Publication costs assisted by the Hahn-Meitner-Instifut BerlinAddition reactions of molecular oxygen to organic sulfur radicals generally appear to be slower than to corresponding carbon centered radicals. No reaction at all has been found to occur between O2 and the radical cations RSSR'., R2S+., and (R2S),+.. The rate constant for the reaction of oxygen with the thiyl radicals from penicillamine h(PenS. + 0,) = 4.0 X lo7 M-l s-l has been determined from direct pulse radiolysis experiments, and h = 3.4 x IOs, 7.8 X IO8, and 2.3 X lo* M-l s-l have been evaluated by a competition method for the addition of O2 to C2H5S-, t-Bu-S-, and HOCH2CH2S., respectively. Higher rate constants up to lo9 M-l s-l w ere measured for the addition of O2 to mesomeric carbon-sulfur radical centers, IC-S--)C=S-. The results are discussed in terms of other O2 addition reactions to various organic and inorganic radicals. IntroductionThe overall reduction and oxidation mechanism of organic disulfides, monosulfides, and thiols is known to be influenced by molecular oxygen.1-8 This is evident from the formation of highly oxygenated stable products such as sulfones, sulfonic acid, etc. in irradiated solutions of these solutes in the presence of molecular oxygen.

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