EPA-744-R-93-001
DETERMINATION OF RATES OF REACTION
IN THE GAS-PHASE IN THE TROPOSPHERE
THEORY AND PRACTICE
5. Rate of Indirect Photoreaction: Evaluation of the
Atmospheric Oxidation Computer Program of Syracuse
Research Corporation for Estimating the Second-Order
Rate Constant for the Reaction of an Organic Chemical
with Hydroxyl Radicals
by
Asa Leifer
U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF POLLUTION PREVENTION AND TOXICS
WASHINGTON, DC 20460
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CONTENTS
Abstract xii
I. Introduction 1
II. Mathematical Synopsis of the Structure/Reactivity
Relationships of Atkinson and Meylan 3
III. Syracuse Research Corporation Atmospheric
Oxidation Computer Program (Developed by
Meylan) 14
III.A. Introduction 14
III.B. Atmospheric Oxidation Computer Program (AOP) . . 15
IV. Evaluation of the Atmospheric Oxidation
Computer Program for Estimating kOH and
the Experimentally Measured KQH Data
Listed in the Program 29
IV.A. Comments on the Group Rate Constants,
Substituent Factors, and Other Parameters
Used by the Atmospheric Oxidation Program ... 29
IV.B. Some Comments on Hydroxyl Radical Addition to
Heteroaromatic and Fused Polyaromatic Ring
Systems 46
IV.C. H-Atom Abstraction from C-H and -OH Groups by
Hydroxyl Radicals 52
IV.C.I. Saturated Alkanes 52
IV.C.I.a. Evaluation of the Experimental kOH Data .... 52
IV.C.l.b. Evaluation of the Estimated kOH Data 57
IV.C.2. Haloalkanes 59
IV.C.2.a. Evaluation of the Experimental kOH Data .... 59
IV.C.2.b. Evaluation of the Estimated k0H Data 62
IV.C.3. Carbonyl Compounds 62
IV.C.3.a. Evaluation of the Experimental kOH Data .... 62
IV.C.3.b. Evaluation of the Estimated kOH Data 68
ii
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IV.C.4. Alcohols, Glycols, Ethers, and Hydroperoxides . 71
IV.C.4.a. Evaluation of the Experimental kOH Data .... 71
IV.C.4.b. Evaluation of the Estimated kOH Data 71
IV.C.5. Alkyl Nitrates and Nitriles 79
IV.C.S.a. Evaluation of the Experimental kOH Data .... 79
IV.C.S.b. Evaluation of the Estimated k0H Data 82
IV.C.6. Nitroalkanes 82
IV.C.S.a. Evaluation of the Experimental kOH Data .... 82
IV.C.e.b. Evaluation of the Estimated k0H Data . 85
IV.C.7. Alkyl Nitrites 87
IV.C.7.a. Evaluation of the Experimental kOH Data .... 87
IV.C.7.b. Evaluation of the Estimated kOH Data 88
IV.D. Addition of Hydroxyl Radicals to Alkenes,
Conjugated Dialkenes, Alkynes, and
1,2-Dialkenes 89
IV.D.I. Unsubstituted Alkenes 89
IV.D.I.a. Evaluation of the Experimental k0n Data .... 89
IV.D.l.b. Evaluation of the Estimated kOH Data 93
IV.D.2. Substituted Alkenes 94
IV.D.2.a. Evaluation of the Experimental kOH Data .... 94
IV.D.2.b. Evaluation of the Estimated k0n Data 97
IV.D.3. Conjugated Dienes 97
IV.D.3.a Evaluation of the Experimental kOH Data .... 97
IV.D.3.b. Evaluation of the Estimated kOH Data 99
IV.D.4. Alkynes and 1,2-Dienes (Allenes) 99
IV.D.4.a. Evaluation of the Experimental k0H Data .... 99
IV.D.4.b. Evaluation of the Estimated kOH Data 99
iii
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IV.E. Reaction of Hydroxyl Radicals with Organic
Compounds Containing Sulfur, Nitrogen, and
Phosphorous Functional Groups 101
IV.E.I. Reaction with Thiols, Sulfides, and Disulfides . 101
IV.E.I.a. Evaluation of the Experimental kOH Data .... 10l
IV.E.l.b. Evaluation of the Estimated k0n Data 104
IV.E.2. Reaction with Sulfoxides and Sulfates 105
IV.E.2.a. Evaluation of the Experimental KOH Data .... 105
IV.E.2.b. Evaluation of the Estimated kOH Data 105
IV.E.3. Reaction with Alkyl Amines, Alkyl Hydrazines,
and N-Substituted Amines 108
IV.E.3.a. Evaluation of the Experimental kOH Data .... 108
IV.E.3.b. Evaluation of the Estimated kOH Data 108
IV.E.4. Reaction with Compounds Containing Phosphorous
Functional Groups 110
IV.E.4.a. Evaluation of the Experimental kOH Data . . . . 110
IV.E.4.b. Evaluation of the Estimated k0n Data 110
IV.F. Reaction of Hydroxyl Radicals with Aromatic
Compounds, Heterocyclic Aromatic Compounds,
and Fused Ring Polyaromatic Compounds 113
IV.F.I. Aromatic Compounds 113
IV.F.I.a. Evaluation of the Experimental k0H Data .... 113
IV.F.l.b. Evaluation of the Estimated Data 119
IV.F.2. Heterocyclic Aromatic Compounds 120
IV.F.2.a. Evaluation of the Experimental kOH Data .... 120
IV.F.2.b. Evaluation of the Estimated k0H Data 122
IV.F.3. Fused Ring Polyaromatic Compounds 123
IV.F.3.a. Evaluation of the Experimental k0jj Data . . . . 123
IV.F.3.b. Evaluation of the Estimated k0n Data 123
IV
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IV.G. Evaluation of the Estimated Half-Life for
the Reaction of Hydroxyl Radicals with
Organic Chemicals in the Troposphere 125
V. References 127
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LIST OF TABLES
Table 1. Group Rate Constants for Hydrogen Abstraction
and Radical Reaction 30
Table 2. Substituent F(X) Factors for Hydrogen
Abstraction 31
Table 3. Factors Used for Aliphatic Ring Strain
Effects 33
Table 4. Group Rate Constants for OH Radical Addition
to Isolated Olefinic Units 34
Table 5. Group Rate Constants for OH Radical Addition
to Conjugated Olefinic Units 35
Table 6. Group Rate Constants for OH Radical Addition
to Alkyne Units 37
Table 7. Group Rate Constants for OH Radical Addition
to 1,2-Dialkene (Allene) Units 38
Table 8. Substituent Factors [C(X)] for OH Radical
Addition to Olefins and Acetylenes 39
Table 9. Electrophilic Substituent Factors for OH
Radical Addition to Aromatic Rings 40
Table 10. Experimental Values of A^ for Some
Monocyclic Heteroaromatic Compounds 47
Table 11. Experimental Values of B^ for Some
Polynuclear Aromatic Compounds 48
Table 12. Values of B^ for Polynuclear Aromatic
Hydrocarbon Structures Derived from
Experimentally Measured lonization
Potentials 49
Table 13. Values of B^ for Polynuclear Heteroaromatic
Structures Derived from Experimentally Measured
lonization Potentials 50
Table 14.A. Comparison of the Estimated Values of
k0H at 298 K for Saturated Acyclic
Alkanes from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand
Calculation (HC) and the Experimental
k0H Data Reported in the Literature
Versus the Experimental kOH Data
Reported in AOP 53
vi
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Table 14.B. Comparison of the Estimated Values of
kOH at 298 K for Saturated Cyclic
Alkanes from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand
Calculation (HC) and the Experimental
k0jj Data Reported in the Literature
Versus the Experimental kOH Data
Reported in AOP
Table 15.
Table 16,
Table 17,
Table 18,
Table 19,
55
Comparison of the Estimated Values of
KOH at 298 K for Haloalkanes from the
Atmospheric Oxidation Computer Program
(AOP) and from a Hand Calculation (HC)
and the Experimental )CQH Data Reported
in the Literature Versus the Experimental
kOH Data in AOP
60
Comparison of the Estimated Values of
k0H at 298 K for Carbonyl Compounds
from the Atmospheric Oxidation Computer
Program (AOP) and from a Hand
Calculation (HC) and the Experimental
kOH Data Reported in the Literature
Versus the Experimental k0n Data in
AOP
Comparison of the Estimated Values of
k0H a^ 298 K for Alcohols, Glycols,
Ethers, and Hydroperoxides from the
Atmospheric Oxidation Computer Program
(AOP) and from a Hand Calculation (HC)
and the Experimental kOH Data Reported
in the Literature Versus the
Experimental kOH Data in AOP
63
72
Comparison of the Estimated Values of
kOH at 298 K for Alkyl Nitrates and
Alkyl Nitriles from the Atmospheric
Oxidation Computer Program (AOP) and
from a Hand Calculation (HC) and the
Experimental kOH Data Reported in the
Literature Versus the Experimental
kOH Data in AOP
80
Comparison of the Estimated Values of
k0H at 298 K for Nitroalkanes and
Alkyl Nitrites from the Atmospheric
Oxidation Computer Program (AOP) and
from a Hand Calculation (HC) and the
Experimental k0n Data Reported in the
Literature Versus the Experiment
Data in AOP
83
vii
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Table 20.
Table 21.
Table 22
Table 23
Table 24,
Comparison of the Estimated Values of
kOH at 298 K for Unsubstituted Alkenes
from the Atmospheric Oxidation Computer
Program (AOP) and from a Hand
Calculation (HC) and the Experimental
k0n Data Reported in the Literature
Versus the Experimental k0H Data in
AOP
Comparison of the Estimated Values of
kOH at 298 K for Substituted Alkenes
from the Atmospheric Oxidation Computer
Program (AOP) and From a Hand
Calculation (HC) and the Experimental
kOH Data Reported in the Literature
Versus the Experimental k0jj Data in
AOP
Comparison of the Estimated Values of
kOH at 298 K for Conjugated Acyclic and
Cyclic Dialkenes from the Atmospheric
Oxidation Computer Program (AOP) and
from a Hand Calculation (HC) and the
Experimental k0H Data Reported in the
Literature Versus the Experimental kOH
Data in AOP
Comparison of the Estimated Values of
kpn at 298 K for Alkynes and 1,2-
Dialkenes (Allenes) from the
Atmospheric Oxidation Computer Program
(AOP) and from a Hand Calculation (HC)
and the Experimental kOH Data Reported
in the Literature Versus the
Experimental kOH Data in AOP
90
95
98
100
Comparison of the Estimated Values of
k0u at 298 K for Alkyl Thiols,
SuIfides, and Disulfides from the
Atmospheric Oxidation Computer Program
(AOP) and from a Hand Calculation (HC)
and the Experimental k0H Data Reported
in the Literature Versus the
Experimental kOH Data in AOP
102
viii
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Table 25. Comparison of Estimated Values of kOH
at 298 K for Alkyl Sulfoxides and
Sulfates from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand
Calculation (HC) and the Experimental
kOH Data Reported in the Literature
Versus the Experimental kOH Data in
AOP 106
Table 26. Comparison of the Estimated Values of
k0u at 298 K for Alkyl Amines,
Hydrazines, and N-Substituted Amines
from the Atmospheric Oxidation Computer
Program (AOP) and from a Hand
Calculation (HC) and the Experimental
kOH Data Reported in the Literature
Versus the Experimental kOn Data in
AOP 109
Table 27. Comparison of the Estimated Values of
kOH at 298 K for Aliphatic Compounds
Containing Phosphorous Functional
Groups from the Atmospheric Oxidation
Program (AOP) and from a Hand
Calculation (HC) and the Experimental
kOH Data Reported in the Literature
Versus the Experimental kOH Data in
AOP Ill
Table 28. Comparison of the Estimated Values of
k0H at 298 K for Aromatic Compounds
from the Atmospheric Oxidation
Program (AOP) and from a Hand
Calculation (HC) and the Experimental
kOH Data Reported in the Literature
Versus the Experimental kOH Data in
AOP 114
Table 29. Comparison of the Estimated Values of
!CQH at 298 K for Heterocyclic Aromatic
Compounds from the Atmospheric
Oxidation Program (AOP) and from a Hand
Calculation (HC) and the Experimental
k0|j Data Reported in the Literature
Versus the Experimental k0n Data in
AOP 121
ix
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Table 30. Comparison of the Estimated Values of
kOH at 298 K for Fused Ring
Polyaromatic Compounds (PAH) from the
Atmospheric Oxidation Program (AOP) and
from a Hand Calculation (HC) and the
Experimental kOH Data Reported in the
Literature Versus the Experimental kOH
Data in AOP 124
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LIST OF FIGURES
Figure 1,
Figure 2
Figure 3,
Figure 4.
Figure 5.
Figure 6,
Atmospheric Oxidation Program Data
Entry Display
16
Atmospheric Oxidation Program Data Display
for the Compound a-Methyl Styrene (2-Phenyl-
1-Propene):
Summary Hydroxyl Radical Data and Experimental
Data.
A. Screen Display when Key PgDn is pressed. . .
B. Screen Display when Key F-10 is pressed. . .
Atmospheric Oxidation Program Data Display
for the Compound a-Methyl Styrene (2-Phenyl-
1-Propene):
Summary Hydroxyl Radical and Ozone Data.
A. Screen Display when Key PgDn is pressed. . .
B. Screen Display when Key F-10 is pressed. . .
Atmospheric Oxidation Program Data Display
for the Compound a-Methyl Styrene (2-Phenyl-
1-Propene):
A. Screen Display of the Detailed Calculations
for Hydrogen Abstraction
Screen Display of the Detailed Calculations
for OH Radical Addition to the Olefinic
Bond
18
19
22
23
B
24
25
Atmospheric Oxidation Program Data Display
for the Compound a-Methyl Styrene (2-Phenyl-
1-Propene):
A. Screen Display of the Detailed
Calculations with 03 Reaction with the
Olefinic Bond
B. Screen Display of the Detailed
Calculations of OH Radical Addition to the
Aromatic Ring
26
27
Atmospheric Oxidation Program Data Display
for the Compound a-Methyl Styrene (2-Phenyl-
1-Propene):
Screen Display for OH Addition to the
Aromatic Ring and the Experimental Data. . .
28
xi
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Abstract
Atkinson (of the University of California at Riverside), in
support of the research programs of the Exposure Assessment
Branch, Office of Pollution Prevention and Toxics, U.S.
Environmental Protection Agency, developed structure/reactivity
relationships (S/R) for estimating the second-order rate constant
for the reaction of hydroxyl radicals with organic chemicals in
the gas-phase in the troposphere (kOjj) * Meylan, of Syracuse
Research Corporation, computerized these S/R relationships and,
in addition, developed S/R relationships for a few other classes
of organic chemicals. This computer program is called the
Atmospheric Oxidation Program (AOP)1. Furthermore, at the
request of Leifer, Meylan incorporated a data base of the
experimental values of kOH for a large number of organic
chemicals in AOP2.
This computer program is operated by inserting in it the
SMILES notation for a given molecular structure. This SMILES
notation is a machine-readable code for the molecular structure
of an organic chemical. AOP then estimates kOH/ lists an
experimental value (if available from the scientific literature),
1 This computer program also contains S/R relationships of
Atkinson for estimating the second-order rate constant for the
reaction of organic chemicals with ozone (k0O in the gas-
phase in the troposphere. This report, however, will only
review the hydroxyl radical portion of this computer program.
2 AOP also lists the experimental values of k0., if available;
and also lists the experimental values of k^0. for the reaction
of an organic chemical with nitrate radicals (N03), if
available.
xii
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gives a detailed description of the calculations, and estimates
the half-life in the troposphere for this chemical. This
computer program was thoroughly evaluated by comparing the
estimated and experimental values of kOH from AOP with the hand
calculated and experimental values of Leifer for 454 organic
compounds covering a wide variety of classes of compounds. These
kOH data are listed in Tables 14-30.
When comparing the estimated values of KOH by AOP and those
by Leifer in a hand calculation (HC), a few comments can be made
about the number of significant figures used. In general, the
summary table in AOP lists k(i) and kOH (the rate constant
corresponding to each individual reaction pathway i and the total
hydroxyl radical rate constant kOH, respectively) with up to a
maximum of six significant figures. However, the group rate
constants (e.g., k° k° k° k*3, k°°, k(>N-), k(-SH), etc.) and
p s t o o
the substituent factors F(i) and C(i) [e.g., F(-CH2-), F(-C1),
F(>N-H), F(for strained rings containing n atoms), C(-F), C(=0),
C(-C=N), etc.] are known, at best, to three significant figures
and, in general, to two significant figures. Therefore, it is
recommended that AOP show the detailed calculations to four
significant figures and list k(la), k(lc), k(>N-), kadd nar,
kadd ar> etc- and ^OH ^n tne summary table with three significant
figures.
In general, after evaluating all 454 chemicals covering a
wide range of chemical classes, it was found that there was
excellent agreement between the estimated values of kOH and HC-
xiii
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Furthermore, the S/R relationships of Meylan for fused ring
polyaromatic hydrocarbons are superior to those of Atkinson. In
addition, Meylan's S/R relationships have been expanded to cover
heterocyclic aromatic compounds such as the thiazoles, oxazoles,
pyridines, furans, etc. whereas Atkinson does not have
corresponding S/R relationships. However, it must be emphasized
that considerably more experimental kOH data are needed for a
number of substituted heterocyclic and fused ring polynuclear
aromatic hydrocarbons to verify the S/R relationships of Meylan.
There are, however, some differences between the estimated values
of kOjj from AOP and HC for a few classes of compounds which will
be described in the following paragraphs.
For the alkyl sulfides (both acyclic and cyclic), a
comparison of the estimated values of kOH from AOP and HC
indicates that k0H is larger from AOP. The reason for this
discrepancy is that kOjj was measured in the absence of oxygen and
from Atkinson's S/R relationships, k(-S-) = 0 so that only H-atom
abstraction is observed. However, AOP estimates kOH by assuming
that k(-S-) =2.0 and not 0. Hence, when estimating kOH for
these compounds it is necessary to specify whether the estimation
is made under the boundary condition of the presence or absence
of oxygen. Therefore, it is recommended that AOP should be
modified to take into account this boundary condition.
For the aromatic compounds 3,5-dimethyl phenol, N,N-
dimethylaniline, and 2,4-toluenediamine, AOP lists the maximum
value for OH addition to an aromatic ring as 200 x 10~12
xiv
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cm3molecule~1s~1 [i.e., k(7) = kadd ar] where HC lists a
maximum value kOH of 20° x 10~12cm3molecule~ -<"i. since the
maximum allowed collision rate is 200 x 10~12cm3molecule~1s~1
[Atkinson (1987)], this boundary condition must be invoked on the
estimation of kOH and not on k(7)[=kadd,ar]• Furthermore, by
using this boundary condition, the estimated values of kOH for
the above mentioned aromatic compounds are much closer to the
experimental values [See Table 28 of this report and Leifer
(1992a)]. It should be noted that this comment is only
applicable to aromatic compounds and not to all compounds.
For the compounds tetralin, indan, fluorene, and
2,3-dihydrobenzofuran, AOP makes a slight error in estimating the
rate constant for the addition of OH radicals to the aromatic
ring [i.e., k(7) = k^^ ar]. For these compounds, AOP uses the
incorrect value of a+(-CH2-) = 0.06 ** instead of the correct
value of 0.064 **. Furthermore, the compounds tetralin, indan,
and fluorene contain five membered strained rings. In
calculating k(lc) for these compounds, AOP makes an error by
omitting the ring strain factor F(5) = 0.80. Thus, k(lc) and
are erroneous.
Atkinson did not develop S/R relationships for alkyl
carboxylie acids, peroxides, sulfoxides, and sulfates because of
the very limited availability of experimental kOH data. Meylan
did develop S/R relationships for these classes of compounds;
however, for a few reasons, these S/R relationships are not
valid. For the alkyl carboxylic acids and hydroperoxides,
xv
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Meylan made an erroneous assumption about the mechanism of OH
reaction for these compounds. For example, for the S/R
relationships of the alkyl carboxylic acids, Meylan assumed that
OH radicals can react with these compounds by H-atom abstraction
from the hydroxyl group in the carboxylic acid group {C(=0)OH,
[k(2)]> and from the C-H groups in the alkyl group [k(la)] and
that the dominant reaction pathway was H-atom abstraction from
the alkyl group. As a result, Meylan assumed that k(-OH) =
0.036, the same value as assigned to H-atom abstraction from the
hydroxyl group in alcohols and glycols. However, based on the
analysis of the experimental data of Wine et al. (1986) and
Singleton et al. (1986), Atkinson (1989) and Leifer concluded
that the major reaction pathway was H-atom abstraction from the
hydroxyl group and k(-OH) > k(la). Therefore, it is recommended
that the S/R relationships for the alkyl carboxylic acids and
hydroperoxides be deleted from AOP. More experimental kOH data
are needed for additional alkyl carboxylic acids and
hydroperoxides to develop reliable S/R relationships.
For the alkyl sulfoxides, Meylan developed S/R
relationships by assuming that only C-H abstraction from the
alkyl groups occurred. However, intuitively, it is expected
that the sulfoxide group would undergo further oxidation to the
sulfone. Therefore, considerably more experimental KOH data are
needed for additional sulfoxides before reliable mechanisms and
S/R relations are developed; and these S/R relationships should
be deleted from AOP.
xvi
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Based on the very limited data of the alkyl sulfates (only
dimethyl and diethyl sulfate), Meylan developed S/R relation-
ships for this class of compounds. Comparison of the estimated
kOH data with the experimental k0n indicated that dimethyl
sulfate gave an error of > +250% and diethyl sulfate gave an
error of +540%. These results are very poor so that it is
recommended that these S/R relationships be deleted from AOP
until considerably more experimental kOH data is available for
additional sulfates to develop reliable S/R relationships.
Meylan, in AOP, used the S/R relationships of Atkinson for
the nitroalkanes based on the available experimental kOH data
for these compounds. However, it must be emphasized that some
of the experimental data is suspect because nitroalkanes are
very labile to direct photolysis and it is not clear whether
photolysis occurred under the experimental conditions of the
relative rate study of Nielson et al. (1988) or whether
photolysis was taken into account. Therefore, it is recommended
that AOP delete these S/R relationships. More reliable experi-
mental k0H data are needed for these nitroalkanes under
carefully controlled experimental conditions to eliminate, or
account for, direct photolysis in order to develop more reliable
S/R relationships.
Comparison of the experimental values of kOH from AOP and
Leifer for 454 chemicals indicates that, in general, the
agreement is excellent. There are, however, a few differences.
The primary difference is related to the number of significant
xvii
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figures used in AOP. For example, for 2-methylpentane, AOP
lists an experimental value of 5.60 while Atkinson (1989) and
Leifer (1992a) list a recommended value of 5.6; for 2,3-
dimethyl-2-butene, AOP lists a value of 110.0 while the
recommended value by Atkinson and Leifer is 110; for dimethyl-
hydroxylamine, AOP lists a value of 90.0 while Atkinson and
Leifer recommend a value of 90; for E"cres°l/ A°P lists a value
of 47.0 while Atkinson and Leifer recommend a value of 47; for
4-chlorobiphenyl, AOP lists a value of 3.9 while Atkinson and
Leifer list a value of 3.86.
For other chemicals with differences, Leifer lists an
average value from the literature while AOP selects one set.
For example, for trans-1,4-hexadiene. Leifer lists an average
value of 90.6 from two sets of experimental data while AOP
selects only one value, namely 90.3; for 2,3-dimethyl-2-pentene,
AOP selects one value which is 108.0 while Leifer cites an
average value of 103 based on both sets of experimental data.
Unless there is good reason for discarding specific sets of
experimental k0n data, it is better to use an average value from
both sets.
