Selectivity in the TiO2- mediated photocatalytic oxidation of thioethers

The relative rates of photooxygenation of substituted diphenyl sulfides on irradiated TiO2 powders suspended in oxygenated acetonitrile correlate linearly with σ+, as is consistent with formation of a surface bound cation radical in the primary photoprocess. Substituted dibenzyl sulfides, in contrast, suffer C-S cleavage upon photocatalyzed oxidation. Factors disposing these reactions toward preferential sulfoxide formation or bond cleavage are discussed.