" *»rt L **O **™~^**O J- L» V»^^J I
* ' duu f ricirr \j ** & £J *• * «J
k(3) = 110(0.2)4 = 0.176
kOH = 0 + 0.176 = 0.176
kOH (Estimated) = 0.176 x 10~12cm3molecule""1s"1
-161-
-------
kOH (Experimental) = 0.167 x 10-12cm3molecule-ls-l (Table 14)
Percent Error = [ (0.176-0.167) /0. 167 1(100) = +5
IV. I. 5. ACRYLONITRILE CH2=CH-CsN
kOH = k(l) + k(3)
k(l) - k(l,UNS CH) = 0
k(3) " *add,nar = kis(CH2=CH-R) [C(-CN) ]
k(3) = 26.3(0.15)
k(3) = 3.95
kOH = 0 + 3.95 = 3.95
(Estimated) = 3.95 x 10~12cm3molecule""1s~1
kOH (Experimental) = 4.1 x 10"12cm3molecule~1s~1 (Table 14)
Percent error = [ (3.95-4.1) /4.1 ] (100) = -4
IV. I. 6. METHYL KETENE
CHCH=C=O
k(l) = k(la) + k(l, UNS CH)
k(la) = k°,F(>C=C<) = 0.144 (1.0) = o.l
-162-
-------
k(l, UNS CH) = 0
k(l) = 0.1 + 0 = 0.1
M3) = *add,nar = 4S(-CH=C<) [C(=0) ]
k(3) = 86.9 (1.0) - 86.9
kOH = 0.1 + 86.9 - 87.0
kOH[Estimated] = 87.0 x 10~12cm3molecule"1s~1
JcOHtExPer^mentalJ = 70 x 10""12cm3molecule~1s~1 [Table 14.B.]
Percent error = [(87.0-70)/70] (100) - +24
IV.J. Conjugated Diolefins
IV.J.I. £is-l,3-PBNTADIBNB
V/>ij /"*tJ
v-ii x 3
HX NH
kOH -
k(l) = k(la) + 2 k(l,UNS CH)
k(la) - kgP(>O=C<) = 0.144(1.00) =0.1
k(l,UNS CH) = 0
k(l) = 0.1 + 2(0) = 0.1
-163-
-------
Using the appropriate group rate constants and substituent
factors from Tables 11 and 10, respectively, yields
= k§°(CH2=CH-CH=C-R) [C(CH3-)]
= 105(1.00) = 105
kOH - 0.1 + 105 = 105
(Estimated) = 105 x 10~12cm3molecule~1s~1
kOH (Experimental) = 101 x 10"12cm3molecule"1s""1 (Table 15)
Percent error - [ (105-101) /101 ](100) = +4
IV . J . 2 . 1,3 -CYCLOHEXADIENE
H
kOH = k(l) + k(3)
= k(lc) + 2k(l,UNS CH)
k(lc) = [ 2k|F(-CH2-)F(>C=C<)] F(6)
= [ 2(0.838) (1.29) (1.0)] (1.00)
k(lc) = 2.2
k(l,UNS CH) = 0
k(l) = 2.2 + 2(0) = 2.2
-164-
-------
= kadd,nar = kS°[R-CH=CH-CH=CH-R] [C2(-CH2-]
k(3) = 135(1.00)2 » 135
kOH - 2.2 + 135 = 137
kOH (Estimated) = 137 x 10~12cm3molecule~1s~1
kOH (Experimental) = 164 x 10~12cm3molecule~1s~1 (Table 15.B.)
Percent Error = [ (137-164)/164 ](100) = -16
IV.J.3. 2,5-DIMETHYL-2,4-HEXADIENE (CH3)2C=CH-CH=C(CH3) 2
kOH - k(l) + k(3)
k(l) = k(la) + 2k(l/UNS CH)
k(la) = 2[2k°F(>C=C<)] = 2(2)(0.144)(1.0)
k(la) - 0.6
k(l,UNS CH) = 0
k(l) = 0.6 + 2(0) = 0.6
k(3) " kadd,nar = Jcg°[RRC=CH-CH=CRR] [C4(CH3-)]
k(3) = 230(1.OO)4 = 230
kOH = 0.6-1- 230 = 231
k0H (Estimated) = 231 x I0~12cm3molecule~1s~1
-165-
-------
kOH (Experimental) = 210 x 10-12cm3molecule-ls-l (Table 15. A.)
Percent Error - [ (231-210) /210 ](100) = +10
IV. J. 4. 4-METHYL-l,3-PENTADIENB CH2=CH-CH=C(CH3) 2
kOH = k(l) + k(3)
= k(la) + 2k(l,UNS CH)
k(la) = 2k°F(>C=C<) = 2(0.144) (1.0) - 0.288
k(la) = 0.3
k(l,UNS CH) - 0
k(l) = 0.3 + 2(0) = 0.3
*(3) = *add,nar = k°°[CH2=CH-CH=CRR] [C2(CH3-)] = 135(1. 00) 2
k(3) = 135
kOH = 0.3 + 135
kOH (Estimated) = 135 x 10"12cm3molecule~1s"1
kOH (Experimental) = 131 x 10~12cm3molecule~1s~1 (Table 15. A.)
Percent Error = [ (135-131) /131 ] (100) » +3
IV. K. Alkvnes
IV. K.I. 1-BUTYNB CH3CH2CsCH
-166-
-------
+ k(3)
k(la) + k(l,UNS CH)
k(la) = kgF(-CH2-) + ksF(CH3-)F(-CsC-)
k(la) - 0.144(1.29) + 0.838(1.00) (1.0)
k(la) - 1.02
k(l/UNS CH) = 0
k(l) = 1.02 + 0 = 1.02
Using the appropriate group rate constants and substituent
factors from Tables 12 and 9, respectively, yields
k<3) - kadd,nar = *§U(R-C*CH) [C(CH3-)] = 6.4(1.00)
k(3) = 6.40
kOH = 1.02 + 6.40 = 7.42
kOH (Estimated) = 7.42 x 10"12cm3molecule~1s~1
k0H (Experimental) = 8.0 x 10~12cm3molecule~1s~1 (Table 16. A.)
Percent Error - [ (7.42-8.0) /8.0 ] (100) = -7
IV.L. Allenes
IV.L.I. 1,2-PENTADIBNB CH2=C=CH-CH2CH3
-167-
-------
kOH = k(l) + k(3)
k(l) = k(la) + k(l,UNS CH)
k(la) = k°F(-CH2-) + k°,F(>C=C<)F(CH3-)
k(la) = 0.144(1.29) + 0.838(1.0) (1.00)
k(la) = 1.0
k(l,UNS CH) = 0
k(l) = 1.0 + 2(0) = 1.0
k(3) = kadd,nar = k§u[RCH=C=CH2][C(CH3CH2-)]
Using the appropriate group rate constants and substituent
factors from Tables 12 and 9, respectively, yields
k(3) = 31(1.00)
k(3) = 31.0
kOH = 1.0 + 31.0 = 32.0
kOH (Estimated) = 32.0 x 10~12cm3molecule~1s~1
kOH (Experimental) = 35.5 x 10~12cm3molecule~1s~1 (Table 16.B.)
