1H and 2H NMR of methanes partially oriented in liquid–crystal phases: Separation of rigid and nonrigid molecule effects

1H and 2H NMR results are presented for methane and its deuterated analogs dissolved in various nematic liquid crystals. Anisotropic couplings observed in CHD3, CH2D2, and CH3D arise partly from the small deviation from tetrahedral symmetry due to the deuterium substitution, and partly from nonrigid molecule effects which give rise to anisotropic couplings in CH4 and CD4. Excellent agreement is obtained with a simple model based on separability and additivity of these rigid and nonrigid molecule contributions. Order parameters for the rigid molecule contribution are positive along the longest and negative along the shortest molecular directions.