The Oxidation of Sulfur Dioxide by Single and Double Oxygen Transfer Paths

The oxidation of SO 2 by nonmetal oxoanions in the gas phase is investigated in an experimental and theoretical study of the structure of the species involved and the reaction kinetics and mechanism. SO 3 , SO 3 .− and SO 4 .− are efficiently produced by reaction of O n XO − anions (X=Cl, Br, and I; n =0 and 1) with SO 2 ; XO − ions mainly react to give SO 3 by oxygen‐atom transfer, whereas OXO − ions mainly give SO 3 .− by oxygen‐anion transfer. On descending the halogen group from chlorine to iodine, the SO 3 /SO 3 .− ratio decreases and increases for reactions involving XO − and OXO − anions, respectively, whereas the formation of SO 4 .− is particularly significant with OIO − . Kinetic factors play a major role in the reactions of O n XO − , depending on the halogen atom and its oxidation state.