Sulfur-sulfur bond dissociation enthalpies: A high-level ab initio study

The sulfur-sulfur bond dissociation enthalpies in 12 disulfide compounds were calculated using high-level ab initio methods including G3, G3B3, CBS-Q, CBS-4M, CCSD(T), and ROMP2. The theoretical bond dissociation enthalpies calculated by different methods generally agreed well with each other. However, when compared to the available experimental data, only seven experimental values were consistent with the theoretical predictions, whereas the theoretical values for three molecules, i.e. FSSF, ClSSCl, HSSSSH, differed dramatically from the experimental ones. The origin for the inconsistency between the theory and experiment was discussed. Furthermore, the electronic effect of the substituents on sulfur-sulfur bond dissociation enthalpies was investigated.