Quantum-chemical study of transformations of C1-C6 carbonium ions

The formation and transformations of the carbonium ions of normal C-1-C-6 alkanes were simulated by ab initio Hartree-Fock and semiempirical PM3 calculations. The relative stability of the cations and their degradation routes were determined depending on the protonation site. Based on the simulations, the number of fragments into which these alkoniums decompose was calculated. Good agreement between the calculated enthalpies of formation and relative stability of the resulting structures with experimental values was observed. The semiempirical PM3 method reproduced well the results of ab initio calculation on both energies and degradation routes for carbonium ions.