Ab initio study of the reaction of OH radical with methyl sulfinic acid (MSIA)

The potential energy surface and various reaction channels of the MSIA + OH reaction have been investigated at the CCSD(T)/6-311 + G(2d, p)//B3LYP/6-31 + G(2d, p) level of theory. Four different hydrogen-bonded complexes were formed in the reactions. The calculations indicate that there are mainly two kinds of reaction mechanisms in the studied reactions, the direct CH3 radical-abstraction reaction and the association-decomposition reaction. Owing to the higher barrier heights, the CH3-abstraction pathway is not expected to be the favorable pathway. While, the association-decomposition reaction pathway, MSIA-b + OH → M2b → TS9 → H2O +  CH3SO2 → TS4 + H2O → SO2 + CH3 + H2O, is the most feasible reaction pathway, and SO2 is the dominant final sulfur-containing product.