Effect of nitrogen substituents on CN rotational barriers in enamine derivatives

Rates of rotation around the CN bond in a series of ten N,N‐disubstituted 3‐amino‐5,5‐dimethylcyclohex‐2‐enones were determined from total NMR line shape analysis. Linear correlations are shown to exist between Δ and parameters describing the inductive and steric effects of N‐alkyl substituents. The substituent effects on the barriers seem to occur mainly through a change in the potential energy of non‐bonded interactions between the nitrogen substituents and the hydrogen atoms in the ortho position to the amino group.