Abstract
The 14C-labeled organophosphorus insecticide, propaphos [dipropyl 4-(methylthio) phenyl phosphate], degraded rapidly when exposed to sunlight as deposits on silica gel plates, glass surface, or in water solution. The half-life of the chemical was less than 2 hours in each case. Degradation pathways included oxidation of the methylthio sulfur to sulfoxide and sulfone derivatives, hydrolysis of the phosphorous-O-phenyl ester, and undefined transformations leading to highly polar products that increased in quantity with time of exposure. Exposure of water solution of the chemical to artificial UV light resulted in very rapid degradation to the same major photoproducts as were generated by exposure to sunlight and in liberation of 14C-carbon dioxide.
