Theoretical ab initio and low-temperature ESR study of the cyclohexane cation.

The cyclohexane cation has been studied theoretically using ab initio MO-LCAO-UHF calculations, as well as experimentally, by means of low-temperature ESR measurements in a CF3CCl3 matrix between 4 and 140 K. It is found that the most stable conformation of the free cation is a distorted chair conformation with Cs symmetry, with one carbon atom being separated from the others by bonds that are approximately 0.1 Å larger than the remaining C–C bonds. The symmetrical chair conformation of C2h symmetry is predicted by the calculations to lie approximately 6 kcal/mol above this lowest state. The possibility of a change of ground state because of matrix interactions is discussed in connection with the temperature dependence of the spectra. [ABSTRACT FROM AUTHOR]