The equilibrium structure of benzene

The r(e) structure of benzene is revised on the basis of high-level quantum chemical calculations at the CCSD(T)/ cc-pVQZ level as well a reanalysis o f the experimental rotational constants using computed vibrational correcti ons. A least-squares fit to empirically determined B-e constants yields r(e )(CC) = 1.3914 +/- 0.0010 Angstrom and r(e)(CN) = 1.0802 +/- 0.0020 Angstro m; the latter distance is significantly shorter than the best previous esti mate based on experimental data. Comparison of computed r(g) and r(z) dista nces with experiment as well as considerations of bond lengthening due to a nharmonicity are consistent with the estimated r(e) distance, indicating th at the recommended structural parameters are very accurate.