Photodegradation of Mepronil

Abstract

Mepronil remaining after 80 days exposure to sunlight on the silica gel chromatoplate was 34.1 and 62.2% depending on the season (Sept. to Dec. and Nov. to Jan., respectively). The half-life is estimated as 36 days during Sept. to Dec. which was shortened to half when a photosensitizer, xanthone, was mixed with it. The degradation in water when irradiated with ultraviolet light was only 32.0% after 80 hr at 30°C. Twelve photoproducts were identified as 3′-(1-hydroxymethylethoxy)-2-methylbenzanilide; 3′-isopropoxy-2-hydroxymethylbenzanilide; 3′-isopropoxy-4′-hydroxy-2-methylbenzanilide; 3′-hydroxy-2-methylbenzanilide; 1-hydroxy-3-oxo-2-(3′-isopropoxyphenyl)isoindoline; 3′-(1-carboxyethoxy)-2-methylbenzanilide; 3′,4′-dihydroxy-2-methylbenzanilide; 2-methylbenzamide; 2-methylbenzoic acid; 2-hydroxymethylbenzoic acid; phthalide; and 2-carboxybenzaldehyde. The results indicate that initially hydroxylation of mepronil occurs on the four positions, followed by further oxidation, hydrolysis, cyclization or cleavage. © 1982, Pesticide Science Society of Japan. All rights reserved.