Monochromatic Light-induced Reactions of Benzophenone Hydrazones and the N-Acetyl Derivatives in Carbon Tetrachloride in the Presence of Oxygen

Abstract

Abstract Irradiation of hydrazones of benzophenone, 4-methylbenzophenone and 4-methoxybenzophenone in carbon tetrachloride with monochromatic light in the presence of oxygen afforded the corresponding azine, resulting from N–N bond cleavage, as the major product together with the hydrazone hydrochloride. In contrast to the hydrazones, benzophenone acetylhydrazone in carbon tetrachloride in the presence of oxygen afforded an unstable hydroperoxide as the only product, on photolysis with monochromatic light (288±8 nm); this product was transformed spontaneously into benzophenone on evaporation of the solvent at room temperature. 4-Methylbenzophenone acetylhyd razone and 4-methoxybenzophenone acetylhydrazone reacted in a manner similar to benzophenone acetylhydrazone. Irradiation of benzophenone diacetylhydrazone with 266±8 nm light under conditions analogous to the photo-reactions of hydrazones and acetylhydrazones resulted in loss of an acetyl group, resulting in N–CO bond cleavage to afford acetylhydrazone. The mechanism of the photooxygenation of benzophenone acetylhydrazones is interpreted in terms of chlorine radical-induced autoxidation.