Internal rotation of methyl groups in NN-dimethylamides studied by nuclear magnetic resonance methods

Abstract

The diffusion constants for anisotropic reorientation and internal rotation rates of methyl groups in DMF have been recalculated using longitudinal relaxation times for ¹⁴N, ¹⁷O, ²H, ¹³C, and quadrupolar parameters available in the literature. Within the framework of an isotropic reorientation model the rates of internal rotation of CH₂D groups in NN-di([²H]methyl)-formamide, -benzamide, and -2-methoxybenzamide have been determined on the basis of ¹⁴N and ²H relaxation data. It seems that generally in NN-dimethylamides internal rotation of the E-methyl group is more hindered than that of the Z-methyl group.