Study of molecular motion in liquid methylamines by nuclear magnetic resonance. I

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Abstract
Measurements of nuclear magnetic relaxation times T 1 and T 2 for the nitrogen and deuterium nuclei in deuterated and ordinary liquid methyl-, dimethyl and trimethylamine are reported. Attempts to interpret the results in terms of the small-angle anisotropic rotational diffusion model seem to fail. Instead, interpretation in terms of a large-step isotropic reorientation model has been performed. The main conclusion is that the methyl group internal reorientations are fast compared to the overall molecular rotations in methylamine, comparable in magnitude in dimethylamine and slow in trimethylamine. The activation energies for reorientation and the possible evaluation of molecular radii are also discussed.