Phototransformation of 3,5-dihalogeno-4-hydroxybenzonitriles (ioxynil and chloroxynil) in aqueous solution

Abstract

The main initial photochemical reaction of ioxynil and chloroxynil in pure water is the photohydrolysis of C–halogen bond, leading, in both cases, to a monohalogenated dihydroxybenzonitrile. Reduction is observed as a minor pathway, especially when irradiation is carried out in the presence of humic acids. In a second stage, similar reactions occur with the remaining C–halogen bond. The photochemical reactivity is not significantly affected by the nature of the halogen Cl, Br or I.