Conformations of trans-1,2-disubstituted-1-trimethylsilylcyclohexanes in solution and in the solid state. Crystal and molecular structure of 2-trimethylsilyl-trans-2-methoxycyclohexanol

Abstract

The ¹H n.m.r. spectra of a series of 14 trans-1,2-disubstituted-1-trimethylsilylcyclohexanes provided evidence for conformational equilibria favouring the conformer with the axial trimethylsilyl group in those compounds in which an intramolecular hydrogen bond can exist between the two electronegative substituents. Where such a bond is absent the conformation with an equatorial trimethylsilyl group is highly preferred. An X-ray diffraction study on 2-trimethylsilyl-trans-2-methoxycyclohexanol has shown that this molecule exists in the crystal in the conformation with an equatorial trimethylsilyl group, owing to stabilization by a strong intermolecular hydrogen bond between the axial hydroxy and methoxy groups of neighbouring molecules.