RESTRICTED ROTATION IN LIQUID STATE BENZENOID MOLECULES

Abstract

Reorientational relaxation in liquid a state planar derivatives of benzene and benzenoid molecules is complicated by substitution in various parts of the molecular structure. A number of species have been studied using Raman spectroscopic techniques and, where appropriate, by nuclear magnetic resonance methods. For the simplest case, $C_{6}H_{6}$, the rotational motions are highly anisotropic and the two motions, parallel and perpendicular to the major symmetry axes, show quite different temperature behavior. Substitution of hydrogen by fluorine introduces intermolecular forces that more seriously affect the pseudo-free rotation of the rings parallel to each other. Data on related molecules will also be discussed.