Theoretical study of adducts of dimethyl sulfide with hydroperoxyl and hydroxyl radicals

Structures and energies of complexes of dimethyl sulfide (DMS) with hydroxyl (OH) and hydroperoxyl (HO2) radicals have been studied using ab initio and density functional theory. Two isomers of the complex between OH and DMS were found, one dipole-dipole complex and one 3e-/2c complex. The binding energies (D0) of these two complexes have been found to be consistent with previous studies. This is the first reported study of the complex between DMS and HO2. One structure was found for this complex, and the binding energy (D0) has been determined to be 9.0 kcal mol-1 using the fully optimized MP2/6-311++G(3df,3pd) level of theory. Vibrational and rotational constants are also presented for all of complexes calculated. Thermodynamic parameters and equilibrium constants for the formation of these complexes from the monomers have been calculated. The results have been related to laboratory experiments studying these reactions, and some implications to oxidation of DMS in the atmosphere have been discussed.