Hydrolysis Rate Constants for Enhancing
Property-Reactivity Relationships
by
J. Jackson Ellington
Measurements Branch
Environmental Research Laboratory
Athens, GA 30613-7799
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ATHENS, GA 30613-7799
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DISCLAIMER
The information in this document has been funded wtaily anr
in part by the United States Environmental Protection Ajeney. It
has been subject to the Agency's peer and administrative re-wifflw,,
and it has been approved for publication as an EPA document.
Mention of trade names or commercial products does not const drttmtte
endorsement or recommendation for use by the U.S. Environmental!
Protection Agency.
ii
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FOREWORD
As environmental controls become more expensive and
penalties for judgement errors become more severe, environmental
management requires more precise assessment tools based on
greater knowledge of relevant phenomena. As a part of this
Laboratory's research on occurrence, movement, transformation,
impact, and control of chemical contaminants, the Measurements
Branch determines the occurrence of unsuspected organic
pollutants in the aquatic environment and develops and applies
techniques to measure physical, chemical, and microbial
transformation and equilibrium constants for use in assessment
models and for development of property-reactivity correlations.
In response to the land banning provision of the 1984
Hazardous and Solid Waste Amendments to PL 98-616, the Resource
Conservation and Recovery Act (RCRA), a mathematical model was
developed to estimate potential groundwater contamination from
chemicals placed in land disposal sites. Application of the
model requires as input the hydrolysis rate constant(s) for
chemical(s) of concern. Measured hydrolysis rate constants and
the development of property-reactivity correlations to predict
them for similar chemicals are discussed relative to their
potential application to new chemicals being considered by EPA's
Office of Solid Waste for regulation.
Rosemarie C. Russo, Ph.D.
Director
Environmental Research Laboratory, Athens, GA
iii
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ABSTRACT
This report examines the rate constants for hydrolysis in
water of 10 classes of organic compounds with the objective of
establishing new or expanding existing property-reactivity
correlations. These relationships can then be used to predict
the environmental hydrolysis fate of chemicals that have similar
molecular structure. The compound classes covered by this report
include: aliphatic and aromatic carboxylate esters, alkyl and
aromatic halides, amides, carbamates, epoxides, nitriles,
phosphate esters, alkylating agents, halogenated ethers, and
oxidized sulfur compounds. Three predictive techniques (one
based on empirical correlations with derived constants, another
using infrared spectra and a third relying on fundamental
calculations requiring only chemical structure) were used to
predict and compare hydrolysis rate constants for simple alkyl
esters. The predicted rate constants were generally within a
factor of two of each other and the laboratory-determined values.
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Contents
Page
Foreword iii
Abstract iv
List of Tables and Illustrations vi
Acknowledgments vii
1. Introduction 1
2. Property-Reactivity Correlations (PRCs) 2
and Prediction Programs
3. Hydrolysis Background 3
4. Hydrolysis Rate Constants and Half-Lives 7
at pH 7 and 25°C
4.1 Aliphatic and Aromatic Carboxylate Esters 7
4.2 Alkyl and Aromatic Halides 11
A. Chlorinated Alkyls 11
B. Brominated Alkyls 13
C. Bifunctional Chloroalkanes 14
D. Polycyclic and Aromatic Halogenated
Hydrocarbons 15
4.3 Amides (Primary and N-Substituted) 20
4.4 Carbamates 23
4.5 Epoxides 26
4.6 Nitriles 29
4.7 Phosphate Esters 31
4.8 Alkylating Agents 35
4.9 Halogenated Ethers 38
4.10 Oxidized Sulfur Compounds 40
4.11 Other Miscellaneous Compounds 43
5. Predictive Techniques 46
6. References 49
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List of Tables and Illustrations
Page
Tables
1. Aliphatic and Aromatic Carboxylate Esters 9
2. Alkyl and Aromatic Halides 16,17,18
3. Primary and N-Substituted Amides 21
4. Carbamates 24
5. Epoxides 27
6. Nitriles 30
7. Phosphate Esters 33
8. Alkylating Agents 36
9. Halogenated Ethers 39
10. Oxidized Sulfur Compounds 41
11. Miscellaneous Compounds 44,45
12. Predicted and Laboratory-Determined Hydrolysis Rate
Constants of Carboxylate Esters 47
Illustrations
1. Aliphatic and Aromatic Carboxylate Esters 10
2. Alkyl and Aromatic Halides 19
3. Primary and N-Substituted Amides 22
4. Carbamates 25
5. Epoxides 28
6. Phosphate Esters 34
7. Alkylating Agents 37
8. Oxidized Sulfur Compounds 42
9. SPARC Generated pH-rate Profile of Methyl Methacrylate 48
VI
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Acknowledgments
The assistance of Ms. Cheryl Trusty in preparation of the
draft manuscript, figures, and tables is gratefully acknowledged.
Ms Mimi Houston's effort in retyping the draft and subsequent
revisions was always timely and professional. The review of the
manuscript by Drs. Peter Jeffers and Timothy Collete is also
gratefully acknowledged.
VII
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Hydrolysis Rate Constants for Enhancing
Property Reactivity Relationships
1.0 Introduction
Each year more than 1000 new chemicals are introduced into
commerce and thus into the environment worldwide. Regulators and
scientists need reliable data on the persistence, mobility,
toxicity and possible risk to humans or the ecosystem associated
with these new chemicals as well as the more than 65,000
currently in use (1). The possible persistence of these
chemicals and accompanying risk of exposure to humans and other
species of concern has resulted in a demand on regulators to
provide effective techniques for quantifying their mobility and
fate.
As part of the effort to evaluate potential mobility and
fate associated with chemical constituents of wastes under
consideration for land disposal, EPA's Office of Solid Waste
(OSW) uses a relatively simple model to estimate potential
groundwater contamination at specified withdrawal points in
proximity to a landfill. This model calculates horizontal
chemical movement in the aquifer based on advection, dispersion,
sorption and transformation. Hydrolysis is the only
transformation process specifically considered at this time.
To apply this model to chemicals of interest to OSW,
hydrolysis rate constants for 98 chemicals were previously
obtained either from literature sources or laboratory
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determinations (2-4) using protocols developed at ERL-Athens (5).
The objective of this report was to examine the rate data
presented in references 2-4 and organize them by compound class,
with the goal of either enhancing existing property-reactivity
correlations (PRCs) or developing new PRCs if sufficient data
have been generated for a particular class of chemicals. These
correlations then can be applied to new chemicals in wastes being
considered by OSW for regulation.
2.0 Property Reactivity Correlations (PRCs) and Prediction
Programs
The use of PRCs for predicting rate and equilibrium
constants for organic reactions is well established (6).
