Proton Solvation in Nonaqueous HF as a Main Factor That Determines Its Superacidic Properties

The Hartree–Fock method and electron correlation at the MP2 level in the 6-31++G** basis set is used together with the combined method for taking into account solvation (the discrete model of microsolvation and the polarizable continuum model (PCM)) to study the following molecular systems in the medium of liquid HF: [HFH]⁺, [HFHFH]⁺, [HF...HFH...FH]⁺, [HF...HFHFH...FH]⁺, and [HF...HF...HFH...FH...FH]⁺. The results of calculation make it possible to explain the anomalously high activity of protons in nonaqueous HF by a lower solvation energy of protons in liquid HF (by 48 kcal/mol) than in water. A conclusion is drawn that the combined method used in this work (the discrete model of microsolvation and PCM) is an efficient tool in estimating the contribution from the solvation to the thermodynamic parameters of the reaction in liquid HF.