Conformational studies of quaternary ammonium ions. Part III. Conformational analyses of substituted piperidinium ions by 1H nuclear magnetic resonance spectroscopy and evaluation of the contribution of electrostatic interaction energy in controlling conformation

Abstract

Conformations of piperidinium and NN-dimethylpiperidinium ions having a hydroxy- or acetoxy-group at C-4 or C-3, and of the corresponding free amines in solution have been studied by ¹H n.m.r. spectroscopy. The population of the form with an axial hydroxy- or acetoxy-group of these ammonium ions is larger than that of the corresponding form in the free amines, without exception. The effect of 1,3-diaxial interaction energy and electrostatic interaction energy is discussed and an approximate value for the contribution of the latter in the conformation control of some ammonium ions is estimated.