Quantum-chemical study of various pathways to carbenium ions from olefins and alkyl fluorides in the medium of hydrofluoric acid

Elementary reactions of carbenium ion generation from olefins and alkyl flu orides in the medium of hydrofluoric acid are studied by the Hartree-Fock m ethod taking into account electron correlation at the MP2 level and by the DFT (B3LYP) method in the 6-31++G** basis set. Based on enthalpies calculat ed for these reactions,, possible pathways to carbenium ions in the olefin- HF system are determined. A conclusion is drawn that carbenium ions can be formed from olefins by protonation and from the corresponding alkyl fluorid es and their protonated forms. Ie is shown that the heterolytic decompositi on of alkyl fluoride in the medium of liquid KF is possible due to the stab ilization of carbenium and fluoride ions by hydrogen bonds with HF molecule s. The discrete model of microsolvation and the polarizable continuum model (PCM) are used to estimate a decrease in the activation barrier of the het erolytic decomposition of alkyl fluorides due to solvation in the medium of liquid hydrofluoric acid.