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

Abstract

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.