Metofluthrin [I, 2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl (EZ)-(1R,3R)-2,2-dimethyl-3-(prop-1-enyl)cyclopropanecarboxylate] was resistant to hydrolysis at pH 4 and 7 but moderately hydrolyzed with a half-life of 36.8 days at pH 9 and 25 o C to form the corresponding acid and alcohol via ester cleavage. The activation energy was estimated to be 105 kJ mol Ϫ1 based on the hydrolysis rates at 25-50 o C. By continuous exposure to light at Ͼ290 nm from a Xenon arc lamp at hydrolytically stable pH 4 and 25 o C, I was rapidly photodegraded with half-lives of 1.1-3.4 days, mainly via ester cleavage and successive oxidation followed by mineralization to carbon dioxide. Spectroscopic analyses together with co-chromatography with authentic standards showed that the major degradates having an ester linkage were the aldehyde and carboxylic acid derivatives formed via oxidative cleavage of the prop-1-enyl group together with the diol formed possibly through an oxidative intermediate, such as an epoxide.

Photodegradation of a new strobilurin fungicide, mandestrobin, was investigated in buffered aqueous solution and synthetic humic water (SHW) under continuous irradiation with artificial sunlight (λ > 290 nm). In both aquatic media, the direct photolysis preferentially proceeded via homolytic bond cleavage at the benzyl phenyl ether, and the subsequent recombination of geminate radicals in a solvent cage gave the photo-Claisen rearrangement products. A radical mechanism in the photochemical rearrangement was strongly supported by a radical-trapping technique using a novel nitroxide spin label combined with electron spin resonance (ESR) and liquid chromatography-mass spectrometry (LC-MS) analyses. Photosensitized generation of hydroxyl radical in SHW might significantly contribute to enhancing the formation of a benzyl alcohol derivative. The series of photolysis products steadily degraded and finally mineralized to carbon dioxide.

Photodegradation of pyrethroid insecticide metofluthrin (I) [2,3,5,6-tetrafluoro-4-(methoxymethyl)benzyl (EZ )-(1R,3R)-2,2-dimethyl-3-(prop-1-enyl)cyclopropanecarboxylate] on soil, clay minerals, and glass surfaces was examined using a xenon arc lamp (Ͼ290 nm). I was rapidly photodegraded via oxidation of the double bond at the prop-1-enyl moiety and cleavage of the ester linkage followed by mineralization to carbon dioxide, while photoisomerization to other isomers was a minor route. The major photodegradates having an intact ester linkage were the caronaldehyde and carboxylic acid derivatives formed via 1,2,4-trioxolane (ozonide) and the diol derivatives formed via epoxide, which strongly suggested the involvement of ozone and hydrogen peroxide as the active oxygen species.