Photodegradation of chlorpyrifos-methyl

LOBATTO, VIRGINIA; BUJAN, ELBA I.; ARGÜELLO, A. GUSTAVO

Villa Carlos Paz, Córdoba

Conferencia; 13th Latin American Conference on Physical Organic Chemistry; 2015

Universidad Nacional de Córdoba

Chlorpyrifos-Methyl (1) is an organophosphorus pesticide registered for use in the control of insects on certain stored grains, including wheat, barley, oats, rice, and sorghum as well as for empty grain bins. Available methods for destroying organophosphorus compounds include thermic, enzymatic, or photochemical degradation as well as reactions with strong oxidants or nucleophiles. We have previously reported on the reactivity of 1 toward hydroxyl and perhydroxyl ion1 and now we present the results on the photodegradation of 1. Solutions of 1 (in ACN or 1% ACN/H2O) were irradiated with 4 Low Pressure Hg lamps at 254 nm and the kinetics of photodegradation was determined by UV-vis spectroscopy. The photolysis in ACN was followed up to 290 min and two kinetic processes were observed and their rate constants calculated. In the photolysis in 1% ACN/H2O only one kinetic process was observed up to 190 min; the observed rate constant being similar to the first process measured in ACN. Several products were formed. Among them, we were able to identify the oxon 2, trichloropyridinol 3, and compounds 4 and 5. Similar products were reported for the photodegradation of Chlorpyrifos. The photodegradation pathways will be discussed.