Photodecomposition of Prothiofos (<i>O</i>-2, 4-Dichlorophenyl <i>O</i>-Ethyl <i>S</i>-Propyl Phosphorodithioate)

Abstract

The photodecomposition of prothiofos (0-2, 4-dichlorophenyl 0-ethyl S-propyl phosphorodithioate) under ultraviolet (UV) light and sunlight was studied. In aqueous and hexane solutions, prothiofos exposed to UV light was rapidly decomposed. Decomposition proceeded mainly from dechlorination at the 2-position of the phenyl group, oxidative desulfuration of the P=S moiety, cleavage of P-0-aryl and P-S-alkyl linkages and the subsequent liberation of phenols.More than 12 photodecomposed products from prothiofos were detected by gas-liquid chromatography (glc); 10 of these were identified. In hexane solution, prothiofos formed a phospholane compound upon UV-irradiation; glc, GC-MS and GCmillimass techniques suggested it to be 5-chloro-2-ethoxy-1, 3, 2-benzoxathiaphosphole 2-sulfide.Practically, no significant differences were observed between the photoproducts formed by UV light and sunlight.