Pharmaceutical and pesticide manufacturers routinely use
historical data on existing compounds in designing new products
to either increase or decrease potency and/or persistence while
decreasing or eliminating unwanted side effects. Any chemical
released to the environment is subjected to a wide variety of
conditions that can transform it to a different product. PRCs
offer a means for estimating kinetic constants for important
transformation processes such as hydrolysis, photolysis, and
redox reactions.
For example, a symposium, "Structure-Activity Relationships
in Environmental Toxicology and Chemistry" was part of the
American Chemical Society Meeting April 6-8,1987, in Denver,
Colorado. The symposium topics included SARs to estimate rate
constants for oxidation by HO* radicals in the troposphere and
peroxy radical and singlet oxygen reactions in surface waters,
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and to estimate salinity constants for ligands and selected metal
ions. Several SARs correlated molecular structure with toxicity
to aquatic organisms.
The reliability of any PRC/SAR is directly related to the
accuracy of data input and to how well the selected data
represent the particular process. Most existing PRCs are
empirical correlations (based on derived measures of the polar
and/or steric effects of compound structure) that predict new
kinetic constants only for reaction pathways for which data exist
for similar transformations. Using this approach, Drossman,
Johnson and Mill developed SARs for base-promoted hydrolysis of
esters and carbamates using a* and Es values for the compounds of
interest (7).
Two approaches that are less dependent on measured kinetic
data are being developed at ERL-Athens. Collette (8) is
developing a method for predicting environmental fate constants
of chemicals based on their infrared spectra. Even though many
reactivity parameters may be amenable to this approach, to date,
only alkaline hydrolysis of organic esters has been considered in
depth. Karickhoff et al. (9) is developing a prototype computer
program SPARC (SPARC Performs Automated Reasoning in Chemistry)
that uses computational alogrithms based on fundamental chemical
structure theory. This allows estimation of values for a broad
variety of reactivity parameters both kinetic and equilibrium: Uv
light absorption, pKa, and various reaction rate constants, or
any parameters that depend on molecular structure. The agreement
of the alkaline hydrolysis rate constants for carboxylate esters
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calculated by all of the above methods as well as determinedE im
the laboratory will be discussed in more detail later.
3.0 Hydrolysis Background
Hydrolysis of organic compounds refers to reaction of t2us>
compound with water in which bonds are broken and new bonds
HO- and H- are formed. A common example is the react ion of ant
alkyl halide with water resulting in the loss of halide lore (,-
RX + HOH - > ROH + HX (or H*, X')
The rate of the reaction may be promoted by the hydrondum
ion (H+, or H3O+) or the hydroxyl ion (OH") . The former is
referred to as specific acid catalysis and the latter as
base catalysis. These two processes together with the neviititaJ!
water reaction were the only mechanisms considered in lefesrenxD
2-5.
Some chemicals show a pH-dependent elimination reactions
H X
II H+ or
- C - C - - > C = C + HX
OH"
For the hydrolysis rate constants reported in references 2>-5>t
only the disappearance of substrate was monitored with no
attempts to identify mechanisms.
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If all processes referred to as hydrolysis are included, the
rate of hydrolysis is given by the equation,
d[C]
dt
= kjc] = kA[H*][C] +
where [C] is the concentration of reactant and k,, is the observed
pseudo-first-order rate constant at a specific pH and
temperature, kA, kg, and k,,1 are second-order rate constants for
the acid, base and neutral promoted processes, respectively. The
water concentration is essentially not depleted by the reaction
and is much greater than [C], thus k^tHjO] is a constant (k^,) ,
the pseudo-first order neutral rate constant.
Equation 1 assumes each individual rate process is first
order in substrate, thus k,, can be defined as:
kj, = kA[H+] + kgCOlf] + k, (2)
Equation 1 then becomes simply,
d[C]
(3)
dt
which integrates to
[C]t = [C]0 exp^t) (4)
or
[C]t
In - = k,,t (5)
[C]0
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Equation 5 allows calculation of the concentration of a
reactant at any time (t). Specifically, when [C]t = h[C]0,
equation 5 reduces to:
lnT
50 In 2 0.693
t = t.h = = = (6)
For many chemicals, hydrolysis can be the dominant pathway
for degradation in the environment. Functional groups that are
potentially susceptible to hydrolysis are:
1. Aliphatic and aromatic carboxylate esters
2. Alkyl and aromatic halides
3. Amides
4. Carbamates
5. Epoxides
6. Nitriles
7. Phosphate esters
8. Alkylating agents
9. Halogenated ethers
10. Oxidized sulfur compounds
Tables 1 through 10 contain hydrolysis rate constant data
and half-lives for chemicals in the above classes at pH 7 in
aqueous solution at 25°C. The corresponding figures contain
structures of selected chemicals in these classes. The data in
Tables 1 through 10 were either reported in references 2-4 or
extracted from the indicated references for comparison purposes.
For data generated at other temperatures, the rate constants were
extrapolated to 25°C using either the experimentally-determined
activation energies for each chemical, or an assumed activation
energy (Ea) of 20 kcal/mol for each path (acid, neutral, or base
hydrolysis). Since the majority of compounds have measured Ea
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values in the range of 15 to 25 kcal/mol, the assumption of 20
kcal/mol for Ea generally introduce less than an order of
magnitude error in the extrapolated rate constant.
Mabey and Mill (10) completed a critical review of the
hydrolysis of organic compounds in water under environmental
conditions. Hydrolysis rate constant values from Mabey and Mill
are herein used, where available, for comparison purposes.
4.0 Hydrolysis Rate Constants and Half-Lives at pH 7 and 25"C
4.1 Aliphatic and Aromatic Carboxylate Esters
Table 1 summarizes data for hydrolysis of aliphatic and
aromatic esters at 25°C and pH 7. For these compounds, hydrolysis
at pH 7 is dominated by hydroxide ion for simple alkyl and
aromatic esters (10). Thus, the values of kg yield a reliable
calculation of k,, and half-lives at pH 7. For more structurally
complex esters and esters with substitutents that reduce the
electron density of the carbonyl carbon (a-halogenated) neutral
hydrolysis (k,,) will be competitive at pH 7. The general rule is
that methyl esters are twice as reactive as other n-alkyl esters
and branching on the a-carbon on either side of the carboxylate
group will retard hydrolysis by factors of three to ten (7).
