Determination of <i>erythro</i> and <i>threo</i> configurations by nuclear magnetic resonance spectroscopy

Abstract

An examination of the nuclear magnetic resonance spectra of ten pairs of racemic erythro and threo isomers of 1,2-disubstituted-1-arylpropanes shows that the signals of the methyl protons of the erythro isomer always appear at lower field than the threo isomer. The vicinal coupling constant (J ab ) of the erythro isomer is found to be smaller than that of the threo isomer in six of the isomeric pairs indicating that the magnitude of J ab is a poor criterion of configuration of the 1,2-disubstituted-1-arylpropanes.