Abstract: The ¹H NMR spectra of mesa and dl diethyl 2,3-dicyano-2,3-di(p-Xphenyl)succi-nates(X=OCH₃, CH₃, H, Cl, NO₂) and ¹H Noesy spectra of meso and dl isomers of the diethyl ester with X=CH₃were determined by using Bruker Am 400 MHz superconducting NMR spectrometry. The corresponding proton of the substituent groups attached to the two central carbon atoms in the molecules are chemical shift equivalence. The average difference between o ^-1Habsorptions of phenyl in the dl-isomers and that in meso-isomers was found to be △δ_dl-meso= -120. 1 ± 6.1 Hz. All of the meso-isomers, then, have, methylene (ABX₃system) and methyl in the ethoxy at upfield positions, and all of the dl-isorners have that at downfield positions, △δ_dl-meso= 53. 3 ± 5. 9 Hz and △δ_dl-meso= 53. 5 ± 5. 4 Hz for Aand Bprotons in the methyienes, and △δ_dl-meso=39. 3+3. 5 Hz for protons in the methyls. △δ_dl-meso is the mark of influence of molecular configuration on the chemical shift.

Key words: ¹H NMR spectra. Chemical shift, Molecular configuration, Diethyl 2,3-dicyano-2,3-bis(p-substituted phenyDsuccinates