Photoinduced oxidation of benzhydrol and reduction of benzil on titanium dioxide Original Research Article

In the TiO2-photocatalyzed oxidation of benzhydrol in oxygen-purged acetonitrile, benzophenone was observed to be the sole product. The influence of various parameters, like irradiation time, amount of catalyst, concentration of catalyst and other factors on the photocatalytic oxidation, has been investigated. The proposed mechanism envisages the oxidation of benzhydrol by a hole to give the radical cation of benzhydrol and its subsequent reaction with a superoxide radical anion produced by the transfer of a conduction band electron to oxygen. The involvement of superoxide is revealed by (i) the 9,10-dicyanoanthracene-photosensitized oxidation of benzhydrol to benzophenone and also (ii) the absence of photocatalytic oxidation in the presence of nitrogen. Benzil, an example of 1,2-diketone, was converted to benzoin in the TiO2-mediated reduction in nitrogen atmosphere.