Product channels in the reaction of the CH 3 SO radical with NO 2 : DFT and ab initio studies

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