The above effects (i.e., the reduction of electron density by
the phenyl substituent and methyl versus ethyl ester) are evident
in the factor of eight increase in 2,4-D methyl ester hydrolysis
rate compared to ethyl methoxyacetate. The 2,4-D methyl ester was
used as a standard reference compound and the reported rate
constant is the mean of 27 determinations. Lasiocarpine and
reserpine are structurally complex molecules that have two
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hydrolyzable groups (labeled 1 and 2 in Figure 1). Site 1 in
lasiocarpine is structurally similar to methyl methacrylate and
site 2 is structurally similar to ethyl glycolate. Branching on
the o-carbon at site 2 (potentially the most easily hydrolyzed)
retards hydrolysis to the extent that disappearance is dominated
by neutral hydrolysis. Similarly, in reserpine, branching on the
acyl carbon at site 1 (compare with methyl acetate) retards
hydrolysis by hydroxide ion to the extent that neutral hydrolysis
is again dominant at pH 7. Addition of a methyl group to the a-
carbon of the acyl group of methyl acrylate (11) to form methyl
methacrylate decreases the kg by a factor of two. The small kg
for di-n-octylphthalate is consistent with increasing chain length
in the alcohol group (8).
8
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TABLE 1. ALIPHATIC AND ARCMATIC GAEBOXXIATE ESTERS
Rate Constants (25'C)
CAS Number
Compound
-
M - hr
Neutral
hr"1
M hr
Calculated Ref.
Half-Life
pH 7, 25°C
1928-38-7 2,4-D Methyl ester
3938-96-3 Ethyl nethoxyacetate
Ethyl glyoolate
303-34-4 lasiocarpine
96-33-3 Methyl acrylate
79-20-9 Methyl acetate
50-55-5 Reserpine
93-89-0 Ethyl benzoate
80-62-6 Methyl roethacrylate
84-66-2 Diethylphthalate
84-74-2 Ditoutylphthalate
117-84-0 Di-n-Octylphthalate
41,000 ± 5,000 7d 4
4968 58d 7
3636 79d 7
(4.9 ± 0.1JE-5 9.8 ± 0.1 1.6y 3
406a 1.9y 11
655 1.2y 7
(4.5 ± 1.8)E-5 9.8 ± 11 1.7y 2
105 7.5y 7
200 ± 47 3.9y 3
90 8.8y 8
36 22y 8
7.4 107y 3
a. Assumed E& = 20 kcal/mol in extrapolating kg fron 30°C to 25°C.
-------
o
O-CH3
2,4-D Methyl ester
Oft,
HC
OH
CH3
OH o-CH,
Lasiocarpine
H3CO
OCH*
OCH,
; o
Figure 1. Aliphatic and Aromatic Carboxylate Esters
10
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4.2 Alkyl and Aromatic Halides
The halogenated compounds in Table 2 range in complexity from
the simple chloroethane to the multihalogenated polycyclics such
as aldrin. All have in common the potential hydroxide ion or
water mediated cleavage of the carbon-halogen bond to give
alcohols. E2 elimination to give olefins and hydrogen halides,
although not true hydrolysis, can occur in water and may be
enhanced by increasing hydroxide ion concentration and
temperature. Elimination is treated as hydrolysis in the present
text. Multifunctional halogenated chemicals (such as halogenated
ethers and nitriles) are also included in Table 2 because the
point of attack for these compounds is also the carbon-halogen
bond. Table 2 is subdivided into the four groups: chlorinated
alkyls, brominated alkyls, bifunctional chloroalkanes, and
polycyclic and aromatic hydrocarbons.
A. Chlorinated Alkyls (Table 2. Figure 2)
Allyl halides such as allyl chloride are known to hydrolyze
rapidly by a neutral mechanism. Both chlorines in cis and trans-
l/4-dichloro-2-butene (DCB) are allylic. Therefore, because this
compound has two equally reactive groups per molecule, the
disappearance rate constant for the DCBs should be larger than
that for allyl chloride. It is, in fact, larger by a factor of
20. Pentachlorocyclohexene (PCCH) has a chlorine on the gamma
carbon of the allyl fragment. The gamma chlorine on PCCH retards
formation of the carbonium ion and subsequent reaction of the
allylic chlorine by an order of magnitude (half-life =2.1 years).
Benzyl chloride was used as a standard reference compound in the
laboratory determination of hydrolysis rate constants for selected
11
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justified but probably preferred to the uniform assumption of a 20
kcal/mole activation energy.
A second gem-dihalide (p,p'-DDD) undergoes slow neutral
hydrolysis (half-life 28 years), apparently due to
steric/electronic interferences from the two ^-chlorinated phenyls
on the a-carbon (Figure 2). Jeffers reported that a gem-dihalide
with a H-atom on the gem-substituted carbon (1,1-DCA) undergoes
slow neutral hydrolysis in comparison with the perhalogenated gem-
dichloride (2,2-DCP). The methyl group in 1,2-dichloropropane
(1,2 DCP) increases the reactivity by a factor of five versus 1,2-
dichloroethane (1,2 DCA). The third chlorine in 1,2,3-
trichloropropane decreases the hydrolysis rate by a factor of
three versus versus that of 1,2 DCP. The fully chlorinated
hexachloroethane is almost totally resistant to hydrolysis.
B. Brominated Alkyls
The reactivity of the vicinal bromines in the three
brominated alkyls studied should determine the hydrolysis
disappearance rate constants. The factor of nine greater
reactivity of ethylene dibromide (EDB) over 1,2-dichloroethane
(Table 2 Section a) illustrates the increased susceptibility of
brominated compounds to hydrolysis. Statistically, tris(2,3-
dibromopropyl)phosphate (Tris) with three vicinal bromine centers
should have a larger k,, than ethylene dibromide. The two k,,
values are almost identical, however, which leaves alkaline
hydrolysis (kg) of the phosphate ester as the determining factor
for the shorter half-life (4.4y) compared to EDB (8y).
Apparently, disappearance of l,2-dibromo-3-chloropropane (DBCP) is
controlled by hydroxide-ion-mediated dehydrobromination (E2
12
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Appendix VIII chemicals (5). The standard rate constant value in
Table 2 is the average of 28 determinations and agrees well with
the value of 4.6 E-2 h"1 in Mabey and Mill (10). Hydrolysis of
benzyl chloride is similar to that of the allyl chlorides in that
the rate is enhanced by the ease of formation of a reactive
carbonium ion.
Jeffers (12) and Queen and Robertson (13) independently
determined that gem-dihalides are unreactive to nucleophilic
displacement by hydroxide ion but both measured a neutral
hydrolysis rate constant (attack by water) and activation energy
for 2,2-dichloropropane. Jeffers1 and Queen and Robertson's kN
values are approximately a factor of 2 lower than our value (4) .
