Modeling the Formation of Cations in Oleum

A study is performed of the mechanisms of the formation of H 3 SO , HSO , and H 3 S 2 O cations. The cations can act as sulphurizing agents, due to dissociation and rearrangement in oleum. Modeling is done at the level of the density functional theory and the theory of coupled clusters with implicit (COSMO) and combined explicit and implicit allowance for the solvent (sulfuric acid). The thermodynamic characteristics of the formation of sulphurizing agents are determined. The mechanism of the formation of HSO cations via interaction between H 3 SO cations and SO 3 molecules is studied along with the decomposition of H 3 S 2 O cations. The constant of the autoprotolysis of pyrosulfuric acid in sulfuric acid (5.37 × 10 7 ) is calculated. It is more likely to form from H 3 S 2 O cations than from H 3 SO cations, as was thought earlier. The equilibrium constant of HSO forming from H 3 S 2 O ( K = 5.8 × 10 −8 , Δ G = 41.28 kJ/mol) is calculated.