ENVIRONMENTAL AND LABORATORY STUDIES OF THE PHOTODEGRADATION OF THE PESTICIDE FENARIMOL

The photophysics and photochemistry of the pesticide fenarimol were st udied. From the absorption and fluorescence spectra, quantum yields an d lifetimes, it is suggested that the lowest excited singlet state has predominantly n,pi character, and is localized on the pyrimidine rin g. Phosphorescence measurements suggest a small singlet-triplet splitt ing. Halide ions are found to quench fenarimol fluorescence. Photodeco mposition of fenarimol in a variety of solvents was studied by gas chr omatography-mass spectrometry. Although the products have not yet been characterized, degradation of this compound appears to involve cleava ge of bonds to the quaternary carbon without significant dechlorinatio n. Preliminary studies of the kinetics and relative quantum yields of photodegradation show that the reaction proceeds via a first-order pro cess, which is independent of pH, but which involves a photoactive int ermediate. Chloride and bromide ions inhibit the photolysis, whereas t he triplet quencher sorbic acid has no effect.