Fungicides and photochemistry photodegradation of the dicarboximide fungicide procymidone

The photoreactivity of the dicarboximide fungicide procymidone ( ) (3-(3,5-dichlorophenyl)-1,5-dimethyl-3-azabicyclo[3.1.0]hexane-2,4-dione) on plant surfaces was studied by irradiation experiments in different organic solvents simulating the plant cuticle environment. Photodegradation (λ > 280 nm) increased in the order isopropanol, cyclohexane, cyclohexene. In the presence of isopropanol or cyclohexane, mainly photodehalogenation reactions were observed, which, to a minor extent, competed with substitutions by solvent molecules. In the presence of cyclohexene, however, substitution of a phenyl-Cl by the the solvent was strongly preferred and the monodehalogenated procymidone was only found in low percentages.