Photochemistry of αα′-disbstituted azoalkanes. Part II. Photolytic dechlorination, decomposition, and oxidation of αα′-dichloro- and αα′-diacyloxy-azoalkanes

Abstract

The photochemistry of a series of αα′-dichloro (III) and αα′-diacyloxy-azoalkanes (IV) with α-phenyl groups has been studied. Irradiation of (III) yields both products of N2 extrusion (RN2R [graphic omitted] R·+ N2+ R·) well known for unsubstituted azoalkanes and a new reaction leading to the loss of 2Cl· and formation of ketazines. In addition, the radical intermediates produced in both photoreactions are susceptible to oxiadation. The dechlorination: N2 extrusion ratio increases with increasing electron donor character of the substituted α-phenyl group. On the other hand irradiation of (IV) gives only N2 extrusion. A sensitization and quantum yield study of αα′-dichloro-(I) and αα′-diacyloxy-azoalkanes (II) without α-phenyl substituents as well as of (III) and (IV) showed that the various photoreactions of the series proceed only with singlet sensitization. The photochemical mechanisms of these reactions are discussed.