Abstract
The stationary points involved in the CH~3~SO + NO~2~ radical‐radical reaction were examined at the B3LYP/6‐311++G(2df,2pd) and CCSD/cc‐pVDZ levels of theory. Singlet potential energy surface was calculated using the CCSD(T)/aug‐cc‐pVTZ//CCSD/CC‐pVDZ single‐point calculations and the CBS‐QB3 composite method. The association between radicals is confirmed to be a barrierless process and resulted in the two low‐energy intermediates, CH~3~S(O)NO~2~ and CH~3~S(O)ONO. The CH~3~S(O)ONO intermediate decomposes directly to the CH~3~SO~2~ + NO products with the NO bond dissociation energy of 7.9 kcal mol^−1^. Although the dissociation of the CS bond in the CH~3~SO~2~ requires an energy of 16.3 kcal mol^−1^, the formation of final CH~3~ + SO~2~ + NO products is very likely, because their energy level is by 3.4 kcal mol^−1^ still lower relative to that of the reactants. The formation of the CH~2~SO + HONO products from CH~3~S(O)ONO can proceed through the three‐center transition state, but it is not important due to significant barrier well above the energy level of reactants. Eventually, CH~2~SO + HONO may be generated in the direct H‐abstraction from CH~3~SO radical by NO~2~. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011