Nuclear magnetic resonance coupling constants in p-benzoquinones

Abstract

The n.m.r. spectrum of chlorobenzoquinone has been reanalysed, with an assignment for which evidence was obtained from double resonance experiments and relative intensities of different transitions. N.m.r. parameters for p-toluquinone have also been obtained by the “spin-decoupling” technique. The data from the two molecules was then used for reanalysing the ¹³C satellite spectrum of p-benzoquinone. The importance of the inclusion of non-bonded ¹³C proton coupling constants in the analysis of ¹³C satellite spectra has been emphasised. Values of the coupling constants obtained in the present work show considerable differences from those reported earlier, and are in better agreement with theoretical predictions.