PHOTODEOXYGENATION OF DIBENZOTHIOPHENE SULFOXIDE - EVIDENCE FOR A UNIMOLECULAR S-O CLEAVAGE MECHANISM

Photolysis of dibenzothiophene sulfoxide results in the formation of d ibenzothiophene and oxidized solvent. Though quantum yields are low, c hemical yields of the sulfide are quite high. Yields of the oxidized s olvents can also be high. Typical products are phenol from benzene, cy clohexanol, and cyclohexene from cyclohexane and 2-cyclohexenol and ep oxycyclohexane from cyclohexene. A number of experiments designed to e lucidate the mechanism of the hydroxylation were carried out, includin g measurements of quantum yields as a function of concentration, solve nt, quenchers, and excitation wavelength. These data are inconsistent with a mechanism involving a sulfoxide dimer, which also does not prop erly account for the solvent oxidations. It is suggested that the acti ve oxidizing agent may be atomic oxygen O(P-3) or a closely related no ncovalent complex, based on the nature of the oxidation chemistry, com parison to known rate constants for O(P-3) reactivity, and the quantum yield data.