The ¹H chemical shielding anisotropies of acetylene and fluoroform, as measured in a smectic liquid crystal solvent

Abstract

A new method of measuring the chemical shielding anisotropies of C₂H₂ and CHF₃ is reported, which employs the use of a smectic phase liquid crystal solvent. The anisotropies obtained with this method are in good agreement with theoretical calculations. Δσ values are reported for acetylene and fluoroform as being +14·2 ± 0·3 and +9·4 ± 0·2 p.p.m. respectively. Large magnitudes of the ordering parameter S _zz are obtained through the use of this method, which also essentially eliminates most effects due to temperature and phase changes. The method enables one to obtain the chemical shielding anisotropy from measurements in the smectic phase only and at a single temperature.