Reactions of singlet oxygen. Part V. Dye sensitized photooxidation of m-hydroxydiphenylamine

Abstract

Methylene blue sensitized photooxidation of m-hydroxydiphenylamine gives N-(3-hydroxyphenyl)-p-benzoquinoneimine as the primary product in acetonitrile–water medium. The experimental results are in good agreement with the theoretical plots calculated on the basis of the reaction undergoing through the participation of [Formula: see text] as well as the excited dye interacting with the substrate. β-Value and rate constant of reactivity of m-hydroxydiphenylamine with singlet oxygen have been calculated. The effects of β-carotene, 1,4-diazabicyclo[2,2,2]octane, triethylamine, allyl thiourea, 2,5-diphenylfuran, and dielectric of different solvents show the participation of singlet oxygen at low substrate concentration and interaction of the excited dye with the substrate at its high concentrations. The data on oxygen concentration effect fit into the derived rate expressions. No complexation between methylene blue and m-hydroxydiphenylamine is observed.