Nuclear magnetic resonance studies of six-membered rings. Part I. Rings inversion in heterocyclic compounds

Free energies of activation, ΔG‡, for ring inversion are reported for a number of heterocycles. These values are obtained from coalescence temperatures observed for 1H n.m.r. spectra. The observed variations in ΔG‡ are correlated with differences in barriers to internal rotation in analogous acyclic compounds. The limitations and anomalies of the correlation are mentioned, and the implications are discussed.