An NMR study of the structure of and the internal rotation in phenylsilane

Abstract

The proton magnetic resonance spectrum of phenylsilane oriented in the nematic phase of N-(p-methoxybenzylidene)-p-n-butylaniline has been investigated. Values of the chemical shifts and indirect HH coupling are obtained. The shape of the proton skeleton is determined. The ring proton positions do not deviate significantly from those in benzene. The results indicate that the minimum energy conformation is the one where an Si---H bond is in the ring plane. The structural and the conformational information thus derived is compared with the corresponding carbon analog, toluene. The observed conformational differences in phenylsilane and toluene are interpreted in terms of opposite polarizations of the Si---H and C---H bonds.