The Peroxymonocarbonate Anion HCO 4 − as an Effective Oxidant in the Gas Phase: A Mass Spectrometric and Theoretical Study on the Reaction with SO 2.

The peroxymonocarbonate anion, HCO₄⁻, the covalent adduct between the carbon dioxide and hydrogen peroxide anion, effectively reacts with SO₂ in the gas phase following three oxidative routes. Mass spectrometric and electronic structure calculations show that sulphur dioxide is oxidised through a common intermediate to the hydrogen sulphate anion, sulphur trioxide, and sulphur trioxide anion as primary products through formal HO₂⁻, oxygen atom, and oxygen ion transfers. The hydrogen sulphite anion is also formed as a secondary product from the oxygen atom transfer path. The uncommon nucleophilic behaviour of HCO₄⁻ is disclosed by the Lewis acidic properties of SO₂, an amphiphilic molecule that forms intermediates with characteristic and diagnostic geometries with peroxymonocarbonate. [ABSTRACT FROM AUTHOR]