Our rate was determined at 45°C, however, and extrapolated to 25°C
using an assumed activation energy of 20 kcal/mol. If Jeffers'
average value of 25.2 kcal/mol for neutral hydrolysis of
chlorinated alkyls is used to extrapolate our rate from 45°C, we
obtain a value of 2.4±0.12 E-2h~1, which is within experimental
error of Queen and Robertson's (13) value of 2.44 E-2 h"1 (who
reported an activation energy of 26.6 kcal/mol).
Jeffers (12) reported the hydrolysis rate constants for 18
chlorinated methanes, ethanes, ethenes, and propanes that were
measured in dilute aqueous solutions within the temperature range
of 0 to 180°C and at pH values from 3 to 14. The average of
neutral activation energies reported by Jeffers was 25.2±2.87
kcal/mol whereas the average for 15 basic activation energies was
26.2±3.87 kcal/mol. Thus, for chlorinated alkanes when the
activation energy is unknown, use of Jeffers1 values to
extrapolate rates to other temperatures would not only be
13
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elimination) as evidenced by the kg term, whereas for another
similarly substituted trihaloalkyl, 1,2,3 trichloropropane (Table
2, Section a), disappearance is dominated by reaction with water
(k,,) . The electronegative chlorine on the
/3-carbon in DBCP apparently enhances elimination of HBr to make
dehydrobromination the dominant pathway at pH 7.
C. Bifunctional Chloroalkanes
The halogenated alkanes in this group contain either
hydroxyl, cyano, or the ether linkage as the second functional
group. The two chloropropanols (1,3-DCA and 2,3-DCA) differ in
reactivity by two orders of magnitude. As a first approximation,
one might expect that the reactivity of 1,3-DCA should be
comparable to 1,3-dichloropropane (1,3-DCP), but the observed rate
constant for 1,3-DCP is closer to the value of 2,3-DCA. The
enhanced reactivity of 1,3-DCA can be attributed to the 2-hydroxyl
group. Electronegative substituents on the /3-carbon are known to
enhance reactivity of a-halogens (13). Additionally, the acid
character of the hydroxyl is enhanced by the two chlorines. The
oxyanion resulting from ionization of the weak acid can, through
intramolecular cyclization, displace either adjacent chlorine to
form epichlorohydrin, a reactive intermediate. Similar ionization
and cyclization enhances the reactivity of 2-chloroethanol (2-CE)
versus 1,2-dichloroethane (1,2-DCA). The 2,3-DCA contains vicinal
chlorines but the hydroxyl substituent enhances reactivity by only
one order of magnitude over 1,2-DCA.
The bis-dichloroethyl ether (DCE) reactivity, as expected,
was similar to that of ethyl chloride. The 2-(2-chloroethoxy)
ethanol (CEE) with one less reactive chlorine than DCE has a
14
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slightly enhanced rate over DCE, again due to intramolecular
oxyanion displacement of the chlorine to form the cyclic dioxane.
The oxygen substituent on the a-carbon of chloromethyl methyl
ether enhances reactivity by six orders of magnitude over bis-
dichloroethyl ether. The ease of formation and stability of the
methoxymethyl carbonium ion has been proposed to explain the
enhanced reactivity of chloromethyl ethers (20) over chlorethyl
ethers.
D. Polycylic and Aromatic Halogenated Hydrocarbons
The halogenated polycyclic and aromatic hydrocarbons comprise
a very persistent group of chemicals in the environment. The
three most reactive polycyclic compounds studied (Aldrin,
Dieldrin, and Isodrin) all contain a perchlorinated gem-dichloro
carbon. Dieldrin (Aldrin epoxide) also contains an epoxide
oxygen, and, with two reactive centers, would be expected to have
the shortest half-life. Apparently hydrolysis of the epoxide is
stericly hindered and the orientation of the cyclic ring is such
that hydrolysis of the gem-dihalide also is retarded in comparison
to 1,2-DCP.
Structural orientation is also the reason that the cis isomer
of chlordane is more susceptible to hydroxide-ion-mediated
dehydrohalogenation. The 1-exo, 2-exo orientation of the chlorine
atoms in cis-chlordane facilitates the E2 elimination of HC1. No
disappearance of trans-chlordane was observed under the same
conditions. All the chlorinated aromatics studied were very
stable to hydrolysis.
15
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TABLE 2. AIK¥L AND ARCMAXIC
CAS Number
Ccnpound M hr
Rate Constants (25'C)
Neutral Base
hr'1 M"1 hr'1
Calculated
Half-life
pH 7, 25°C
Ref.
a. CHLORINATED ALKYIS
107-05-1
764-41-0
110-57-6
319-94-8
100-44-7
594-20-7
72-54-8
58-89-9
78-87-5
107-06-2
96-18-4
67-72-1
Allyl Chloride
cis-1 , 4-Dichloro-2-butene
trans-1 , 4-Dichloro-2-butene
Pentachlorocychlohexene (PCCH)
Benzyl Chloride
2,2-Dichloropropane (2,2-DCP)
p,p'DDD
1,1-Dichloroethane (1,1-DCA)
Lindane
1 , 2-Dichloropropane
1,2-Dichlorethane (1,2-DCA)
1,2, 3-Trichloropropane
Hexachloroethane
4.6E-4
(9.1 ± l.l)E-3
(9.0 ± 0.5JE-3
3.0E-5 74 ± 3
(5.1 ± 0.3JE-2
(4.7 ± 0.2)E-2
1.9E-2
2.4E-2
(2.8 ± 0.9)E-6 5.2
1.29E-6 4.32E-5
(1.2 ± 0.2)E-4 198 ± 6
(5.0 ± 0.2)E-6 4.3E-4
1.1E-6
(1.8 ± 0.6)E-6 9.9E-4
4.3E-7
63d
3.2d
3.2d
2.1y
14h
15h
36h
29h
28y
61y
207d
15. 8y
72y
44y
1.8E9
10
2
2
4
4
4
12
13
3
12
3
3
12
2
12
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T&HCE 2. MK£L AND ARCMATIC HAUDES - continued
CAS Number
b. BRCMINA
106-93-4
126-72-7
92-12-8
Ccopcund M hr
TTD AUKANES
Ethylene dibrcmidfp (FOB)
,2-DiDrcBO— 3-cxiJLorppropane (DBCP;
Rate Constants (25°a
Neutral Base
nr"1 M"1 hr"1
9.9E-6
tris) (1.0 ± 1.1) E-5 78
20.6
Calculated Bef.
