Substituent Effects on the N.M.R. Spectra of Carboxylic Acid Derivatives. IV. ¹³C N.M.R. Spectra of para-Substituted Phenols, Phenylureas and Phenyl Propionates

Abstract

The ¹³C n.m.r. spectra of 9 para-substituted phenols, 12 para-substituted phenylureas and 11 para-substituted phenyl propionates have been measured in (CD₃)₂SO and the observed substituent chemical shifts have been found to be non-additive with respect to those of the corresponding monosubstituted benzenes. The ¹H n.m.r. spectra of the phenols and phenyl propionates and the i.r . carbonyl stretching frequencies of the phenyl propionates have also been determined. The spectral data have been treated by single parameter and dual substituent parameter linear free energy relationships ( l.f.e.r .) and σ_R values of best fit have been identified. In general, treatment by single parameter l.f.e.r . Are at least as satisfactory as those by DSP l.f.e.r.