Thermochemistry of Perthiyl Radicals

Article abstract of DOI:10.1021/ja00272a021

Mass spectrometry was used to measure appearance energies for the reaction RSS-t-Bu -> RSS. + t-Bu⁺ for R = Me, Et, i-Pr, and t-Bu.The data lead to the heats of formation of perthiyl radicals, RSS., and hence to S-C bond dissociation energies in disulfides (ca. 54 kcal mol^-1) and to S-S bond dissociation energies for the central bonds of tetrasulfides (32.3 +/- 1.0 kcal mol^-1).The appearance energy method was also used to measure the ionization energy of t-BuSS. (8.25 +/- 0.08 eV) and the heat of formation of the ion t-BuSS⁺ (195 +/- 2 kcal mol^-1).