title: The gas-phase reaction of methane sulfonic acid with the hydroxyl radical without and with water vapor.
abstract: The gas phase reaction between methane sulfonic acid (CH3SO3H; MSA) and the hydroxyl radical (HO), without and with a water molecule, was investigated with DFT-B3LYP and CCSD(T)-F12 methods. For the bare reaction we have found two reaction mechanisms, involving proton coupled electron transfer and hydrogen atom transfer processes that produce CH3SO3 and H2O. We also found a third reaction mechanism involving the double proton transfer process, where the products and reactants are identical. The computed rate constant for the oxidation process is 8.3 × 10(-15) cm(3) s(-1) molecule(-1). CH3SO3H forms two very stable complexes with water with computed binding energies of about 10 kcal mol(-1). The presence of a single water molecule makes the reaction between CH3SO3H and HO much more complex, introducing a new reaction that consists in the interchange of H2O between HO and CH3SO3H. Our kinetic calculations show that 99.5% of the reaction involves this interchange of the water molecule and, consequently, water vapor does not play any role in the oxidation reaction of methane sulfonic acid by the hydroxyl radical.
authors: Department of Chemistry, University of Copenhagen, Copenhagen O, Denmark. solvejg@chem.ku.dk
authors: Solvejg
authors: S
authors: Jørgensen
authors: Camilla
authors: C
authors: Jensen
authors: Henrik G
authors: HG
authors: Kjaergaard
authors: Josep M
authors: JM
authors: Anglada
mesh_terms: D005740:Gases / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D008698:Mesylates / Q000737:chemistry*; D011789:Quantum Theory; D014835:Volatilization; D014867:Water / Q000737:chemistry
chemical_list: D005740:Gases; D008698:Mesylates; D014867:Water; C045880:methanesulfonic acid; D017665:Hydroxyl Radical