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RECORD NUMBER: 26 OF 39

OLS Field Name OLS Field Data
Main Title New Perspectives on the Hydrolytic Degradation of the Organophosphorothioate Insecticide Chlorpyrifos.
Author Macalady, D. L. ; Wolfe, N. L. ;
CORP Author Colorado School of Mines, Golden.;Environmental Research Lab., Athens, GA.
Year Published 1983
Report Number EPA-600/J-83-169;
Stock Number PB84-171024
Additional Subjects Hydrolysis ; Degradation ; Water pollution ; Pesticides ; Insecticides ; Reaction kinetics ; pH ; Phosphorothioates ; Phosphorus organic compounds ; Reprints ; Dursban ; Ecosystems
Holdings
Library Call Number Additional Info Location Last
Modified
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Status
NTIS  PB84-171024 Most EPA libraries have a fiche copy filed under the call number shown. Check with individual libraries about paper copy. NTIS 06/23/1988
Collation 11p
Abstract
The disappearance kinetics in water for chlorpyrifos (O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate), an important insecticide, has been investigated to provide a kinetic expression to define the hydrolysis process in aquatic ecosystems. Pseudo-first-order kinetics are observed over the pH range of 1-13. The rate constant is independent of pH from pH 1 to pH 7 and has a value of (6.2 + or - 0.9) x 10 to the 6th power/min at 25 deg. C. At alkaline pHs, the rate constant is much larger but is not directly proportional to hydroxide activity. The observed behavior over the pH range 10-12 is consistent, however, with equilibrium formation of a 5-coordinate charged hydroxyphosphorothioate intermediate and the rate-controlling decomposition of this intermediate to products. Thus, the second-order rate expression does not accurately describe the kinetics of degradation at alkaline pHs. Product studies over the alkaline pH range (9-13) show that the only major products are 3,5,6-trichloro-2-pyridinol and O,O-diethyl phosphorothioic acid. (Copyright (c) 1983 by the American Chemical Society.)