Percent Error - f (32.0-35.5)/35.5 ](100) = -10
IV.M. Thiols. Sulfides. and Disulfides
IV.M.I. 2-METHYL-l-PROPANETHIOL (CH3)2CHCH2SH
-168-
-------
From equation 20
kOH = k(l) + k(4)
- k(la) - 2k°F(>CH-) + k°F2 (CH3-)F(-CH2-)
+ kgF(>CH-)F(-SH)
k(l) = 2(0.144) (1.29) + 1.83(1.00)2(1.29) + 0. 838 (1. 29) (9 . 0)
k(l) - 12.5
k(5) = k(-SH) = 31 (Table 1)
kOH = 12.5 + 31 = 43.5
kOH (Estimated) = 43.5 x 10~12cm3molecule~1s"1
kOH (Experimental) = 45 x 10~12cm3molecule~1s~1 (Table 18. A.)
Percent Error - [ (43.5 - 45) /45 ] (100) = -3
IV.M.2. TETRAHYDROTHIOPHENE
CH2 CH2
,2 ,2
CH2 CH2
Calculation of kQH in the absence of 02 >>s
= Ml) + M4)
- k(lc) - [2kgF2(-CH2-) -I- 2kgF(-CH2-)F(-S-)3F(5)
k(l) = [2(0.838)(1.29)2 + 2(0.838)(1.29)(9.0)](0.80)
k(l) - 17.8
-169-
-------
k(5) - k(-S-) = 0 (Table 1)
kOH = 17.8 + 0 » 17.8
kOH (Estimated) - 17.8 x 10~12cm3molecule~1s~1
kOH (Experimental) = 19.7 x 10~ cm3molecule~1s~1
(Table 18. B. 2.)
Percent Error - [ (17. 8-19. 7) /19. 7 ](100) - -10
IV. M. 3. DIMETHYL DISULFIDE CH3-S-S-CH3
kOH = k(l) + k(4)
k(l) = k(la) - 2k°,F(-S-S-) = 2 (0.144) (9.0)
k(l) = 2.59
k(5) = k(-S-S-) - 200 (Table 1)
kOH = 2.6 + 200 = 203
kOH (Estimated) - 203 x 10~12cm3molecule~1s"1
k0u (Experimental) = 211 x 10~12cm3molecule~1s~1 (Table 18. C.)
Percent Error =( (203-211) /2li ](100) = -4
IV. H. Compounds Containing Nitrogen Functional Groups
IV . N . 1 . DIMETHYLHYDROXYETHYLAMINE ( CH3 ) 2NCH2 CH2OH
-170-
-------
= k(la) = 2k°F(>N-) + k°F(>N-)F(-CH2-)
+ kjF(-CH2-)F(-OH)
k(l) = 2(0.144)(10) + 0.838(10)(1.29) + 0.838(1.29)(3.4)
k(l) = 17.4
k(2) = k(-OH) = 0.036 (Table 1)
k(4) = k(>N-) = 60 (Table 1)
kOH = 17.4 + 0.04 + 60 = 77.4
kOH (Estimated) = 77.4 x 10~2cm3molecule"1s"1
kOH (Experimental) = 90 x 10~12cm3molecule~1s~1 (Table 19.A.)
Percent Error = [ (77.4-90)/90 ](100) = -14
IV.N.2. DIMETHYL-N-NITROSAMINE (CH3)2N-NO
kOH = k(l) + k(5)
k(l) = k(la) = 2k°F(>N-NO) » 2(0.144)(10)
k(l) = 2.88
k(4) = k(>M-NO) = 0 (Table 1)
kOH = 2.88 + 0 - 2.88
kOH (Estimated) = 2.88 x 10~12cm3molecule~1s~1
-171-
-------
(Experimental) = 2.53 x 10-12 Cm3molecule~1s~1
(Table 19. c.)
Percent Error = [ (2.88-2.53) /2. 53 ] (100) - +14
IV. N. 3. METHYL HYDRAZINB CH3NHNH2
koH = k(l) + k(5)
k(l) = k(la) = kgF(>NH) - 0.144(10) = 1.44
k(4) = k(CH3NH-) + k(-NH2)
k(4) =60+20 (Table 1)
k(4) = 80
JCQH = 1.4 + 80 - 81.4
kOH (Estimated) = 81.4 x 10-12cm3molecule-1s-1
koH (Experimental) - 65 x 10"12 ^molecule'^-s'1 (Table 19. E.)
Percent Error - f (81. 4-65) /65 ](100) - +25
IV. N . 4 . DIBTHYL-N-HYDROXYLAMINE ( CH3CH2 ) 2N-OH
= k(la) - 2[ kpF(-CH2-) + kgF(CH3-)F(>NOH)
k(l) = 2[0. 144(1. 29) + 0.838(1.00) (10) ] - 17.14
-172-
-------
k(2) = 0.036 (Table 1)
k(4) = k(>H-) - 60 (Table 1)
a 17.14 + 0.04 + 60 = 77.2
(Estimated) = 77.2 x 10"12 cm3molecule"1s"1
kOH (Experimental) * 101 x 10~12 cm3molecule~1s~1 (Table 19.B.)
Percent Error = [ (77.2 - 101)/101 ] (100) =• -24
IV.O. Compounds Containing Phosphorus Functional Groups
IV.0.1. TRIETHYL PHOSPHATE (CH3CH2O)3P=O
kOH = k(l) + k(6)
k(l) = k(la) = 3[k°,F(-CH2-0-) + k°,F(CH3-)F(O-P<) ]
k(l) a 3[0.144(4.5) -I- 0.838(1.00) (20)]
k(l) = 52.2
k(6) = k[P(0)] - 0 (Table 1)
koH = 52.2 + 0 = 52.2
kOH (Estimated) = 52.2 x 10"12cm3molecule~1s~1
kOH (Experimental) = 55.3 x 10"12cm3molecule~1s"1 (Table 20.A.)
Percent Error = [ (52.2-55.3J/55.3 1(100) = -6
-173-
-------
IV.0.2 O,O-DIMBTHYL CHLOROPHO8PHOROTHIOATB
S
II
(CH30)2P-C1
kOH = k(l) + k(6)
k(l) = k(la) = 2[kpF(-0-P<)] = 2(0.144)(20)
k(l) - 5.76
k(6) - k[P(S)] + k[P-Cl]
k(6) =55+0 (Table 1)
k(6) =55
kOH = 5.8 + 55 = 60.8
)CQH (Estimated) = 60.8 x 10~12cm3molecule~1s~1
JCQJI (Experimental) = 59.0 x 10"12cm3molecule~1s~1 (Table 20.B.)
