Photolysis, Oxidation, and Hydrolysis of ¹⁴C-Ethyl Prothiofos [O-(2, 4-Dichlorophenyl) O-Ethyl S-Propyl Phosphorodithioate]

Abstract

The chemical stability of the widely used organophosphorus insecticide ¹⁴C-prothiofos was studied. For this study prothiofos insecticide and some of its degradation products have been prepared. The oxon of the parent compound was obtained through the oxidation of the insecticide with various oxidizing agents, where yields depended on the type and nature of oxidizing agent. The effect of ultraviolet light and direct sunlight on prothiofos were investigated. Exposure to direct sunlight caused gradual degradation of prothiofos giving the same products as UV irradiation.The hydrolysis of ¹⁴C-prothiofos at pH 5, 7, 8, and 9 in buffered aqueous media at 25°C, 40°C and 55°C was studied. The results indicated that prothiofos was stable in acid medium, but it was hydrolyzed to 2,4-dichlorophenol and O-ethyl S-propyl phosphorodithioate in alkaline medium.The degradation products identified by TLC and GC/MS were prothiofos oxon, O-ethyl S-propyl phosphordithioate, des-propyl thioprothiofos, prothiofos oxon sulfoxide, and one unknown compound in addition to the parent compound. The phenolic compound was identified by GC/MS and by its color.Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Keywords:

• ¹⁴C-Prothiofos
• degradation products
• hydrolysis and oxidation
• sunlight
• UV light

Notes

*Data are the average of two replicates.

**Percent remaining of prothiofos and its degradation products.

*Data are the average of two replicates.

**Percent remaining of prothiofos and its degradation product.

*Data are the average of two replicates.

*Data are the average of two replicates.

**Percent remaining of prothiofos and its degradation products.