Photoreaction of benzoic acid with sodium hypochlorite in aqueous alkali

Abstract

The photoreaction of benzoic acid with sodium hypochlorite in aqueous alkali (pH 12) has been studied. At a low initial ratio of [ClO^–]/[PhCOO^–], e.g. 0.1, hydroxylation and chlorination at the aromatic ring occur simultaneously with ipso-substitution of the carboxylate group to give hydroxy- and chloro-benzoic acids together with phenol. The product distribution depends on the wavelength of light, which implies the dependence on the concentration of active species generated from ClO^– and on the light stability of products. At comparable concentrations of ClO^– and PhCOO^–, the products initially formed from the photoreaction react further with ClO^– in the dark to give polychlorinated derivatives. The initial steps for the photoreaction are discussed on the basis of the reactivity of the active species, O(³P), O(¹D), O^–˙, and Cl·, generated by photolysis of ClO^–.