Theoretical studies on the reactions of NO2 with CH3SO, CH3SS, CH3SO2 and CH3S(S)O

The reactions of NO2 with CH3SO, CH3SS, CH3SO2 and CH3S(S)O have been studied at MP2/6-311++G(d, p)//B3LYP/6-311++G (d, p) level. Geometries of the reactants, intermediates (IM), transition states (TS) and products have been optimized and geometries of the transition states are found for the first time. The different structures among four transition states have been discussed by the method of topological analysis of electronic density. The calculated results show that these reactions can proceed via singlet-state or triplet-state potential energy surface (PES). Because of the high energy barrier of triplet PES, the singlet PES reaction is dominant. The reaction mechanisms of NO2 with CH3SO, CH3SS, CH3SO2, CH3S(S)O are similar. On the singlet-state PES, one of O atom of NO2 attacks the reactants first formed an intermediate, then the intermediate decomposed to CH3SO2, CH3S(S)O, CH3SO3, CH3S(S)O2 and NO. And because of the low dissociation energy of the processes, these four reactions could occur easily.