Sanborn_1972_J.Agric.Food.Chem_20_926

The insecticidal, anticholinesterase, and hydrolytic properties for a series of S-phenyl phosphoramidothioates and 5-phenyl phosphonamidothioates were examined. The compounds were moderately toxic to the housefly and were effective inhibitors of cholinesterase. Attempts to correlate cholinesterase inhibition of housefly toxicity with physical organic parameters were unsuccessful. However, an excellent linear relationship was obtained between Hammett's sigma constant and alkaline hydrolysis rates of the O-ethyl substituted S-phenyl phosphoramidothioates. In addition, a kinetic study of the alkaline hydrolysis of these esters was carried out for the purpose of examining the mechanism of reaction. The results indicate that hydrolysis takes place by a direct nucleophilic attack on the phosphoryl center by hydroxide ion and the increase in hydrolytic stability with progressive nitrogen substitution can be accounted for by less favorable polar and steric effects.