Half-life
pH 7, 25'C
8y 14
4.4y 3
38y 2
C. ETFUNCTIONAL CHDORQAIJ^ANES
142-28-9 1,3-Dichlcjroprupane (1,3-DCP)
96-23-1 l,3-Dichlaro-2^jrcpanol (1,3-DCA)
616-23-9 2,3^idiLoro-l-^rapanol (2,3-DCA)
542-76-7 3-ChlorDpropanenitrile
Hl-44-4 bis-Dichloroethylether (DCE)
628-89-7 2-(2-Qaaroethoxy)ethanol (GEE)
107-07-3 2-Chloroethanol (2-CE)
75-00-3 Ethyl chloride
107-30-2 Chloranethyl methylether
3.5E-5 1E-3 2.3y 12
(3.1 ± 0.2)E-3 850 ± 87 9.Id 2
(5.3 ± 0.8JE-5 20.6 ± 2.2 1.4y 2
(1.3 ± 0.1JE-4 12,071 ± 1,960 22d 3
(2.6 ± 0.1JE-5 3.0y 3
(3.2 ± 0.1)E-5 2.5y 4
4.5E-6 36 9.8y 4
4.5E-5 1.8y 15
21 2 min 20
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CO
M/AEM^*; ^ » AJLJ^IVlLf ANo /VRCMAJ.JLO HAJLJLOEjS continued.
CAS Number
Pate Constants (25°C>
Acid Neutral Base
Compound M"1 hr'1 hr"1 M'1 hr"1
Calculated
Half-Life
pH 7, 25°C
Ref.
d. POLSfCYCLTC AND ARCMftTIC HAIOGENMED HYDROCARBONS
60-57-1
28291-10-3
309-00-2
465-73-6
5103-74-2
5103-71-9
108-90-7
95-50-1
541-73-1
106-46-7
24009-05-0
608-93-5
95-94-3
88-06-2
101-14-4
Dieldrin (7.5 ± 3.3)E-6
DL-trans-4-ChlorostiIbene
Oxide 1080 ± 108 (61 ± 7.2)E-4
Aldrin (3.8 ± 2.3)E-5
Isodrin 1.7E-6
Cis-chlordane 4.3E-3
trans-Chlordane zero hydrolysis after 5 days at 85 °C, pH
Chlorobenzenea <0 . 9
1, 2-Dichlorobenzenea <0 . 9
1 , 3-Dichlorobenzenea <0 . 9
l,4-Didtilorobenzenea <0.9
lHHydroxychlordeneb <1 x 10-4
Pentadilorobenzenea <0.9
l,2,4,5-Tetrachlorobenzenea <0.9
2,4,6-Trichlorophenolc (2.3 ± 3.5)E-7
4 , 4-^fethvlene-bis- (2-Chloroaniline) <9E-8
10. 5y
112h
760d
46y
>184,000
11
>900y
>900y
>900y
>900y
200,000y
>900y
>900y
>300y
>800y
2
4, 16
2
3
3
4
4
4
4
4
4
4
4
2
a. Based on assumed base mediated 1% disappearance after 16d at 85eC and pH 9.70 (pH 11.26 at room
temperature).
b. Based on assumed base mediated 5% disappearance after 48d at 85°C and pH 9.71 (pH 11.04 at room
temperature).
c. Based on assumed 5% disappearance after 330 hr at 85 °C.
-------
Cl
Pentachlorocyclohexene (PCCH)
Lindane
(Br-CH2-CHBr-CH2-O)3-P = O
Tris(2,3-dibromopropyl)phosphate
N
H
H
Cl
H
H
3-Chloropropanenitrile
Cl Cl
Dieldrin
Cl
\
Cl
Aldrin
Isodrin
Cl
H
Cl
cis-Chlordane
HC1
trans-Chlordane
Figure!. Alkyl and Aromatic Halides
19
-------
4.3 Amides (Primary and N-Substituted)
Amides generally hydrolyze by acid- nnd baso-m«d Lit i>d
processes to carboxylla no Ids and amines. When the ratos
determined at pH's 3 and 7 or pH's 11 and 7 were the snmo, the
rate was reported as the neutral rate constant.
Table 3 summarlzoa the rite datti at pH 7 nnd 25°C foe nevoral
primary and N-substituted amides. Thioacetamide Illustrates tho
instability introduced when sulfur ia substituted for oxygon.
(Acetamide is the oxygen analog.) Electronegative substltuents
(fluoro- and ohloroaoetamide) or subutitutientu that doloc.ilizo
the carbonyl electrons (acrylamido) enhance reactivity of tho
amide. Pronamide hydrolysis nlso is enhanced by tho
delocalization of electrons into the dichlorophony1 substituont.
20
-------
TABLE 3. FKEMARY AND N-SUBSTTUJTED AMIDES
CAS Number
a. PRIMARY
62-55-5
60-35-5
640-19-7
79-07-2
79-06-1
Rate
-!°id-i
Conpcund M hr
Thioacetamide (6.0 ± 0.06)E-2
Acetamide 3 . OE-2
2-Fluoroacetamide
2-Chloroacetamide 4 . OE-2
Acrylamide <3 . 6E-3 <
Constants (25°C)
Neutral
hr"1
(8.6 ± l.l)E-5
(3.3 ± 0.3)E-5
(2.1 ± 2.1)E-6
Calculated
Base Half-£ife
M'1 hr"1 pH 7, 258C
1.4 ± 0.09 336d
0.17 3,440y
2.4y
540 1.5y
>38y
Ref.
3
10
3
10
2
b. N-SUBSTTTOIED
23950-58-5
591-08-2
53-96-3
Pronamide 4.3E-3
N- (aminothioxonethyl) acetaitd.de
2-Acetylaminofluorene
<1.5E-5
(1.7 ± 0.2)E-5
2.3E-6
7.4E-2 >5y
1.5 ± 0.09 4.6y
6E-3 34y
2
3
3
-------
NH2
Thioacetamide
H
O
H
Acrylamide
O
NH2
2-Fluoroacetamide
H
CH
N-(Aminothioxomethyl)-Acetamide
O
I
H
Pronaraide
Cl
Cl
CH,
2-Acetylaminofluorene
Figure 3. Primary and N-Substituted Amides
22
-------
4.4 Carbamates
Hydrolysis of carbamates proceeds by acidic, basic, or
neutral processes to give alcohols, amines, and carbon dioxide.
Half-lives of carbamates as illustrated in Table 4 vary from
seconds to centuries (10). Mitomycin C contains among its
functional groups a carbamate, an aziridine, and a labile methoxy
group. The rate limiting step in disappearance of mitomycin C is
expulsion of the methoxide prior to opening of the aziridine ring
(22, 23). The half-life of mitomycin C is comparable to 2-
methylaziridine in Table 11. Ethyl carbamate, contrary to most
carbamates, is not N-substituted. The reactivity of ethyl
carbamate is comparable to the simple alkyl amides.