For 12 chemicals, AOP does not list experimental values:
for example, four ketenes; A3-carene; sec-butyl acetate; and 2-
(chloromethyl)-3-chloro-l-propene. Differences were observed
for a few compounds: e.g., for methane, AOP lists a value of
0.00841 while Atkinson and Leifer list a recommended value of
0.00836; for 2-octanone, AOP lists a value of 10.0 while
xviii
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Atkinson and Leifer list a value of 11.0; for 1,1,1-trifluoro-
ethane, AOP lists a value of 0.017 while Atkinson and Leifer
list a value of 0.0017.
xix
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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
, and KQ . The rate constant k^g represents the first-order
rate constant for direct photoreaction, while kOH an<* k0
represent second-order rate constants for indirect photoreaction
and oxidation with OH and 03, respectively.
-1-
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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 k^j;, kOH, and k0 and the half-lives
for each transformation process and the net half-life in the
troposphere [Leifer (1989a)]. The second report describes a
screening-level test guideline for determining the maximum rate
of direct photoreaction [k
-------
in the literature [Meylan (1990b)]. This document, describes an
assessment of this computer program for estimating kOn a^d
represents report No.5 in this series.
II. Mathematical Synopsis of the Structure/Reactivity
Relationships of Atkinson and Meylan
Atkinson (1986, 1986a, 1987, 1987b, 1988, 1988a) critically
analyzed the hydroxyl radical rate data (k0jj) 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:
Ml)
H-atom abstraction from acyclic
saturated, cyclic saturated, and
(1)
unsaturated C-H groups by OH radicals,
v/oi - v [~H-atom abstraction from 0-H groups"! . .
k(2) - k Lby OR radicals J (2)
addition to >C=C<,
k(3) - k |>C=C-C=C<, -CsC-, and >C=C=C<,I (3)
oH radical interaction with -SH,
_s_s_ groups
1
J
|~OH radical interaction with -NH2,1
1>NH, and >N- groups J
L^wn, ana *n- gro
-3-
-------
= v FOH radical interaction with"!
[phosphorus groups J (6'
k(7) = k [OH radical addition to aromatic rings] (7)
OH radical addition to fused ring'
k(8)
polyaromatic compounds (i.e.,
(8)
polyaromatic hydrocarbons)
Atkinson postulated that the overall OH radical rate constant k_u
On
is equal to the sum of the rate constants for each of these
reaction pathways. Therefore, the OH radical rate constant is
given by the equation
8
*OH - Z *<*) (9)
and the individual rate constants [k(l), k(2), , k(8)] and
kQu are all in the units cm3molecule~1s~1. Structure/
reactivity relationships will be described for each of these
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 l is given
by the equation
k(l) - k(la) + k(lc) + k(l, UNS CH) (10)
where k(la) represents the rate constant for H-atom abstraction
from all acyclic saturated C-H groups by OH radicals at 298 K;
-4-
-------
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) +£ kiF-jWFjfY)
Ua) * J(a) J J
(ID
F(n) (12)
a)
k(lc) = E k|Fj(X)Fj(Y) + k°.Fm(X)Fm(Y)Fm(Z)
J J
jTc) J J m(c)
k(l, UNS CH) = 0 (13)
where kg, k§, k° represent the group rate constants for primary
(CH3-), secondary (>CH2), and tertiary (>CH-) groups,
respectively, and the values for these parameters at 298 K are
listed in Table 1 of an EPA report by Leifer (1992a), in Table 1
of a report by Meylan (1990b)3, and in Table 1, Section IV, of
this report; £ , ]P / ]£ / ]C ' £ ' represent the
iTa) j(a) m(a) jTc) mTc)
summation over all primary acyclic, secondary acyclic, tertiary
acyclic, secondary and tertiary cyclic groups, respectively, in
3 Group Rate Constants and Substituent Values Used by the
Atmospheric Oxidation Program, Version 1.30, November l,
1990.
-5-
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the molecule; F(X), F(Y), F(Z) represent the substituent factors
for substituents X, Y, and Z and the values for various
substituents at 298 K are listed in Table 2 of an EPA report by
Leifer (1992a), in Table 6 of a report by Meylan
(199Gb)3, and in Table 2, Section IV, of this report; F(n)
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 of an EPA report by Leifer
(1992a), in Table 10 of a report by Meylan (1990b)3, and in
Table 3, Section IV, of this report. For rings with n(6,7,8,
etc.)/ with essentially no ring strain, F(n) « 1.0 at 298 K.
Pathway 2; H-Atom abstraction from -0-H groups in alcohols and
glycols by OH radicals
The overall rate constant for reaction pathway 2 is given
by the equation
k(2) = n(-O-H) k(-OH) (14)
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 in alcohols and glycols
and is equal to 0.036 x 10~^2Cm3mo^ecu^e-ls-l a^ 298 K [Table 1
of an EPA report by Leifer (1992a), in Table 1 of a report by
Meylan (1990b)3, and in Table 1, Section IV, of this report].
-6-
-------
Pathway 3; OH radical addition to isolated alkene groups
(>C=C<) , nonaromatic conjugated groups
(>C=OC=C<) , and other unsaturated groups
(-Csc-, >C=C=C<, >C=C=0)
The overall rate constant for reaction pathway 3 is given
by the equation
kadd,nar
+ 5>§°Cj(X)Cj(Y) +
(15)
+ E k§uCm(X)Cm(Y)
•
where k^8, k§°, k§u represent the group rate constants for OH
radical addition (add) to isolated (is) carbon-carbon double
bonds, nonaromatic (nar) conjugated (co) carbon-carbon bond
systems, and other unsaturated (ou) carbon-carbon systems,
respectively, and the values of these group rate constants at
298 K are given in Tables 9, 11, and 12, respectively, of an EPA
report by Leifer (1992a) , in Tables 2, 5, (3 and 4),
respectively, of a report by Meylan (199 Ob)3, and in Tables 4,
5, (6 and 7), respectively, Section IV, of this report; £, ]JT ,
i j
, 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) and C(Y) represent the
substituent factors at 298 K for substituents X and Y and are
listed in Table 10 of an EPA report by Leifer (1992a) , in Table
-7-
-------
7 of a report by Meylan (1990b)3, and in Table 8, Section IV, of
this report.
Pathway 4t 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-) (16)
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 at
298 K are listed in Table 1 of an EPA report by Leifer (1992a) ,
in Table 1 of a report by Meylan (1990b)3, and in Table 1,
Section IV, of this report.
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-) (17)
where n(-NH2), n(>NH) , n(>N-) represent the number of -NH2, >NH,
and >N- groups, respectively, in the molecule; k(-NH2) , k(>NH) ,
k(>N-) represent the group rate constants for -NH2, >NH, and
>N-, respectively, and the values of these group rate constants
-8-
-------
at 298 K are listed in Table 1 of an EPA report by Leifer
(1992a) , in Table 1 of a report by Meylan (1990b)3, and in Table
1, Section IV, of this report.
Pathway 6; OH radical interaction with phosphorous groups
The overall rate constant for reaction pathway 6 is given
by the equation
k(6) =
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(0)-], 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 at 298 K are listed in Table 1 of an
EPA report by Leifer (1992a) , in Table 1 of a report by Meylan
(1990b)3, and in Table 1, Section IV, of this report.
Pathway 7; OH radical addition to aromatic rings
The overall rate constant k(7) [=kadd ar] for reaction
pathway 7 is given by the equation
k(7) = k(7A) + k(7B) (19)
where k(7A) corresponds to the addition of OH radicals to an
aromatic ring (ar) and k(7B) corresponds to OH reaction with an
heteroaromatic (monocyclic) ring (ar').
-9-
-------
For reaction of OH radicals with an aromatic ring
k(7A) = *add,ar (20)
Iog10k'add,ar = E f 0.31 - 1.35 Min ( J>+ ) (21)
*add,ar - 1°~12 *add,ar (22)
where ]£ represents the summation over all aromatic rings in the
molecule; ( ]£fft ) represents the summation of the electrophilic
j J
substituent constants of Brown and Okamoto (1958) with respect to
a given ring position (i.e., ortho, meta, para); and Min( ^Pat )
at ) 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 (ajjj and ai) for a number of substituents
are given in Table 22 of an EPA report by Leifer (1992a) , in
Table 8 of a report by Meylan (1990b)3, and in Table 9, Section
IV, of this report.
Atkinson did not develop S/R relationships for OH radical
addition to a heteroaromatic ring (monocyclic) while Meylan
(1990b)4 did develop S/R relationships. For OH radical addition
to the heteroaromatic ring (ar'); AOP uses the equation
4 User's Guide for the Atmospheric Oxidation Program, Version
1.10, November 1, 1990.
-10-
-------
k(7B) - kadd/ar, (23)
Io9l0kadd,ar' = £ I Ai ~ 1'35 Min (
where £ represents the summation over all heteroaromatic rings,
i
AI is a function of the experimental value of kadd ar/ of the
basic, or parent, heteroaromatic ring in the units 10~12
cm3molecule~1s~^ [Table 10, Section IV, of this report and on
page 7 of a document by Meylan (1990b)4]; and the other
parameters have been described previously. The use of equations
23 and 24 will be discussed in more detail in Section IV. B.
Pathway 8; OH radical addition to fused ring polyaromatic
compounds
The overall rate constant k(8) for reaction pathway 8 is
given by the equation
k(8) = k(8A) + k(8B) (25)
where k(8A) corresponds to the addition of OH radicals to a
polynuclear aromatic hydrocarbon ring (PAH) and k(8B) corresponds
to the OH radical addition of OH radicals to a polynuclear
heteroaromatic ring (PAH7). For OH addition to the polyaromatic
hydrocarbon ring
k(8A) = kadd/PAH (26)
lo9lO*add,PAH = 10-11 ' 1'08 i - 1'35 Min< EaD > (27)
-11-
-------
kadd,PAH = 10~12k'add,PAH (28)
where £ 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); ( £a} ) is derived for 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 ( V'tft ) represents the summation of
the electrophilic substituent constants with respect to the ring
hydrogen position that gives the most negative summation (i.e.,
Min ) . Electrophilic substituent constants (ajjj and ai) for a
number of substituents are given in Table 22 of an EPA report by
Leifer (1992a) , in Table 8 of a report by Meylan (1990b)3, and in
Table 9, Section IV, of this report.
For OH radical addition to fused polynuclear aromatic
hydrocarbon rings, Meylan (1990b)3, developed a different
approach to estimate kadd PAH* Meylan, in AOP, uses the equation
l°9lO*add,PAH - £ I Bi - i'35 deD I (29)
where represents the summation over all fused polynuclear
aromatic hydrocarbon rings, B^ is a function of the experimental
value of kadd,PAH of the basic, or parent, polynuclear
hydrocarbon aromatic ring in the units 10~12cm3molecule~1s~1
-12-
-------
[Table 11, Section IV, of this report and from Meylan (1990b)4
for naphthalene, anthracene, and phenanthrene] or is given an
assigned value based primarily on the experimental ionization
potential of the basic, or parent, polynuclear aromatic
hydrocarbon ring in the units 10~12cm3molecule~1s""1 [Table 12,
Section IV, of this report and from Meylan (199Ob)4] for 4, 5,
and 6 fused benzene rings. The term de^ is related to the
substituent factors a£ and ai for various substituents and is
determined in the following way. For monosubstituted PAH
compounds, de^ corresponds to the most negative value of a£ or ap"
for a given substituent on the ring. For polysubstituted PAH
compounds, de^ corresponds to the sum of the average values of aj
and ai for each substituent on both rings.
For OH radical addition to polynuclear heteroaromatic rings
(PAH'), Meylan (1990b)4 uses a modified form of equation 29 which
is
(30)
l°9lOkadd,PAH' = £ I Bi ' l'25 dej
where B^ is now related to the experimental ionization potential
of the basic, or parent, fused polynuclear heteroaromatic ring in
the units 10~12cm3molecule~1s~1 [obtained from Table 13, Section
IV, of this report for a few fused polynuclear heteroaromatic
rings and from Meylan (1990b)4]. The term de^ is the same as the
one described previously. It should be noted that at present,
AOP cannot estimate ka(j(j PAH' for fused ring structures contain-
-13-
-------
ing five-membered heterocyclic rings. The use of equations 29
and 30 will be discussed in more detail in Section IV.B.
III. Syracuse Research Corporation Atmospheric Oxidation
Computer Program (Developed by Meylan)
III.A. Introduction
The Atmospheric Oxidation Computer Program [designated as
AOP] was purchased from Syracuse Research Corporation by the
Exposure Assessment Branch of the Office of Pollution Prevention
and Toxics, U.S. Environmental Protection Agency, based on the
recommendation of Leifer. The first version, labeled Version
1.00, was received July 10, 1990 [Meylan (1990a)]. The
Atmospheric Oxidation Program estimates the second-order rate
constant for the reaction of an organic chemical with hydroxyl
radicals ()COH) and ozone (ko.) in the gas-phase. These rate
constants are then used to calculate the half-life [t^^JE^ for
these two reaction pathways based on average hydroxyl radical and
ozone concentrations in the troposphere.
Based on a very preliminary evaluation of the hydroxyl
radical portion of this program, a few errors were uncovered.
After a discussion by phone with Meylan on August 2, 1990,
changes were made in the hydroxyl radical portion of this
program. The new AOP computer program, Version 1.30, was
received on November 1, 1990 and contained a data base for
experimental values for the reaction of organic chemicals with
hydroxyl radicals (kOH), ozone (k03), and nitrate radicals
(kNO_). This report covers the evaluation of the hydroxyl
-14-
-------
radical portion of AOP. Future EPA reports will be devoted to
the discussion of the S/R relationships of Atkinson and Carter
(1984) for ozone and the evaluation of AOP for estimating ko and
the corresponding half-life
III.B. Atmospheric Oxidation Computer Program (AOP)
The estimation methods used in AOP are based on the
structure/reactivity relationships of Atkinson (1986, 1986a,
1987, 1987a, 1988, 1988a) for the gas-phase reaction of hydroxyl
radicals with organic chemicals in the troposphere as described
in detail in the report by Leifer (1992a) and the structure/
reactivity relationships of Atkinson and Carter (1984) for the
gas-phase reaction of ozone with organic chemicals in the
troposphere. As stated in Section III. A., only the AOP program
for estimating kOH and t^^JE wi-11 be discussed in this report.
AOP has been designed for use in an IBM or an IBM-compatible
series of personal computers running the MS-DOS or PC-DOS
operating systems. Approximately 350 K of free memory are
required to run AOP. All program outputs occur in the text mode
and are run from a floppy disk drive.
The AOP program is started by pressing key F-8 of the
Workstation Menu, typing in AOP, and then pressing the Enter key.
Program execution begins by displaying the data input screen
shown in Figure 1. The program version and date are displayed in
the upper left corner of the screen. The present version is
specified in three lines:Version:/SRC 1.30/Nov 1990. The large
-15-
-------
Figure 1. Atmospheric Oxidation Program Data Entry Display
Version:
SRC 1.30
Nov 1990
IHHMHHi'1i'1l'1HHI1l1HHHHHt1MMMMHMHMI'1MHMHMMHHH:
ATMOSPHERIC OXIDATION PROGRAM
: Rate o-f Hydroxyl Radical ?< Ozone ;
; Reaction -from Chemical Structure /
Enter SMILES:0
0 0 0 0 0 <~><~> (') <"> t~> 0 0 0 0 <~>
INS: OFF
J Fl: CLEAR Input
3 F2: PREVIOUS Input
3 F4: User FILE Input
F6: Save Input to User File
F8: CAS File Input
F10: CALC ?< SAVE Results
PgDn: CALCULATE
Alt-H: SMILES HELP
Esc: EXIT to DOS
-16-
-------
rectangular box in the upper center of the screen contains the
program name and purpose. A large box in the middle portion of
the screen is used to enter the SMILES notation corresponding to
the chemical to be used in the estimation. The SMILES notation
is a computer readable molecular structure system. Currently, a
maximum of 120 characters are allotted for the SMILES notation.
Directly below the Enter SMILES box, is a box with Enter NAME.
This box is used to enter the name of the chemical and a maximum
of 60 characters are allotted for this purpose. The blank space
in the lower portion of the screen is used to display error
messages corresponding to the SMILES entry. Finally, the lower
box contains the various edit keys. The reader is referred to
the USERS GUIDE for AOP, Version 1.10, prepared by William Meylan
of Syracuse Research Corporation, for a detailed discussion of
the operation of AOP.
The only data required for AOP to produce estimated and
experimental values of kOH and t/i/2)E is the SMILES notation
corresponding to the molecular structure of the chemical. The
name of the chemical is optional and is not required to run AOP.
As an illustration of the operation of AOP and the output data to
the monitor screen, consider the chemical a-methyl styrene,
(2-phenyl-l-propene) which has a SMILES notation C=C(C)clcccccl.
This SMILES notation is entered at the point adjacent to the
ENTER SMILES notation on the screen and pressing key PgDn. If
the SMILES notation is correct, the data entry screen is removed
and the k0n data are displayed on the screen, Figure 2.A. The
-17-
-------
Figure 2. Atmospheric Oxidation Program Data Display for the
Compound a-Methyl Styrene (2-Phenyl-l-Propene):
Summary Hydroxyl Radical Data and Experimental Data.
Figure 2A
A. Screen Display when Key PgDn is pressed.
SMILES :
CHEM :
MOL FOR:
MOL WT :
C=C(C)clcccccl
C9 H10
118.18
Hydrogen Abstraction =
Reaction with N, S and -OH =
Addition to Triple Bonds =
** Addition to Ole-finic Bonds =
** Addition to Aromatic Rings =
Addition to Fused Rings =
SUMMARY: HYDROXYL RADICALS
= .1440 E-12 cm3/molecule-sec
. GOOD
. 0000
51.4000
1.9187
E-12
E-12
E-
cm3/molecule-sec
cm3/molecule-sec
12 cm3/molecule-sec
E-12 cm3/molecule-sec
0000 E-12 cm3/molecule-sec
OVERALL yOH Rate
HALF-LIFE =
- —— "7
OV3
HA3
3
3
3
3
Name: 2-F'henyl-1-propene
CAS Number: 00098-83-9
Exper OH rate constant
Exper Ozone rate constant
Exper N03 rate constant
«-methyl styrene)
Constant = 53.4627 E-12 cm3/molecule—sec
.300 Days (at cone 5E5 yOH/cm3)
** Designates Estimation(s) Using ASSUMED Value(s)
DDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD?
3-
3
3
0 E-12 cm3/molecule-sec 3
3
3
3
3
CDDDDDDDDDDDDDDDDDDDY
E-12 cm3/molecule-sec
cm3/molecule-sec
cm3/molecule-sec.
QDDDDDDDDDDDDDDDDDD4 Press any key to continue.
-18-
-------
Figure 2B
B. Screen Display when Key F-10 is pressed.
SMILES :
CHEM :
MOL FOR:
MOL WT :
C=C(C)clcccccl
C9 H10
118.18
Hydrogen Abstraction =
Reaction with N, S and -OH =
Addition to Triple Bonds =
** Addition to Ole-finic Bonds =
** Addition to Aromatic Rings =
Addition to Fused Rinqs =
I /•/ /•/ M111111IIHIIIIIIIIIIII11 MIIIIII1111:
: Summary Saved to:
; -file —> AOP1.DAT .;
HIIIIIIIIIIIIIIH11111111II11II11HIIH H11 <
SUMMARY: HYDROXYL RADICALS
= .1440 E-12 cm3/molecule-sec
0000 E-12 cm3/molecule-sec
0000 E-12 cm3/molecule-sec
51.4000 E-12 cm3/molecule-sec
1.9187 E-12 cm3/molecule-sec
0000 E-12 cm3/molecule-sec
OVERALL yOH Rate Constant = 53.4627 E-12 cm3/molecule-sec
HALF-LIFE = .300 Days
-------
SMILES notation, molecular formula, and molecular vsight of
o-methyl styrene are displayed at the top left portion of the
screen. Directly below these data and in the center of the
screen, this figure displays the SUMMARY: HYDROXYL RADICALS data
and the EXPERIMENTAL DATA. Directly under SUMMARY: HYDROXYL
RADICALS, the estimated rate constants for each of the specific
reaction pathways (k^) for a-methyl styrene are listed.
Immediately below the summary data, the overall kOH rate constant
{which represents the sum of each of the individual rate
constants [k(i)]> and the corresponding half-life are listed.
The half-life (in days) corresponds to an average OH radical
concentration of 5E5 radicals cm'3 and a 24-hour daylight day.
The table in the lower box summarizes the available
experimental kOH, k03/ and kN03 data for this compound. The
experimental value of kon *s listed as 52.0 E-12 cm-^molecule'^-s'1
as obtained from Atkinson (1989). No experimental rate data are
available for the reaction of a-methyl styrene with ozone (k0_)
and with nitrate radicals (kN03). If/ after the SMILES notation
for a-methyl styrene is entered, key F-10 is pressed instead of
PgDn, the results are then displayed on the screen as shown in
Figure 2.B. In this case, the estimated and experimental data
are the same as the data in Figure 2.A. except that the estimated
data are now stored in a file as indicated in the top right
corner box.
Pressing key PgDn displays the same OH rate data but now the
SUMMARY: OZONE REACTION data replaces the available experimental
-20-
-------
data, Figure 3A. The ozone data corresponds to the overall
estimated ozone rate constant (k0;3) and the associated half-life
tt(l/2)E3 *-n days corresponding to an average ozone concentration
of 7E11 molecules cm~3 and a 24-hour day. If, after the SMILES
notation for a-methyl styrene is entered, key F-10 is pressed
twice, then the results are depicted in Figure 3.B. In this
case, the estimated data is the same as the data displayed in
Figure 3.A. except that the data is now stored in a file as
indicated in the box in the upper right corner.
When pressing key F-9 five times, the screen displays
sequentially for a-methyl styrene:
(1) the detailed calculations for hydrogen abstraction
[k(la)], Figure 4.A.;
(2) OH addition to the olefinic group [k(3) = ka
-------
Figure 3. Atmospheric Oxidation Program Data Display for the
Compound a-Methyl Styrene (2-Phenyl-l-Propene):
Summary Hydroxyl Radical and Ozone Data.
Figure 3A
A. Screen Display when Key PgDn is pressed.
SMILES :
CHEM :
MOL FOR:
MOL WT :
C=C(C)clcccccl
C9 H10
118.13
Hydrogen Abstraction =
Reaction with N, S and -OH =
Addition to Triple Bonds =
** Addition to Olefinic Bonds =
** Addition to Aromatic Rings =
Addition to Fused Rings =
SUMMARY: HYDROXYL RADICALS
= . 1440 E--12 cm3/molecule-sec
.0000 E-12 cm3/molecule-sec
.0000 E-12 cm.3/molecLile-sec
51.4000 E-12 cm3/molecule-sec
1.9187 E-12 cm3/molecule-sec
.OOOO E-12 cm3/mo1ecu 1e-sec
OVERALL yOH
HALF-LIFE =
Rate Constant = 53.4627 E—12 cm3/molecule-sec
.300 Days (at cone 5E5 yOH/cm3)
, ** Designates Estimation(s) Using ASSUMED Value(
SUMMARY: OZONE REACTION
OVERALL OZONE Rate Constant = 13.650000 £-17 cm3/molecule-sec
HALF-LIFE = .084 Days
-------
Figure 3B
B. Screen Display when Key F-10 is pressed.
SMILES :
CHEM :
MOL FOR:
MOL WT :
C=C(C)clcccccl
C9 H10
118. 18
Hydrogen Abstraction =
Reaction with N, S and -OH =
Addition to Triple Bonds =
** Addition to Ole-finic Bonds =
** Addition to Aromatic Rings =
Addition to Fused Rings =
IH H H H H H 11 H H H H H H il H H H H H H H
: Summary Saved to:
; tiTe —> AOF'l.DAT
H H H H H H H H H H /•/ H H H H HIIII11H H H
SUMMARY: HYDROXYL RADICALS
= .1440 E-12 cm3/molecule-sec
.0000 E-12 cm3/molecule-sec
.0000 E-12 cm3/molecule~sec
51.4000 E-12 cm3/molecule-sec
1.9187 E-12 cm3/molecule-sec
.OOOO E-12 cm3/molecule-sec
OVERALL yOH Rate Constant = 53.4627 E-12 cm3/molecule~sec
HALF-LIFE = .300 Days (at cone 5E5 yOH/cm3)
** Designates Estimation(s) Using ASSUMED Value(s)
SUMMARY: OZONE REACTION
OVERALL OZONE Rate Constant = 13.650000 E-17 cm3/molecule-sec
HALF-LIFE = .084 Days (at cone 7E11 mol/cm3)
Press F9 to Show Calc
Press ESC to STOP.... anything else to continue
-23-
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Figure 4. Atmospheric Oxidation Program Data Display for the
Compound o-Methyl Styrene (2-Phenyl-l-Propene):
Figure 4A
A. Screen Display of the Detailed Calculations for
Hydrogen Abstraction.
