A theoretical study of the H+SO₂ reaction

Ab initio UHF and MP2 calculations have been used to characterize the relative stabilities, equilibrium geometries, and harmonic frequencies of the intermediates involved in the H+SO₂ reaction. Calculations for the entrance channel potentials at the MP2/DZP level of theory indicate pure repulsion for planar attack (²A′ surface) by the H atom on the S atom of SO₂ and an 11 kcal/mol barrier to the nonplanar (²A″ surface) attack. Much larger barriers are predicted for the formation of the HOSO adducts on this surface. Implications to experiments involving the reaction of SO₂ with translationally hot H atoms are discussed.