Vicinal C-H Coupling as an Aid to Stereochemical Assignments in Substituted Propenoic Acids

Abstract

Two isomeric pairs of 3-bromopropenoic acids were prepared and vicinal C-H couplings were measured in their ¹³C n.m.r. spectra. Complete C-H coupling schemes were also obtained for these and several other propenoic acids. It was seen that the ranges for ³J_trans and ³J_cis did not overlap, and so a stereochemical assignment based upon n.m.r. data for a single isomer can be made with confidence.