Mass spectral study of diastereomers by electron impact

Abstract

The electron impact mass spectra of some diastereomeric dialkyl tartrates and isopropylidine derivatives of dimethyl tartrate show diagnostic differences in the relative abundances of some ions. The differences have been explained based on preferred conformations of these isomers. The configuration of the carbomethoxy groups has been correlated with the configuration of carbomethoxy groups in dimethyl maleate and fumarate. The interaction between the two carbomethoxy groups is relatively larger in conformations where there is a gauche interaction between them. The results could also be correlated with the solution phase conformations of these compounds reported in the literature using nuclear magnetic resonance techniques. The difference, which is small in diastereomeric dimethyl tartrates, is very reproducible and has been confirmed using six different mass spectrometers.