Solvation of protons in anhydrous H2SO4 as the main factor determining itssuperacidic properties

The energies of solvation of H3SO4+ cations and HSO4- anions by a sulfuric acid molecule in the gas phase are calculated at the 6-31++G** level using the GAMESS program. The energy of additional solvation of the resulting com plexes with liquid sulfuric acid was modeled within the framework of the PC M continuum model. The results obtained enable almost quantitative descript ion of the energy of self-dissociation of 100% liquid sulfuric acid. The en ergy of proton solvation by 100% sulfuric acid calculated in a similar way was similar to 20 kcal/mol lower than the heat of proton hydration in aqueo us solutions. This result explains the superacidic properties of anhydrous H2SO4.