Hydrogen Abst ract i on
Kprim = 0.144 FO-C=C<) = 0.144 ( 1.000) ~ .144
H Abstraction TOTAL = .144 E--12 cm3/moiecule-sec
Pr ess an y key t o c ont i nue
-24-
-------
Figure 4B
B. Screen Display of the Detailed Calculations for
OH Radical Addition to the Olefinic Bond.
GH Add i t ion to 0.1 ef i nic Bond s
Kd = K(CH2=COC(-PhenyJ. **>
= 51.400(1.00) = 51.40O E-12 cm3/molecule-sec
ASSUMED Value designated by: **
Press any key to continue
-25-
-------
Figure 5. Atmospheric Oxidation Program Data Display for the
Compound cr-Methyl Styrene (2-Phenyl-l-Propene) :
Figure 5A
A. Screen Display of the Detailed Calculations with
03 Reaction with the Olefinic Bond.
Ozone Reaction with 01 etins
Ko = K (CH2--C--R2) Ox (--CH3) Ox (-Aromatic)
= . 175000 ( 6. 500) (12. 000) = 13.650000 E- .1. 7 cm3/malecul e-sec
F' r e s s any k e y t o c CD n t i n u. e
-26-
-------
Figure 5B
B. Screen Display of the Detailed Calculations of
OH Radical Addition to the Aromatic Ring.
OH Addition to Aromatic Rings
de + = host negative value of ep+ or em+ <-C=C **) - .020
Log Kar = -11.69 - 1.35 de+ cm3/molecule-sec
Ring ttl Kar := 1.9187 E--12 cm3/molecule-sec
TOTAL Kar = 1.9187 E--12 c:m3/molecule-sec
Assumed values designated by **
-r e s s any ke y t o con tinue
-27-
-------
Figure 6. Atmospheric Oxidation Program Data Display for the
Compound a-Methyl Styrene (2-Phenyl-l-Propene):
Screen Display for OH Addition to the Aromatic Ring
and the Experimental Data.
OH Addition to Aromatic Rings
de + - Most negative value of ep + or em+ (~C=C **) =
Log Kar = --11 .69 - 1.35 de-i- cm3/ molecule-sec
Ring ttl Kar = 1.9187 E--12 cm3/mo.lscule-sec
TOTAL Kar = 1., 9187 E--1.2 cm3/molecule-sec
...................... Assumed values designated by **
ZDDDDDDDDDDDDDDDDDDDDDD4 EXPERIMENTAL DATA CDDDDDDDDDDDDDDDDDDDDDDDDDD2_
3
3 Name: 2-Pheny 1-1-propene (^(-methyl styrene)
3 CAS Number: 00098-83-9 ' 3
3 Exper OH rate constant : 52.0 E-12 cm3/molecule-sec 3
3 Exper O^one rate constant : cm3/molecule-sec 3
3 Exper N03 rate constant : cm3/molecule-sec 3
3 3
3 3
QDDDDDDDDDDDDDDDDDD4 Press any key to continue... CDDDDDDDDDDDDDDDDDDDYs
-28-
-------
is reproduced with the original SMILES notation for a-methyl
styrene.
IV. Evaluation of the Atmospheric Oxidation Computer Program
for Estimating kOH and the Experimentally Measured KOH
Data Listed in the Program
IV.A. Comments on the Group Rate Constants, Substituent Factors,
and Other Parameters Used by the Atmospheric Oxidation
Program
The group rate constants, substituent factors, and other
parameters are listed in Tables 1 through 9 for a large number of
classes of compounds as obtained from Meylan (1990b). A few
comments will be made in this section on the numerical values of
these parameters listed in these tables. More details will be
given in Sections IV.C. through IV.F. on specific classes of
compounds and specific compounds in each of these classes.
First, consider Table 1 which summarizes the group rate
constants for hydrogen abstraction and radical reaction. The
value of the group rate constant k(>C<) is listed as zero with
one significant figure. However, this value is known much more
accurately; conservatively, it is known to three significant
figures. Therefore, it is recommended that AOP use k(>C<) =
0.000 which is consistent with the accuracy of the S/R
relationships of Atkinson.
Table 1 does not have an entry for H-atom abstraction from
unsaturated carbon-carbon functional groups (i.e., =C-H). Even
at temperatures up to 500 K, H-atom abstraction from these
functional groups is zero [Atkinson (1987)]. Therefore, it is
-29-
-------
Table 1. Group Rate Constants for Hydrogen Abstraction and
Radical Reaction1
Group Rate Constant k X 1012 cm3/molecule-sec
k(-CH3) 0.144
k(-CH2-) 0.838
k(>CH-) 1.83
k(>C<) 0
k(-OH) 0.0362
k(-NH2) 20
k(-NH-) 60
k(>N-) 60
k(-SH) 313
k(-S-) 2.0
k(-S-S-) 200
k(>N-NO) 0
k(>N-N02) 0
k[P(=0)] 0
k[P(=S)] 55
1 Data from Table 1 in Group Rate Constants and Substituent
Values Used by the Atmospheric Oxidation Program, Version
1.30, November 1990 [Meylan (1990b)].
2 This group rate constant is only applicable to hydroxyl groups
in alcohols and glycols.
3 Used only for aliphatic connections; connection to aromatics
not included based upon experimental rate constant for
thiophenol.
-30-
-------
Table 2. Subatituent F(X) Factors for Hydrogen Abstraction1
(values marked with "**" are estimated/assumed values)
Substituent
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
-CH3
-CH2-
-CH2CL
-CH2Br
-CH2F
-CH2C(«O)-
-CH2ONO2
-CH2CN
-CH2I **
>CH-
-CHCL2
-CHF2
-CHBr2 **
-CHI 2 **
XJHCf-O)-
>CHONO2
XX
-CCL3
-CF3
-CBr3 **
-CI3 **
>CC(-O)-
>CONO2
-CF2CL
-F
-CL
-Br
-I •*
=O
-Aromatic
-OH
-0-
-ON02
-CN
-OC(=0)R
-C=(O)CL
-C(=0)-
-CHO
-C(*O)OR
X>C<
-c»c-
-SH
Factor
1.
1.
.00
.29
0.57
0.57
0.85
4.4
0.30
0.5
0.57
1.29
0.57
.0.10
0.57
0.57
4.4
0.30
1.29
0.09
0.075
0.09
0.09
4.4
0.30
0.025
0.099
0.38
0.30
0.30
8.8
1.0
3.4
6.1
0.18
0.14
,5
,5
0.76
0.76
0.0
1.0
1.0
1.
0.
(given same value as -CH2Br)
(given same value as -CHCL2)
(given same value as -CHCL2)
(given same values as -CCL3)
(given same values as -CCL3)
(given same value as -Br)
9.0
-31-
-------
Table 2. Continued
Subatituent
43. -S-
44. -SS-
45. -NH2
46. -NH-
47. -N<
48. -NNO
49. -NN02
50. -N02
51. -OP-
52. -SP-
53. -P- **
54. »P **
55. =M **
56. =S **
57. CH-Halogen **
58. S(+4)-0 **
59. blank
60. Missing
61. -CH-2Halogena **
62. -C-3Halogens **
63. -CHF-Halogen **
64. -0-0- **
65. -O-N» **
66. >CNO2 **
67. >CHNO2 **
68. CH2-NO2
69. CH2-O-
70. 2nd -O-
71. Sulfonic acid **
72. 2nd alkyl ketone
73. -CH(Halogen)OO **
74. -CH(NO2)OO **
75. -CH(NO2)Halogen **
76. XJ(NO2)C»O- **
77. >C(ONO2)C=O- **
78. -CH(ONO2)C-O **
79. XJ-O- **
Factor
9.0
9.0
10
10
10
10
10
0.18
20
20
,0
,0
1.0
9.0
0.57
99.0
1.0
0.0
0.57
0.09
0.30
50
2.0
0.30
0.30
0.30
.50
.00
4.
1.
0.20
.00
.10
1.
3.
1.3
0.21
1.3
1.3
1.3
4.5
(new Atkinson value)
(arbitrarily assigned a value of unity)
(arbitrarily assigned a value of unity)
(arbitrarily assigned a value of unity)
(given same value as sulfur Is 42, 43, 44)
(estimated by Asa Leifer)
(based on dimethyl sulfoxide data)
(given same value as -CHCL2)
(given same value as -CCL3)
(assigned a value between -CHF2 and
-CHCL2)
(based on experimental OH rate constants
for methyl and t-butyl hydroperoxides)
(arbitrarily assigned based on other
values for oxygen and nitrogen
connections)
(given same value as 68)
(given same value as 68)
(new nitroalkane data)
(new Atkinson value)
(new Atkinson value)
(arbitrary estimate)
(data for cyclobutanone)
(combination of previous)
(combination of previous)
(combination of previous)
(combination of previous)
(combination of previous)
(combination of previous)
(given same value as CH2-O-)
1 Data from Table 6 in Group Rate Constants and Substituent Values Used by the
Atmospheric Oxidation Program, Version 1.30, November 1990 [Meylan (1990b)].
-32-
-------
Table 3. Factors Used for Aliphatic Ring Strain Effects1
Factor
3-Membered Ring 0.017
4-Membered Ring 0.22
5-Membered Ring 0.80
6-Membered Ring 1.00
7 to 10-Membered Ring 1002
1 Data from Table 10 in Group Rate Constants and Substituent
Values Used by the Atmospheric Oxidation Program, Version 1.30,
November 1990 [Meylan (1990b)].
2 Note: aliphatic rings containing more than 10 members do not
have any ring strain effect factor applied to them.
-33-
-------
Table 4. Group Rate Constants for OH Radical Addition to
Isolated Olefinic Units1
Structure k X 1012 cm3/molecule-sec
CH2=CH- 26.3
CH2=CH< 51.4
-CH=CH- (cis-) 56.1
-CH=CH- (trans-) 63.7
-CH=C< 86.9
>C=C< 110.0
-CH=CH- (cyclic) 56.I2
1 Data from Table 2 in Group Rate Constants and Substituent
Values Used by the Atmospheric Oxidation Program, Version
1.30, November 1990 [Meylan (1990b)].
2 The group rate constant for cyclic alkenes such as cyclopentene
and cyclohexene is assumed to be the same as the cis-iosmer
value although the trans-isomer value yields slightly better
estimates.
-34-
-------
Table 5. Group Rate Constants for OH Radical Addition to
Conjugated Olefinic Units1
No. Alkyl Groups
1
1
2
2
2
2
2
3
3
3
3
Structure
CH2=CH-CH=CH-
CH2=CH-C=CH2
CH2=CH-CH=C<
CH2=CH-C=CH-
CH2=C-CH=CH-
-CH=CH-CH=CH-
CH2=C-C=CH2
CH2=CH-C=C<
CH2=C-CH=C<
-CH=CH-CH=C<
CH5=C-C=CH-
k X 1012 cm-3 /molecule-sec
105
105
135
135
135
135
135
180
180
180
180
-CH=CH-C=CH- 180
-35-
-------
Table 5. Continued
No. Alkyl Groups
Structure
k X 1012 cm3/molecule-sec
4
4
>C=CH-CH=C<
-CH=C-CH=C<
230
230
-CH=CH-C=C<
230
CH2=C-C=C<
2 I I
230
-CH=C-C-CH-
I I
230
>C=C-C=CH-
I I
2852
>C=CH-C=C<
285J
>C=C-C=C<
C-C=(
350s
1 Data from Table 5 in Group Rate Constants and Substituent
Values Used by the Atmospheric Oxidation Program, Version 1.30,
November 1990 [Meylan (1990b)].
2 These values have been estimated....estimates are based upon
the increasing relationship for the l to 4 alkyl group
structures.
-36-
-------
Table 6. Group Rate Constants for OH Radical Addition to
Alkyne Units1
Structure k X lO cm/molecule-sec
CH»C- 6.4
-O»c- 29.0
1 Data from Table 3 in Group Rate Constants and Substituent
Values Used by the Atmospheric Oxidation Program, Version 1.30,
November 1990 [Meylan (1990b)].
-37-
-------
Table 7. Group Rate Constants for OH Radical Addition to
1,2-Dialkene (Allene) Units1
Structure k X 1012 cm3/molecule-sec
CH2=C=CH- 31.0
-CH=C=CH- 57.0
CH2=C=C< 57.O2
-CH=C=C< 85.02
>C=C=C< 110.02
1 Data from Table 4 in Group Rate Constants and Substituent
Values Used by the Atmospheric Oxidation Program, Version 1.30,
November 1990 [Meylan (1990b)].
2 These values have been estimated....the estimates are based
upon analogy to the single unit olefin rate constants (see
Table 2).
-38-
-------
Table 8. Substituent Factors [C(X)] for OH Radical Addition to
Olefins and Acetylenes1
(values marked with "**" are estimated/assumed values)
Substituent
Factor
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
-F
-CL
-Br
-CH2CL 0.76
-CN
-CHO
-C(»O)CH3
-OCH3
-O
-I ** 0.26
-CH2Br **
-CH2P **
-CH2I **
-oc **
not used
-Phenyl **
-C(-O)X **
-OC **
-C«C **
-S ** 1.0
-O ** 1.0
-P ** 1.0
-N02 **
-ONO2 **
=S ** 1.0
-N ** 0.6
=P ** 1.0
-M ** 1.0
cyclic C»O **
Miasing
R
0.4
0.20
0.26
0.15
0.26
0.91
1.3
1.0
(giy«
0.76
0.76
0.76
0.85
1.0
0.91
1.3
1.10
(arb:
(arb:
(arb;
0.5
0.6
(arb
(arb
(arb
(arb
0.20
1.0
1.00
(given same value as -Br)
0.76 (given same value as -CH2CL)
0.76 (given same value as -CH2CL)
0.76 (given same value as -CH2CL)
(Atkinson assumption, Int. J. Chera. Kinet. 19:822.)
(given same value as -C(»O)CH3
(given same value a* -OCH3)
(based on experimental rate constant for
diacetylene)
(arbitrarily assigned a value of unity)
(arbitrarily assigned a value of unity)
(arbitrarily assigned a value of unity)
(arbitrary estimate)
(arbitrary estimate)
(arbitrarily assigned a value of unity)
(arbitrary estimate)
(arbitrarily assigned a value of unity)
(arbitrarily assigned a value of unity)
(based on data for naphthaquinone)
(for an alkyl or a cycloalkyl group)
1 Data from Table 7 in Group Rate Constants and Substituent Values Used by the
Atmospheric Oxidation Program, Version 1.30, November 1990 [Meylan (1990b)].
-39-
-------
Table 9. Electrophilic Substituent Factors for OH Radical
Addition to Aromatic Rings1
(values marked with "**" are estimated/assumed values)
The oj and c£ values which are not considered "assumed" values are taken
directly from the following reference: Brown, H.C. and Okamoto, Y (1958),
"Electrophilic Substituent Constanta", J. Am. Chem. Soc. 80: 4979-4987.
Various "assumed" values are based on similar structures with known a* values.
1. Amino (-NH2) -0.16 -1.3
2. Dimethylamino (CH3-N-CH3) -0.16 ** -1.7
3. Aniline- (C6H5-NH-) -0.16 ** -1.4
4. Acetylamino (CH3C(«O)-NH-) 0.21 ** -0.6
5. Benzoylamino (C6H5-C(=O)-NH-) 0.21 ** -0.6
6. Hydroxy (-OH) 0.121 ** -0.92
7. Methoxy (-OCH3) 0.047 -0.778
8. Phenoxy (C6H5-O-) 0.10 ** -0.50
9. Methylthio (CH3-S-) 0.158 -0.604
10. Methyl (CH3-) -0.066 -0.311
11. Ethyl (CH3-CH2-) -0.064 -0.295
12. Isopropyl (CH3-CH-CH3) -0.060 -0.280
13. tert-Butyl (-C(CH3)(CH3)(CH3)) -0.059 -0.256
14. Aromatic (phenyl) 0.109 -0.179
15. Chloromethyl (-CH2-CL) 0.14 -0.01
16. Fluoro (-F) 0.352 -0.073
17. Bromo (-Br) 0.405 0.150
18. Chloro (-CL) 0.399 0.114
19. lodo (-1) 0.359 0.135
20. Trifluoro (-C-F3) 0.520 0.612
21. Cyano (-CsN) 0.562 0.659
22. Nitro (-N02) 0.674 0.790
23. Carboxy (-C(=O)-OH) 0.322 0.421
24. Carbomethoxy (-C(=O)-O-CH3) 0.368 0.489
25. Carboethoxy (-C(=O)-O-CH2-CH3) 0.366 0.482
26. Carbethoxymethyl (-CH2-C(=O)-O-CH2-CH3) -0.01 -0.164
27. Bromomethyl (-CH2-Br) 0.14 ** -0.01 **
28. lodomethyl (-CH2-I) 0.14 ** -0.01 **
29. Nitrate (-ONO2) 0.674 ** 0.790 **
30. Olefinic (-C=C) 0.02 ** 0.02 **
31. Acetylenic (-CsC) 0.21 ** 0.23 **
32. -O-R (assume methoxy) 0.047 ** -0.778 **
33. Phosporus (-P) 0.0 ** 0.0 **
34. Sulfur (-S) (assume methylthio) 0.158 ** -0.604 **
35. Carbonyl (-OO) 0.10 ** 0.35 **
36. Aldehyde (-CHO) 0.36 ** 0.22 **
37. -C-CL3 0.55 ** 0.65 **
38. -C-Br3 0.55 ** 0.65 **
39. -C-I3 0.55 ** 0.65 **
40. -CH2-F 0.10 ** -0.05 **
41. -CH2- (assume ethyl) 0.06 ** -0.295 **
42. -CH- (assume isopropyl) 0.06 ** -0.280 **
43. -CH-Halogen (assume chloromethyl) 0.14 ** -0.01 **
44. XX (assume t-butyl) -0.059 ** -0.256 **
-40-
-------
Table 9. Continued
45. -NH- -0.16 ** -1.0 **
46. -N= -0.03 ** 0.15 **
47. -CH2-CN 0.17 ** 0.01 **
48. -N=N 0.30 ** 0.64 **
49. -O-C(-O)- 0.10 ** -0.10 **
50. Undefined 0.0 ** 0.0 **
51. -O-P 0.10 ** -0.20 **
52. -S-CN 0.30 ** 0.25 **
53. -S-CO 0.20 ** 0.15 **
54. -O-Halogen 0.15 ** -0.10 **
For the 55-59, the X refers primarily to halogens, but the program also
considers nitro and cyano groups. The estimated values are taken from
Atkinson publications pertaining to estimated rate constants for PCBs.
55. -C6H4-X1 0.25 ** 0.02 **
56. -C6H3-X2 0.39 ** 0.22 **
57. -C6H2-X3 0.53 ** 0.42 **
58. -C6H1-X4 0.67 ** 0.62 **
59. -Phenyl-X5 0.81 ** 0.82 **
60. -SO3 0.50 ** 0.50 **
61. -S-O -0.16 ** -1.30 **
1 Data from Table 8 in Group Rate Constants and Substituent Values Used by the
Atmospheric Oxidation Program, Version 1.30, November 1990 (Meylan (1990b)].
-41-
-------
recommended that AOP adopt the group rate constant k(l, UNS CH) =
0.000, list it in Table 1, and show it in all detailed
calculations for H-atom abstraction from various unsaturated
functional groups (=C-H).
For the compound 0,0-dimethyl chlorophosphorothioate,
Atkinson et al. (1988) indicated that the group rate constant
k(P-Cl) = 0.00; and this should be added to Table 1 and to the
computer program. Furthermore, the group rate constants k(>NNO),
k(>N-N02), and k[P(=0)] should be listed as 0.00.
Inspection of the data in Table 1 indicates that k(-S-) =
2.0s. This value is applicable to OH radical reaction in the
presence of air at 1 atmosphere pressure and thus in the presence
of oxygen. In the absence of oxygen, k(-S-) =0.00 [Atkinson et
al. (1988)]. These facts are pertinent since AOP incorrectly
estimates kOH for acyclic and cyclic sulfides and compares the
estimated values with the experimental values6. For example, for
dimethyl sulfide, the recommended experimental value of k0jj from
Atkinson (1989) is 4.56, Table 24, which is valid in the absence
of oxygen. Therefore, in the data base for these compounds, the
experimental value should be qualified to indicate that kOH was
5 It should be noted that for convenience, the factor
10~12cm3molecule"1s~1 has been omitted. In all subsequent
discussions on group rate constants, this factor will be
omitted. In addition, in all subsequent discussions, all
rate constants k(i) for all individual reaction pathways and
kOH will be written without the factor I0~12cm3molecule~1s~1,
6 From Meylan (1990b), page 10, "Estimation Accuracy of AOP
vs. PCFAP."
-42-
-------
obtained from measurements in the absence of oxygen. If one
wants to compare the estimated value with the experimental value,
then KQJJ should be estimated under the boundary condition in the
absence of oxygen and kOH = 2.59 [since k(-S-) = 0.00]. Thus, a
footnote should be added to the numerical value of the group rate
constant k(-S-) in Table 1 [i.e., for k(-S-)]. The numerical
value should be (2.0)3 and the footnote 3 at the bottom of this
table should be 3 Applicble at 298 K and a total pressure of
1 atmosphere in air (and thus in the presence of oxygen). In the
absence of air, and thus in the absence of oxygen, k(-S-) = 0.00.
This is discussed in more detail in Section IV.E.l.b.
From the experimental kOH data of diethylhydroxylamine, it
was found that k(>NOH) = 0.00 [Leifer (1991a)] and this group
rate constant should be entered into Table 1 and in the AOP
Computer program.
In Table 1, it is indicated that k(-SH) =31 for RSH, where
R is an alkyl group. This group rate constant is not valid when
R is an aromatic group, based on the experimental rate constant
for thiophenol [Meylan (1990b)]. For the present, this
assignment can be tentatively used. However, the experimental
kOH data from Barnes et al. (1986) may not be valid. Therefore,
more experimental data is needed on thiophenol and other alkyl
and aromatic thiols to confirm the assignment for k(-SH).
In Table 1, the value of the group rate constant k(-OH) is
only applicable to H-atom abstraction from the hydroxyl groups in
alcohols and glycols and this fact must be noted in Table 1 for
-43-
-------
k(-OH) and in the computer program. This group rate constant is
not applicable to H-atom abstraction from the hydroxyl groups in
carboxylic acids and alkyl peroxides. See Section IV.C.3.b. for
the discussion of the estimation of kOH for carboxylic acids and
Section IV.C.4.b. for the discussion of the estimation of kOH for
alkyl peroxides.
In Table 2, item, No. 57, should be changed to F(R2CHC1) =
0.57 [estimated by Leifer from the experimental data of 2,3-
dichlorobutane from Mill et al. (1982); and an additional item
F(R2CH- 1 Halogen **) = 0.57 (based on the assignment in No. 57)
should be added before item 60.
