Solvation of protons and the strength of superacids

Analysis of literature indicates that the strength of superacids is mainly determined by unusual chemical properties of weakly solvated protons while the extent of dissociation of superacids is rather low and is less important. A higher chemical activity of protons in very concentrated acids and in such water-free superacids as liquid HF or 100% H2SO4 results from a weaker solvation of these species with the molecules of superacids which are less basic than water. In contrast, solvation by superacids of the negatively charged anions is stronger than in water solutions. These conclusions are illustrated by the ab initio quantum chemical calculations performed for self-dissociation of anhydrous liquid hydrofluoric acid.