Percent Error = [ (60.8-59.0)/59.0 1(100) = +3
IV.0.3 0,O,H-TRIMBTHYL PH08PHOROAMIDOTHIOATE
S
(CH30)2P-NH-CH3
k(la) = 2[kg(-0-P<)] + kgF(>NH)
-174-
-------
k(l) = 2(0.144)(20) + 0.144(10)
k(l) - 7.2
k(4) = k(>NH) = 60 (Table 1)
k(6) - k[P(S)] - 55 (Table 1)
kOH «- 7.2 + 60 + 55 - 122
(Estimated) - 122 x 10~12cm3molecule~1s~1
kOH (Experimental) = 233 x 10"12cm3molecule~1s~1 (Table 20.C.)
Percent Error - [ (122-233)/233 ](100) = -48
IV.P. Aromatic Compounds
IV.P.I. TOLUENE
Using equation 20
k(OH) = k(l) + k(7) = k(l) + kadd/ar
k(l) = k(la) -«• k(l,UNS CH)
k(l) = kgF(-C6H5) = 0.144(1.0) = 0.14
k(l, UNS CH) - 0
-175-
-------
k(l) = 0.14 + 0 - 0.14
Using equations 127 and 128 and the appropriate values of a+
from Table 22
logic* add,ar * °-31 ' 1-35
a+(CH3-) = -0.066 ; a+(CH3-) - -0.311 (Table 22)
From rule 2, page 112 a£(CH3-) = a£(CH3-) - -0.311
From the molecular structure shown above and symmetry
= aJ(CH3-) - -0.311
=, a+(CH3-) = -0.066
a+(CH3-) - -0.311
Using the most negative value of £
-------
IV.P.2. trans-1-PHENYL-l-PROPENE
H(l)
kOH =
k(3) + k(7) =
H(2)
k(3)
= k(la) + 2k(l,UNS CH)
k(la) = kpF(>C=C<) » 0.144(1.0) = 0.14
k(l,UNS CH) = 0
k(l) = 0.14 -f 2(0) = 0.14
As proposed by Atkinson (1987) , it is assumed that there is no
interaction between the two carbon-carbon double bond systems
so that the OH radical adds separately to the alkene group and
the benzene ring. Using equations 90 and 91
= kadd,nar =
k(3) = kis [RCH=CHR ] [C(CH3-)c(c6H5-)]
1 J
trans
k(3) = 63.7(1.00) (1.00) = 63.7 (Tables 9 and 10)
From Table 22
ajj(CH2=CH-) =0.02
-177-
-------
a+(CH2=CH-) = aJ(CH2=CH-) =0.02
From the molecular structure shown above and symmetry for the
benzene ring
-) =0.02
= +
= <7(CH2=CH-) =0.02
= 53a+(4) = a+(CH2=CH-) = 0.02 (most negative)
*add,ar = °-31 - 1.35(0.02)
* add , ar = 1 . 9
kOH = 0.1 + 63.7 4- 1.9 = 65.7
kOH (Estimated) = 65.7 x I0~12cm3molecule~1s~1
k0H (Experimental) = 59 x 10~12cm3molecule~1s~1 [Table 23. C.]
Percent Error = [ (65.7-59)/59 ] (100) = +11
IV . P . 3 . 4 -CHLOROBBNZOTRIFLUORIDB
Cl
H(3) i
o
r"
CF3
kOH = *(l) + k(?) = k(1) + k'add,ar
-178-
-------
k(l) = k(l,UNS CH) = 0
a+(Cl-) - 0.399 a+(CF3-) = 0.52
a+(Cl-) = aJ(Cl-) = 0.114 a+(CF3-) - aJ(CF3-) = 0.612
From the above molecular structure and symmetry
) = 0.612 + 0.399 = 1.011
) + a+(CF3-) = 0.114 + 0.52 = 0.634
(most negative)
I°9l0kadd,ar = °-31 - 1-35(0.634)
kadd,ar = °-285
kOH = ° +0.285 = 0.285
kOH (Estimated) = 0.285 x 10~12cm3molecule"1s~1
kOH (Experimental) = 0.24 x 10~12cm3molecule~1s~1 (Table 23. E.)
Percent Error = [ (0.285-0.24) /0. 24 ](100) » +19
IV. P. 4. 1,2,4-TRICHLOROBENZENE
Cl
OH = k(l) + k(7) = k(l) + k'add/ar
-179-
-------
k(l) = k(l,UNS CH) = 0
aJ(Cl-) = 0.399; aJ(Cl-) » a+(Cl-) = 0.114
From the molecular structure
= 2a+(Cl-) + aJ(Cl-) =2(0.114) + 0.399 = 0.627
= aJ(Cl-) -I- a+(Cl-) + aJ(Cl-) = 2(0.114) + 0.399
= 0.627 (most negative)
£CT+(3) = a+(Cl-) -I- 2ffJ(Cl-) = 0.114 + 2(0.399) = 0.912
Iog10 *-add/ar = 0.31 - 1.35 (0.627)
k'add,ar = °-291
kOH = ° + 0-291 = 0.291
kOH (Estimated) = 0.291 x 10~12cm3molecule~1s"1
kOH (Experimental) = 0.532 x 10~12cm3molecule~1s~1
(Table 23.D.)
Percent Error - [ (0.291-0.532)/0.532 ](100) = -45
-180-
-------
IV.P.5. o-CRESOL
OH
H(2)
kOH = k(l) + k(2) + k(7) = k(l) + k(2) + k'add/ar
k(l) = k(la) + k(l,UNS CH)
k(la) - k°F(C6H5-) = 0.144(1.0) = 0.144
k(l,UNS CH) = 0
k(l) = 0.14 + 0 = 0.14
k(2) = k(-OH) = 0.036
= 0.121 a+(CH3-) = -0.066
= -0.92 a+(CH3-) = -0.311
= a'I'(-OH) = -0.92 ffj"(CH3-) = a+(CH3-) = -0.311
^ ft ^J ^J '
From the molecular structure shown above
r+f-
= a+(CH3-) + a(~OH) = -0.311 + 0.121 = -0.190
Va+(2) = a+(CH3-) + <7p(-OH) = -0.066 - 0.92 = -0.986
£a+(3) - aJ(-OH) + a+(CH3-) = ^a+(D = -0.190
-181-
-------
= -0.986
(most negative)
l°9lokadd,ar = °*31 " i-35^0
kadd,ar = 43.8
kOH = 0.14 + 0.04 + 43.8 = 44.0
KQH (Estimated) = 44.0 x 10""12cm3molecule~1s"1
kOH (Experimental) = 42 x 10-12cm3molecule-1s~1 (Table 23. G.)
