Relative stabilities of ortho-, meta- and para-tolyl cations

Relative energies of the tropylium ion and tolyl cations with respect to the benzyl cation were estimated using ab initio calculations. The relative energies of tolyl cations are in ascending order ortho<meta<para. After correcting for zero-point energies, correlation effects, and basis-set deficiencies, the best estimates for the relative energies were converted to 0 K heats of formation by taking ΔH°f0=919 kJ mol−1 for the benzyl cation as an anchor. The best ΔH°f0 estimates are 896, 1087, 1093, and 1101 kJ mol−1 for the tropylium, ortho-, meta-, and para-tolyl cations, respectively.