23
-------
TABLE 4. CARBAMAIES
Rate Constants (25° a Calculated Ref .
CAS Number Compound
Acid Neutral
M hr hr
Base Half-Life
M'1 hr"1 pH 7, 25°C
50-07-7 Mitcmycin C
51-79-6 Ethyl Carbamate
2303-16-4 Diallate
4320
1.8E-3 43
<2.6E-7 1.1E-1
(1.2 ± 0.7JE-5 0.9 ± 0.4
12.9d 22, 23
>300y 2
6.6y 3
to
-------
H,C
Ethyl carbamate
trans-Diallate
Figure 4. Carbamates
25
-------
4.5 Epoxides
Hydrolysis of epoxides in acid, neutral or base catalyzed
reactions yields diols as the final product. Epoxides are
reactive compounds with half-lives generally minutes to less than
15 days (10), see Table 5. Aromatic or conjugated epoxides tend
to be more reactive than strictly aliphatic epoxides. Acid-
catalyzed hydrolysis is sensitive to the stability of the
transient carbonium ion formed by protonation of the oxirane ring
and subsequent breaking of one of the carbon-oxygen bonds. This
enhanced reactivity is reflected in the hydrolysis rate constant
of D.L-trans-4-chlorostilbene oxide (CSO). The stability of
Dieldrin is possibly due to shielding of the oxirane group from
attack by water and to lower reactivity of alkyl epoxides.
26
-------
TABLE 5. EPOXEDES
Rate Constants (25"C) Calculated Ref.
Acid Neutral Base Half-Life
CAS Number Oonpound M"1 hr""1 hr"1 M"1 hr'1 pH 7, 25*C
28291-10-3 DEr-trans-4-Chlorostilbene
Oxide 1080 ± 108 (61 ± 7.2)E-4a 112h 4, 16
60-57-1 Dieldrin (7.5 ± 3.3)E-6 10.5y 2
a. Neutral rate from Reference 16.
-------
trans-4-chlorostilbene oxide
Cl Cl
Dieldrin
FigureS. Epoxides
28
-------
4.6 Nitriles
The hydrolysis of nitriles normally takes place only in the
presence of either strong acids or strong bases. In both cases,
amides are the first reaction products, but amides cannot be
isolated as intermediates unless their rate of hydrolysis is lower
than that of the parent nitrile. Nitrile data, summarized in
Table 6, confirms the stability of the monofunctional alkyl
nitriles (acrylonitrile and acetonitrile) under environmental
conditions. Malonitrile (1,1-dicyanomethane), by comparison, is
very labile to degradation even under neutral conditions. This
can be attributed to the activation (ionization) of the a-
hydrogens. The anion formed is unstable and some form of cleavage
or hydrolysis occurs when malonitrile loses a proton to form the
monoanion.
29
-------
TABLE 6. NITRITES
CAS Number
Ocropound
Rate Constants (25'C)
-
M hr
Neutral
hr"1
Calculated Ref.
Half-life
-S336-!
M *- hr *• pH 7, 25°C
109-77-3 Malorxanitrile
75-05-8 Acetonitrile
107-13-1 Acrylonitrile
(4.2 ± 0.3)E-2
(1.30 ± 0.40)E-3 806 ± 45 21d 3
5.8E-3 >130,000y 3
(6.1 ± 6.5)E-1 1220y 2
u>
o
-------
4.7 Phosphate Esters
Organothiophosphate and organodithiophosphate triesters,
depending on the substituents, may undergo hydronium-ion-catalyzed
hydrolysis, hydroxide-ion-catalyzed hydrolysis and neutral
hydrolysis and are quite reactive species. Under environmental
conditions, only the neutral and hydroxide-ion-mediated hydrolyses
are relevant as illustrated in Table 7. Most phosphate pesticides
have the general structure:
where R = an alkyl group (usually methyl or ethyl) and X = an
organic radical. Hydrolysis involves cleavage of either the P-OX
(-SX) bond (hydroxide ion and neutral) or the 0-X (S-X) bond
(hydronium ion) depending on conditions.
When sulfur is substituted for oxygen in the P=O position,
the rate of hydrolysis is decreased, whereas substitution of S for
O in the P-O-X position increases the rate of hydrolysis. The
greater electronegativity of the oxygen atom in the P=0(S)
position enhances the positive character of the phosphorus atom
and thus the attraction for the electrons on the hydroxide ion or
the water molecule (17).
In breaking the P-O(S) single bond, the mercaptide anion is a
better leaving group than the alkoxide. Rates of hydrolysis are
therefore accelerated when S is substituted for O in this
31
-------
position. The second-order alkaline hydrolysis rate constants of
thioesters have been correlated to the pKa of the conjugate acid
of the leaving group by the relationship:
log k = m'pKa + c
where m is the slope and c the intercept (18).
Using the m and c values from Wolfe (18), and conjugate acid
pKa values calculated (9) by SPARC (2-hydroxypyrazine) or Perrin
[(19) p-N,N-dimethylsulfamoyl phenol], we calculated second-order
alkaline hydrolysis rate constants for O,O-diethyl-O-pyrazinyl
phosphorothioate and Famphur. The calculated values in Table 7
agree within a factor of two with the laboratory-determined
values. The hydrolysis of the trialkylthioester is an order of
magnitude slower than the above thioesters with at least one
aromatic substituent.
The greater reactivity when 0 is replaced by S in the leaving
group is evidenced by the 50% increase in the neutral hydrolysis
rate constant of O,O,S-triethyl ester over the O,0,O-triethyl
ester. The reactivity of the dithioesters Phorate and Dimethoate
is further enhanced by reactive groups in the alkyl side chain to
yield half-lives of less than five days compared to a half-life of
115 days for Famphur.
32
-------
TABIE 7. EHOSEHATE ESTERS
u>
CAS Number Compound
a. THIOESTERS
297-97-2 OfO-Diethyl-o-pyranzinyl
phosphorothioate
52-85-7 Fatnphur
126-68-1 O,O,O-Triethylester
phosphorothioic acid
b. DITHIOESTERS
298-02-2 Riorate
60-51-5 Diaethoate
298-04-4 Disulfoton
Rate Constants (25°a
Acid Neutral Base
M"1 hr"1 hr""1 M"1 hr"1
(1.0 ± 0.1JE-3 7.3 ± 0.7
3.8a
(2.5 ± 0.9)E-4 5.0
8.6a
(2.0 ± 0.2)E-5
7.2E-3
1.7E-4 756
(2.8 ± 0.4)E-4 5.99
Calculated Ref.
