Christopher S. Foote, University of California, Los Angeles
The intermediates in the reactions of singlet oxygen with HS and MeS have been calculated at Hartree-Fock, Møller-Plesset, and multiconfiguration levels of theory. A peroxy sulfoxide structure, which has been proposed as an intermediate in the photooxidation of organic sulfides, was found to be a stable intermediate, but the barrier for dissociation to reactants is calculated to be only a few kilocalories per mole. The infrared frequencies and intensities of this intermediate were calculated for the purpose of possible spectroscopic identification. A cyclic thiadioxirane, which also has been suggested as a possible intermediate, was found not to be a minimum on the potential energy surface. Large-scale MCSCF calculation shows that the peroxy sulfoxide is best described by a zwitterionic, not a biradical, structure. Calculated activation energies and overall reaction energies are found to require a very large basis set in order to give reasonable agreement with experimental results.