The substituent factor F(-0-0 **) =50 should be deleted
from Table 2 because of the erroneous assumption that k(-OH) =
0.036 for methyl and t-butyl hydroperoxide. For the details, see
Section IV.C.4.b. Similarly, the substituent factor dimethyl
sulfoxide, No. 58, Table 2, should be deleted since it is
expected that the sulfoxide would be readily oxidized to the
sulfone. For the details, see Section IV.E.2.b.
Table 4 lists the group rate constant for the functional
group >C=C< as 110.0; it should be 110 based on the experimental
kOH data for 2,3-dimethyl-2-butene and the recommended value by
Atkinson (1986,1989). Therefore, the last significant figure
should be deleted. Similarly, the group rate constant for -CsC-
in Table 6 should be 29 and not 29.0 based on the recommendation
of Atkinson (1987, page 814).
-44-
-------
In Table 8, some of the substituent factors C(X) are marked
with the symbol ** to indicate that they are based on estimated/
assumed values. However, if a substituent factor is based on
experimental kOH data, then the symbol ** should be omitted. For
example, consider diacetylene, in Table 8, No. 19; this
substituent factor is listed as {C[-CsC-**]> = 1.10 (based on the
experimental data for diacetylene). The entry in this table
should be No. 19 C[-CsC-] = 1.10 (based on the experimental data
of diacetylene). Similar comments are applicable to the
substituent factors C(X) for numbers 29 and 16, Table 8.
Therefore, for the substituent factor C[Cyclic C=0 **] (No. 29),
the double asterisks should be removed since the value is based
on the experimental kOH data of 1,4-naphthoquinone; similarly,
for No. 16, C(phenyl **) = 1.0 should be C(phenyl) = 1.00, based
on the experimental ICQJJ data of styrene, a- and /3-methyl styrene,
and /3-dimethyl styrene [Atkinson (1987, page 828)]. These
comments also apply to the substituent factors F(X) marked with
** in Table 2.
In Table 8, No. 14 is listed as C(C=C- **) =0.85 without
any notation as to how this value was derived. Since this
represents an estimated/assumed value, a qualifying statement
should be added to designate how this assignment was made.
Finally, in Table 9, the a£ value for substituent -CH2- (No.
41) is listed as 0.06 ** by analogy with the ethyl group.
However, a^ for the ethyl group is -0.064 and this value should
be listed in No. 4, Table 9.
-45-
-------
IV.B. Some Comments on Hydroxyl Radical Addition to
Heteroaromatic and Fused Polyaromatic Ring Systems
Meylan (1990b) developed elegant S/R relationships for
estimating the second-order rate constant for OH radical addition
to heteroaromatic (mono and fused polycyclic) rings and to fused
polynuclear aromatic hydrocarbon (PAH) rings. For monocyclic
heteroaromatic compounds (ar'), AOP uses equation 24; for fused
ring polynuclear aromatic hydrocarbon compounds (PAH), AOP uses
equation 29; and for fused ring polynuclear heterocyclic
compounds (PAH'), AOP uses equation 30. The first term in each
of these equations [i.e., A^, B^, and B£, respectively] was
derived by Meylan from: (1) the experimental values of kOH for
the basic, or parent, heterocyclic ring or the fused polynuclear
aromatic hydrocarbon ring structure; or from (2) the experimental
ionization potentials for the parent fused ring polynuclear
aromatic hydrocarbons and fused ring polynuclear heteroaromatic
compounds. Tables 10 and 11 list the values of A^ and B^,
respectively, for various heteroaromatic ring structures and
polyaromatic hydrocarbons derived from the experimental kOH data
for the parent aromatic compounds. Tables 12 and 13 list the
values of B^ and B£ , respectively, derived from the experimental
ionization potentials of the parent ring compounds.
AOP has a SMILES interpreter which allows it to identify the
parent aromatic ring structure and assign it the appropriate
value of AI, Bi, or B£ . AOP then adjusts this value for any
substituent on the ring by utilizing the appropriate substituent
-46-
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Table 10. Experimental Values of A^ for Some Monocyclic
Heteroaromatic Compounds*
Experimental Value of A
Heterocyclic Aromatic Ring Structure (10~12cm3molecule"1s~1)
Pyrrole 110.0
Furan 40.5
Thiofuran 9.53
Imidazole 36.0
Oxazole 9.1
Thiazole 1.4
Pyridine 0.37
1,3,5-Triazine 0.15
* Data from page 7 of the User's Guide for the Atmospheric
Oxidation Program, Version 1.10, November 1, 1990 [Meylan
(1990b)].
-47-
-------
Table 11. Experimental Values of B^ for Some Polynuclear
Aromatic Compounds*
Experimental Value of B
Polynuclear Aromatic Ring Structure (10"12cm3molecule"1s~1)
Naphthalene 21.6
Anthracene 110.0
Phenanthrene 31.0
* Data from page 7 of the User's Guide for the Atmospheric
Oxidation Program, Version 1.10, November 1, 1990 [Meylan
(1990b)].
-48-
-------
Table 12. Values of BI for Polynuclear Aromatic Hydrocarbon
Structures Derived from Experimentally Measured
lonization Potentials*
Polynuclear Aromatic Ring Structure
Assigned Value of
BI Based on the
Experimentally Measured
lonization Potential
(10~3-2cm3molecule~1s~1)
4 Fused Benzene Rings
5 Fused Benzene Rings
6 Fused Benzene Rings
80.0
150.0
200.0
* Data from page 7 of the User's Guide for the Atmospheric
Oxidation Program, Version 1.10, November 1, 1990 [Meylan
(1990b)].
-49-
-------
Table 13. Values of B^ for Polynuclear Heteroaromatic
Structures Derived from Experimentally Measured
lonization Potentials*
Polynuclear Heteroaromatic Structure
Assigned Value of B[
Based on the Experi-
mentally Measured
lonization Potential
(10~12cm3molecule~1s~1)
Quinoline
Isoquinoline
Quinoxaline
Quinazoline
Acridine
6.5
6.5
2.0
2.0
27.5
* Data from page 7 of the User's Guide for the Atmospheric
Oxidation Program, Version 1.10, November 1, 1990 [Meylan
(1990b)].
-50-
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factors aj and ai for the substituents on the ring. For
example, for 1-chloronaphthalene, the SMILES interpreter in AOP
identifies the parent naphthalene ring and selects the value of
AI for this ring. AOP then adjusts this value by considering
the effect of the chlorine substituent on the reactivity of the
ring.
It should be noted that Meylan did not develop S/R
relationships for fused ring aromatic compounds containing five
membered heterocyclic rings. For example, AOP cannot estimate
kOH for benzothiazole. In principle, however, the basic
concepts of Meylan can be used. For example, if kOH is
measured for benzothiazole, then B£ from equation 30 can be
determined. Therefore, with this value of B£, kOH can be
estimated for substituted benzothiazoles utilizing the
appropriate substituent factors a^j and <7p for the substituents
on the ring.
More experimental kOH data is needed on a number of
additional derivatives of these heteroaromatic (ar'), polynuclear
aromatic hydrocarbons (PAH), and polynuclear heteroaromatic ring
(PAH') structures to confirm the S/R relationships of Meylan
(1990b) [i.e., confirm the validity of equations 24, 29, and 30].
It should be noted that in Tables 10, 11, and 12, AOP lists
a few of the values of A^ and B^ to four significant figures. At
best, the experimental data used to derive these constants are
only valid to three significant figures. Therefore, it is
-51-
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recommended that the values of A^ and B^ for pyrrole, anthracene,
and for 4, 5, and 6 fused benzene rings should be listed to three
significant figures.
IV.C. H-Atom Abstraction from C-H and -OH Groups by Hydroxyl
Radicals
IV.C.I. Saturated Alkanes
IV.C.I.a. Evaluation of the Experimental kOH Data
Tables 14.A. and 14.B. summarize the pertinent experimental
!CQH data at 298 K for the reaction of OH radicals with acyclic
and cyclic alkanes, respectively, as obtained from AOP and the
literature. For this class of compounds, hydroxyl radical
reaction only involves the abstraction of H-atoms from the
various primary, secondary, or tertiary C-H groups. The first
column in these two tables lists the name of each alkane; the
second column lists the experimental value of kOH at 298 K in AOP
[Meylan (1990b)] and is labeled Experimental/AOP; the third
column lists kOH at 298 K as obtained by Leifer from Atkinson
(1989) and/or from the literature and is labeled
Experimental/(a); the fourth column lists the estimated value of
k0H at 298 K as obtained from AOP and is labeled Estimated/AOP;
and finally the fifth column lists the estimated, hand calculated
(HC), value of koH at 298 K as obtained by Leifer using the S/R
relationships of Atkinson and is labeled Estimated/HC.
Atkinson (1989) critically analyzed the available
experimental kOH data and recommended the best values along with
the rationale behind each recommendation and the uncertainty for
-52-
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Table 14.A.
Comparison of the Estimated Values of kOH at 298 K for
Saturated Acyclic Alkanes from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand Calculation (HC) and the
Experimental kOn Data Reported in the Literature Versus the
Experimental kOH Data Reported in AOP
Chemical
Methane
Ethane
Propane
n-Butane
2 -Methy Ipr opane
n-Pentane
-2 -Methy Ibutane
2, , 2-Dimethylpropane
n-Hexane
2 -Methy Ipentane
3 -Methy Ipentane
2 , 2 -Dimethy Ibutane
2 , 3 -Dimethy Ibutane
n-Heptane
2 , 2 -Dimethy Ipentane
2 , 4 -Dimethy Ipentane
2,2, 3 -Trimethy Ibutane
n-Octane
2 , 2-Dimethylhexane
2,2, 4 -Trimethy Ipentane
2,3, 4 -Trimethy Ipentane
1012kou(cm3molecule""1s~1)
Experimental
AOP
0.00841
0.268
1.15
2.54
2.34
3.94
3.90
0.849
5.61
5.60
5.70
2.32
6.20
7.15
3.37
5.16
4.23
8.68
4.83
3.68
7.0
(a)
0.00836*
0.268*
1.15*
2.54*
2.34*
3.94*
3.9*
0.849*
5.61*
5.6*
5.7*
2.32*
6.2*
7.15*
3.37d
5.16d/
4.23*
8.68*
4.83d
3.68*
6.97e
Estimated
AOP
0.00841b
0.288
1.21
2.53
2.39
3.93
4.00
0.743
5.32
5.39
5.77
1.82
5.46
6.72
3.22
6.86
3.29
8.11
4.61
4.68
8.70
HC
(C)
0.288
1.21
2.53
2.39
3.93
4.00
0.743
5.32
5.39
5.77
1.83
5.46
6.71
3.22
6.85
3.30
8.11
4.61
4.68
8.70
-53-
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Table 14.A. Continued
Chemical
2,2,3, 3-Tetramethylbutane
H-Nonane
2 -Methy loctane
4-Methyloctane
2,3, 5-Trimethylhexane
Q-Decane
Q-Undecane
n-Dodecane
H-Tridecane
H-Tetradecane
n-Pentadecane
Q-Hexadecane
1012kOH(cm3molecule"1s~1)
Experimental
AOP
1.08
10.20
10.1
9.72
7.88
11.6
13.2
14.2
16.0
19.2
22.2
24.9
(a)
1.08*
10.2*
10. ld
9.72d
7.88d
11.6*
13.2*
14.2*
16*
19.2*
22. 2f
24. 9f
Estimated
AOP
1.11
9.51
9.58
9.95
10.1
10.9
12.3
13.7
15.1
16.5
17.9
19.3
HC
1.11
9.50
9.58
9.95
10.1
10.9
12.3
13.7
15.0
16.5
17.9
19.3
a Experimental values from Atkinson (1989) and the literature.
b Estimated value is based on the measured value.
c Cannot be estimated by the S/R methods of Atkinson.
d Experimental value from Behnke et al. (1988).
d' Experimental value from Atkinson et al. (1984).
e Experimental value from Harris and Kerr (1988).
f Experimental value from Nolting et al. (1988).
-54-
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Table 14.B.
Comparison of the Estimated Values of kOH at 298 K for
Saturated Cyclic Alkanes from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand Calculation (HC) and the
Experimental kOH Data Reported in the Literature Versus the
Experimental XOH Data Reported in AOP
Chemical
Cyclopropane
i-Propylcyclopropane
cyclobutane
Cyclopentane
Cyclohexane
Methylcyclohexane
1,1, 3-Trimethylcyclohexane
Cycloheptane
Cyclooctane
Bicyclo [2.2.1] heptane
Bicyclo [2.2.2] octane
'-Bicyclo [3.3.0] octane
jis-Bicyclo [4.3.0] nonane
trans-Bicyclo [4.3.0] nonane
cis-Bicyclo [4.4.0] decane
trans-Bicyclo [4.4.0] decane
Tricyclo [5.2.1.0 2>6] decane
Tricyclo [3.3.1.1 3>7] decane
1012kOH (cm-^molecule'^-s"1
Experimental
AOP
0.07
2.84
1.20
5.16
7.49
10.4
8.73
12.5
13.7
5.49
14.7
11.0
17.2
17.6
19.9
20.4
11.3
22.6
(a)
0.071b
2.84C
1.2*
5.16*
7.49*
10. 4e
8.73f
12.59
13. 7h
5.491
14. 71
11. 0*
17.21
17.61
19.91
20.41
11. 3*
22. 6^
Estimated
AOP
0.0711
2.85
1.23
5.58
8.37
10.2
9.18
9.76
11.2
9.49
16.2
10.4
14.1
14.1
19.0
19.0
12.3
24.1
HC
0.0711
2.85
1.23
5.58
8.37
10.2
9.18
9.77
11.2
9.49
16.2
10.4
14.1
14.1
19.0
19.0
12.3
24.1
a Experimental values from Atkinson (1989) and the literature.
b Average value from the experimental data of Zetzsch (1980) and Jolly et al.
(1983) .
c Experimental value from Atkinson and Aschmann (1988).
^ Experimental value from Gorse and Volman (1974).
e Experimental value from Atkinson et al. (1984).
f Experimental value from Behnke et al. (1988) as reported in Atkinson (1989).
9 Average value of the experimental data of Zetzsch (1980) and Jolly et al.
(1985).
" Experimental value from Behnke et al. (1988) as reported in Atkinson
. (1989).
* Experimental value from Atkinson, Aschmann, Carter (1983a).
J Average value from the experimental data of Atkinson, Aschmann, and Carter
(1983a) and Behnke et al. (1988).
Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-55-
-------
each recommendation. These recommended values have an asterisk
after each value.
In general, the experimental values of kOH listed in AOP are
the same as those obtained by Leifer; there are, however, a few
differences. For methane, the recommended Atkinson value is
0.00836* while AOP lists 0.00841. For 2,3,4-trimethylpentane,
the k0H value of 6.97 was obtained by extrapolation of the data
and Kerr (1988) and appears to be the best value. The best value
of k0jj for cyclopropane should be 0.071 as obtained by averaging
the data of Zetzsch (1980) and Jolly et al. (1985) rather than
the value of 0.07 listed in AOP. For a few compounds, the
incorrect number of significant figures was cited by AOP; the
recommended values list two significant figures whereas AOP lists
three significant figures. For example, for 2-methylbutane, the
Atkinson recommended value is 3.9* while AOP lists 3.90. For
cyclobutane, the value of kOH reported by Gorse and Volman (1974)
and Atkinson (1989) is 1.2 and not 1.20 as listed in AOP. The
experimental kOH data of Gorse and Volman is only good to two
significant figures.
It should be noted that the names of two tricyclic decanes
{tricyclo [5.2.1.0] decane and tricyclo [3.3.1.1] decane} entered
in AOP are incorrect. The correct names should be tricyclo
[5.2.1.0 2-6] and tricyclo [3.3.1.1 3-7] decane since the
superscript numbers on the last digit must be specified to
identify the bridgehead carbons on the last ring. Finally, the
-56-
-------
name of methylcyclohexane is the correct name and not
1-methylcyclohexane as listed in AOP.
IV.C.l.b. Evaluation of the Estimated kOH Data
A preliminary evaluation of the AOP computer program [Meylan
(1990a)] in July 1990 indicated that for some bicyclic and
tricyclic alkanes, the method of estimating kOH in AOP was
incorrect. The AOP computer program did not use the ring strain
factors [F(3), F(4), F(5), or in Meylan's notation RS3, RS4, RS5]
correctly in the calculations. The discrepancies were discussed
with Meylan by phone and a set of the calculations were sent to
him for evaluation. As a result, Meylan (1990b) revised the AOP
computer program for these types of compounds to accurately
reflect the Atkinson S/R relationships for strained ring
compounds [Version 1.30, November 1, 1990].
In evaluating the estimated values of k0n bY AOP and HC, a
few comments can be made about the number of significant figures
used. In general, the summary table in AOP lists the estimated
kOH with a maximum of six significant figures and the detailed
calculations list k(la) or k(lc) with a maximum of five
significant figures. However, the group rate constants k°, k°,
and k°, [or kprim, ksec, and ktert in Meylan's notation] and the
substituent factors F(CH3-), F(-CH2-), and F(>C<) are, at best,
known to three significant figures. Therefore, it is recommended
that AOP show the detailed calculations with four significant
figures and list k(la) or k(lc), or k(la) + k(lc), and kOH in the
-57-
-------
summary table rounded off to 3 significant figures. These
comments on the use of an excessive number of significant figures
apply to all classes of chemicals and specific chemicals.
Comparison of the estimated values of k0n from AOP with
those from HC (after rounding off all estimated values to three
significant figures) in the last two columns in Tables 14.A. and
14.B. indicates that, except for methane, the values are
essentially the same. The trivial differences in the last digit
are due to the method of rounding off the last digit in HC. For
methane, AOP lists a value of 0.00841 which is the experimental
value [which really should be 0.00836* as recommended by
Atkinson] whereas HC does not list a value; kOH cannot be
estimated by the S/R relationships of Atkinson for this compound.
The number of significant figures for RS3, RS4, and RS5 for
strained rings is incorrect. For example, for cyclobutane, RS4 =
0.22000 is used in the detailed calculation section. However,
for RS4, Atkinson listed it as 0.22.
The detailed calculations for H-atom abstraction are
somewhat confusing when the ring strain factor is used. For
example, for bicyclo [2.2.1] heptane, AOP gives
ksec = 0.838 F(-CH2-)F(>CH-)(RS5)(RS5)
- 0.838(1.29)(1.29)(0.64)
= 0.892
It seems to me that a more consistent notation for RS5 would be
(RS5)2 = (0.80)2 rather than (RS5)(RS5) = 0.64. Therefore, ksec
-58-
-------
should read
ksec = 0.838 F(-CH2-)F(>CH-)(RS5)2
= 0.838 (1.29) (1.29) (0.80)2
= 0.892
or
ksec = 0.838 F(-CH2-)F(>CH-)(RS5)(RS5)
- 0.838(1.29)(1.29)(0.80)(0.80)
= 0.892
IV.C.2. Haloalkanes
IV.C.2.a. Evaluation of the Experimental kOH Data
Table 15 summarizes the pertinent experimental KOH data at
298 K for the reaction of OH radicals with haloalkanes as
reported in AOP, in Atkinson (1989), and in the literature. In
general, the literature values listed in the column
Experimental/(a) are the same as those in the column
Experimental/AOP; there are, however, some differences. For
1,1,1-trifluoroethane, AOP lists a value of 0.017, a ten-fold
higher value than the correct value of 0.00171 from Martin and
Paraskevopoulos (1983) and Atkinson (1989). [Please note that
these values are listed in the units 10~12cm3molecule~1s~1 rather
than 10~14cm3molecule~1s~1 as listed in Table 15; see footnote 5,
page 42.] For 1,1,2-trichloroethane, the extrapolated value from
the data of Jeong and Kaufmann (1979) and Jeong et al. (1984)
obtained by Leifer is 0.324 while AOP lists a value of 0.328.
For three haloalkanes, AOP does not list an experimental value
-59-
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Table 15. Comparison of the Estimated Values of kOH at 298 K for Haloalkanes
from the Atmospheric Oxidation Computer Program (AOP) and from a
Hand Calculation (HC) and the Experimental kpH Data Reported in
Literature Versus the Experimental kOH Data in AOP
Chemical
Fluor omethane
Chloromethane
Bromomethane
Dif luoromethane
Fluorochloromethane
Di Chloromethane
Tr i f luoromethane
Difluorochloromethane
Fluorodichloromethane
Tr ich lor omethane
Fluoroethane
Ch lor oe thane
1, 1-Dif luoroethane
1 , 2-Dif luoroethane
1, 1-Dichloroethane
I , 2-Dichloroethane
1 , 2-Dibromoethane
1,1, 1-Trif luoroethane
1,1, 1-Trichloroethane
1 , 1-Dif luoro-1-chloroethane
1, 1, 2 -Tr if luoroethane
1, 1, 2-Trichloroethane
1,1,1, 2 -Tetraf luoroethane
l-Chloro-2 , 2 , 2-Trif luoro-
ethane
1,1,2, 2 -Tetraf luoroethane
1014koH(cm3niolecule~ls~1)
Experimental
AOP
1.68
4.36
4.02
1.09
4.41
14.2
0.024
0.468
3.03
10.3
23.2
39
3.4
11.2
26
22
25
1.7
1.19
0.358
1.8
32.8
0.854
1.62
(j)
(a)
1.68*
4.36*
4.02*
1.09*
4.41*
14.2*
0.024b
0.468*
3.03*
10.3*
23.2°
39*
3.4*
11. 2d
26. Oe
22. Oe
25.0e
0.171d
1.19*
0.358*
1.83d
32. 4f
0.854*
1.62*
0.679
Estimated
AOP
1.43
5.47
4.32
0.82
3.15
12.1
0.18
0.682
2.62
10.0
20.5
40.1
3.23
14.1
34.6
36.3
28.7
1.08
1.30
0.36
2.35
33.2
0.62
2.39
0.36
HC
1.43
5.47
4.32
0.821
3.15
12.1
0.178
0.682
2.62
10.0
20.5
40.0
3.23
14.1
34.6
36.3
28.7
1.08
1.30
0.360
2.35
33.3
0.622
2.39
0.359
-60-
-------
Table 15. Continued
Chemical
Pentaf luoroethane
1-Chloro-l, 2 , 2 , 2 -Tetraf luoroethane
1 , l-Dichloro-2 , 2 , 2-Tr if luoroethane
1, 2-Dibromo-3-chloropropane
2 -Chlor obutane
2 , 3-Dichlorobutane
1014kOH(cm3molecule~1s *)
Experimental
AOP
0.25
1.02
3.35
44
(j)
(j)
(a)
0.249d
1.02*
3.35*
43. 5k
2301
961
Estimated
AOP
0.13
0.52
1.98
50.3
164
95.7
HC
0.135
0.516
1.98
50.3
164
95.7
c
d
e
Experimental values from Atkinson (1989) and the literature.
Since the experimental data was obtained at temperatures > 387 K, the value
at 298 K should be used with caution [Atkinson (1989)].
Experimental value from Nip et al. (1979).
Experimental value from Martin and Paraskevapoulos (1983).
Experimental value from Howard and Evenson (1976) .
Extrapolated from the experimental data of Jeong and Karfmann (1979) and
Jeong et al. (1984).
Extrapolated from the experimental data of Clyne and Holt (1979).
Experimental value from Tuazon et al. (1986).
Experimental value from Mill et al. (1982) .
No experimental value given in the AOP data base.
Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-61-
-------
(i.e., for 1,1,2,2- tetrafluoroethane, 2-chlorobutane, and 2,3-
dichlorobutane). For six compounds, the literature values have
three significant figures while AOP lists two significant figures
[e.g., for 1,1-dichloroethane, the literature value of Howard and
Evenson (1976) is 0.260 while AOP lists 0.26].
