Organophosphate and organophosphorothionate esters: Application of linear free energy relationships to estimate hydrolysis rate constants for use in environmental fate assessment

Hydrolysis rate constants required for assessing the environmental fate of certain organophosphate and organophosphorothionate esters may be estimated by use of linear free energy relationships (LFERs). LFERs for the second-order alkaline hydrolysis rate constants and the pKa of the conjugate acid of the leaving groups were established for 0,0-dimethyl- and 0,0-diethyl-0-substituted phosphates and phosphorothionates. Also, the second-order alkaline hydrolysis rate constants of selected triaryl phosphates were correlated with the Hammett-sigma constants. Existing LFERs for diaryl phosphate ester anions along with monoaryl phosphate ester mono- and dianions were used to predict hydrolytic half-lives under reaction conditions that are characteristic of aquatic environments.