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, HCO 4 - , the covalent adduct between the carbon dioxide and hydrogen peroxide anion, effectively reacts with SO 2 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 HO 2 - , 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 HCO 4 - is disclosed by the Lewis acidic properties of SO 2 , an amphiphilic molecule that forms intermediates with characteristic and diagnostic geometries with peroxymonocarbonate.