United States
Environmental Protection
Agency
Environmental
Research Laboratory
Athens GA 30613-7799
Research and Development
EPA/600/S3-89/063 Jan. 1990
Project Summary
Hydrolysis Rate Constants for
Enhancing Property-Reactivity
Relationships
J. Jackson Ellington
Rate constants for hydrolysis in
water of 10 classes of organic com-
pounds are examined with the ob-
jective of establishing new or ex-
panding existing property-reactivity
correlations. These relationships
then can be used to predict the envi-
ronmental hydrolysis of chemicals
that have similar molecular structure.
The compound classes covered by
this report include aliphatic and aro-
matic carboxylate esters, alkyl and
aromatic halides, amides, carba-
mates, epoxides, nitrites, phosphate
esters, alkylating agents, halogenated
ethers, and oxidized sulfur com-
pounds. Three predictive techniques
(the first based on empirical cor-
relations with derived constants, the
second using Infrared spectra, and
the third relying on fundamental cal-
culations 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.
This Project Summary was devel-
oped by EPA's Environmental Re-
search Laboratory, Athens, GA, to an-
nounce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Ordering information at back).
Introduction
Each year more than 1000 new chemi-
cals 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 envi-
ronmental ecosystems associated with
these new chemicals as well as the more
than 65,000 compounds currently in use.
The possible persistence of these chem-
icals and accompanying risk of exposure
to humans and other species of concern
has resulted in a demand on regulators to
provide effective techniques for quanti-
fying chemical mobility and fate.
As part of the effort to evaluate chem-
ical constituents of wastes under consid-
eration for land disposal, EPA's Office of
Solid Waste (OSW) uses a relatively sim-
ple model to estimate potential ground-
water contamination at specified with-
drawal points in proximity to a landfill.
This model calculates horizontal chemical
movement in the aquifer based on ad-
vection, dispersion, sorption and transfor-
mation. Hydrolysis is the only transforma-
tion process specifically considered at
this time.
To apply this model to chemicals of in-
terest to OSW, hydrolysis rate constants
for 98 chemicals were previously ob-
tained either from literature sources or
laboratory determinations using protocols
developed at EPA's Environmental Re-
search Laboratory-Athens. The objective
of this report was to examine the rate
data and organize them by compound
class, with the goal of either enhancing
existing property-reactivity correlations
(PRCs) or developing new PRCs if suffi-
cient 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.
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Property Reactivity Correlations
and Prediction Programs
The use of PRCs for predicting rate
and equilibrium constants for organic re-
actions is well established. Pharmaceu-
tical and pesticide manufacturers rou-
tinely 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 prod-
uct. PRCs offer a means for estimating
kinetic constants for important transfor-
mation processes such as hydrolysis,
photolysis, and redox reactions.
Two approaches for establishing PRCs
that are less dependent on measured
kinetic data are being developed at ERL-
Athens. One approach involves develop-
ing a method for predicting environ-
mental 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. Another ap-
proach involves developing a prototype
computer program SPARC (SPARC Per-
forms Automated Reasoning in Chem-
istry) 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--
ultraviolet light absorption, dissociation
constants, and various reaction rate
constants, or any parameters that depend
on molecular structure. The agreement of
the alkaline hydrolysis rate constants for
carboxylate esters calculated by all of the
above methods as well as determined in
the laboratory is discussed.
Hydrolysis Rate Constant Data
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
11. Miscellaneous Compounds
The report summarizes hydrolysis rate
constant data and half-lives for chemicals
in the above classes at pH 7 in aqueous
solution at 25°C.
The EPA author, J. Jackson Ellington (also the EPA Project Officer, see below) is
with the Environmental Research Laboratory, Athens, GA 30613-7799.
The complete report, entitled "Hydrolysis Rate Constants for Enhancing Property-
Reactivity Relationships." (Order No. PB 89-220 479/AS; Cost: $15.95, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Athens, GA 30613-7799
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-89/063
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