AN 18O-TRACER STUDY ON THE TiO2-SENSITIZED PHOTOOXIDATION OF AROMATIC COMPOUNDS

Abstract
TiO2-sensitized photooxidation of benzenes has been studied to disclose the origin of the ring hydroxylating species. An 18O-tracer study using 18O2 gas revealed that the hydroxyl group of phenols comes essentially from molecular oxygen at higher pH region. At lower pH, however, the oxygen atom in phenols originates mostly from solvent water. These findings are compatible with two different mechanisms proposed By Osa et al. and Tokumaru et al.; that is, the major pathway changes with pH.