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Kinetics of the Reactions Between Sulfide Radical Cation Complexes,[S(S]^+^ and [S(N]^+^, and Superoxide or Carbon Dioxide Radical Anions

The reaction of superoxide radical anions with sulfide radical cation complexes represents an important sulfoxide forming process. Here, absolute rate constants for the reaction of sulfur-sulfur ([>S(S<]^+^) and sulfur-nitrogen ([>S(NH"2"R]^+^ three-electron bonded sulfide radical cation complexes with superoxide and, for comparison, carbon dioxide radical anion have been measured by pulse radiolysis. For two different sulfur-sulfur bonded species, the intermolecular complex from dimethylsulfide and the intramolecular complex from 1,5-dithia-3-hydroxycyclooctane, the rate constant for the reaction with superoxide are on the order of (6.5 ( 0.2)x10^9^ M^–1^s^–1^. The fact that the stronger reducing carbon dioxide radical anion shows the lower rate constant can be interpreted by different reaction mechanisms, electron transfer for the carbon dioxide radical anion and addition by the superoxide radical anion. The latter is consistent with earlier product studies on the reaction of superoxide radical anion with sulfide radical cation complexes.

carbon dioxide radical anion; pulse radiolysis; rate constants; reaction mechanism; sulfide radical cation; superoxide

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