Abstract: Meso- and dl-diethyl 2, 3-dicyano-2, 3-di(p-Xsubstituted phenyl)succinates(X=OCH₃, CH₃, H, Cl, NO₂) are studied by means of ¹³C NMRspectra, The results indicate that the chemical shifts of carbon atoms in the same group on both sides of central carbon-carbon bond are equivalent, and the chemical shifts of C₇-C₉ atoms in the dl-isomers are smaller than that in corresponding meso-isomers.The average difference Δδ_β-menvare found to be 1.80±0.16 ppm for C₇, 0.39±0.16 ppm for C₈ and 0.23±0.16 ppm for C₉ respectivly.The plots of chemical shifts of C₆, C₇ and C₈ atoms versus Hammett constant σ of substituents on p-position of benzene ring are good in linear line.

Key words: Diethyl₂, 3-dicyano-2, 3-di(p-X substituted phenyl)succinate, ¹³C NMR chemical shift, Hammett substitutent constant