NMR Determination of Some Deuterium Quadrupole Coupling Constants in Nematic Solutions

Abstract

The analysis of the NMR spectra of suitable nematic liquid‐crystal solutions appears to offer a convenient and desirable method for the determination of small nuclear quadrupole coupling constants for molecules in the liquid state. Nuclear quadrupole coupling constants have been determined for deuterium in the $\mathrm{C}–\mathrm{H}$ bond of a number of small molecules. Assuming that the field gradient has axial symmetry, values of e²qQ/h along the bond axis are as follows: $$\begin{array}{cc}{\mathrm{CH}}_3{\mathrm{CD}}_3& \text{167± 18\hspace{0.17em}}\mathrm{kHz}\\ {\mathrm{C}}_3{\mathrm{D}}_6& \text{184± 20}\\ {\mathrm{C}}_2{\mathrm{D}}_2& \text{198± 7}\\ {\mathrm{CH}}_3{\mathrm{C}}_2\mathrm{D}& \text{199.4± 2.0}\\ \mathrm{DCN}& \text{199.0± 3.0.}\end{array}$$ The results are discussed in terms of various theoretical calculations of the field gradient at the deuteron, and a compilation of some of the accurate experimentally determined deuterium coupling constants is presented.