Abstract: The crystal and molecular structure of meso- and dl-2,3-diethoxy-2,3-diphe-nylsuccinonitriles, 1a(meso)and 1a(dl), which are substituted ethane derivatives with capto-dative substituents, have been determined by X-ray crystallography. It is found that the central carbon-carbon bonds and chemical bonds attached to them are all obviously stretched. The deformation of the molecules is explained by steric, electronic and capto-dative subtituent effects through conformational analysis.