Unsensitized photooxidation of sulfur compounds with molecular oxygen in solution

International audienceThe short wavelength irradiation of aliphatic disulfides, sulfides and of n-butanethiol in alcohols or aqueous acetonitrile in the presence of oxygen was investigated: the corresponding sulfonic acids are produced in good yields for short alkyl chain compounds, together with smaller amounts of sulfuric and carboxylic acids. In acetonitrile, the influence of added water on the reaction course is evidenced: increased reaction rate and acid yields, control of sulfuric acid formation. Intermediates such as sulfinic acid and thiosulfonate were detected and their rates of formation were monitored. The reaction appears to involve thiyl radicals giving rise to sulfonyl radicals in the presence of oxygen. A first tentative hypothesis concerning the mechanism is advanced