The conformational analysis of saturated heterocycles. Part XXII. Conformation of piperidine: evidence and conclusions from dipole moment studies

Abstract

Electric dipole moments of suitably substituted piperidines indicate that the N-hydrogen atom prefers the equatorial position. A survey of the available evidence indicates that a value of ΔG°= 0·4 ± 0·2 kcal./mole favouring NH-equatorial for piperidine in the gas phase and non-interacting solvents is in agreement with all known facts. Reasons for the NH-equatorial preference are discussed.