Half-life
pH 7, 258C
29d 3
calculated
115d 2
3.9y 3
96h 3
118h 3
103d 2
2524-09-6 OfOfS-Triethylester
phosphorodithioic acid
(3.0 ± 0.2)E-5 l.OE-2
2.6y
a. Calculated ty the equation of Wolfe in Reference 18.
-------
P(OCH3)2
(EtO)2P—O
O,O-Diethyl-O-pyrazinyl
phosphorothioate
O = S — N(CH3)2
(EtO)2P
(EtO)2P
Disulfoton
Phorate
'CH,
(MeO)2P
O
Dimethoate
.NH
CH,
Figure 6. Phosphate Esters
34
-------
4.8 Alkylating Agents
The four alkylating agents are all nitrogen mustards with the
general structure I,
/C-C-Cl
c
R N: »- R -N C
SC-C-C1 C-C-Cl
II
where R is a substitutent that modifies reactivity. The rate
determining step in aqueous solutions is formation of the highly
reactive ethyleneimmonium ion II. The factor of five decrease in
reactivity of chlornaphazine compared to cyclophosphamide is most
likely due to the delocalization of the free pair of nitrogen
electrons over the phosphamide ring, slowing the rate determining
formation of the ethyleneimonium ion (Table 8, Figure 7).
Uracil mustard (Figure 7) on the other hand is approximately
three orders of magnitude more reactive than cyclophosphamide.
35
-------
TABLE 8. AIKYIATING AGENTS
CAS Number
Ocxnpound
Rate Constants (25*0
-4°id-i
M * hr *
Neutral
hr"1
-
M - hr
Calculated Ref.
Half-Life
pH 7, 25°C
66-75-1 Uracil mustard
305-03-3 Chlorantoucil
148-82-3 Melphalan
494-03-1 Qilornaphazine
50-18-0 cyclqphosphamide
0.57 ± 0.08 (2.05 ± 0.2)E5 1.2h 2
0.40 l.Th 3
0.15 • 4.6h 3
3.2E-3 216h 3
7.1E-4 41d 3
-------
Uracil Mustard
NH-
Melphalan
Chlorambucil
Cl
o
.NH
Cl
•H^O
Chlornaphazine
Cyclophosphamide
Figure?. AlkylatingAgents
37
-------
4.9 Halogenated Ethers
The halogenated ethers were discussed in the section on
bifunctional chloroalkanes (Section 4.2C). The chloromethyl
ethers are orders of magnitude more reactive than ethers that have
two or more carbons interspersed between the chlorine and oxygen
(Table 9). The 2-(2-chloroethoxy)ethanol is a product of
hydrolysis of bis-dichloroethyl ether but due to its larger
hydrolysis rate constant the concentration of 2-(2-chloroethoxy)
ethanol will remain low.
38
-------
TABLE 9. HAIOGENATED ETHERS
Rate Constants f25°C) Calculated Ref .
CAS Number
107-30-2
111-44-4
628-89-7
Compound M hr
Chloronethyl methyl ether
bis-Dichloroethyl ether
2- (2-
-------
4.10 Oxidized Sulfur compounds
The oxidized sulfur containing compounds in Table 10 are all
highly reactive. It is of intrest that the hydrolysis rate
constants of the exo (Endosulfan I) and endo (Endosulfan II)
isomers of Endosulfan, for practical purposes, are identical.
40
-------
TABLE 10. OXIDIZED SULFUR GCMPOUNDS
Rate Constants (25° C} Calculated Ref.
CAS Number Oonpound
Acid Neutral
M'1 hr"1 hr"1
Base Half-Life
M"1 hr"1 pH 7, 25eC
77-78-1 Dimethylsulfate 0.6 1.2 rain 10
1120-71-4 1,3-Eropane Sultone 8.2E-2 8.5h 3
959-98-8 Endosulfan I (8.1 ± 2.7)E-3 (3.2 ± 2.0JE-3 (1.0 ± 0.7)E4 165h 2
33213-65-9 Endosulfan II (7.4 ± 3.9)E-3 (3.7 ± 2.0)E-3 (1.5 ± 0.9)E4 133h 2
62-50-0 Ethyl metnanesulfonate 1.5E-2 46h 3
-------
o
O
o
Cl
1,3-Propane Sultone
S=0
Endosulfan I
Endosulfan II
HC - S
O
H
{-
H
Ethyl methanesulfonate
Figure 8. Oxidized Sulfur Compounds
42
-------
4.11 Other Miscellaneous Compounds
The half-lives of the pyrophosphates and nitroso compounds in
Table 11 are so short, PRC discussions are meaningless. Ethylene-
bis-(cithiocarbamic acid), 2,4-dithiobiuret, auramine, azaserine,
daunomycin, methylthiouracil, nitroglycerine, warfarin,
fluoroacetic acid sodium salt, and octamethylpyrophosphoramide
lack sufficient data for PRC discussion. With the exception of a-
naphthylthiourea, thiourea and its substituted analogs are
resistant to hydrolysis. Possibly the stability of the resulting
a-napthylamine enhances hydrolysis of a-napthylthiourea. The rate
constants reported for chlorinated aromatics in part d of Table 2
make the reported hydrolysis rate constants for
pentachloronitrobenzene and /3-chloronaphthalene suspect.
43
-------
TABLE 11. MISCELLANEOUS COMPOUNDS
CAS Number
126-99-8
759-73-9
107-49-3
757-58-4
70-25-7
615-53-2
111-54-6
50-07-7
75-55-8
541-53-7
492-80-8
115-02-6
20830-81-3
86-88-4
82-68-8
56-84-2
-&**-!
Compound M ^ hr ^
2-Chloro-l , 3-butadiene
N-Nitroso-N-ethylurea
Tetraethyl pyrophosphate
Hexaethyl pyrophosphate
N-Methyl-N-riitro-N-nitrosoguaiiidine
N-Nitroso-N-methylurethane
Ethylene-bis (dithiocarbamic
acid) 848
Mitomycin C 4320
2-Methylaziridine
2 , 4-Dithiobiuret
Auramine
Azaserine 328 ± 20
Daunonycin
a-Naphthylthicurea
Pentacliloronitrobenzene
Methylthiouracil
Rate Constants ^25"
Neutral
hr'1
Polymerizes in
0.19
9.3E-2
9.3E-2
2.7E-2
2.9E-2
0.01
1.8E-3
8.0E-3
7.1 ± 1.3E-3
3.9E-4
2.6 ± 0.4E-4
9.7 ± 0.5E-5
8.0 ± 2.4E-5
2.8 ± 0.7E-5
9.7 ± 2.7E-6
C1 Calculated
Base Half-Life
M"1 hr"1 pH 7, 25°C
absence of inhibitors
5.3E6 0.96h
7.5h
7.5h
9.5E4 19h
2.9E3 24h
1 69h
4.30 12. 9d
87h
98h
74d
6.8 ± 0.7 99d
10 298d
9.9E2 361d
2.8y
8.2y
Ref.