Percent Error = [(44.0-42) /42] (100) = +5
IV. P. 6. ANILINE
H(3)
kOH = k(l) + k(5) + k(7) = k(l) + k(5)
k(l) = k(l,UNS CH) - 0
k(5) = k(-NH2) - 20 (Table 1)
-0.16
(Table 22)
-1.3
-182-
-------
From the above molecular structure and symmetry
= -1.3
aJ(-NH2) = -0.16
= a + (-NH2) = -1.3 (most negative)
I°9l0kadd,ar " °-31 ~ l-35(-1.3)
kOH = 0 + 20 + 116 = 136
k0jj (Estimated) = 136 x 10~12 cm3molecule"1s~1
kOH (Experimental) = 111 x 10~12cm3molecule~1s~1 (Table 23.1.)
Percent Error = [ (136-111) /111 ](100) = +23
IV . P . 7 . HEXAFLUOROBENZENE
kOH = k(l) + k(7) = k(l) -f kadd/ar
k(l) = k(l,UNS CH) = 0
= 0.352; ^J(F-) = ffJ(F-) = -0.073
-183-
-------
From symmetry and the above molecular structure
For a completely substituted benzene, all the positions are
considered. Therefore, for a+(l) we have
Position No.
(1) (2) (3) (4) (5) (6)
E°+'
o m p ' m o
Using rule 5, p. 113, the ipso position is the (1) position so
that a+(l) = a+(F-). Therefore
= *i(F-) + ffJ(F-) + ^J(F-) + ^(F-) + ffJ(F-) + aJ(F-)
- 3aJ(F-) + 2aJ(F-) + aJ(F-)
= 3(0.352) + 2(-0.073) + (-0.073) = 0.837
Furthermore,
a+(2) = \^a"l"(3) = 5^cr"l"(4) = Y^a+(5) = T^a+(6) = 0.837
Since this is the only value, it is the most negative value;
Iogi0kadd,ar = °-31 " 1-35(0.837)
^ add,ar = u'15^
kOH = 0 + 0.151 = 0.151
kOH (Estimated) = 0.151 x 10~12cm3molecule~1s~1
-184-
-------
kOH (Experimental) = 0.172 x 10-l2cm3molecule-ls-l
(Table 23. D.)
Percent Error - [ (0.151-0.172) /0. 172 ](100) » -12
IV.P.8. 2,3-DIHYDROBENZOFURAN
H(4)
OH
k(7)
+ k'add/ar
= k(lc) + k(l,UNS CH)
For the five-membered heterocyclic ring
k(lc) = [k°F(-CH2-0-)F(C6H5-) + k°F(-CH2-)F(-0-)]F(5)
k(lc) = [0.838(4.5)(1.0) + 0.838(1.29)(6.1)](0.80)
k(lc) = 8.3
k(l,UNS CH) = 0
k(l) = 8.3 + 0 = 8.3
ffm(~CH2") = -0.064
a+(-0-) = 0.047
ff£(-CH2-) = aJ(-CH2-) = -0.295
a+(-O-) = a+(-0-) = -0.778
= aJ(-CH2-)
-O-) = -0.295 + 0.047 = -0.248
-185-
-------
(-CH2-) + ff(-O-) = -0.064 - 0.778 = -0.842
$>+(3) = a^(-O-) + cr£(-CH2-) = J>+(1) = -0.248
= -0.842
(most negative)
°-31 - 1.35(-0.842)
kadd,ar = 28.0
kOH =8. 3+ 28.0= 36. 3
(Estimated) = 36.3 x 10-12cm3molecule~"1s-1
kOH (Experimental) = 36.6 x 10~12cm3molecule-1s-1 (Table 23. J.)
Percent Error = [ (36.3-36.6) /36. 6 1(100) = -1
IV . P . 9 . 3 -CHLOROBIPHENYL
Ring A Ring B
kOH = k(l) + k'addfar(Ring A) + k-add,ar(Ring B)
k(l) = 2k(l,UNS CH) =2(0) =0 for both rings
-186-
-------
For Ring A
+-
a(-C6H4Cl) = 0.25
a+(-C6H4Cl)
=0.02
From Symmetry
J>+(5) = aJ(-C6H4Cl) = 0.02
$>+(2) o £a+(4) = a+(-C6H4Cl) = 0.25
J)a+(3) = a+(-C6H4Cl) =
0.02 (most negative)
Iog10k'add/ar (Ring A) = 0.31 - 1.35(0.02)
kadd,ar (Rin? A) " i-
For Ring B
H(2)
Cl
") = 0.399
-187-
-------
a+(C6H5-) = aJ(C6H5-) = -0.179 aJ(Cl-) = a+(Cl-) = 0.114
) + a(Cl-) = -0.179 + 0.114 = -0.065
J(Cl-) + ffJ(C6H5-) = J>+(1) = -0.065
) = °'109 + 0.399 = 0.508
J>+(4) = a+(C6H5-) + aJ(Cl-) = ^a+(l) = -0.065
* (most negative)
B) - 0.31 - 1.35(-0.065)
kadd,ar(Rin
-------
k(l) = 0.1 + 2(0) = 0.1
Using equation 138 for OH radical addition to the aromatic ring
lo
-------
IV . P . 1 1 . 1,4 -DICHLORONAPHTHALENE
OH
kOH
K(8)
-I- k
add,PAH
k(l) = k(l, UNS CH) = 0
IP = 8.13 eV for naphthalene [Weast (1976 - 1977)]
Cl
H(l)
H(2)
Cl
From Table 22
-) = ap-(Cl-) = 0.114
-) = 0.399
-) = 0.513
= 0.513 (most negative)
k'add,PAH = 10-H " 1.08(8.13) - 1.35(0.513)
k'add,PAH
= 4-37
kOH = 0 + 4.37 = 4.37
kOH [Estimated] = 4.37 x 10~l2cm3molecule~ls~l
k0H [Experimental] = 5.8 x 10""l2cm3molecule~ls~l (Table 24)
Percent Error = [ (4.37-5.8)/5.8] (100) - -25
V. Tropospheric Half-Life
The half-life in the troposphere, t(i/2)E' *-s 9iven bV
equation 7 which is
-190-
-------
t(l/2)E " 0.693/kOH(OH) (141)
where k0n is the instantaneous rate constant for the reaction
of an organic chemical with hydroxyl radicals in the units
cm3molecule"1s~1 and (OH) is the hydroxyl radical concentration
in the units molecules (or radicals) cm"3. Equation 141
represents an instantaneous half-life. However, in the
troposphere, (OH) represents an average concentration which is
a function of a number of variables such as season, time-of-
day, temperature, altitude, and geographical location. To use
equation 141, an average OH concentration (OH) over these
variables is needed.
