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Report | Regular issue | Vol 23, No. 11, 1985, pp.2917-2926
Published online, 1st January, 1970
DOI: 10.3987/R-1985-11-2917
Photodegradation of Pesticides: Photolysis of 2-Mercaptobnzothiaozle and 2-Mercaptobenzimidazole

Cyril Párkányi and Abdou O. Abdelhamid*

*Department of Chemistry, The University of Texas at El Paso, El Paso, Texas 79968-0513, U.S.A.


Upon their application, organic pesticides are usually exposed to light under a variety of conditions. After some time, most of them undergo photodecomposition, especially in solution, and give degradation products with properties different from those of the original compounds. Thus, studies of the photochemistry of pesticides under controlled laboratory conditions are of interest. As an example, model studies of the photodegradation of 2-mercaptobenzothiazole (1, used as fungicide, bactericide, and disinfectant) and of the Π-isoelectronic, biologically active 2-mercaptobenzimidazole (2) have been carried out. Uv irradiation of 1 in the presence of air oxygen in a pyrex flask yielded bis-(2-benzothiazolyl) disulfide when dry benzene or toluene were used as the reaction medium. With solutions of 1 in methanol, ethanol, or acetonitrile, the corresponding bis-(2-benzothiazolyl) disulfone was obtained as the intermediate, with benzothiazole sulfate as the final reaction product. Similarly, photolysis of 2 in methanol, ethanol, or acetonitrile yielded bis-(2-benzimidazolyl) disulfone and benzimidazole sulfate as the final product.