IV.C.2.b. Evaluation of the Estimated kOH Data
A comparison of the estimated values of kOH by AOP with HC
in Table 15 indicates that they are essentially the same. The
only differences being that in a few cases, AOP rounds off the
estimated values to two significant figures. The estimated
values of kOH are good to three significant figures. For
example, for trifluoromethane, the estimated value of kOH by HC
is 0.178, while AOP rounds it off to 0.18.
IV.C.3. Carbonyl Compounds
IV.C.3.a. Evaluation of the Experimental KQH Data
Table 16 summarizes the pertinent experimental kOH data at
298 K for the reaction of OH radicals with 57 carbonyl compounds
as reported in AOP, in Atkinson (1989), and in the literature.
These carbonyl compounds can be divided into several classes of
compounds: 11 aldehydes, 19 ketones, 3 a-dicarbonyls, 1 acyl
halide, 18 esters, and 5 carboxylic acids. First, consider all
the compounds except the carboxylic acids. In these classes of
compounds, 12 of them listed by AOP had experimental kOH data
with two significant figures. If the original literature sources
and Atkinson (1989) are checked, all the kOH data are listed with
three significant figures (e.g., formal, 3-hexanone, n-butyl
-62-
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le 16. Comparison of the Estimated Values of kOH at 298 K for Carbonyl
Compounds from the Atmospheric Oxidation Computer Program (AOP) and
from a Hand Calculation (HC) and the Experimental kOH Data Reported
in the Literature Versus the Experimental kOH Data in AOP
Chemical Class/Chemical
A. ALDEHYDES
Formal
Ethanal
Propanal
Butanal
2 -Methyl Propanal
Pentanal
3-Methylbutanal
[^ , 2-Dimethylpropanal
mtr ich lor oaceta Idehyde
Hydr oxyethana 1
( G ly co 1 a Idehyde )
Pentane-1 , 5-Dial
B. ACYCLIC KETONES
Propanone
2-Butanone
2-Pentanone
3-Pentanone
2-Hexanone
3-Hexanone
4 -Methyl -2 -pentanone
3 , 3-Dimethyl-2-butanone
2-Heptanone
1012kOH(cm3molecule~1s~1)
Experimental
AOP
9.7
15.8
19.6
23.5
26.3
28.5
27.4
26.5
1.73
9.9
23.8
0.226
1.15
4.9
2.0
9.1
6.9
14.1
1.21
8.67
(a)
9.77*
15.8*
19.6*
23.5*
26.3*
28.5*
27.4*
26.5*
1.73a/
9.9b
23.8°
0.226*
1.15*
4.9*
2.0*
9.1*
6.90d
14.1*
1.21e
8.67e
Estimated
AOP (% Err or)0
7.37
16.2
22.0
25.5
23.4
27.6
30.0
22.7
1.45
23.0
46.9
0.219
1.38
4.80
2.54
6.95
5.97
9.35
2.01
8.35
HC
7.37
16.2
22.0
25.5
23.4
27.6
30.0
22.7
1.45
23.0
46.9
0.219
1.38
4.81
2.55
6.96
5.97
9.35
2.01
8.35
-63-
-------
Table 16. Continued
Chemical Class/Chemical
2 , 4 -Dimethyl- 3 -pentanone
2-Octanone
2-Nonanone
2 , 6-Dimethyl-4-heptanone
2-Decanone
2 , 4-Pentanedione
2 , 5-Hexanedione
C. CYCLIC KETONES
Cyclobutanone
Cyclopentanone
Cyclohexanone
D. Ot-DICARBONYLS
Glyoxal
Methylglyoxal
Biacetyl
E. ACYL CHLORIDES
Acetyl chloride
F . ESTERS
Methyl formate
1012kOH(cm3molecule"1s~1)
Experimental
AOP
5.38
10.0
12.2
27.5
13.2
1.15
7.13
0.87
2.94
6.39
11.4
17.2
0.238
0.068
0.23
(a)
5.38d
11. Oe
12. 2e
27.5*
13. 2e
1.15*
7.13f
0.87f
2.94f
6.39f
11.4*
17.2*
0.238*
0.0689
0.227h
Estimated
AOP (% Err or)0
5.32
9.74
11.1
18.5
12.5
0.703
5.82
1.17
8.92
12.6
24.5
12.3
0.219
0.0720
0.216
HC
5.31
9.74
11.1
18.5
12.5
0.703
5.82
1.17^
8.9^
12.6
24.5
12.3
0.219
0.0720
0.216
-64-
-------
le 16. Continued
Chemical Class/Chemical
Ethyl formate
H-Propyl formate
n-Butyl formate
Methyl acetate
Ethyl acetate
H-Propyl acetate
i-Propyl acetate
n-Butyl acetate
s-Butyl acetate
Ethyl propionate
n-Propyl propionate
glethyl butyrate
IRhyl butynrate
n-Propyl butyrate
n-Butyl butyrate
Ethoxy ethyl acetate
Methyl trifluoroacetate
G. CARBOXYLIC ACIDS
Formic acid
Acetic acid
Propionic acid
n-Butyric acid
i-Butyric acid
lp12kOH(cm3molecule'"1s~1)
Experimental
AOP
1.0
2.4
3.1
0.34
1.6
3.4
3.4
4.2
(n)
2.1
4.0
3.0
4.9
7.4
10.6
13.0
0.05
0.45
0.74
1.22
2.4
2.00
(a)
1.02h
2.38h
3.12h
0.341i
1.6*
3.4*
3.4*
4.2*
5.5*
2.141
4.02h
3.04h
4.94h
7.41h
10. 6h
13*'
0.052h
0.45*
0.741
1.221
2.4m
2.001
Estimated
AOP(%Error)°
1.44
2.89
4.28
0.216
1.44
2.89
3.12
4.28
4.99
1.63
3.08
1.48
2.71
4.16
5.55
14.0
0.216
0.4363(-3)
0.145(-80)
0.859(-30)
2.12(-12)
1.80(-10)
HC
1.44
2.89
4.28
0.216
1.44
2.89
3.12
4.28
4.99
1.63
3.07
1.48
2.71
4.16
5.55
14.0
0.0518
(k)
(k)
(k)
(k)
(k)
a
Experimental values from Atkinson (1989) and the literature.
Experimental value from Nelson et al. (1984) as reported by Atkinson
(1989) .
-65-
-------
Table 16. continued
b Experimental value from Niki et al. (1987)
c Experimental data from Rogers (1989}. This value of kOH represents the
average value of 25.2 and 22.4xlO~12cm3molecule~1s~1 as measured with
the reference compounds propene and trans-2-butene, respectively.
d Experimental value from Atkinson et al. (1982).
e Experimental value from Wallington and Kurylo (1987).
f Experimental value from Dagaut et al. (1988).
9 Experimental value from Atkinson (1987).
n,Experimental value from Wallington et al. (1988).
ft Experimental data from Hartmann et al. (1986, 1987) as reported by Atkinson
. (1989).
1 Experimental value from Wallington et al. (1988). The data from Campbell
and Parkinson (1978) was not used since the experimental method was probably
. not valid/Atkinson (1989)].
3 Estimated by [Meylan (1990b)] assuming that k(HCOOH **) was 0.400.
* Atkinson did not develop S/R relationships for carboxylie acids.
1 Experimental value from Dagaut et al. (1988b). The rate data of Zetzsch
and Stuhl (1981) as reported in Atkinson (1989) is subject to significant
uncertainties; hence it should not be used [Atkinson (1989)].
m Experimental value from Zetzsch and Stuhl (1981) as reported in Atkinson
(1989). This value is subject to significant uncertainties and must be used
with extreme caution [Atkinson (1989)].
n No experimental value is given in the AOP data base. A value of
5.5xlO"12cm3molecule~1s~1 is given in the document "Estimated Accuracy o
AOP versus PCFAP.
0 Based on the experimental values of k0g listed in column Experimental/(a).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-66-
-------
formate, methyl butyrate). For ethoxyethyl acetate, AOP lists
the experimental value of KQH with three significant figures
while Atkinson (1989) and Hartmann et al. (1986, 1987) list it
with two significant figures. For 2-octanone, AOP lists a value
of k0H of 10.0 while Wallington and Kurylo (1987) and Atkinson
(1989) list a value of 11.0. For s-butyl acetate, AOP does not
list a value in the data base; from the document "Estimated
accuracy of AOP versus PCFAP, AOP does list a value of 5.5 for
this compound. The recommended value by Atkinson (1989) is 5.5*.
Experimental kOH data listed in Table 16G. are available for
a few alkyl carboxylic acids formic, acetic, propionic, and
n- and i-butyric acids as obtained from Atkinson (1989) and the
literature. The kOH data from Zetzsch and Stuhl (1981) for
acetic, propionic, and Q-butyric acids had very large
uncertainties since the vapor pressures of these compounds were
unknown. Hence, these data should not be used [Atkinson (1989)].
The experimental kOn data for acetic, propionic, and i-butyric
acids were obtained from a single source [Dagaut et al. (1988)];
hence, these data should be used with caution until additional
kOH data are obtained from other researchers to corroborate the
assignments.
It should be noted that for the aldehydes, the incorrect
names are used in the AOP data base. Since, the aldehyde
functional group can only be at the end of the alkyl chain, there
is no need to specify its position with a number.
-67-
-------
IV.C.3.b. Evaluation of the Estimated KQH Data
A comparison of the estimated values of kOH reported by AOP
with those from HC in Table 16 indicate that they are essentially
the same except for methyl trifluoroacetate and the carboxylic
acids. For most of these compounds, the differences are trivial
and are due to the method of rounding off the third significant
figure. For methyl trifluoroacetate, the estimated value of kOH
in AOP is 0.216 in contrast to the estimated value of 0.0518 in
HC from Leifer. The apparent error is due to the effect of the
very electrophilic group -CF3 on the substituent factor
F[-OC(0)R]. Leifer (1991a) derived a substitutent factor
F[-OC(0)CF3] = 0.36 (31)
which gives an estimated value of 0.0518. Therefore, it is
recommended that the substituent factor listed in 31 be used in
the AOP computer program and in Table 2.
There are problems with the S/R relationships of Meylan
(1990b) for the class of carboxylic acid compounds which will be
described in the following paragraphs.
For the alkyl carboxylic acids, Atkinson did not develop S/R
relationships while Meylan (1990b), in AOP, did develop S/R
relationships. For these compounds, two reaction pathways were
postulated by Meylan: H-atom abstraction from an alkyl group and
H-atom abstraction from the OH group. Therefore, for these two
reaction pathways,
-68-
-------
= k(la)
R(=0)OH + -OH - » -R C(=0)OH + HOH (32)
k(2) = k(-OH)
RC(=0)OH + 'OH - » RC(=0)0- + HOH (33)
where R' is an alkyl free radical [i.e., -R' or for formic acid,
it is -C(=0)OH]. The overall rate of reaction with hydroxyl
radicals is then
kOH = k(l) + k(2) = k(la) + k(-OH) (34)
and Meylan assumed that reaction pathway 32 was the dominant
pathway [i.e., k(la) > k(-OH)]. Therefore, Meylan used the group
rate constant k(-OH) = 0.036, derived from the alcohols; and the
rate constant k(la) , for H-atom abstraction from the alkyl group,
was calculated in the standard manner using the S/R relationship
of Atkinson. These results were then used in equation 34 to
calculate kOH-
For formic acid, Meylan (1990b) assumed that
k(la) = k[HC(=0)OH ** ] = 0.400 (35)
so that
(formic acid, estimated) =0.436 (36)
and this result is listed in the fourth column of Table 16. The
values of kOH (estimated) for the other carboxylic acids are
calculated in the standard manner in AOP and these results are
listed in Table 16. The percent error for these compounds, based
-69-
-------
on the experimental values of kOH listed in the column
Experimental/(a), are listed in parentheses in the column
Estimated/AOP. Inspection of these results indicate that kOH
(estimated) for acetic acid was very poor (an error of -80%). On
the other hand, the average percent error for the other
carboxylie acids was -14 which is excellent.
Atkinson (1989) reviewed the available kOH data for the
reaction of OH radicals (or OD radicals) with formic acid (or
deuteroformic acids) over the temperature range 297-445 K. Based
on the experimental data of Wine et al. (1986) and Singleton et
al. (1986) for the reaction of OH radicals with HC(O)OH and
DC(0)OH and OD radicals with HC(0)OD and DC(0)OD, Atkinson (1989)
concluded that the major reaction pathway was H- or D-atom
abstraction from the -OH(or-OD) groups. This contradicts the
assumption of Meylan (1990b) in AOP; that is, k(-OH) = 0.036 and
reaction 33 is the minor reaction pathway. Furthermore, as
stated in Section IV.C.3.a., the experimental kOH data for these
carboxylic acids are available from a single source and the kOH
data for acetic, propionic, and butyric acids have large
uncertainties so that these data must be used with caution.
Considerably more experimental kOH data are needed for these
carboxylic acids and for additional compounds in this class
before reliable S/R relationships can be developed.
It should be noted that for formic acid, the detailed
calculation for H-atom abstraction from formic acid is listed in
-70-
-------
AOP as k[HCOOH **] = 0.400 (Measured). The molecular structure
for formic acid is [HC(=0)OH] and not HCOOH.
IV.C.4. Alcohols, Glycols, Ethers, and Hydroperoxides
IV.C.4.a. Evaluation of the Experimental kOH Data
Table 17 summarizes the pertinent experimental kOH data at
298 K for the reaction of OH radicals with 16 alcohols, 3
glycols, 26 acyclic ethers, 10 cyclic ethers, and 2
hydroperoxides as reported in AOP, in Atkinson (1989), and in the
literature. Inspection of the experimental k0H data listed in
columns 2 and 3 indicate that five compounds have differences.
The differences in four of these compounds are related to the
number of significant figures used. Inspection of the original
literature references and the data in Atkinson (1989) clearly
indicated that the preferred values are listed in the column
Experimental/(a). The experimental values for l-chloro-2,3-
epoxypropane are different; the preferred value listed in the
third column represents the average value from the experimental
kOH data of Zetzsch (1985) and Edney et al. (1986) assuming that
kOH = 0.55 of Edney.
IV.C.4.b. Evaluation of the Estimated kOH Data
Comparison of the estimated values of kOH from AOP and HC
for the alcohols, glycols, and ethers indicates that they are
essentially the same. The trivial differences are due to the
method of rounding off the third significant figure in HC.
-71-
-------
Table 17. Comparison of the Estimated Values of kOH at 298 K for Alcohols, A
Glycols, Ethers, and Hydroperoxides from the Atmospheric OxidatidH
Computer Program (AOP) and from a Hand Calculation (HC) and the
Experimental KQH Data Reported in the Literature Versus the
Experimental kOH Data in AOP
Chemical Class/Chemical
A. ALCOHOLS
Methanol
Ethanol
1-Propanol
2-Propanol
1-Butanol
2-Methyl-2-Propanol
1-Pentanol
2-Pentanol
3-Pentanol
3-Methyl-2-butanol
1-Hexanol
2-Hexanol
1-Heptanol
2 -Chloroethanol
1 -Hydr oxy- 2 -pr opanone
Cyclopentanol
B. GLYCOLS
1,2-Ethanediol
1 , 2-Propanediol
1012kOH(cm3molecule~1s~1)
Experimental
AOP
0.932
3.27
5.34
5.21
8.3
1.12
10.8
11.8
12.2
12.4
12.4
12.1
13.6
1.4
3.02
10.7
7.7
12.0
(a)
0.932*
3.27*
5.34*
5.21*
8.31b
1.12*
10. 8C
11. 8d
12. 2d
12. 4d
12. 4d
12. ld
13. 6d
1.4
3.02e
10. 7d
7.7
12
Estimated
AOP(%Error)m
0.526
3.07
4.98
6.63
6.37
0.593
7.77
10.9
12.9
11.0
9.17
12.3
10.6
2.07
2.31
12.8
7.42
12.0
HC
0.526
3.08
4.99
6.63
6.38
0.593
7.77
10.9
12.9
11.0
9.17
12.3
10.6
2.07
2.32
12.7
7.42
11.9
-72-
-------
Ible 17. Continued
Chemical Class/Chemical
C. ACYCLIC ETHERS
Dimethyl ether
Diethyl 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
fei-i-butyl ether
Di-n-pentyl ether
1,1-Dimethoxy ethane
Diethoxymethane
1 , 2-Dimethoxypropane
2 , 2-Dimethoxypropane
2 , 2-Diethoxypropane
2-Methoxyethyl ether
1,1, 3-Trimethoxypropane
2-Ethoxyethyl ether
Methoxy acetone
2-Methoxy ethanol
2-Ethoxy ethanol
3 -Ethoxy- 1 -pr opano 1
3-Methoxy-l-butanol
2-Butoxy ethanol
1012kOH(cm3molecule~1s~1)
Experimental
AOP
2.98
13.3
17.2
2.83
16.4
18.1
6.9
7.91
22.4
26.0
34.7
8.89
16.8
14.3
3.92
11.7
17.5
19.2
26.8
6.77
12.5
15.4
22.0
23.6
18.6
(a)
2.98*
13.3*
17.2*
2.83*
16. 4d
18. lf
6.88f
7.91d
22. 4f
26.09
8.89e
16. 8e
14. 3e
3.92e
11. 7e
17. 5e
19. 2e
26. 8e
6.77e
12. 5e
15. 4h
22. Oe
23. 6e
18. 6n
Estimated
AOP(%Error)m
1.76
11.5
21.1
2.82
13.6
18.5
7.70
6.13
25.5
30.4
28.2
13.1
16.6
22.9
3.05
12.8
28.1
28.5
37.9
4.87
11.2
16.1
20.9
20.6
23.0
HC
1.76
11.5
21.1
2.82
13.6
18.5
7.20
6.13
25.5
30.4
28.2
13.1
16.6
22.9
3.05
12.8
28.1
28.5
37.8
4.87
11.2
16.1
20.9
20.6
23.0
-73-
-------
Table 17. Continued
Chemical Class/Chemical
2-Hydroxyethyl ether
(Dihydroxy ethyl ether)
D. CYCLIC ETHERS
Ethylene oxide
1 , 2-Epoxypropane (propylene
oxide)
1-2-Epoxy butane (1,2-
Butylene oxide)
l-Chloro-2 , 3-epoxypropane
Trimethylene oxide
Tetrahydrofuran
1,3-Dioxane
1,4-Dioxane
1,3,5-Trioxane
Oxepane (Hexamethylene oxide)
E. ALKYL HYDROPEROXIDES
Methyl hydroperoxide
t-Butyl hydroperoxide
1012k0H(cm3molecule"1s~1)
Experimental
AOP
30.0
0.076
0.052
2.1
0.44
10.3
16.1
9.15
10.9
6.2
15.4
5.54
3.0
(a)
30
0.076*
0.52*
2.1
0.501
10. 3e
16.1*
9.15e
10. 9e
6.2J
15. 4e
5.54*
3.0k
Estimated
AOP(%Error)m
20.6
0.224
0.543
1.69
0.662
3.73
18.3
22.1
26.4
15.3
25.7
7.24(+31)
1.98(-34)
HC
20.6
0.224
0.543
1.69
0.662
3.73
18.3
22.1
26.4
15.3
2.57
(D
(D
a Experimental values from Atkinson (1989) and the literature.
b Experimental value 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)].
c Experimental value from Wallington and Kurylo (1987a).
d Experimental value from Wallington et al. (1988b).
-74-
-------
e 17. continued
e Experimental value from Dagaut et al. (1988a).
f Average value from the experimental data of Wallington et al. (1988b) and
Bennet and Kerr (1989).
9 Experimental value from Bennett and Kerr (1989).
n Experimental value from the experimental data of Hartmann et al. (1987) and
. Dagaut et al. (1988a).
1 Average value from the experimental data of Zetzsch (1980) and Edney et al.
. (1986) assuming XQH = 0.55xlO~12cm3molecule"1s~1 of Edney.
J Extropolated from the experimental data of Zabernick et al. (1988).
* Experimental value from Anastasi et al. (1978).
1 Atkinson did not develop S/R relationships for alkyl hydroperoxides.
m Based on the experimental values of k0u listed in column Experimental/(a).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-75-
-------
There are, however, problems with the S/R relationships for
the alkyl hydroperoxides in AOP which will be described below.
For the alkyl peroxides [RCOOH] , Atkinson did not develop
S/R relationships while Meylan (1990b) , based on the experimental
koH data of methyl and t-butyl hydroperoxide , did develop S/R
relationships. For alkyl peroxides, two reaction pathways were
postulated by Meylan: H-atom abstraction from the alkyl group and
H-atom abstraction from the hydroperoxy groups. Therefore,
- k(la)
RCOOH + -OH - » -R COOH + HOH (37)
k(2) = k(-OH)
RCOOH + -OH - > ROO- + HOH (38)
where R is an alkyl group and -R' is an alkyl free radical group.
The overall reaction with OH radicals is then
kOH = k(l) + k(2) = k(la) + k(-OH) (39)
and reaction pathway 37 was considered by Meylan (1990b) to be
the dominant reaction pathway. Therefore, Meylan assumed that
k(-OH) = 0.036 and
F(-0-0- ** ) = 50 (40)
and k(la) and kOH were calculated in the standard manner. For
methyl and £-butylhydroperoxides, the estimated values from AOP
were 7.24 and 1.98, respectively. The percent error for these
two compounds, based on the experimental values listed in column
Experimental/ (a) , were +31 and -34, respectively, and these
-76-
-------
results were very good. However, these results, and the S/R
relationships of Meylan must be evaluated very carefully in the
light of the experimental kOH data as described in the following
paragraphs .
Atkinson (1989) analyzed the experimental rate data of
Vaghjiani and Ravishankara (1989) and Niki et al. (1983) for
methyl hydroper oxide. The most comprehensive study is that of
Vaghjiani and Ravishankara (1989) who studied the rates of
reaction of 16OH, 18OH, and 16OD radicals with CH3OOH and 16OD
radicals with CH3OOD. Based on an analysis of all the
experimental data, the mechanism involves two reaction pathways;
H-atom abstraction from the CH3 group and from the OH group.
Therefore,
k(2) = k(-OH)
CH3OOH + -OH - » CH3OO- + HOH (41)
= k(la)
CH3OOH + -OH - »• -CH2OOH + HOH (42)
with the -CH2OOH radical rapidly decomposing to give hydroxyl
radicals and formaldehyde
Rapid
CH2-0-0-H - » CH2=0 + -OH (43)
The overall rate, from reactions 41 and 42, is
kOH = k(l) + k(2) = k(la) + k (-OH) (44)
-77-
-------
Relative rate studies gives kOH [= k(la) + k(-OH)] while
flash photolysis or laser photolysis experiments, which measure
the disappearance of OH radicals, gives only the rate constant
k(-OH) assuming that OH radical regenerated contains the same
oxygen isotope as the reactant OH radical. Therefore, the
reaction of the 16OH radical with CH3016OH (or 16OD radical with
CH3O16OD) gives the rate constant k(-OH). Furthermore, reaction
of OD radicals with CH3OOH yields the overall rate constant
koH [= k(la) + k(-OH)] for the OD radical reaction.
Atkinson (1989) carried out a unit-weighted least-squares
analysis of the experimental data of Vaghjiani and Ravishankara
(1989) for the reaction of 18OH and OD radical with CH3OOH over
the temperature range 203-348K. Based on these data, Atkinson
recommended the value of
k(-OH) = 3.73 (45)
at 298 K (in the units 10~12cm3molecule"1s~1); from the
experimental data involving 18OH and OD radicals over the
temperature range 223-423 K, Atkinson recommended a value of
kOH = 5.54 (46)
at 298 K (in the units 10"12cm3molecule~1s"1). Hence,
k(la) = 1.81 (47)
and H-atom abstraction from the OH radical in methyl
hydroperoxide is the major reaction pathway.