Based on the modeling work of Crutzen (1982), Atkinson
(1986) recommended that the seasonally and diurnally averaged
hydroxyl radical concentrations at 298 K should be:
5 x 105 molecules cm"3 in the northern hemisphere;
6 x 10^ molecules cm"3 in the southern hemisphere.
Prinn et al. (1987) made a recent estimate of the average
global OH concentration using the latest kinetic data on the
disappearance of methylchloroform [CH3CC13]. These researchers
used 7 years of analytical data on the concentration of
methylchloroform in the troposphere (approximately 60,000
measurements). Because the reaction of hydroxyl radicals is
known to be a major loss for atmospheric methylchloroform,
these scientists were able to deduce the concentration of OH
radicals by combining measured trends in the methylchloroform
-191-
-------
levels in the troposphere with the industrial emissions of that
chemical. Based on the data of Prinn et al. (1987), Atkinson
[in Arey et al. (1989) and Atkinson et al. (1990)] estimated
that the diurnally and annually averaged 12-h daylight hydroxyl
radical concentration is
(OH) = 1.5 x 106 molecules(radicals)cm"3 (142)
Atkinson [in Arey et al. (1989)] measured the diurnal
concentrations of 8 volatile polycyclic aromatic hydrocarbons
(naphthalene, 1- and 2-methylnaphthalene, acenaphthylene,
biphenyl, acenaphthene, fluorene, and phenanthrene) with 12-h
daytime and 12-h nighttime sampling intervals over a 9-day
period in August 1986 at Glendora, California. Based on these
ambient concentrations and the known second-order rate
constants for the reaction of these polyaromatic compounds with
hydroxyl radicals, the average ambient hydroxyl radical
concentration was found to be 2.2 x 106 molecules-cm"3 which
agreed reasonably well with the average hydroxyl radical
concentration given in equation 142.
Using the(OH)radical concentration defined in 142 as the
best seasonal and diurnal value at 298 K in equation 141 yields
t(1/2)E(s) - £^613—_
I fcoH(cm''*mo^ecu^e~ls~1)j ( OH (molecules cm"3)]
t(l/2)E(d> "
^ 0.693
kOH(cm;imolecule";Ls~1)] [ 4.32 x lO^sd"1] [ 1.5 x 105molecules cnT
-192-
-------
10.7 X 10~12 (143)
koufcm^moiecuie^s'1)]
Thus, with the value of k0g in cm-^molecule^s'1, either measured
experimentally or estimated by S/R methods at 298 K, the
tropospheric half-life (in a 12-h daylight day) can be estimated
using equation 143. Since the average temperature in the
troposphere is less than 298 K, the use of k0H at 298 K will
introduce some error in the estimation of t(i/2)E* Furthermore,
for chemicals in the troposphere with t^^JE ^ 1 daY» (i«e.,
with t/2/2)E which is short relative to the mixing time in the
troposphere) the use of an average OH concentration will lead to
an additional error. Hence, t(i/2)E represents an approximate
value, especially when t/T/2\E ^ ! day.
VI. Screening-Level Test Guideline: Estimation of KOH and
t(l/2)E for a Chemical (S) Produced by Chemical Company X
via the Estimation Techniques of Atkinson
In order to illustrate the use of the S/R relationships
developed by Atkinson for estimating kQH and t/i/2\E under
Section 4 of TSCA, the following hypothetical scenario is
postulated. Chemical Company X manufactures a wide range of
dyes for the textile, carpet, paper, and photographic
industries. This chemical company is currently manufacturing a
solvent 2,3-difluoro-4-[l-methylpropyl]nitrobenzene (S) for use
in the manufacture of a number of disperse dyes used in the
textile and carpet industries.
-193-
-------
The manufacturing plant is located at 32.5° N. latitude in
the northwest corner of Louisiana on Cross Lake, just west of
Shreveport. The plant manufactures 2 million kg of S per year
which is used as an "on-site" solvent. This chemical is
manufactured and used continuously throughout the year except
for two weeks at the end of December when the plant is closed
for maintenance and repairs.
The plant contains primary and secondary treatment
facilities; the solid and solvent wastes are incinerated while
the aqueous wastes are discharged into Cross Lake. Because the
plant is operated at relatively high temperatures and is not
"completely closed", chemical S vapors escape into the
atmosphere during manufacturing and use of the solvent.
Since S volatilizes to the troposphere, it is important to
determine the chemical fate of this chemical in this
environmental compartment.6 Thus, screening-level tests in the
hierarchal test scheme developed by Leifer [USEPA (1989a)] will
be used as the first step in determining the chemical fate of S
in the troposphere. Since the chemical can react with hydroxyl
radicals, the S/R relationships of Atkinson will be used to
estimate )CQJJ and t(i/2)E*
Chemical S has the following molecular structure
6 It should be noted that S is also discharged into Cross Lake
so that the environmental fate in aquatic media would also
be needed. However, for the purposes of this report, the
environmental fate in freshwater media will'not be considered,
-194-
-------
CH3CHCH2CH3
(144)
H(2)
1
N02
Using equation 20,
kOH = k(l) + k(7) (145)
where: k(l) represents the rate constant for H-atom abstraction
from the secondary butyl group and from the aromatic ring by OH
radicals; and k(7) represents the OH- radical addition to the
aromatic ring.
The rate constant k(l) is given by the relationship
k(l) = k(la) + k(l,UNS CH) (146)
Using equation 28 and the appropriate group rate constants and
substituent factors listed in Tables 1 and 2, k(l) can be
calculated as follows:
k(la) = k°,F(>CH-) +
+ k|F(CH3-)F(>CH-) + k°F(-CH2-) (147)
For the purposes of this calculation, it is assumed that
F(C6H2F2N02-) = 1.0.
