Reaction mechanism of oxidative desulfurization of heterocyclic organic sulfides: a computational study

The potential energy surfaces of the oxidation of two model heterocyclic organic sulfides thiophene and benzothiophene were examined using H2O2 and HCO3H as oxidants adopting CCSD(T), ωB97X-D, M06-2X and B3LYP at the 6-311+G (d,p) level of theory. Stationary points on the potential energy surfaces for the first and second oxidation reaction were fully optimized and characterized. The natural orbital population analysis was also performed to understand the charge distribution. The results suggest that the oxidation of benzothiophene is faster than that of thiophene using both oxidants, and HCO3H is more efficient than H2O2 in oxidation of both sulfides, which are in accordance with the experimental observation. Such results may assist in understanding the reaction mechanism of the oxidative desulfurization of sulfides.