Thermal Decomposition of Dimethoate

Decomposition of Organophosphorus Pesticides (Part 3)

Abstract

It was observed that the apparent degradation of dimethoate in a closed system is significantly greater than that in an open system, although their difference is not so large as in the case of fenitrothion. For this observation, an autocatalytic degradation mechanism is proposed which includes S-methyl isomerization reaction catalyzed by both carbamoyl group in the dimethoate molecule and dimethyl sulfide gas which is evolved during further decomposition of S-methyl-dimethoate, where the catalytic role of dimethyl sulfide is relatively small. Stabilization of dimethoate by the adduct formation with 4-methyl-2-t-butylphenol and by the inclusion into β-cyclodextrin were established, and their stabilization mechanism was discussed on the basis of their physicochemical properties and the proposed degradation pathway.