ABIOTIC DEGRADATION PATHWAYS OF ISOXABEN IN THE ENVIRONMENT

Photolysis of isoxaben [N-[3-(1-ethyl-1-methylpropyl)isoxazol-5-yl]2,6-dimethoxybenzamide] in dilute aqueous solutions, adsorbed on silica gel plates, has been investigated under natural and simulated solar light conditions. Eight photoproducts were isolated and identified by spectroscopic methods. Photodecomposition with sunlight led to the formation of three isomers, dimethoxybenzonitrile and dimethoxybenzamide as major photoproducts. The rearrangement has been shown to proceed in two photochemical steps by way of an azirine and a non-identified photoproduct as stable intermediates. The azirine rearranges almost quantitatively to an oxazole and rearranges back to the starting isoxaben.