-78-
-------
For t-butyl hydroperoxide, Atkinson (1989) indicated that
because the C-H bonds in the CH3 group are stronger than the 0-H
bond, the reaction is expected to proceed principally via H-atom
abstraction from the weaker OH bond (reaction pathway 41) and
this result is consistent with the magnitude of kgjj determined
experimentally by Anastasi et al. (1978).
Therefore, all the data presented by Atkinson (1989)
contradicts the S/R relationships of Meylan (1990b) for the alkyl
hydroperoxides. Considerably more experimental rate data is
needed for additional alkyl hydroperoxides to develop S/R
relationships for this class of compounds.
IV.C.5. Alkyl Nitrates and Nitriles
IV.C.S.a. Evaluation of the Experimental kOH Data
Table 18 summarizes the pertinent experimental kOH data at
298 K for acyclic and cyclic alkyl nitrates and acyclic alkyl
nitriles as reported in AOP, in Atkinson (1989), and in the
literature. Inspection of the k0n data in columns 2 and 3
indicate that the experimental values for all acyclic and cyclic
nitrates are identical. However, for the nitriles, there are
differences. For acetonitrile, the correct value of kOH is
0.0214* as recommended by Atkinson (1989) and the correct value
for propionitrile is 0.194 as given by Harris et al. (1981) and
Atkinson (1989).
-79-
-------
Table 18. Comparison of the Estimated Values of kOH at 298 K for Alkyl
Nitrates and Alkyl Nitriles from the Atmospheric Oxidation Computer
Program (AOP) and from a Hand Calculation (HC) and the Experimen
kOjj Data Reported in the Literature Versus the Experimental kOH
in AOP
Chemical Class/Chemical
A. ACYCLIC NITRATES
Methyl nitrate
Ethyl nitrate
1-Propyl nitrate
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
B. CYCLIC NITRATES
Cyclohexyl nitrate
C. ALKYL NITRILES
Acetonitrile
Propionitrile
1012kOH (cm3molecule~1s"1)
Experimental
AOP
0.034
0.49°
0.67
0.41
1.78
0.92
1.85
1.12
1.72
0.85
3.17
2.70
1.72
3.02
3.69
3.88
3.30
0.021
0.19
(a)
0.034b
0.49C
0.67d
0.41e
1.78®
0.92e
1.85f
1.12f
1.729
0.85?
3.17f
2.70f
1.729
3.029
3.699
3.88f
3.309
0.0214*
0.194h
Estimated
AOP
0.0259
0.194
0.632
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
5.38
0.0202
0.189
HC
0.0259
0.194
0.632
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
5.38
0.0202
0.189
-80-
-------
Table 18. continued
^Experimental values from Atkinson (1989) and the literature.
b Atkinson (1987, 1989) reported a value of 0.034xlO~12 and
0.38xlO~12cm3molecule~1s~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 kQjj 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 Gaffney
et al. (1986) since the value of Kerr and Stocker was too high.
c The experimental data of Kerr and Stocker (1986) was considered too high
and was not considered to be valid [Atkinson (1987, 1989)].
01 This value of k0n represents the average value from the experimental data of
Kerr and Stocker (1986) and Atkinson and Aschmann (1989a).
e Experimental value from Atkinson and Aschmann (1989a).
f Experimental value from Atkinson et al. (1982a).
9 Experimental value from Atkinson et al. (1984b).
n Experimental value from Harris et al. (1981).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-81-
-------
IV.C.S.b. Evaluation of the Estimated kOH Data
Inspection of the estimated values for the nitrates and
nitriles in columns 4 and 5 indicate that both AOP and HC have
exactly the same kOH data.
IV.C.6. Nitroalkanes
IV.C.e.a. Evaluation of the Experimental kOH Data
Table 19.A. summarizes the pertinent experimental kOH data
at 298 K for nitroalkanes as reported in Atkinson (1989), in
AOP, and in the literature. For nitromethane, AOP lists a range
of experimental values for kOH. Atkinson (1989) evaluated the
existing experimental kOH data for nitromethane and indicated
that the data of Zabarnick et al. (1988) is preferred. Atkinson
carried out a unit-weighted least squares analysis of the
Zabarnick data using the equation
ken = CT2exp(-D/T) (48)
where C and D are constants and T is the absolute temperature in
K and found that
kOH = 5.6 x 10~19T2exp(-360/T) cm3molecule~'1s~1 (49)
over the temperature range 299-671 K. At 298 K, equation 49
gives
- 0.0149 x 10~12cm3molecule~1s~1 (50)
-82-
-------
ble 19. Comparison of the Estimated Values of kOH at 298 K for
Nitroalkanes and Alkyl Nitrites from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand Calculation (HC) and the
Experimental KQH Data Reported in the Literature Versus the
Experiment kOH Data in AOP
Chemical Class/ Chemical
A. NITROALKANES
Nitrome thane
Nitroethane
1-Nitropropane
1-Nitrobutane
1-Nitropentane
B. ALKYL NITRITES
Methyl nitrite
Ethyl nitrite
1-Propyl nitrite
1-Butyl nitrite
2 -Butyl nitrite
2-Methyl-l-propyl nitrite
2-Methyl-2-propyl nitrite
1012kOH(cm3molecule""1s~1)
Experimental
AOP
(0.016-0.16)
0.15
0.24
1.45
3.30
(0.12-1.08)?
1.75?
2.38?
(2.31-5.2)?
5.93?
5.31?
1.40?
(a)
0.0149b
0.15d
0.34d
1.45e
3.30d
(0.12-1.09)f
1.779
2.36h
5.02h
5.97*
5.351
1.411
Estimated
AOP(%Error) 3
0.0259(+74)
0.194(+29)
0.632(+86)
1.79(+23)
3.18(-4)
0.288 ( )
2.32(+31)
6.12(+160)
8.29(+65)
6.17(+3)
10.8(+101)
1.94(-l-38)
HC
(C)
(c)
(C)
(C)
(c)
(C)
(C)
(C)
(C)
(C)
(c)
(C)
a Experimental values from Atkinson (1989) and the literature.
b Experimental value from Zabarnick et al. (1988) which represents the
preferred value by Atkinson (1989).
c Could not be calculated by Leifer since the S/R relationships and
substituent factors were unknown.
-83-
-------
Table 19A. continued
d Experimental value from Nielsen et al. (1988). Atkinson (1989)
tentatively accepted this data since "The nitroalkanes are expected to
photolyze [Taylor et al. (1990)] and it is not clear whether photolysis
occurred under the experimental conditions of the relative rate study of
Nielsen et al. (1988) or whether or not photolysis (if it occurred) was
taken into account". More experimental kOH data are needed under controlled
laboratory conditions to eliminate photolysis.
e The average value from the data of Atkinson (1989) and Nielsen et al.
(1988). See footnote (d) above relative to the experimental value from
Nielsen et al. (1988).
f Range in experimental kQH data as obtained from Atkinson (1989) and the
literature in the units 10~12cm3molecule~1s~1: 0.12 relative to dimethyl
ether and 0.21 relative to Q-hexane [Tuazon et al. (1983)]; 1.00 [Baulch
et al. (1985); 1.09 [Audley et al. (1982)]; and the data of Campbell and
Goodman (1975) was omitted since there were fundamental problems associated
with the relative method used [Atkinson (1989)].
9 Experimental value from Audley et al. (1982) and Atkinson (1989).
h Average value from the experimental data of Audley et al. (1982) and Baulch
. et al. (1985) is obtained from Atkinson (1989).
* Experimental value from Audley et al. (1982).
3 Percent error relative to the experimental values listed in column
Experimental/(a).
-84-
-------
and this is the value listed in column three of Table 19.A. and
is the preferred (or recommended) value by Atkinson. For the
remaining nitroalkanes, only for 1-nitropropane is there a
discrepancy in the k0jj data in columns 2 and 3. The correct
experimental value for 1-nitropropane is tentatively 0.34 as
obtained from Nielsen et al. (1988) and Atkinson (1989).
Some comments must be made about the validity of the
experimental kOH data for nitroethane, 1-nitropropane,
1-nitrobutane and 1-nitropentane. For nitroethane,
1-nitropropane, and 1-nitropentane, the experimental data were
obtained from Nielsen et al. (1988) and Atkinson (1989) while the
experimental data for 1-nitrobutane was obtained from Atkinson
and Aschmann (1989) and Nielsen et al. (1988). Atkinson (1989)
critically evaluated the experimental kOH data of Nielsen and
stated that "The nitroalkanes are expected to photolyze [Taylor
et al. (1980)] and it is not clear whether photolysis occurred
under the experimental conditions of the relative rate study of
Nielsen et al. (1988) or whether or not photolysis (if it
occurred) was taken into account." As a result, Atkinson (1989)
indicated that the data listed in the column Experimental/(a) for
nitroethane, 1-nitropropane, and 1-nitropentane from Nielsen are
only tentatively preferred and, therefore, must be used with
extreme caution.
IV.C.e.b. Evaluation of the Estimated kOH Data
Leifer did not have available S/R relationships for the
nitroalkanes from Atkinson; hence, no entries appear in Table
-85-
-------
19.A., column Estimated/HC. Meylan (1990b) did have S/R
relationships available for these compounds from Atkinson
(unpublished results). For this class of compounds (RN02),
Atkinson must have postulated that hydroxyl radicals can only
react by abstracting a hydrogen from the C-H groups in R and the
substituent factors were
F(-N02) = 0.18 (51)
F(-CH2N02) = 0.30 (52)
In addition, Meylan (1990b) gave the substituents >CHN02 and
>CNO2 the same F values as for the substituent -CH2NO2 listed in
equation 52. Thus, the assumed values for these two substitutes
(designated **) are then
F(>CHNO2 ** ) = F(>CNO2 ** ) = 0.30 (53)
Using the above substituent factors, AOP estimated kOH for the
five nitroalkanes listed in Table 19.A. and these results are
listed in the column Estimated/AOP. The percent error, relative
to the experimental k0n data in column 3, are listed in
parentheses adjacent to the estimated value from AOP. Inspection
of these data clearly indicate that the results for nitromethane
and 1-nitropropane are very poor. In addition, the average
percent error ranged from +53 to -4. Therefore, in order to
develop better substituent factors for the nitroalkanes, more
experimental kOH data are needed for these five compounds and
additional nitro compounds under carefully controlled laboratory
-86-
-------
conditions to eliminate direct photolysis. Until this work is
completed, the substituent factors and estimated values of kOH
for the nitroalkanes must be used with extreme caution, or,
better, delete them from AOP.
IV.C.7. Alkyl Nitrites
IV.C.7.a. Evaluation of the Experimental kOH Data
Table 19.B. summarizes the pertinent experimental k0n data
at 298 K for the alkyl nitrites (RONO) as obtained from AOP, from
Atkinson (1989), and from the literature. For these compounds,
the experimental kOH .data from AOP have question marks
immediately after the numbers to indicate that the data are
questionable. For the experimental data for methyl nitrite,
several values are available from the literature. Thus, the
experimental kOH data in columns 2 and 3 list essentially the
same range of values. For 1-butyl nitrite, AOP lists a range of
values while the column Experimental/(a) lists the average value
from the experimental data of Baulch et al. (1985) and Audley et
al. (1982). For the other alkyl nitrates there are minor
differences listed in columns 2 and 3. The values listed in the
third column, as obtained from the literature and Atkinson
(1989), appear to be the correct values.
It should noted that for the compound CH3CH(CH3)CH2ONO, AOP
lists the name 3-methyl-l-propyl nitrite which is incorrect. The
correct name is 2-methyl-l-propyl nitrite.
-87-
-------
IV.C.V.b. Evaluation of the Estimated kOH Data
Leifer did not have available S/R relationships from
Atkinson for the alkyl nitrites; hence, no entries appear in the
column Estimated/HC. However, Meylan (1990b) did develop S/R
relationships for this class of compounds (RONO) by assuming that
the only reaction pathway is H-atom abstraction from the C-H
groups in R. Based on the available experimental kOH data,
Meylan assumed that for the nitrites
F(-0-N = ** ) = 2.00 (54)
Furthermore, for these compounds, where appropriate, Meylan used
the substituent factor F(-CH2-0-) from Table 2.
Using the above substituent factors, AOP calculated kOH; and
these values are listed in Table 19.B. along with the percent
error (in brackets adjacent to the estimated values). From an
inspection of the percent error data, it is clear that the
results are generally very poor; 1-propyl nitrite and 2-methyl-l-
propyl nitrite had percent errors greater than +100 while 1-
butylnitrite had a percent error of +65. These results are not
surprising since Atkinson (1989) Stated "Until the kinetics of OH
radicals with alkyl nitrites are fully understood and product
studies carried out, the reaction mechanisms remain uncertain.
These may proceed via H-atom abstraction from the C-H bonds
and this is expected to be the major, if not the only, reaction
pathway ". Therefore, it is apparent that more reliable kOH
data and product data are needed for the alkyl nitrites listed in
-88-
-------
Table 19.B. and for other alkyl nitrites in order to develop more
reliable S/R relationships.
IV.D. Addition of Hydroxyl Radicals to Alkenes, Conjugated
Dialkenes, Alkynes, and 1,2-Dialkenes
IV.D.I. Unsubstituted Alkenes
IV.D.I.a. Evaluation of the Experimental k0H Data
Table 20 summarizes the pertinent experimental kOH data at
298 K for the reaction of OH radicals with unsubstituted alkenes
as reported in AOP, in Atkinson (1989), and in the literature. A
careful inspection of the experimental k0H data reported in the
columns Experimental/AOP and Experimental/(a) indicates that, in
general, they are the same; there are, however, some differences.
For a few chemicals, AOP lists kOH to 4 significant figures while
Experimental/(a) reports kOH to 3 significant figures. At best,
the experimental kOH data is good to 3 significant figures. For
example, for 2,3-dimethyl-2-butene, the experimental KOH data
reported in the literature is only given to 3 significant and
Atkinson (1989) recommended a value of 110* while AOP lists a
value of 110.0. For the other chemicals with differences,
Experimental/(a) lists an average value from the literature while
AOP selects one set. Unless there is good reason to disregard
specific sets of data, it is best to list an average value from
all the data sets rather than the value from only one set.
It should be noted that AOP does not list an experimental
value for A3- carene in column 2; however, a value is listed in
the document "Estimation Accuracy of AOP versus PCFAP" [Meylan
-89-
-------
Table 20. Comparison of the Estimated Values of kOH at 298 K for
Alkenes from the Atmospheric Oxidation Computer Program (AOP)
from a Hand Calculation (HC) and the Experimental KQH Data Reported
in the Literature Versus the Experimental KOH Data in AOP
Chemical Class/Chemical
A. ACYCLIC ALKENES
Ethene (Ethylene)
Propene (Propylene)
1-Butene
cis- 2 -But ene
trans- 2 -But ene
2 -Methy Ipr opene
1-Pentene
cis-2-Pentene
trans-2 -Pentene
2-Methyl-2-butene
2-Methyl-l-butene
3-Methyl-l-butene
1-Hexene
2 -Methy 1-1-pentene
2 -Methy 1 - 2 -pent ene
trans-4 -Methy 1-2 -pentene
2 , 3-Dimethyl-2-butene
3 , 3-Dimethyl-l-butene
1-Heptene
2 , 3-Dimethyl-2-pentene
trans-4 , 4 -Dimethy 1-2 -pentene
1,4-Pentadiene
trans-1 , 4-Hexadiene
1 , 5-Hexadiene
1012kOH(cm3molecule~1s~1)
Experimental
AOP
8.52
26.3
31.4
56.4
64.0
51.4
31.4
65.4
66.9
86.9
60.7
31.8
37.5
62.6
88.8
60.8
110.0
28.4
40.5
108.0
54.5
53.3
90.3
62.1
(a)
8.52*
26.3*
31.4*
56.4*
64.0*
51.4*
31.4*
65. 7b
66.9°
86.9*
60. 6d
31.8*
35. 2e
62. 6f
89.19
60. 5f
110*
28. 5h
38. 31
1033
54. 5f
53.3°
90.6°
62.0°
Estimated
AOP
8.52003
26.4
27.3
56.4
64.0
51.7
28.6
57.3
64.9
87.3
52.6
28.5
30.0
53.9
88.2
66.0
111
26.9
31.4
111
64.4
53.4
91.0
54.8
HC
(r)
26.4
27.3
56.4
64.0
51.7
28.6
57.3
64.9
87.3
52.6
28.5
30.0
53.9
88.2
66.0
111
26.9
31.4
111
64.4
53.4
91.0
54.8
-90-
-------
ible 20. Continued
Chemical Class/Chemical
2 -Me thy 1-1 , 4 -pentad iene
2-Methyl-l, 5-hexadiene
2 , 5-Dimethyl-l , 5-hexadiene
B. CYCLIC ALKENES
Cyclopentene
Cyclohexene
1 , 4-Cyclohexadiene
Cycloheptene
1 -Me thy 1 cy c 1 ohexene
LBicyclo [2.2.l]-2-heptene
pJicyclo [ 2 . 2 . 1 ] -2 , 5-heptadiene
Bicyclo [ 2 . 2 . 2 ] -2-octene
o-Pinene
j8-Pinene
d-Limonene
A3-Carene
7-Terpinene
1012kOH(cm3molecule~1s~1)
Experimental
AOP
78.8
96.1
120.0
67.3
67.7
99.4
74.4
94.4
49.3
120.0
40.8
53.7
78.9
171.0
(P)
177.0
(a)
78.8°
96.1°
120°
65. 5k
67.7*
99. 51
74. 4m
94. 4n
49. 3m
12 Om
40. 8m
53.7*
78.9*
160n
87.8°
177°
Estimated
AOP
78.7
80.0
105
58.9
61.1
114
62.4
92.0
62.7
116
67.8
89.5
54.2
145
87.6
178
HC
78.7
80.0
105
58.9
61.1
114
62.5
92.0
62.7
116
67.8
89.5
54.1
145
87.6
178
a Experimental values from Atkinson (1989) and the literature.
b Average value from the data of Ohta (1984) and Wu et al. (1976).
c Experimental value from Ohta (1983) and Atkinson (1989).
d Average value from the data of Ohta (1984) and Wu et al. (1976). The
experimental value of kgjj of Morris and Niki (1971) was considered to be too
high and was discounted when making recommendations for other alkenes (e.g.,
for 1-pentene) by Atkinson (1989).
6 Average value from the experimental data of Wu et al. (1976) and Atkinson
and Aschmann (1984).
f Experimental value from Ohta (1984) and Atkinson (1989).
9 Average value of the relative rate data of Ohta (1984) using 2-methyl-2-
butene and cis-2-pentene as reference compounds.
-91-
-------
k Experimental value from Wu et al. (1976) and Atkinson (1989).
1 Average value of the experimental data of Darnall et al. (1976) and
Atkinson and Aschmann (1984).
3 Average value of the relative rate data of Ohta (1984) using 2-methyl-2-
butene and 2,3-dimethyl-2-butene as reference compounds.
k Average value from the experimental data of Atkinson, Aschmann, and Carter
(1983) and the relative rate data of Rogers (1989) with cyclohexene as the
reference compound.
1 Average value from the experimental data of Atkinson, Aschmann, and Carter
(1983) and Ohta (1983).
m Experimental value from Atkinson Aschmann, Carter (1983).
n Experimental value from Darnall et al. (1976).
0 Experimental value from Atkinson, Aschmann, Pitts (1986).
P No experimental value is given in the AOP database. An experimental value
of 87.8xlO~12cm3molecule~*s~1 is given in the document estimation
accuracy of AOP versus PCFAP.
3 Estimated value is the experimental value.
r Cannot be estimated by the S/R relationships of Atkinson.
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-92-
-------
(1990b)]. The value of 87.8 should be listed in the AOP
database.
IV.D.l.b. Evaluation of the Estimated kOH Data
Comparison of the estimated KQH data in columns 4 and 5
indicates that, in general, they are the same; there are,
however, a few differences. For ethene, AOP lists a estimated
value of 8.5200 in the summary table which corresponds to the
experimental value while HC does not list a value; kOH cannot be
estimated by the S/R relationships of Atkinson. Furthermore, AOP
lists the estimated value to five significant figures which is
incorrect since the recommended experimental value by Atkinson
(1989) is 8.52* which only has three significant figures.
For OH addition to olefinic bonds, the detailed calculations
show an inconsistency. From the mathematical synopsis of the S/R
relationships of Atkinson (equation 15), substituent factors
attached to the olefinic group can influence ka(j
-------
kadd,nar = koS(RiR2C=CHR3)(1.00)(1.00)(1.00)
*add,nar - 86-9 (56)
This comment is also applicable to the compounds listed in Table
22 for the conjugated dienes, and in Table 23 for the allenes and
alkynes.
For C-H abstraction from the olefinic group (e.g., =C-H),
the detailed calculations should include this pathway, even
though it is zero [i.e., k(l, UNS CH) = 0]. This comment, as
well as the above comment, also applies to the other classes of
compounds discussed in Section IV.D.
IV.D.2. Substituted Alkenes
IV.D.2.a. Evaluation of the Experimental kOH Data
Table 21 summarizes the pertinent experimental kOH data for
the reaction of OH radicals with substituted alkenes as reported
in Atkinson (1989), in AOP, and in the literature. A comparison
of the experimental )COH data listed in columns 2 and 3 indicate
that, in general, they are the same; there are, however, some
differences. For six compounds [i.e., 2-(chloromethyl)-3-chloro-
1-propene, trans-2-butenal, and the four ketenes, no experimental
kOH values are listed in AOP; however, values are reported in the
document "Estimation Accuracy of AOP versus PCFAP "[Meylan
(1990b)]. The appropriate values should be listed in AOP. For
acrylonitrile, AOP lists an experimental value of 4.0 while the
correct value should be 4.1, the average value of the
-94-
-------
ble 21. Comparison of the Estimated Values of k0H at 298 K for Substituted
Alkenes from the Atmospheric Oxidation Computer Program (AOP) and
From a Hand Calculation (HC) and the Experimental kOH Data Reported
in the Literature Versus the Experimental kOH Data in AOP
Chemical Class/Chemical
A. Haloalkenes
Vinyl fluoride
Vinyl chloride
Vinyl bromide
1 , 1 -D i f luor oethene
cis-1 , 2-Dichloroethene
trans-1 . 2-Dichloroethene
Trichloroethene
(Trichloroethylene)
retrach lor oethene
( Tetrachlor oethy lene )
3-Chloro-l-propene
(3-Chloropropylene)
cis-l , 3-Dichloro-l-propene
trans-1 , 3-Dichloro-l-propene
2-(Chloromethyl) -3-chloro-
1-propene
B. a , B-UNSATURATED CARBONYLS
Acrolein (2-Propenal)
trans-Crotonaldehyde (trans-
2-Butenal)
Methacrolein(2-Methyl-2-
propenal)
lO^KQjjfcm-^molecule'^s'1)
Experimental
AOP
5.56
6.60
6.81
2.1
2.38
1.80
2.36
0.167
17.0
8.41
14.3
(e)
19.9
(e)
33.5
(a)
5.56b
6.60b
6.81b
2.1°
2.38d
1.80d
2.36*
0.167*
17*
8.41d
14.3d
33. 5d
19.9*
36*
33.5*
Estimated
AOP
10.5
5.26
6.84
8.22
2.24
2.55
0.695
0.176
20.3
8.85
10.0
22.9
32.8
29.6
HC
10.5
5.26
6.84
8.22
2.24
2.55
0.695
0.176
20.3
8.85
10.0
30.3
22.9
32.8
29.6
-95-
-------
Table 21. Continued
Chemical Class/ Chemical
Methyl vinyl ketone
Ketene
Methyl ketene
Ethyl ketene
Dimethyl ketene
Gis-3-Hexene-2 , 5-dione
trans-3 -Hexene-2 , 5-dione
C. NITRILOALKENES
Acrylonitrile (Cyanoethene)
D. ALKOXY ALKENES
Methyl vinyl ether
1012kOH (cm3molecule~1s~1
Experimental
AOP
18.8
(e)
(e)
(e)
(e)
63.1
53.1
4.0
33.5
(a)
18.8*
173f
70?
