Substituenteneffekte in kernmagnetischen Protonenresonanzspektren von substituierten Benzolen

Abstract

Substitution effects in proton magnetic resonance spectra of meta‐ and paradisubstituted benzene are shown to be additive at low concentration in hexane. The absolute values of the effects are measured in meta‐disubstituted benzene. Substitution effects in paradisubstituted benzene are separated by substitution of the values thus obtained and are used to predict chemical shifts. In orthodisubstituted and in polysubstituted benzene as well as in paradisubstituted benzene with mesomeric interaction new substitution effects are found and discussed. Correlations of substitution effects with Hammett‐parameters are given. An electrostatic theory of substitution effects is shown to be a good approximation as long as the resonance contribution to the shifts is low.