k(la) = 0.144(1.29) + 1.83(1.00) (1.0) (1.29)
-I- 0.838(1.00) (1.29) + 0.144(1.29)
-195-
-------
k(la) - 3.82 (148)
Since H-atom abstraction from a benzene ring does not occur,
even at elevated temperatures, it is safe to assume that C-H
abstraction from (C6H2F2NO2-) in S at 298 K will also be
negligible. Hence,
k(l,UNS CH) = 0
k(l) = 3.82 + 0 - 3.82
k(l) = 3.82 (149)
Using equation 18 for the addition of OH radicals to the
benzene ring, one obtains
= kadd,ar
and using equations 127 and 128 yields
I°gi0kadd,ar = °*31 " 1*35
where kadd,ar = lol2kadd,ar <152)
Using equation 151 and the molecular structure of S
depicted in 144, k' ,, can be calculated as follows:
c add , ar
Using the rules on pages 107 and 113 and the appropriate
electrophilic substituent constants a+
<7m(-CH<) = -0.060 <7+(F-) = 0.352 <7m(N02-) = 0.674
-0.280 ^p(F-) = -0.073 a^(N02-) = 0.790
-196-
-------
obtained from Table 22 gives
= a+(-CH<) + a+(F-) + a£(F-) + a+(N02-) (153)
= -0.280 + 0.352 + (-0.073) + 0.674 = 0.673 (154)
= a+(N02-) + ai(F-) + a+(F-) + a^(-CH<) (155)
= 0.790 + 0.352 + (-0.073) + (-0.060) = 1.01 (156)
Comparing the values of ^a(l) and ^a(2) given in 154 and
156, it is evident that J^a+(l) represents the most negative
value so that k' , can be calculated using equation 151 as
follows:
Io9 k'add,ar = °-31 - 1-35(0.673)
kadd,ar = °-252 d57)
Using the results from 149 and 157 in equation 145 gives
kOH = 3.82 + 0.252 =4.07
and multiplying this result by the factor 10~12 yields
kOH (Estimated) = 4.07 x 10~12cm3molecule"1s""1 (158)
and substituting the result of equation 158 in equation 143
yields
10.7 x 10~12
t(l/2)E(d) = - — (159)
4.07 X 10~12
t(l/2)E = 2-6 d ^in 12~n daylight days) (160)
-197-
-------
For the purposes of this report, let us assume that direct
photoreaction and reaction with ozone are negligible for
chemical S (i.e., k^g = kg- - 0). Since kgjj (Estimated) is
equal to 4.07 x 10"~12 cm3molecule"1s"1, OH radical reaction with
S is the dominant transformation mode in the troposphere.
Therefore, an upper-tier test guideline shall be used to
determine kOH . Consequently, Test Guideline § 796.3950 {Leifer
[USEPA (1989a)} shall be carried out using the relative rate
technique in a Teflon bag to measure kOH for S.
VII. Mathematical Synopsis of the Structure/Reactivity
Relationships of Atkinson
Atkinson (1986, 1986a, 1987, 1987b, 1988, 1988a), based on
a detailed analysis of the rate data for the reaction of
hydroxyl radicals (OH) with organic chemicals in the gas-phase,
postulated that the overall second-order rate constant (k0jj,
cm3molecule~1s~1) at 298 K is given by the mathematical
relationship
8
kOH * E *<*) (161)
where k(i) represents the second-order rate constant for pathway
8
(i) in the units cm3molecule~1s~1 at 298 K and £, represents
i = 1
the summation over 8 possible reaction pathways.
Pathway 1: H-atom abstraction from acyclic and cyclic
saturated and unsaturated C-H groups by OH
radicals
The overall rate constant for reaction pathway 1 is given
by the equation
-198-
-------
Jc(l) = k(la) + k(lc) + k(l, UNS CH) (162)
where k(la) represents the rate constant for H-atom abstraction
from all acyclic saturated C-H groups by OH radicals at 298 K;
k(lc) represents the rate constant for H-atom abstraction from
all cyclic saturated C-H groups by OH radicals at 298 K; and
k(l, UNS CH) represents the rate constant for H-atom
abstraction from all unsaturated C-H groups (e.g.,=c-H) by OH
radicals at 298 K.
The rate constant k(la) is given by the mathematical
relationship
k(la) = £ k°Fi(X) + £ kiFj(X)Fj(Y)
j(a) (163)
*?Fm(X)Fm(Y)Fm(Z)
F(n) (164)
m(a)
k(lc) =£ kgFjWFjfY) + k?Fm(X)Fm(Y)Fm(Z)
m(c)
k(l, UNS CH) = 0 (165)
where kS, k°., k^ represent the group rate constants for primary
(CH3-) , secondary (>CH2) , and tertiary (>CH-) groups,
respectively, and the values for these parameters are listed in
Table 1 at 298 K; £ , £ , £ , E ' E ' represent
i(a) j(a) m(a) j(c) m(c)
the summation over all primary acyclic, secondary acyclic,
tertiary acyclic, secondary and tertiary cyclic groups,
respectively, in the molecule; F(X), F(Y) , F(Z) represent the
substituent factors for substituents X, Y, and Z and the values
for various substituents are listed in Table 2 at 298 K; F(n)
-199-
-------
represents the ring strain factor for saturated and unsaturated
rings and heterocyclic rings containing n (3,4,5) atoms at
298 K and the values are listed in Table 2. For rings with
n(6,7,8, etc.), with essentially no ring strain, F(n) » 1.0 at
298 K.
Pathway 2t H-Atom abstraction from -0-H groups by OH radicals
The overall rate constant for reaction pathway 2 is given
by the equation
k(2) = n(-O-H) k(-OH) (166)
where n(-O-H) represents the number of hydroxyl groups (-0-H)
in the molecule; k(-OH) represents the group rate constant for
H-atom abstraction from the hydroxyl group and is equal to
0.036 x 10~12cm3molecule~1s~1 at 298 K (Table 1).
Pathway 3; OH radical addition to isolated alkene groups
(>C=C<), nonaromatic conjugated groups
(>C=C-C=C<), and other unsaturated groups
(-CSG-, >c=c=c<, >oc=o)
The overall rate constant for reaction pathway 3 is given
by the equation
= kadd,nar
(167)
+E
m
where k^s, k§°, kgu represent the group rate constants for OH
radical addition (add) to isolated (is) carbon-carbon double
bonds, nonaromatic (nar) conjugated (co) carbon-carbon bond
-200-
-------
systems, and other unsaturated (ou) carbon-carbon systems,
respectively, and the values of these group rate constants are
given in Tables 9, 11, and 12, respectively, at 298 K; £) / £ '
1 1
2s, represent the summation over all isolated carbon-carbon
m
double bond systems, nonaromatic conjugated carbon-carbon
double bond systems, and other unsaturated carbon-carbon
groups, respectively, in the molecule; C(X), C(Y) represent the
substituent factors at 298 K for substituents X and Y, Table
10.
Pathway 4; OH radical interaction with -SH, -S-, and -S-S-
groups
The overall rate constant for reaction pathway 4 is given
by the equation
k(4) = n(-SH)k(-SH) + n(-S-)k(-S-) + n(-S-S-)k(-S-S-) (168)
where n(-SH) , n(-S-) , and n(-S-S-) represent the number of -SH,
-S-, and -S-S- groups, respectively, in the molecule; k(-SH) ,
k(-S-) , k(-S-S-) represent the group rate constants for OH
radical interaction with the -SH, -S-, and -S-S- groups,
respectively, and the values of these group rate constants are
listed in Table 1 at 298 K.
Pathway 5: OH radical interaction with -NH2, >NH, and >N-
groups
The overall rate constant for reaction pathway 5 is given
by the equation
k(5) = n(-NH2)k(-NH2) + n(>NH)k(>NH) + n(>N-)k(>N-) (169)
-201-
-------
where n(-NH2), n(>NH), n(>N-) represent the number of -NH2/
>NH, and >N- groups, respectively, in the molecule; k(-NH2),
k(>NH), Jc(>N-) represent the group rate constants for -NH2,
>NH, and >N-, respectively, and the values of these group rate
constants are listed in Table 1 at 298 K.
