Photochemistry and radiation chemistry of 9,10-anthraquinone-2-sodium sulphonate in aqueous solution. Part 2.—Photochemical products1

Abstract

Anthraquinone-2-sodium sulphonate in “aqueous” solutions within the range pH 14 to 100% H₂SO₄(and also in oleum) is both reduced and hydroxylated when irradiated with u.v. or visible light. The major hydroxy-photoproducts were isolated and identified as a 3 : 2 mixture of isomeric α-and β-hydroxy derivatives of the starting material in the range 40 % H₂SO₄ to pH 9; outside this region the relative amount of α isomer produced falls off rapidly and in strong acid or alkali only the β-hydroxy product is obtained. Prolonged irradiation produces also small amounts of polyhydroxy derivatives. The pH-dependence of the ratio of α- and β-hydroxy product yields is correlated with ionization of hydroxyl radical adduct intermediates.