Photochemistry of vinclozolin in water and methanol–water solution

The photolysis of the fungicide vinclozolin in aqueous and methanol–water (50 + 50 by volume) solution has been examined. Irradiation at λ = 254 nm for 10 minutes resulted in <90% and ≤95% substrate transformation respectively. The dissipation of vinclozolin both in water and methanol + water was linear and the calculated half-lives were 1.01 and 2.0 min respectively. Irradiation (8 h) with UV light (λ ≥ 290 nm) resulted in 10% degradation of the chemical, which is of the same magnitude as that of the control (not irradiated). Irradiation (8 h) under artificial sunlight (Suntest) in the presence of commercially available humic acid (K-salt) resulted in 55% degradation of the chemical. Photolysis leads to the opening of the 2,4-oxazolidine-dione ring, forming 3,5-dichlorophenyl isocyanate and 3,5-dichloroaniline. In addition, dechlorination and elimination of the  CHCH₂ moiety takes place, and one or both the chlorine atoms are replaced by a methoxy group. © 1999 Society of Chemical Industry