Pathway 6; OH radical interaction with phosphorous groups
The overall rate constant for reaction pathway 6 is given
by the equation
k(6) = n
where n[>P(S)-], n[>P(0)], n[>P(Cl)<] represent the number of
>P(S)-, >P(0)-, and >P(C1)< groups, respectively, in the
molecule; k[>P(S)-], k[>P(O)-], k[>P(Cl)<] represent the group
rate constants for OH radical interaction with the >P(S)-,
>P(0)-, and >P(C1)< groups, respectively, and the values of
these group rate constants are listed in Table 1 at 298 K.
Pathway 7; OH radical addition to aromatic rings
The overall rate constant fcadd,ar for reaction pathway 7
is given by the equations
*(7) = *add,ar (171)
(172)
Io9l0k'add,ar = ^ I °-31 ~ I-35 Min< .
^add,ar
-202-
-------
where V represents the summation over all aromatic rings in
the molecule; ( TVt ) represents the summation of the
electrophilic substituent constants of Brown and Okamoto (1958)
with respect to a given ring position (i.e., ortho, meta,
para) ; and Min( £}) (175)
*add,PAH = 10~12k'add,PAH
where ]F, represents the summation of all PAHs, (IP)i represents
i
the ionization potential of the parent PAH in electron volts
(eV) obtained from Weast (1976-1977); ( Va} ) is derived for
J
the monocyclic substituted portion of the molecule to allow for
the effects of substituent groups on the reactivity and
represents the summation of the electrophilic substituent
constants of Brown and Okamoto (1958) with respect to a given
ring position (i.e., ortho, meta, para); and Min (
-203-
-------
represents the summation of the electrophilic substituent
constants with respect to the ring hydrogen position that gives
the most negative summation value (i.e., Min ). Electrophilic
substituent constants (ffjj and
-------
VI11. References
Anderson, L.G.; Stephens, R.D. (1988).
Int. J. Chem. Kinet. 20., 103-110.
Kinetics of the Reaction of Hydroxyl Radicals with
2-(Dimethylamino)ethanol from 234-364 K.
Arey, J.; Atkinson, R.; Zielinska, B.; McElroy, P.A. (1989).
Environ. Sci. Technol. 23, 321-327. Diurnal Concentrations of
Volatile Polycyclic Aromatic Hydrocarbons and Nitroarenes
During a Photochemical Air Pollution Episode in Glendora,
California.
Arrhenius, S. (1887).
Z. Physik Chem. I, 110.
Atkinson, R. (1986).
Chem. Rev. 85. 69-201.
Kinetics and Mechanisms of the Gas Phase Reactions of the
Hydroxyl Radical with Organic Compounds under Atmospheric
Conditions.
Atkinson, R. (1986a).
Int. J. Chem. Kinet. H, 555-568.
Estimation of OH Radical Rate Constants for H-Atom Abstraction
from C-H and 0-H Bonds over the Temperature Range 250-1,000 K.
Atkinson, R. (1987).
Int. J. Chem. Kinet. 19_, 799-828.
A Structure-Activity Relationship for the Estimation of Rate
Constants for the Gas-Phase Reactions of OH Radicals with
Organic Compounds.
Atkinson, R. (1987a).
Environ. Sci. Technol. 21. 305-307.
Estimation of OH Radical Reaction Rate Constants and
Atmospheric Lifetimes for Polychlorobiphenyls, Dibenzo-£-
dioxins, and Dibenzofurans.
Atkinson, R. (1988).
Env. Toxic, and Chem. 7_, 435-442.
Estimation of Gas-Phase Hydroxyl Radical Rate Constants for
Organic Chemicals.
-205-
-------
Atkinson, R. (1987b, 1988a).
In OECD (Organization for Economic Cooperation and Development)
Test Guideline on Photochemical Oxidative Degradation in the
Atmosphere.
1. Draft Final Report Dated January, 1987b. Revision 2,
p. 49-113.
2. Draft Final Report Dated August, 1988a. Revision 3, p. 19-
42 and Annex III (Forty-eight examples are given for the
estimation of the rate constants JCQH) • Umweltbundesamt Berlin,
Bundesrepublik Deutschland. Estimation of OH Rate Constants.
Atkinson, R. (1989).
Monograph No. 1. Kinetics and Mechanisms of the Gas-Phase
Reactions of the Hydroxyl Radical with Organic Compounds.
American Chemical Society, Wash., D.C. and American Inst. of
Physics, New York, N.Y.
Atkinson, R. (1989a).
Unpublished Results.
Updating of the Structure/Reactivity Relationships for the
Reaction of OH Radicals with Organic Chemicals in the Gas-
Phase.
Atkinson, R.; Aschmann, S.M. (1984).
Int. J. Chem. Kinet. ifi, 1175-1186.
Rate Constant for the Reaction of OH Radicals with a Series of
Alkenes and Dialkenes at 295 ± 1 K.
Atkinson, R.; Aschmann, S.M. (1985).
Environ. Sci. and Technol. 19. 462-464.
Rate Constants for the Gas-Phase Reaction of Hydroxyl Radicals
with Biphenyl and the Monochlorobiphenyls at 295 ± 1 K.
Atkinson, R.; Aschmann, S.M. (1986).
Int. J. Chem. Kinet. .18, 569-573.
Kinetics of the Reaction of Naphthalene, 2-Methylnaphthalene,
and 2,3-Dimethylnaphthalene with OH Radicals and with 03 at 295
± 1 K.
Atkinson, R.; Aschmann, S.M. (1987).
Atmos. Environ. 21. 2323-2326.
Kinetics of the Gas-Phase Reactions of Alkylnaphthalenes with
03; N2°5' and OH Radicals at 298 ± 2 K.
Atkinson, R.; Aschmann, S.M. (1988).
Int. J. Chem. Kinet. 2£/ 339-342.
Rate constants for the Reaction of OH Radicals with
Isopropylcyclopropane at 298 + 2 K: Effects of Ring Strain on
Substituted Cycloalkanes.
-206-
-------
Atkinson, R.; Aschmann, S.M. (1988a).
Int. J. Chem. Kinet. 20., 513-539.
Kinetics of the Reactions of Acenaphthalene and Structure-
Related Aromatic Compounds with OH and NO3 radicals, N205, and
03 at 296 ± 2 K.
Atkinson, R.; Aschmann, S.M. (1989).
Int. J. Chem. Kinet. 21,
Rate Constants for the Gas-Phase Reactions of the OH Radical
with a Series of Aromatic Hydrocarbons at 296 + 2 K.
