Oxidation of Thiols by Radical Cations of Organic Sulfides

Article abstract of DOI:10.1021/j100264a030

Sulfur-centered radical cations from organic sulfides have been foun to oxidize thiols and thiolates to yield thiyl radicals.Absolute rate constants have been measured for the reaction of (t-But)2S(1+) radical with EtSH (1.6E9 M^-1s^-1), C6H5SH (6.0E9 M^-1s^-1), and cystaine, CySH (1.9E9 M^-1s^-1).The reactions of Me2S(1+) radical with EtSH, t-ButSH, C6H5SH, and cysteine occur with k = 1.8E9, 2.5E9, 7.2E9. and 9.4E8 M^1-s^-1, respectively.The three-electron bonded (Me2S<*>SMe2)(1+) radical cation oxidizes the cysteine anion (CyS(1-)) with k = 8.1E9 M^-1s^-1 and C6H5SH with k = 5E8 M^-1s^-1, while its reactions with EtSH, t-ButSH, and CySH are slower by several orders of magnitude.The results of kinetics and product analysis are discussed in view of the pronounced tendency of the thiyl radical to undergo electrophilic addition reactions. the optical absorption spectrum of C6H5S radical is also repoted and shown to exhibit maxima at 460 and 295 nm with extintion coefficients of 2 500 and 10 000 M^-1 cm^-1, respectively.