The thermodynamic properties of nine possible reactions for the atmospheric fate of the CH3SCH2O2 radical are analysed in this work. The reactant species considered were NO, NO2, HO2, CH3O2, CH3S, CH3SO, CH3SO2, O and O2. The calculations were performed at the UCCSD(T)/cc-pVTZ//MP2/6-31G(d) level of theory. Reactions of the CH3SCH2O2 radical with NO, NO2, HO2, CH3S, CH3SO, CH3SO2 and O are exothermic and spontaneous. In the reaction with NO2, the equilibrium will be highly dislocated towards the reactants. The reaction with CH3O2 radical is endothermic by a small quantity, but spontaneous. The estimated rate constant indicates that it will not be important. Reaction with O2 leading to the CH3SCH2O and O3 products is thermodynamically unfavourable, having a positive reaction enthalpy. The thermodynamical features of the reactions with O and HO2 radicals indicate that these reactions should be important in this process, and kinetic studies of these reactions are strongly suggested. The heats of formation of the CH3O2, CH3SO, CH3SO2, CH3SO3, CH3SCH2O, CH3SCH2O2H, CH3SCH2O2NO, CH3SCH2O2NO2, CH3SCH2O3 and CH3SCH2O4 species were determined.
S. M. Resende, W. B. Almeida
Physical Chemistry Chemical Physics