The electron impact mass spectra of some diastereomeric dialkyl tartra
tes and isopropylidine derivatives of dimethyl tartrate show diagnosti
c 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 wit
h the configuration of carbomethoxy groups in dimethyl maleate and fum
arate. The interaction between the two carbomethoxy groups is relative
ly larger in conformations where there is a gauche interaction between
them. The results could also be correlated with the solution phase co
nformations of these compounds reported in the literature using nuclea
r magnetic resonance techniques. The difference, which is small in dia
stereomeric dimethyl tartrates, is very reproducible and has been conf
irmed using six different mass spectrometers.