3
3
3
3
3
3
3
22, 23
3
3
3
3
3
3
2
3
-------
TABLE 11. MISCELLANEOUS OCMPCUNDS - continued
CAS Number
91-58-7
55-63-0
81-81-2
62-74-8
5344-82-1
62-56-6
152-16-9
96-45-7
-^-l
Compound M hr
0-Chloronaphthalene
Nitroglycerine
Warfarin 1.4E-4
FLuoroacetic acid,
sodium salt
1- (o-Cnlorophenyl) thiourea
Thiourea
Octamethylpyrophosphoramide 0.23 ± 0
Ethylene thiourea zero hydrolys
Pate Constants f25°C}
Neutral
hr"1
9.5 ± 2.8E-6
4.9E-6
<1.7E-6
(9.8 ± 3.0)E-7
<5.3E-7
.03
is within experimental
Cal c^il at*3^
Base Half-life
M'1 hr"1 pH 7, 25*C
8.3y
77 ± 11 lOy
0.026 16y
>47y
0.14 ± 0.03 81y
>150y
1E-4 3,400y
error after
Ref.
3
2
2
2
3
2
3
3
01
90 days at 90°C and pHs 3~, 7, and 11
-------
Predictive Techniques
Table 12 contains second-order alkaline hydrolysis rate
constants that were either determined from laboratory measurements
(3, 11, 10, and 21), computer-estimated based on fundamental
molecular properties (9, SPARC) or correlation with infrared
spectra (8, Collette), or calculated using a simple regression
equation based on electronic and steric parameters (7). Where
measured values were available for comparison, SPARC generally
predicted a higher value and Collette's correlation a lower value
but both were generally within a factor of two of the measured
value.
The greater reactivity of methyl esters in comparison with
the corresponding ethyl esters is seen (Table 12) in the values
for three methyl-ethyl pairs. SPARC lacked the parameters needed
to calculate a rate for the 2,4-D methyl ester containing the
phenoxy substituent. A methyl substituent on the /3-carbon of a,/3-
unsaturated esters retards hydrolysis compared to a methyl on the
a-carbon. The )8-carbon methyl apparently strengthens the
inductive IT electron resonance with the carbonyl carbon and
retards attack by the negatively charged hydroxyl ion. Steric
hindrance by the methyl on the a-carbon is not a factor due to the
planar orientation of substituents on the double bond.
Figure 9 is a SPARC-generated pH-rate profile for methyl
methacylate. This allows calculation of \ at any pH.
46
-------
TABLE 12. PREDICTED AND lABORATORY DETERMINED HYDROLYSIS RATE CONSTANTS OF CARBOXYIATE ESTERS
CAS Number
80-62-6
96-33-3
93-89-0
1928-38-7
Compound
Methyl methacrylatea
Ethyl methacrylate
Methyl acrylate
Ethyl acrylate
trans-Ethyl crotonate0'
trans-Methyl crotonate
Ethyl benzoate
2,4-D-Methyl ester
Rate Constants (25' a
Acid Neutral Base
M"1 hr'1 hr'1 M"1 hr'1
200 ± 47b
279
70
185
408b
21013
47"
86
10.9
207
108b
134
41,000 ± 5,000**
26,080
Calculated
Half-Life
pH 7, 25°C
3.9y
2.8y
n.3y
4.3y
l.9y
3.8y
16. 8y
9.2y
72y
3.8y
7.3y
5.9y
7d
lid
Ref.
3
9*
8**
9*
11
11
21
9*
_***
9*
10
9*
4
8**
a. Methyl 2-methylacrylate.
b. Determined in the laboratory.
c. Ethyl 3-methylacrylate
d. Halonen also reported an identical rate for the cis isomer.
* SPARC
** Collette
*** Drossman et al
-------
-2
pH Profile methyl methacrylate
&
D>
O
-9
8
PH
Figure 9. SPARC Generated pH-rate Profile of Methyl Methacrylate
48
-------
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Environ. Sci. Technol. 21f 743-745.
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7- Drossman, H., H. Johnson, and T. Mill. 1988. Structure
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49
-------
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Wolfe. 1989. Homogeneous Hydrolysis Rate Constants for Selected
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14. Jungclaus, G.A. and S.Z. Cohen. 1986. Extended
Abstracts, 191st National Meeting of the American Chemical
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Hydrolysis of Chlorosilbene Oxide. Submitted for publication.
17. Cox, J.R. and O.B. Ramsay. 1964. Mechanisms of
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50
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* •• H UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D.C. 20460
OFFICE OF
RESEARCH AND DEVELOPMENT
SUBJECT: Transmittal of ORD Project Report Entitled Hydrolysis
Rate Constants for Enhancing Property-Reactivity
.Relationships (DeJ4xjer,abfhe0 7950A)y
FROM: /^Courtney Riordan _
7 Director, Office^of^Environmental Processes
and Effects Research (RD-682)
TO: Sylvia Lowrance
Director, Office of Solid Waste (OS-300)
The attached copy of the subject ORD project report is being
delivered to your office in response to the Agency's need ro
accurate hydrolysis rate constants foruse in mathematical models
for predicting chemical movement form hazardous waste sites and
other pollution sources. The document has been subjected to the
Agency's peer and administrative review, and will be published as
an EPA report.
A major objective of this work was to establish new, or
expand existing, property-reactivity correlations by examining
rate constants for hydrolysis in water of 10 classes of organic
compounds. Such correlations can then be used to predict
environmental hydrolysis fate of chemicals that have similar
molecular structure.
The compound classes covered by this report include
aliphatic and aromatic carboxylate esters, alkyl and aromatic
halides, amides, carbamates, epoxides, nitriles, phosphate
esters, alkylating agents, halogenated ethers, and oxidized
sulfur compounds. Three predictive techniques (one based on
empirical correlation with derived constants, the second based on
infrared spectra, and the third based on fundamental calculations
required only chemical structure) were used and compared for the
predicted rate constants were generally within a factor of two of
each other and the laboratory-determined values.
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This document is a product of the Land Disposal Assessment
and Evaluation of Other Management Systems research program at
the Environmental Research Laboratory-Athens. Dr. Zubair Saleem
of your Characterization and Assessment Division is familiar
with and has been an active contributor to the project's results.
Attachment
cc: Elizabeth Bryan (TS-798)
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