Wide-line nuclear magnetic resonance study of solid methanols

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Abstract
A proton magnetic resonance study of dry CH3OH and CH3OD between 1.8°K and the melting points shows rotation of the CH3 group over the complete temperature range, a well‐defined decrease in line‐width at the temperatures of the monoclinic to orthorhombic transformation, and absence of the narrow line found in earlier NMR studies. Inconsistencies between previous NMR results are ascribed to the effects of saturation, inadequate thermal conditioning, and the presence of water. Second moments of the monoclinic form show adjacent CH3 groups to be further apart than given by Tauer and Lipscomb's x‐ray structure. Second moments of the orthorhombic form agree with dielectric results in showing large‐amplitude rotatory motion. The ``second transition'' found in earlier volumetric and dielectric studies of CH3OH and CH3OD probably marks the eutectic temperature where monoclinic methanol, methanol monohydrate, and liquid phase coexist. The second moment of CD3OH is almost invariant between 4 and 155°K although there is a significant change in line shape.