PHOTOOXIDATION OF SOME AROMATIC SULFONIC ACIDS WITH ALKALINE HYPOCHLORITE.

Abstract

Photochemical oxidation of aromatic sulfonic acids such as p-cumenesulfonic, 2-mesitylenesulfonic, 1- and 2-naphthalensulfonic acids with aqueous sodium hypochlorite has been studied. Addition of a large excess of alkali enhances the decomposition of sulfonic acids remarkably. p-Cumenesulfonic and 2-mesitylenesulfonic acids are oxidized faster than 1- and 2-naphthalenesulfonic acids. The photooxidation of sulfonic acids with an equimolar amount of hypochlorite gives intermediary oxidation products involving desulfonation to parent hydrocarbons, aromatic hydroxylation, side-chain oxidation, and ring cleavage; e. g. , p-cumenesulfonic acid gives cumene, 2- and 4-isopropylphenol and 2-phenyl-2-propanol; 1- and 2-naphthalenesulfonic acids give phthalic anhydride. Light-absorbing aromatic sulfonic acids sensitize the decomposition of hypochlorite ion leading to hydroxyl radical, which reacts mainly with ground state sulfonic acid to give radical intermediates.