Atkinson, R.; Pitts Jr., J.N. (1977).
J. Chem. Phys. 6J, 2492-2495.
Absolute Reaction Rate Constants for the Reaction of O3(P)
Atoms with Allene, 1,3-Butadiene, and Vinyl Methyl Ether. Over
the Temperature Range 297-439 K.
Atkinson, R.; Pitts Jr., J.N. (1981).
Principal Investigator: Atkinson. Co-Investigators: Pitts
Jr., J.N.; Winer, A.M.; and the Research Staff of S.A. Aschmann
and W.P.L. Carter.
Cooperative Agreement No. CR 809247.
B.W. Gay Jr., Project Officer
Atmospheric Research Laboratory, U.S. Environmental Protection
Agency, Research Triangle Park, NC 27711.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L. (1983).
Int. J. Chem. Kinet. 15, 1161-1177.
Effects of Ring Strain on Gas-Phase Rate Constants; 2. OH
Radical Reactions with Cycloalkenes.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L. (1983a).
Int. J. Chem. Kinet. IS, 37-50.
Rate Constants for the Gas-Phase Reactions of OH Radicals with
a Series of Bi- and Tricycloalkanes at 299 + 2 K. Effects of
Ring Strain.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L. (1984a)
Int. J. Chem. Kin. Ife, 967-976.
Kinetics of the Reactions of 03 and OH Radicals with a Series
of Dialkenea at 294 ± 2 K.
Atkinson, R.; Aschmann, S.M.; Pitts, Jr., J.N. (1986).
Int. J. Chen. Kinet. 1S_, 287-299.
Rate Constants for the Gas-Phase Reactions of the OH Radicals
with a Series of Monoterpenes at 294 + 1 K.
Atkinson, R.; Perry, R.A.; Pitts, Jr., J.N. (1977).
J. Chem. Phys. ££, 1578-1581.
Rate Constants for the Reaction of the OH Radical with CH3SH,
CH3NH2 over the Temperature Range 299-426 K.
-207-
-------
Atkinson, R.; Perry, R.A.; Pitts, Jr., J.N. (1978).
J. Chem. Phys., 1850-1853.
Rate Constants for the Reactions of the OH Radical with
(CH3)2NH, (CH3)3N, and C2H5NH2 over the Temperature Range
298-426 K.
Atkinson, R.; Carter, W.P.L.; Winer, A.M.; Pitts Jr., J.N.
(1981).
J. Air Poll. Control Ass. H, 1090-1093.
An Experimental Protocol for the Determination of OH Radical
Rate Constants with Organics Using Methyl Nitrite Photolysis as
an OH Radical Source.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Pitts Jr., J.N.
(1982) .
Int. J. Chem. Kinet. ii, 839-847.
Rate Constants for the Gas-Phase Reaction of OH Radicals with a
Series of Ketones at 299 ± 2 K.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Winer, A.M.
(1982a).
Int. J. Chem. Kinet. H, 919-926.
Kinetics of the Gas-Phase Reactions of OH Radicals with Alkyl
Nitrates at 299 + 2 K.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Winer, A.M.;
Pitts Jr., J.N. (1982b).
Int. J. Chem. Kinet. 14, 781-788.
Kinetics of the Reactions of OH Radicals with n-Alkanes at 299
± 2 K.
Atkinson, R.; Carter, W.P.L.; Aschmann, S.M.; Winer, A.M.;
Pitts Jr., J.N. (1984).
Int. J. Chem. Kinet. I£, 469-481.
Kinetics of the Reactions of OH Radicals with a Series of
Alkanes at 297 ± 2 K.
Atkinson, R.; Aschmann, S.M.; Carter, W.P.L.; Winer, A.M.;
Pitts Jr., J.N. (1984b).
Int. J. Chem. Kinet. 16, 1085-1101.
Formation of Alkyl Nitrates from the Reaction of Branched and
Cyclic Alkyl Peroxy Radicals with NO.
Atkinson, R.; Pitts Jr., J.N.; Winer, A.M.; Aschmann, S.M.;
Carter, W.P.L. (1985).
EPA Report EPA-600/09/85.
Atmospheric Fates of Organic Chemicals: Prediction of Ozone
and Hydroxyl Radical Rates and Mechanisms.
Statewide Air Pollution Research Center, University of
California, Riverside, CA 92521.
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REPORT DOCUMENTATION
PAGE
. J. «eeio>»nrj Acention NO.
«. Title and subtitle Determination of Rates of Reaction in the Gas-Phase s. Report Date
in the Troposphere. Theory and Practice. 3. Rate of Indirect
Photoreaction: Technical- Support Document for Test Guideline
$ 796.3900.
7. Autftorfi)
Asa Leifer
f. Performing Organization Nam* and Addreaa
U.S. Environmental Protection Agency
Office of Toxic Substances
Exposure Assessment Branch (TS-798)
401 M Street, SW
Washington, DC 20460
Organliation Rept.
10. Proteet/Teafc/Wor* Unit No.
11. ContraettO or GrarrKO) No.
(O
12. Sponsoring Organisation Name and Addreaa
13. Type of Report A Period Covered
14.
IS. Supplementary Nate*
Abatract (Limit: 200 worda)
This report describes the development of structure/ reactivity (S/R) relation-
ships of Atkinson for the estimation of the 2&d--order rate constant (k0H) for tha
reaction of OH radicals with organic chemicals in the troposphere. These S/R
relationships were used to estimate kQH at 298 K of 405 chemicals covering a
variety of classes and compares them with the experimental values (% Error). Of
the 405 chemicals, 20 had a % error > +100 and were omitted in the analyses. For
the 385 remaining chemicals, the average % error ranged from +21 to -19. One
hundred fifty-four chemicals were not used by Atkinson to derive the parameters in
the S/R relationships and, therefore, were good candidates to test the validity of
the S/R relationships. The average percent error of the 154 chemicals ranged from
+24 to -20, thereby confirming these S/R relationships. A discussion is given on
the estimation of the half-life of a chemical in the troposphere from k^o and the
average OH concentration. This report represents the technical support document
for a test guideline which can be used under section 4 of the Toxic Substances
Control Act.
17. Document Analjrala a. Deecrtotor*
o. Identlftera/Ooen-Cfldod Terma
OH radical reaction rates in the troposphere (koH), structure/reactivity
relationships to estimate Icgg, estimation of the half-life for OH radical
reactions, Toxic Substances Control Act section 4 test guideline, screening-level
test guideline.
c. COSATI Field/Group
It. Availability Statement
Release unlimited
It. Security Claaa (Till* Report)
Unclassified
! 20. Security Claaa (Thla Page)
21. No. of Page*
237
22. Price
(See ANSt-Of .!•)
See Inatructfene an ffevervo
mutt 272 («-7
(formerly NTIS-3!)
Department of Commerce
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