Record Display for the EPA National Library Catalog


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
Library Call Number Additional Info Location Last
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
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.)