118f
107f
63. ln
53. lh
4. 11
33. 5b
Estimated
AOP
24.0
51.4
87.0
87.9
110
46.7
53.0
3.95
35.1
HC
24.0
51.4
87.0
87.9
110
46.7
53.0
3.95
35.1
a Experimental values from Atkinson (1989) and the literature.
b Experimental value from Perry, Atkinson, Pitts (1977a).
c Experimental data not reliable [Atkinson (1989)].
d Experimental value from Tuazon et al. (1988). This data is preferred since
these experiments avoided or have taken into account the side reactions of
chlorine atoms with the reference compounds [Atkinson (1989)].
e No experimental value is given in the AOP data base. However, experimental
values are given in the document Estimation Accuracy of AOP versus PCFAP
[Meylan (1990b)].
f Experimental value from Hatakeyama et al. (1985).
9 Average value from the data of Hatakeyama et al. (1985).
h Experimental value from Tuazon et al. (1985).
1 Average value from the experimental data of Harris et al. (1988) and
Zetzsch (1983) as reported in Atkinson (1989).
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-96-
-------
experimental data of Harris et al. (1981) and Zetzsch (1983) as
reported in Atkinson (1989). For 3-chloro-l-propene, the
recommended value from Atkinson (1989) is 17*, which only has two
significant figures, compared to a value of 17.0 listed in AOP.
IV.D.2.b. Evaluation of the Estimated kOH Data
A comparison of the estimated values of kOH listed in AOP
and HC for the compounds listed in Table 21 give the same
results.
The use of four significant figures in the detailed
calculations and three significant figures in the summary table
are applicable in the same manner as described in previous
sections.
IV.D.3. Conjugated Dienes
IV.D.3.a Evaluation of the Experimental JCQH Data
Table 22 compares the pertinent experimental kQH data at
298 K for the reaction of OH radicals with conjugated dienes as
reported in Atkinson (1989), in AOP, and in the literature. A
comparison of the experimental kOH data in columns 2 and 3
indicate that they are all different. The difference involves
the number of significant figures used. For 2-methyl-l,3-
butadiene, Atkinson (1989) lists a recommended value of 101* and
not 101.0 as listed in AOP. In all the other cases, AOP
incorrectly lists kgjj to four significant figures whereas the
literature values listed in Atkinson (1989) and the literature
contain only three significant figures.
-97-
-------
Table 22. Comparison of the Estimated Values of kOH at 298 K for Conjugated
Acyclic and Cyclic Dialkenes from the Atmospheric Oxidation Comp
Program (AOP) and from a Hand Calculation (HC) and the Experimen
kOH Data Reported in the Literature Versus the Experimental kOH D"
in AOP
Chemical Class/Chemical
A. ACYCLIC DIALKENES
1,3 -Butadiene
cis-1 . 3-Pentadiene
2-Methyl-l, 3-butadiene
trans- l , 4-Hexadiene
3 -Me thy 1 - 1 , 3 -pent ad i ene
4-Methyl-l, 3-pentadiene
2 , 3 -Dime thy 1-1 , 3-butadiene
2 , 5-Dimethyl-2 , 4-hexadiene
3-Methylene-7-methyl-l, 6-
octadiene (Myrcene)
3 , 7-Dimethyl-l , 3 , 6-octatriene
B. CYCLIC DIALKENES
1, 3-Cyclohexadiene
1 , 3 -Cycloheptadiene
ot-Phellandrene
o-Terpinene
1012kOH(cm3molecule~1s~1)
Experimental
AOP
66.6
101.0
101.0
112.0
136.0
131.0
122.0
210.0
215.0
252.0
164.0
139.0
313.0
363.0
(a)
66.6*
101b
101*
112b
136b
131b
122b
210b
215°
252°
164d
139e
313*
363*
Estimated
AOP
66.60009
105
105
106
135
135
135
231
194
223
137
139
187
235
HC
(h)
105
105
106
135
135
135
231
194
223
137
139
187
235
a Experimental values from Atkinson (1989) and the literature.
b Experimental value from Ohta (1983).
c Experimental value from Atkinson, Aschmann, Pitts (1986).
^ Experimental value from Atkinson, Aschmann, Carter (1983).
e Experimental value from Atkinson, Aschmann, Carter (1984a).
f Experimental value from Atkinson et al. (1986).
9 Estimated value is the experimental value.
n Cannot be estimated by the S/R relationship of Atkinson.
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-98-
-------
IV.D.3.b. Evaluation of the Estimated kOH Data.
A comparison of the estimated data in columns 4 and 5 of
Table 22 indicates that they are identical except for the entree
for 1,3-butadiene. For this compound, the value of 66.6000
corresponds to the experimental value [which should be 66.6* as
recommended by Atkinson (1989)] and is not an estimated value.
There is no entry under the column HC since there is no S/R
relationship for this compound.
IV.D.4. Alkynes and 1,2-Dienes (Allenes)
IV.D.4.a. Evaluation of the Experimental kOH Data
Table 23 summarizes the pertinent experimental kOH at 298 K
for the reaction of OH radicals with alkynes and 1,2-dienes
(allenes) as reported in Atkinson (1989), in AOP, and in the
literature. A comparison of the experimental kOH data reported
in columns 2 and 3 are the same except for three differences;
for propyne and 1-butyne, the correct values with two significant
figures, as recommended in Atkinson (1989), should be used in
AOP; the value for 1-hexyne reported by Boodegheans et al. (1987)
and Atkinson (1989) is 12.6 and not 11.9 as reported by AOP; and
finally for propadiene, Atkinson (1989) recommended a value of
9.84* and not 9.82 as reported by AOP.
IV.D.4.b. Evaluation of the Estimated k0H Data
Except for ethyne, butadiyne, and propadiene, the estimated
values of kOH at 298 K in columns 4 and 5 are identical. For
these three compounds, no estimated values appear under the
-99-
-------
Table 23. Comparison of the Estimated Values of kOH at 298 K for Alkynes arfl
1,2-Dialkenes (Allenes) from the Atmospheric Oxidation Computer
Program (AOP) and from a Hand Calculation (HC) and the Experimental
k0H Data Reported in the Literature Versus the Experimental kOH Data
in AOP
Chemical Class/Chemical
A. ALKYNES
Ethyne (Acetylene)
Propyne
1-Butyne
2-Butyne
1-Pentyne
l-Hexyne
Butadiyne (Diacetylene)
B. 1,2 DIENES (ALLENES)
Propadiene
1,2 -Butadiene
1,2-Pentadiene
3-Methyl-l, 2-butadiene
1012koH(cm3molecule~1s~1)
Experimental
AOP
0.815
5.90
8.00
27.4
11.2
11.9
18.9
9.82
26.1
35.5
56.9
(a)
0.815
5.9*
8.0*
27.4*
11. 2d
12. 6d
18.9*
9.84*
26. le
35. 5e
56. 9e
Estimated
AOP
0.8150b
6.54
7.42
29.3
8.75
10.1
14.08
9.820b
31.1
32.0
57.3
HC
(c)
6.54
7.42
29.3
8.25
10.1
(c)
(C)
31.1
32.0
57.3
a Experimental values from Atkinson et al. (1989) and the literature.
b Estimated value is the experimental value.
c Cannot be estimated by the S/R relationships of Atkinson.
d Experimental value from Boodaghians et al. (1987).
e Experimental value from Ohta (1983).
* Recommended by Atkinson (1989) with the rationale for the recommendation,
and the uncertainty for the recommendation.
-100-
-------
column Estimated/HC since Atkinson never developed S/R
relationships for these compounds. It should be noted that the
values listed under the column Estimated/AOP for these three
compounds are not estimated values but are experimental values
and there are too many significant figures; they should only have
3 significant figures.
IV.E. Reaction of Hydroxyl Radicals with Organic Compounds
Containing Sulfur, Nitrogen, and Phosphorous Functional
Groups
IV.E.I. Reaction with Thiols, Sulfides, and Oisulfides
IV.E.I.a. Evaluation of the Experimental kOH Data
Table 24 summarizes the pertinent experimental kOH data for
the reaction of OH radicals with alkyl thiols, sulfides, and
disulfides as reported in Atkinson (1989), in AOP, and in the
literature. A careful inspection of the experimental kOH data in
columns 2 and 3 indicate that they are the same except for a few
differences. For a few of the compounds, the experimental values
in Experimental/(a) are listed with only two significant figures
whereas the data listed in Experimental/AOP have three
significant figures. A check on the original literature sources
indicate that the kOK values with two significant figures are the
correct ones. For example, for 1-butanethiol, the recommended
value of koH from Atkinson (1989) is 51* while AOP lists 51.0.
For methyl ethyl sulfide, the experimental value from Hynes et
al. (1986) and Atkinson (1989) is 8.50 and not 8.5 as listed in
AOP. For dimethyl disulfide, AOP does not have an entry in
column 2 whereas Atkinson (1989) recommends a value of 211*.
-101-
-------
Table 24. Comparison of the Estimated Values of kOH at 298 K for Alkyl
Thiols, Sulfides, and Disulfides from the Atmospheric Oxidation
Computer Program (AOP) and from a Hand Calculation (HC) and the
Experimental KQH Data Reported in the Literature Versus the
Experimental kQH Data in AOP
Chemical Class/Chemical
A. THIOLS
Methanethiol
Ethanethiol
1-Propanethiol
2 -Propanethiol
1-Butanethiol
2-Methyl-l-propanethiol
2 -Butanethiol
2 -Me thy 1-2 -pr opaneth io 1
2-Methyl-l-butanethiol
B.I. ACYCLIC SULFIDES6
Dimethyl sulfide
Methyl ethyl sulfide
Diethyl sulfide
Di-n-Propyl Sulfide
B.2. CYCLIC SULFIDES6
Tetrahydrothiophene
C. DISULFIDES
Dimethyl disulfide
1012kOH(cm3molecule~1s""1)
Experimental
AOP
32.9
46.8
48.3
42.0
51.0
45.0
40.0
33.1
54.0
4.56
8.5
15.0
20.0
19.7
(f)
(a)
32.9*
46.8*
48.3*
42.0*
51*
45*
40*
33.1*
54. 3b
4.56*
8.50°
15*
20. Od
19.7*
211*
Estimated
AOP
32.3
38.7
42.0
47.8
43.4
43.5
53.7
31.6
44.9
4.59
11.0
17.5
24.0
19.8
203
HC
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
17.8
203
a Experimental values from Atkinson (1989) and the literature.
b Experimental value from Barnes et al. (1986).
c Experimental value from Hynes et al. (1986).
^ Experimental value from Barnes et al. (1986). The experimental value
of Nielsen et al. (1987) appear to be erroneous [Atkinson (1989)].
6 For these compounds, kOH was measured in the absence of oxygen.
-102-
-------
24. continued
f No experimental value is given in the AOP database. An experimental
value of 211xlO"12cm3molecule"1s~1 is given in the document "Estimation
Accuracy of AOP versus PCFAP" [Meylan (1990b)].
* Recommended value by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-103-
-------
Finally, for 2-methyl-l-butanethiol, the correct experimental
value of kOn in column 3 is 54.3 obtained from Barnes et al.
(1986) and Atkinson (1989), and not 54.0 as reported by AOP.
IV.E.l.b. Evaluation of the Estimated kOH Data
A comparison of the estimated kOH data from AOP and HC
indicates that they are the same except for the alkyl sulfides
(acyclic and cyclic) . For all these sulfides, kOH is larger
from AOP than from HC. The reason for the differences will be
described in the following paragraphs.
In estimating kOH, there are two reaction pathways for the
reaction of OH radicals with alkyl (acyclic and cyclic) sulfides:
(1) H-atom abstraction from the C-H groups in the alkyl groups;
and (2) OH radical interaction with the sulfide group to form the
adduct [>S'**'OH] which then decomposes rapidly in the presence
of oxygen to form the products. The total rate of reaction is
then given by the equation
kOH - k(i) + k(4) = k(l) + k(-S-) (57)
In the absence of oxygen, k(-S-) is zero [Atkinson (1987) and
Leifer (1992a)] so that equation 57 becomes
kOH = k(l) (58)
and only C-H abstraction from the alkyl groups takes place.
In estimating k0jj, AOP uses equation 57 while HC uses
equation 58 and this is the reason why kOH (AOP) > kOn(HC) •
Since the experimental values listed in the column
-104-
-------
Experimental/(a) were obtained in rate measurements without
oxygen, KQH must be evaluated using equation 58. Therefore, AOP
must qualify the experimental kOH value for the alkyl sulfides to
indicate that the data were obtained in the absence of oxygen;
and thus, only H-atom abstraction occurs. Then, in the detailed
calculation section, AOP must indicate that k(-S-) = 0 in the
absence of oxygen.
IV.E.2. Reaction with Sulfoxides and Sulfates
IV.E.2.a. Evaluation of the Experimental kOH Data
Table 25 summarizes the pertinent experimental kOH data at
298 K for alkyl sulfoxides and sulfates as reported in Atkinson
(1989), in AOP, and in the literature. A comparison of the
experimental data in columns 2 and 3 indicate that only for
dimethyl sulfoxide is there a difference. The experimental value
from Barnes et al. (1986) and Atkinson (1989) is 62 and not 62.0
as listed in AOP.
IV.E.2.b. Evaluation of the Estimated kOH Data
Atkinson did not develop S/R relationships for alkyl
sulfoxides and sulfates; hence, there are no estimated values
listed under the column Estimated/HC. Meylan (1990b) did develop
S/R relationships for these classes of compounds as described in
the following paragraphs.
In developing S/R relationships for the alkyl sulfoxides,
Meylan (1990b) assumed that only C-H abstraction occurred from
the alkyl group. Therefore,
-105-
-------
Table 25. Comparison of Estimated Values of kOH at 298 K for Alkyl
and Sulfates from the Atmospheric Oxidation Computer Program (
and from a Hand Calculation (HC) and the Experimental kOH Data
Reported in the Literature Versus the Experimental kOH Data in AOP
Chemical Class/ Chemical
A. SULFOXIDES
Dimethyl sulfoxide
B. SULFATES
Dimethyl sulfate
Diethyl sulfate
1012kOH(cm3molecule~1s"1)
Experimental
AOP
62.0
<0.5
1.8
(a)
62b
<0.5C
1.8d
Estimated
AOP(%Error)f
28.5(-54)
1.76(>+250)
11.5(+540)
HC
(e)
(e)
(e)
a Experimental values from Atkinson (1989) and the literature.
b Experimental value from Barnes et al. (1986).
c Experimental value from Japar et al. (1990).
a Experimental value from Japar et al. (1990a).
e Atkinson did not develop S/R relationships for alkyl sulfoxides and
sulfates.
f Calculated using the experimental value listed in Experimental/(a).
-106-
-------
kOH = k(l) (59)
F[S(+4) ** ] = 99.000 (Table 2) (60)
Using equations 59, 60, and 11, AOP estimated that kOH was 28.5
and the percent error, relative to the experimental value listed
in the column Experimental/(a), was -54 (listed in parentheses
adjacent to the estimated value in column 4). However,
intuitively, it is expected that the sulfoxide group would
undergo further oxidation to the sulfone in the presence of
oxygen
0
R-S(=0) + -OH » R S OH
Rapid
Products (61)
and this reaction pathway should be considered in the S/R
relationships. Therefore, considerably more experimental kOH
data are needed on OH radical reaction with a member of alkyl
sulfoxides (both acyclic and cyclic) and aromatic sulfoxides to
determine the reaction mechanism and to develop S/R relationships
for this class of compounds. As a result, it is recommended that
Meylan drop the S/R relationships for this class of compounds
from AOP.
For the alkyl sulfates, Meylan (1990b) assumed that
kOH = k(l) (62)
and the substituent factors F(-O-) and F(-CH2-0-) were valid.
Using equations 62 and 11 along with the appropriate substituent
-107-
-------
factors, AOP calculated kOH f°r dimethyl and diethyl sulfate.
The percent error for each of these compounds were greater than
+250 and +540, respectively. Hence, these results are very poor
and more experimental kOH data are needed for a number of
additional sulfates to derive better S/R relationships for this
class of compounds. Therefore, it is recommended that Meylan
delete the S/R relationships for the sulfates from AOP.
IV.E.3. Reaction with Alkyl Amines, Alkyl Hydrazines, and
N-Substituted Amines
IV.E.3.a. Evaluation of the Experimental k0n Data
Table 26 summarizes the pertinent experimental kOH data at
298 K for alkyl amines, alkyl hydrazines, and N-substituted
amines as obtained from Atkinson (1989), AOP, and the literature.
A comparison of the experimental k0n data for these compounds in
columns 2 and 3 indicates that they are the same except for two
differences. One difference is related to the number of
significant figures used. Thus, for diethylhydroxylamine, the
reported literature value is 101 which was obtained from Gorse et
al. (1977) and Atkinson (1989) while AOP lists a value of 101.0.
Similar comments apply to 2-methyl-2-amino-l-propanol,
diethylhydroxylamine, and methyl hydrazine. For the other
difference, AOP does not report an experimental value for
hydrazine.
IV.E.3.b. Evaluation of the Estimated kOH Data
A comparison of the estimated values of kOH reported by AOP
and HC (columns 4 and 5, respectively) indicate that they are the
-108-
-------
Table 26. Comparison of the Estimated Values of k0jj at 298 K for Alkyl
Amines, Hydrazines, and N-Substituted Amines from the Atmospheric
Oxidation Computer Program (AOP) and from a Hand Calculation (HC)
and the Experimental KQH Data Reported in the Literature Versus the
Experimental kOH Data in AOP
Chemical Class/Chemical
A. ALKYL AMINES
Methylamine
Ethyl am ine
Dimethylamine
Trimethylamine
Dimethylhydroxyethylamine
(2-Dimethylaminoethanol)
2-Methyl-2-Amino-l-
propanol
B . N-HYDROXYLAMINES
Diethylhydroxylamine
C. N-NITROSAMINES
Dimethyl-N-nitrosamine
D. N-NITRAMINES
Dimethyl-N-nitramine
E. ALKYL HYDRAZINES
Hydrazine
Me thy Ihydraz ine
1012kOH(cm3molecule~1s~1)
Experimental
AOP
22.0
27.7
65.4
60.9
90.0
28.0
101.0
2.53
3.84
(h)
65.0
(a)
22. Ob
27.7°
65.4°
60.9°
90d
28e
101f
2.539
3.849
611
651
Estimated
AOP
21.4
28.6
62.9
64.3
77.4
24.1
77.2
2.88
2.88
(j)
81.4
HC
21.4
28.6
62.9
64.3
77.4
24.1
77.2
2.88
2.88
40.0
81.4
a
b
c
d
Experimental data from Atkinson (1989) and the literature.
Experimental value from Atkinson, Perry, Pitts (1977) .
Experimental value from Atkinson, Perry, Pitts (1978) .
Original experimental data is from Anderson and Stephens (1988) which
represents the most reliable data [Atkinson (1989)].
Experimental value from Harris and Pitts (1983) .
Experimental value from Gorse et al. (1977) .
Experimental value from Tuazon et al. (1984).
AOP does not list an experimental value.
Experimental value from Harris et al. (1979) as reported by Atkinson (1987)
AOP cannot estimate k0n for this compound since it does not contain carbon.
-109-
-------
same except for hydrazine. AOP cannot estimate kOH for hydrazine
since it does not contain carbon while HC lists an estimated
value of 40.0. In order for AOP to estimate k0H, the chemical
must contain carbon. As stated previously in AOP, the
experimental value should be entered in column 4 and qualify it
to state that this is the experimental value.
IV.E.4. Reaction with Compounds Containing Phosphorous
Functional Groups
IV.E.4.a. Evaluation of the Experimental kOH Data
Table 27 summarizes the pertinent experimental kOH data at
298 K for several classes of organophosphorous compounds as
reported in Atkinson (1989), in AOP, and in the literature. A
comparison of the experimental JCQJJ data in columns 2 and 3
indicate that there are differences. For trimethylphosphate,
triethyl phosphate, 0,0,8-trimethyl phosphorothioate, and O,S,S-
trimethyl phosphorodithioate, there are slight differences. The
correct values, as obtained from Atkinson (1989) and the
literature, are 7.37, 55.3, 9.29, and 9.59, respectively. For
the compounds 0,0-dimethyl phosphoroamidothioate and 0,0,N-
trimethyl phosphoroamidothioate, the values from Atkinson (1989)
and the literature are only good to three significant figures
rather than the 4 significant figures listed in AOP.
IV.E.4.b. Evaluation of the Estimated kOH Data
A comparison of the estimated kOH data from AOP and HC
indicates that they are the same. It should be noted that the
summary table and detailed calculations in AOP should include
reaction with phosphorous functional groups. For example, for
-110-
-------
Table 27. Comparison of the Estimated Values of kOH at 298 K for Aliphatic
Compounds Containing Phosphorous Functional Groups from the
Atmospheric Oxidation Program (AOP) and from a Hand Calculation
(HC) and the Experimental kOH Data Reported in the Literature
Versus the Experimental kOH Data in AOP
Chemical Class/Chemical
A. ALKYL PHOSPHATES/
THIOPHOSPHATES
Trimethyl phosphate
(CH30)3P-0
Trie thy 1 phosphate
(CH3CH20)3P=0
0,0,0-Trimethyl
phosphorothioate
(CH30) 3P=S
O,O, S-Tr imethy 1
phosphorodithioate
(CH30)2P(S)CH3
0,0, S-Tr imethy 1
phosphorothioate
(CH30)2P(O)SCH3
O , S , S-Tr imethy 1
phosphor od ith ioate
(CH3S)2P(0)OCH3
1012kOH(cm3molecule"1s~1)
Experimental
AOP
7.4
55.0
69.7
56.0
9.3
9.6
(a)
7.37b
55. 3C
69. 7d
56. Od
9.29d
9.59d
Estimated
AOP
8.64
52.2
63.6
65.6
10.6
12.6
HC
8.64
52.2
63.6
65.6
10.6
12.6
-111-
-------
Table 27. continued
Chemical Class/Chemical
B. DIALKYL CHLORO-
PHOSPHOROTHIOATES
0,0-Dimethyl chloro-
phosphorothioate
(CH30)2P(S)C1
C. ALKYL PHOSPHOROAMIDATES
AND ALKYL PHOSPHORO-
THIOAMIDATES
O,0-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 , 0 , N , N-Tetramethy 1
phosphoroamidate
(CH30)2P(0)N(CH3)2
1012kOH (cm-^molecule'^-s'1
Experimental
AOP
59.0
244.0
232.0
46.8
31.9
(a)
59.0°
244e
232e
46. 8e
31. 9e
Estimated
AOP
60.8
80.8
122
124
68.6
HC
60.8
80.8
122
124
68.6
a Experimental data from the literature.
b Experimental data from Atkinson (1989) and Tuazon et al. (1986).
c Experimental data from Atkinson (1989) and Atkinson et al. (1988).
d Experimental data from Atkinson (1989) and Goodman et al. (1988).
e Experimental data from Atkinson (1989) and Goodman et al. (1988a).
