The conformation of thioanisoles studied using nuclear magnetic resonance spectra of liquid crystalline solutions

Abstract

The n.m.r. spectra of [¹³CH₃]thioanisole, 4-chloro[¹³CH₃]thioanisole and 4-nitro[¹³CH₃]thioanisole as solutes in liquid crystal solvents have been analysed. The results are used to test models of the potential function V(ϕ) describing the reorientation of the SCH₃ group about the phenyl–S bond. It is concluded that the molecules cannot be entirely in the forms with all the heavy atoms coplanar. The data are shown to be consistent with two models for V(ϕ), one with a single minimum between ϕ 0 and 90° and the other having minima of different values at ϕ 0 and 90°. The latter model, a mixture of planar and orthogonal forms, is considered to be the more probable and gives the percentage in the planar form to be between 84 and 50% for thioanisole and between 87 and 78% for 4-nitrothioanisole.