PHOTODEGRADATION OF THE CARBAMATE INSECTICIDE ETHIOFENCARB

In order to study the photoreactivity and possible photodegradation pathways of ethiofencarb (2-ethylthiomethylphenyl methylcarbamate) on plant surfaces, model experiments in the presence of cyclohexane, cyclohexene and isopropanol were performed. Both artificial light (lambda > 280 nm) and natural sunlight were used. Half-lives of the ethiofencarb photodegradation were in the order cyclohexane < isopropanol < cyclohexene and ranged from 75 min to more than 20 h. Depending on the solvent and the light source chosen, different photoproducts were obtained. When ethiofencarb was irradiated in the presence of cyclohexane, photo-oxidation to the corresponding sulfoxide was the main degradation pathway, followed by a cyclization reaction. In the case of isopropanol as model solvent, numerous photoproducts were detected as a result of photooxidation, hydrolysis and the addition to ethiofencarb of the solvent molecule.