Magnetic susceptibility tensors and deuterium quadrupole coupling constants of the methyl halides

High-resolution 95.2 MHz deuteron NMR spectra were obtained from dilute ether solutions of the monodeuteromethyl halides (X = Cl, Br, I). Small quadrupole splittings were resolved, resulting from molecular alignment by the 14.57 T field. These splittings relate the deuterium quadrupole coupling constants (qcc) to the anisotropy in the molecular diamagnetic susceptibility (Δξ). The results are consistent with literature qcc and Δξ values for CH₃CI and CH₃ Br, but suggest that Δξ of CH₃I determined by microwave spectroscopy is high by about 14%. A survey of literature qcc data for the complete series of halomethanes is given. The data indicate a good agreement between qcc's found from gas-phase studies (microwave), low-temperature solid-state NMR and NQR experiments, and investigations using certain well-chosen liquid crystal mixtures. The values judged to be most accurate were combined with quadrupole splitting data to obtain molecular and bond susceptibilities for this series of compounds.