Photooxidation of m-Phenoxytoluene at Colloidal Titanium Dioxide/Non-Aqueous Solution Interfaces

Abstract

The selective photooxidation of m- phenoxytoluene to m-phenoxybenzaldehyde has been investigated in the system m-phenoxytoluene/O₂/titanium dioxide/non-aqueous solvent/light. In acetonitrile the conversion was found to be c. 20% with starting concentrations of m-phenoxytoluene in the range 0.05-0.5 mol dm^-3. Adsorption of m-phenoxytoluene, m-phenoxybenzaldehyde or the intermediate product m-phenoxybenzyl alcohol from acetonitrile on titanium dioxide was not detectable by an equilibration/centrifugation/supernatant analysis technique. Photoemission and photoexcitation measurements, however, showed that m- phenoxytoluene and m-phenoxybenzyl alcohol, but not m-phenoxybenzaldehyde , formed charge-transfer complexes with titanium dioxide surfaces. The selectivity of the photooxidation is explained in terms of pathways involving these charge-transfer complexes.