¹H, ¹⁹F and ²H NMR of monofluoromethane and deuterated analogues partially oriented in nematic liquid crystals

Abstract

A ¹H, ¹⁹F and ²H nuclear magnetic resonance study of eight isotopomers of fluoromethane (CH₃F) has been carried out under virtually identical experimental conditions. An analysis of the observed anisotropic couplings on the basis of bond additivity has been performed and the underlying assumption of bond additivity has been found to be adequate.In an accurate description of the solute orientation ‘non-rigid’ contributions such as vibration–rotation interaction, and harmonic and especially anharmonic vibrational corrections have to be included. The present study indicates the presence of a contribution to the observed anisotropic carbon–fluorine couplings due to an anisotropy in J _CF.