NMR spectra of paradifluorobenzene in a lyotropic nematic solvent. Molecular geometry and anisotropy of the indirect fluorine-fluorine coupling

Abstract

Proton and fluorine NMR spectra of paradifluorobenzene in a lyotropic nematic solvent have been measured and interpreted. Contrary to earlier experiments in a thermotropic liquid crystal, all of the dipole-dipole couplings and the indirect HH and FF couplings could be determined separately, by virtue of an essentially different degree of orientation. A relative molecular geometry has been calculated by using solely the dipolar HH and HF couplings. From these results the dipolar FF coupling has been derived and the existence of a small anisotropy of the corresponding indirect coupling has been demonstrated.