Thermochemistry of Sulfenic Esters (RSOR′): Not Just Another Pretty Peroxide

A computational study on the thermochemistry of several simple sulfenic acids (RSOH) and esters (RSOR′) is reported. The enthalpies of R-S, S-O, and O-R′ homolytic cleavage are calculated at the G2 level of theory and compared to related peroxides and disulfides. Less expensive B3LYP calculations were unsatisfactory. When R and R′ are both alkyl, the O-C bond is expected to be the weakest in the molecule; for CH3SOCH3, C-S, S-O, and O-C bond dissociation enthalpies of 67, 64, and 49 kcal/mol are predicted by G2. Compared to peroxides, sulfenic esters are predicted to have weaker O-C bonds and S-O bonds that are stronger than the analogous O-O bonds. The C-S bonds of sulfenic esters are predicted to be somewhat stronger than those of disulfides. A rationalization is given for the observation that radical stabilization is greater for RSO• than ROO•, RSS•, or ROS•.