Hindered Internal Rotation of N, N-Dimethylpropylamines

抄録

The N-methyls in 2, 3-disubstituted N, N-dimethylpropylamines (I-VIII) have given two peaks with an equal intensity in an acid solution owing to the hindered internal rotation about the C-NMe₂H⁺ bond. The energy barriers between two staggered forms have been estimated to be 0.7 (benzylthio)-7 (thiocyanato) kcal mole^-1 from the temperature dependence of the peak separations. The high-field shift and the largest separation of the N-methyls in the benzylthio derivative (I) have been ascribed to an anisotropic effect of the benzene ring. 1, 3-Disubstituted 2-N, N-dimethylaminopropanes (IX) and 2-substituted N, N-dimethylethylamines (XII-XV) have shown a single peak for the N-methyls. A restricted rotation about the CH₂-CH bond in 2, N, N-trimethylaminoethyl disulfide (X) has been studied by the temperature dependence of the vicinal coupling constants.