NMR Determination of Deuterium Quadrupole Coupling Constants in Nematic Solutions

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 CD3 groups of methyl iodide, methyl bromide, and acetonitrile and for deuterium in fully deuterated benzene. Values of e2qQ / h measured along the molecular symmetry axis were found to be 66.9 ± 1.2 kHz for CD3I, 63.0 ± 1.0 for CD3Br, and 54.5 ± 1.5 for CD3CN. If the assumption is made that the C–D bond has rough axial symmetry then values of e2qQ / h along the bond axis are found to be 180 ± 5 kHz for CD3I, 171 ± 4 for CD3Br, and 165 ± 5 for CD3CN. e2qQ / h along the bond axis was found to have a value of 194 ± 4 for C6D6.