Theoretical abinitio 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 A 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.