On the structure and torsional potential of trifluoromethoxybenzene: an ab initio and density functional study

The torsional potential of trifluoromethoxybenzene around the aryl–O bond was investigated with the aid of large-scale ab initio calculations performed at the Møller–Plesset second order (MP2) level, with several post-MP2 methods, and with a hybrid density functional method (B3LYP). Contrary to several recent reports, we do not find substantial qualitative differences between MP2 and B3LYP results, provided sufficiently large basis sets are used. The results are confronted with analogous MP2 and B3LYP data for methoxybenzene, for hypothetical anions as obtained by deprotonation at the para-position, and for ethylbenzene. The trends in the calculated torsional potentials, barrier heights and energy differences between conformers are discussed and correlated with selected structural parameters.