Proton magnetic resonance studies of cyclic compounds. Part IX. The spectra of protonated piperidines and morpholines

Abstract

The position of equilibrium, with respect to nitrogen inversion, for cis-3,5-dimethylpiperidine (54% Ione pair axial, 46% Ione pair equatorial) was inferred from the proportions of configurations possessing [graphic omitted]–D (axial) and [graphic omitted]–D (equatorial) which were produced on mixing the amine with an excess of CF₃·CO₂D. The validity of the method was supported by experiments with model compounds, which showed (a) that exchange of H⁺(or D⁺) during the mixing period was relatively unimportant, and (b) that exchange of H⁺(or D⁺) in piperidine salts dissolved in CF₃·CO₂H (or CF₃·CO₂D) was exceptionally slow.