-112-
-------
trimethyl phosphate, the summary table should be Reaction with
N,P,S, and OH and the detailed calculation should be
Reaction with Nitrogen. Phosphorous. Sulfur, and -OH
k[P(=0)] = 0.000 (63)
and for (CH30)2P(=S)NH2, the summary table should be Reaction
with N,P,S, and OH and the detailed calculation should be
Reaction with Nitrogen. Phosphorous. Sulfur, and -OH
k[P(=S)] = 55.0 (64)
k(NH2) = 20.0 (65)
IV.F. Reaction of Hydroxyl Radicals with Aromatic Compounds,
Heterocyclic Aromatic Compounds, and Fused Ring
Polyaromatic Compounds
IV.F.1. Aromatic Compounds
IV.F.I.a. Evaluation of the Experimental k0n Data
Table 28 summarizes the pertinent kOH data for the reaction
of hydroxyl radicals with a number of chemicals in a variety of
classes of aromatic compounds as reported in Atkinson (1989), in
AOP, and in the literature. A careful inspection of the
experimental kQjj data in columns 2 and 3 indicate that they are
the same except for some differences. In a few cases, AOP lists
the experimental values with more significant figures than the
values reported on the literature. For example, for styrene, AOP
lists a value of 58.0 while the recommended value by Atkinson
(1989) is 58*. For aniline, AOP lists a value of lii.o while
-113-
-------
Table 28. Comparison of Estimated Values of kOH at 298 K for Aromatic
Compounds from the Atmospheric Oxidation Program (AOP) and from a
Hand Calculation (HC) and the Experimental kOH Data Reported in
Literature Versus the Experimental kOH Data in AOP
Chemical Class/Chemical
A. UNSUBSTITUTED AROMATIC
COMPOUNDS
Benzene
Biphenyl
B. ALKYLBENZENES
Methylbenzene (Toluene)
Ethyl benzene
S-Propylbenzene
i-Propylbenzene
t-Butylbenzene
o-Xylene
m-Xylene
B-Xylene
Q-Ethyltoluene
m,-Ethyltoluene
E- Ethy 1 t o luene
1,2, 3 -Tr imethylbenzene
1,2, 4-Tr imethylbenzene
1,3, 5-Tr imethylbenzene
1012k0H(cm3molecule~1s~1)
Experimental
AOP
1.23
7.2
5.96
7.1
6.0
6.5
4.60
13.7
23.6
14.3
12.3
19.2
12.1
32.7
32.5
57.5
(a)
1.23*
7.2*
5.96*
7.1*
6.0*
6.5*
4.60b
13.7*
23.6*
14.3*
12.3*
19.2*
12.1*
32.7*
32.5*
57.5*
Estimated
AOP
2.04
7.12
5.51
6.13
7.46
7.08
5.08
6.88
14.4
6.88
7.72
14.6
7.72
17.8
17.8
37.5
HC
2.04
7.12
5.51
6.13
7.46
7.08
5.08
6.88
14.4
6.88
7.72
14.6
7.72
17.8
17.8
37.5
-114-
-------
Table 28. continued
Chemical Class/Chemical
C. ALKENYLBENZENES
Phenylethene (Styrene)
2-Phenyl-l-propene
(ot-Methylstyrene)
1-Phenyl-l-propene
(0-Methylstyrene)
1 -Pheny 1-2 -me thy 1 -
1-propene
( j8 -D imethy 1 sty r ene >
D. HALOBENZENES
Fluorobenzene
Chlorobenzene
Bromobenzene
lodobenzene
3-Dichlorobenzene
m,-D i ch 1 or oben z ene
g-Dichlorobenzene
1,2, 4-Trichlorobenzene
Hexafluorobenzene
H-Pr opy Ipent af luor o-
benzene
E. HALOALKYLBENZENES
Benzotrif luoride
4-Chlorobenzotrifluoride
Benzyl chloride
1012kOH(cm3molecule~"1s~1)
Experimental
AOP
58.0
33.0
0.69
0.77
0.77
1.1
0.42
0.72
0.32
0.532
0.172
3.06
0.46
0.24
2.9
(a)
58*
52C
59°
33*
0.69*
0.77*
0.77*
1.1*
0.42®
0.72e
0.32e
0.532f
0.172*
3.06"?
0.46n
0.24n
2.9*
Estimated
AOP
28.2
53.5
65.8
89.1
2.56
1.43
1.28
1.34
0.414
1.01
0.414
0.291
0.151
2.89
0.406
0.285
2.42
HC
28.2
53.5
65.7
89.1
2.56
1.42
1.28
1.34
0.414
1.01
0.414
0.291
0.151
2.90
0.406
0.285
2.43
-115-
-------
Table 28. continued
Chemical Class/Chemical
F. MONOCHLOROBIPHENYLS
2-Chlorobiphenyl
3-Chlorobiphenyl
4-Chlorobiphenyl
G. HYDROXYBENZENES
Phenol
o-Cresol
nj-Cresol
E-Cresol
2 , 3-Dimethylphenol
2 , 4-Dimethylphenol
2 , 5-Dimethylphenol
2 , 6-Dimethylphenol
3 , 4-Dimethylphenol
3 , 5-Dimethylphenol
2 , 3-Dichlorophenol
2 , 4-Dichlorophenol
H. NITROBENZENES
Nitrobenzene
o-Nitrophenol
2-Nitrotoluene
ffi-Nitrotoluene
1012kOH(cm3molecule"1s~1)
Experimental
AOP
2.8
5.3
3.9
26.3
42.0
64.0
47.0
80.2
71.5
80.0
65.9
81.4
113.0
1.66
1.06
0.14
0.90
0.70
0.95
(a)
2.821
5.281
3.861
26.3*
42*
64*
47*
80.23
71.53
80. OJ
65. 9J
81.43
113J
1.66k
1.06k
0.1491
0.90
0.70
0.95
Estimated
AOP
2.95
4.42
2.95
35.7
43.9
93.9
43.9
115
54.1
115
54.1
115
200.3
7.27
3.02
0.251
4.42
0.805
0.605
HC
2.95
4.42
2.95
35.6
43.9
93.9
43.9
115
54.1
115
54.1
115
200
7.27
3.02
0.251
4.42
0.805
0.605
-116-
-------
Table 28. continued
Chemical Class/Chemical
I . AMINOBENZENES
Aniline
N,N-Dimethylaniline
E-Chloroaniline
2 , 4-Toluenediamine
J. ADDITIONAL SUBSTITUTED
BENZENES
Methoxy benzene
Benzonitrile
Benz aldehyde
Acetophenone
Thiophenol
(Mercaptobenzene)
Benzyl alcohol
Tetralin (1,2,3,4-
Tetr ahydr onaphtha lene )
Indan (2,3-Dihydro-
IH-indene)
Fluorene (9H-Fluorene)
1 , 4-Benzodioxin
2 , 3-Dihydrobenzofuran
1 , 4-Naphthoquinone
1012koH(cm3m°lecule~ls~1)
Experimental
AOP
111.0
148.0
83.0
192.0
17.3
0.33
12.9
2.74
11.2
22.9
34.3
9.2
13.0
25.2
36.6
3.1
(a)
111*
148m
83. On
192°
17.3*
0.33
12.9*
2.74P
11.29
22.9
34.3s
9.2t
13. Ou
25.2
36.6
3.1
Estimated
AOP
136
263
53.6
240
23.8
0.356
17.1
1.61
13. 3r
7.99
11.1
9.71
9.42
33.0
38.0
2.75
HC
136
200
53.6
200
23.8
0.356
17.1
1.61
13. 3r
7.99
11.2
9.09
9.37
33.0
36.3
2.75
-117-
-------
Table 28. continued
a
b
c
m
n
0
P
r
8
t
u
Experimental data from Atkinson (1989) and the literature.
Experimental data from Ohta and Ohyama (1985) .
Experimental data from Bignozzi et al. (1981) .
Experimental data from Chiorboli et al. (1983).
Experimental data from Wanner and Zetzsch (1983) .
Experimental data from Rinke and Zetzsch (1984) .
Experimental data from Ravishankara et al. (1978a) .
Experimental data from Atkinson et al. (1985a).
Experimental data from Atkinson and Aschmann (1985) .
Experimental data from Atkinson and Aschmann (1989) .
Experimental data from No It ing et al. (1987) .
Average of the experimental data of Witle et al. (1986) and
Zetzsch (1982) as reported in Atkinson (1989) .
Experimental data from Atkinson et al. (1987) .
Experimental data from Wahner and Zetzsch (1983) .
Experimental data from Becker et al. (1988).
Experimental data from Nolting et al. (1987) and Atkinson
(1989) .
Experimental data from Barnes et al. (1986) .
For the thiol group on an aromatic ring, it was assumed that
k(4)=k(-SH)=0 [Meylan (1990)].
Experimental data from Atkinson and Aschmann (1988a) .
Experimental data from Baulch et al. (1986) as reported by
Atkinson (1989).
Experimental data from Klopffer et al. (1986) and Becker et
al. (1984) as reported in Atkinson (1989).
Recommended value by Atkinson (1989) with the rationale for
the recommendation and the uncertainty for the
recommendation .
-118-
-------
Atkinson (1989) recommends a value of 111*. In a few cases, AOP
lists fewer significant figures than the values reported in the
literature. For example, for 4-chlorobiphenyl, AOP reports a
value of 3.9 while Atkinson and Aschmann (1985) and Atkinson
report a value of 3.86.
It should be noted that for 1,4-benzodioxin, AOP lists the
erroneous name 1,4-dibenzodioxin; and finally, for aniline, AOP
first lists the experimental value for iodobenzene and when a key
is pressed, the correct experimental value for aniline is
displayed.
IV.F.l.b. Evaluation of the Estimated Data
A comparison of the estimated values of kOH by AOP and HC
in Table 28 indicates that they are the same except for some
differences. First, consider the compounds 3,5-dimethylphenol,
N,N-dimethylaniline, and 2,4-toluenediamine. In all three cases,
AOP lists a maximum value of the rate constant for OH addition
to an aromatic ring [i.e., k(7) = ka(j
-------
compounds, AOP uses the incorrect value of ajjj (-CH2-) = 0.06**
instead of the correct value of -0.064** [see Section IV.A., page
40, Table 9, No. 41 and Leifer (1992a), Table 22, page 109].
Furthermore, for the compounds tetralin, indan, fluorene, and
2,3-dihydrobenzofuran, which contain five membered rings, AOP
calculates k(lc) erroneously. That is, for these compounds, AOP
makes an error by omitting the ring strain factor F(5) for the
five membered ring. As a result, the values of KQH for these
compounds are erroneous.
Finally, for the compounds /3-methylstyrene, chlorobenzene,
n-propylpentafluorobenzene, benzylchloride, and phenol, the small
differences between the estimated kOH from AOP and HC are a
result of the method of rounding off the last digit.
IV.F.2. Heterocyclic Aromatic Compounds
IV.F.2.a. Evaluation of the Experimental kOH Data
Table 29 summarizes the pertinent kOH data for the reaction
of hydroxyl radicals with heterocyclic aromatic compounds as
reported in Atkinson (1989), in AOP, and in the literature.
Inspection of the experimental kOH data in columns 2 and 3
indicate that there are a few differences. For pyrrole, the
recommended value by Atkinson (1989) is 110* whereas AOP reports
a value of 110.0 which contains one more significant figure than
is warranted from the experimental data; and for 1,3,5-triazine,
the value from Atkinson et al. (1987) and Atkinson (1989) is
0.145 whereas AOP rounds off the data to 0.15. For imidazole and
-120-
-------
>le 29. Comparison of the Estimated Values of kOH at 298 K for
Heterocyclic Aromatic Compounds from the Atmospheric
Oxidation Program (AOP) and from a Hand Calculation (HC)
and the Experimental kOH Data Reported in the Literature
Versus the Experimental kOH Data in AOP
Chemical
Furan
3 -Methyl fur an
Thiophene
Pyrrole
Imidazole
Oxazole
Thiazole
Pyridine
1,3,5-Triazine
1012kOH(cm3molecule~1s""1)
Experimental
AOP
40.5
93.5
9.53
110.0
36.0
9.1
1.40
0.37
0.15
(a)
40.5*
93. 5d
9.53*
110*
35. 9e
9.1e
1.41e
0.37f
0.1459
Estimated
AOP
40. 5b
106.7(+14)h
9.53b
110. Ob
36. Ob
9.10b
1.40b
0.370b
0.150b
HC
(c)
(c)
(C)
(c)
(c)
(c)
(c)
(c)
(c)
^ Experimental data from Atkinson (1989) and the literature.
b Experimental data for this compound.
c Cannot be calculated by HC since Atkinson did not develop
S/R relationships for these types of compounds.
** Experimental data from Atkinson et al. (1989b).
e Experimental data from Witte and Zetzsch (1986) and Atkinson (1989).
f Average value from the data of Atkinson et al. (1987) and
Witle and Zetzsch (1986) as reported by Atkinson (1989) .
9 Experimental value from Atkinson et al. (1987) as reported by Atkinson
(1989).
" Percent Error from the value of kOn in column Experimental/(a).
-121-
-------
thiazole, the correct values of kOH obtained from Witte and
Zetzsch (1986) and Atkinson (1989) are 35.9 and 1.41,
respectively, and not 36.0 and 1.40 as listed in AOP.
IV.F.2.b. Evaluation of the Estimated kOH Data
Atkinson did not develop S/R relationships for heterocyclic
aromatic compounds whereas Meylan (1990b) did develop S/R
relationships for this class of compounds. Meylan used an
approach similar to the one used by Atkinson for aromatic
compounds (equations 20, 21, and 22). Thus, Meylan postulated
that equations 23 and 24 are applicable to heterocyclic aromatic
compounds where: (1) A^ is a constant which is equal to the
experimental value of kOH for the parent heterocyclic aromatic
ring; and (2) the second term is identical to the one used by
Atkinson for substituents on the aromatic ring [i.e., -1.35 Min
( ^at ) in equation 21]. The values of A^ are given in Table
10 for a number of parent heterocyclic aromatic rings.
The only available experimental kOH data for this class of
compounds is for 3-methylfuran, a substituted furan. Atkinson
(1989b) reported a value of 93.5 for this compound. The
estimated value of kOH obtained from equations 23 and 24 is
106.7 which gives a percent error of +14 which is excellent.
However, more experimental kOH data are needed for a number of
substituted heterocyclic aromatic compounds listed in Table 29
to confirm the validity of equations 23 and 24.
-122-
-------
IV.F.3. Fused Ring Polyaromatic Compounds
IV.F.3.a. Evaluation of the Experimental k0n Data
Table 30 summarizes the pertinent experimental kOH data for
the reaction of hydroxyl radicals with fused ring polyaromatic
compounds [i.e., fused ring polyaromatic hydrocarbons (PAH)].
Inspection of the data in columns 2 and 3 indicate that they are
the same except for a few differences. For anthracene, the
correct value is 112 as reported by Biermann et al. (1985) and
Atkinson (1989) and not 110.0 as reported by AOP. For
phenanthrene, the recommended value by Atkinson (1989) is 31*
and not 31.0 as reported by AOP.
Unfortunately, there are no available experimental kOH data
for fused ring polyheteroaromatic compounds published in the
literature. Hence, there are no entries in Table 30 for this
class of compounds.
IV.F.3.b. Evaluation of the Estimated kOH Data
A comparison of the estimated values of kOH in columns 4 and
5 of Table 30 indicate that they are the same except for a few
differences. The differences are related directly to the
dissimilarity between the S/R relationships of Atkinson
[equations 26, 27 and 28] and Meylan [equation 29]. First of
all, AOP uses the experimental value of k0H for the parent PAH
(which is B^ in equation 29) while Atkinson uses the ionization
potential of the parent PAH. For naphthalene, both methods give
essentially the same results; however, for anthracene and
-123-
-------
Table 30. Comparison of the Estimated Values of kOH at 298 K for
Fused Ring Polyaromatic Compounds (PAH) from the
Atmospheric Oxidation Program (AOP) and from a Hand
Calculation (HC) and the Experimental kOH Data Reported
in the Literature Versus the Experimental k0H Data in AOP
Chemical
Naphthalene
1-Methylnaphthalene
2 -Methy Inaphthalene
2 , 3 -Dimethy Inaphthalene
1 -N i tr onaphtha lene
2-Nitronaphthalene
1, 4-Dichloronaphthalene
Anthracene
Phenanthrene
1012kOH(cm3molecule~1s~1)
Experimental
AOP
21.6
53.0
52.3
76.8
5.4
5.6
5.8
110.0
31.0
(a)
21.6*
53.0°
52.3d
76. 8d
5.4e
5.6®
5.8*
1129
31*
Estimated
AOP
21. 6b
56.9
56.9
70.0
2.66
2.66
4.38
110. Ob
31. Ob
HC
21.4
56.3
56.3
69.5
2.63
2.63
4.37
91.2
22.9
a Experimental data from Atkinson (1989) and the literature.
b Experimental data for this compound.
c Experimental data from Atkinson and Aschmann (1987).
d Experimental data from Atkinson and Aschmann (1986).
e Experimental data from Atkinson et al. (1989d).
f Experimental data from Kl&pffer et al. (1986) and Becker et al. (1984)
as reported in Atkinson (1989).
9 Experimental data from Biermann et al. (1985).
* Recommended values by Atkinson (1989) with the rationale for the
recommendation, and the uncertainty for the recommendation.
-124-
-------
phenanthrene, AOP gives the most reliable results. For the
substituted naphthalenes, AOP and Atkinson (HC) give essentially
the same results. However, more experimental kOH data are needed
for considerably more substituted polyaromatic hydrocarbons to
see how reliable both methods are.
Since there are no experimental kOH data for fused ring
heterocyclic polyaromatic compounds (i.e., guinoline,
isoquinoline, quinoxaline, quinazoline, and acridine), Meylan's
S/R method cannot be evaluated. Thus, experimental kOH data is
needed on a number of compounds in this class of compounds to
confirm and refine the AOP method (i.e., eguation 30).
IV.G. Evaluation of the Estimated Half-Life for the Reaction
of Hydroxyl Radicals with Organic Chemicals in the
Troposphere
Meylan (1990b), in AOP, estimated the half-life [t(1/2)E3
for the reaction of hydroxyl radicals with organic chemicals in
the troposphere by assuming that the average OH radical
concentration was 5 x 105 radicals cm"3 and a 24-hour daylight
day. The assumption of a 24-hour daylight day is incorrect. On
the average, a 12-hour daylight day is more reasonable. [Leifer
(1992a)]. In addition, based on the literature data [Leifer
(1992a)], the average OH radical concentration is closer to 1.5 x
106 radicals cm~3. Therefore, it was recommended that the AOP
computer program be changed to the atmospheric conditions
described above. This has been done by Meylan in a later version
of AOP.
-125-
-------
For olefins and acetylenes, which can react with hydroxyl
radicals and ozone, it is desirable to have knowledge of the
overall oxidative half-life in the troposphere. Therefore,
J^OX - k/OH + k03 (66)
where k'0n and k'03 are the first-order rate constants for
reaction of an organic chemical in the troposphere with respect
to hydroxyl radicals and ozone, respectively, as calculated under
the atmospheric conditions (OH) = 1.5 x 106 radicals cm'3 and a
12-hour daylight day and (03) = 7 x 10*1 molecules cm"3; and the
overall oxidative half-life is given by the equation
(1/2)
QX = 0.693/kQX (67)
Thus, AOP should add
SUMMARY: OXIDATION
(68)
t(l/2)ox - (69)
-126-
-------
V. References
Anderson, L.G.; Stephens, R.D. (1988).
Int. J. Chem. Kinet. 10, 103-110.
Kinetics of the Reaction of Hydroxyl Radicals with
2-(Dimethylamino)ethanol from 234-364 K.
Anastasi, C.; Smith, I.W.M.; Parkes, D.A. (1987).
J. Chem. Soc. Faraday Trans. 1, 74. 1693.
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. 18, 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-jj-dioxins, and
Dibenzofurans.
Atkinson, R. (1988).
Env. Toxic, and Chem. "]_, 435-442.
Estimation of Gas-Phase Hydroxyl Radical Rate Constants for
Organic Chemicals.
-127-
-------
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 kOH). 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. 16, 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,
N205, 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.
-128-
-------
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 N03 radicals, N205, and 03 at 296
± 2 K.
Atkinson, R.; Aschmann, S.M. (1989).
Int. J. Chem. Kinet. 21, 355-365.
Rate Constants for the Gas-Phase Reactions of the OH Radical with
a Series of Aromatic Hydrocarbons at 296 + 2 K.
Atkinson, R.; Aschmann, S.M. (1989a).
Int. J. Chem. Kinet. £1, 1123-1129.
Rate Constants for the Reaction of the OH Radical with the Propyl
and Butyl Nitrates and 1-Nitrobutane at 298 ± 2 K.
Atkinson, R.; Carter, W.P.L. (1984).
Chem. Rev. 8_i, 437-470
Kinetics and Mechanisms of the Gas-Phase Reactors of Ozone with
Organic Compounds Under Atmospheric Conditions.
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. 15., 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. 16, 967-976.
Kinetics of the Reactions of 03 and OH Radicals with a Series of
Dialkenes at 294 ± 2 K.
Atkinson, R.; Aschmann, S.M.; Pitts, Jr., J.N. (1986).
Int. J. Chem. Kinet. 18., 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.
-129-
-------
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.; Aschmann, S.M.; Carter, W.P.L.; Pitts Jr., J.N.
(1982).
Int. J. Chem. Kinet. 14_/ 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. .M, 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. 16, 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. 1£, 1085-1101.
Formation of Alkyl Nitrates from the Reaction of Branched and
Cyclic Alkyl Peroxy Radicals with NO.
Atkinson, R.; Aschmann, S.M.; Winer, A.M.; Pitts Jr., J.N.
(1985a).
Arch. Environ. Contam. Toxicol. 14., 417-425.
Atmospheric Gas Phase Loss Processes for Chlorobenzene,
Benzotrifluoride, and 4-Chlorobenzotrifluoride and Generalization
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f REPORT DOCUMENTATION
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1. REPORT NO.
EPA-744-R-93-001
3. Recipient's Accession No.
title and Subtitle DETERMINATION OF RATES OF REACTION IN THE GAS-PHASE IN THE
^TROPOSPHERE. THEORY AND PRACTICE. 5. Rate of Indirect Photoreaction: Evaluation of the
Atmospheric Oxidation Computer Program of Syracuse Research Corporation for Estimating the
Second-Order Rate Constant for the Reaction of an Organic Chemical with Hydroxyl Radicals
5. Report Date
January 1993
6.
7. Author(s)
Asa Leifer
8. Performing Organization Rept. No.
9. Performaing Organization Name and Address
U.S. Environmental Protection Agency
Office of Pollution Prevention and Toxics
Exposure Assessment Branch (TS-779)
401 M Street. SW
Washington, DC 20460
10. Project/Task/Work Unit No.
11. ContractIC) or Grant(G) No.
(C)
(G)
12. Sponoring Organization Name and Address
13. Type of Report & Period Covered
14.
15. Supplementary Notes
Abstract (Limit: 200 words)
This document contains a critical review of the Atmospheric Oxidation Computer Program (AOP) for estimating the second-order rate constant
(kQ|_|) for the reaction of an organic chemical with hydroxyl radicals in the gas-phase in the troposphere. AOP is being used to regulate industrial
chemicals under Sections 4 and 5 of the Toxic Substances Control Act. It describes the computerization of the structure/reactivity relationships
of Atkinson of the University of California/Riverside by Syracuse Research Corporation. The only input needed to operate AOP is the SMILES
notation, a computerized notation of the molecular structure of the chemical. The computer program will estimate kg^ and the associated half-
life for the reaction of organic chemicals in the atmosphere. AOP will also list an experimental value of kg^ if it is available in the scientific
literature.
17. Document Analysis a. Descriptions
b. Identifiers/Open-Ended Terms
Rates of reaction with hydroxyl radicals with organic chemicals in the gas-phase in the troposphere (kg^); Atmospheric Oxidation Computer
Program (AOP); computerized structure/reactivitiy relationships to estimate kg^ and the associated half-life; estimation methods used to estimate
k0(-| under Sections 4 and 5 of the Toxic Substances Control Act.
18. Availability Statement
Release Unlimited
19. Security Class (This Report)
Unclassified
20. Security Class (This Page)
21. No. of Pages
160
22. Price
(See ANSI-Z39.18)
SM Imtructiora on Revtrae
OPTIONAL FORM 272 (4-77)
(Formerly NTIS-3E)
Department of Commerce
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