The Photochemical Rearrangement of Phenyl Acetate

The photochemical rearrangements of phenyl acetate and p-substituted phenyl acetates have been studied. The quantum yields of the rearrangements of phenyl acetate in cyclohexane were independent of the irradiation time, the concentration of phenyl acetate (<2×10−2 mol/l), the temperature (20–70°C), and the presence of piperylene (a triplet quencher) or oxygen. The quantum yields for the formations of o- and p-hydroxyl acetophenones and of phenol were 0.17, 0.15, and 0.06 respectively in cyclohexane. Comparing the quantum yields for phenyl acetate rearrangements with those for p-methylphenyl acetate, the quantum yields for the predissociation of the O–CO bond and the back reaction, and the recombination ratio were estimated to be 0.61, 0.23, and 0.9 respectively in cyclohexane. The relative rate constants of the back reaction and the o- and p-rearrangements were parallel to the odd π electron densities of the phenoxy radical. These results have shown that the reaction scheme of phenyl acetate in the liquid phase at 2537 Å is similar to that of acetanilide.