The crystal and molecular structures of meso- and dl-diethyl 2, 3- dicyano-2, 3-di(p-X substituted. phenyl) succinates (X=OCH~3, meso-1, dl-1'; X=CH~3 meso-2, dl-2'; X=Cl, meso-8, dl-3') were determined. meso-1 decomposed when its data of diffraction intensity was beening collected. dl-1', C~2~4H~2~4N~2O~6, space group P2~1/c, a=1.7296(1), b=1.5394(1), c=0.8916(1)(nm); β=104.24(20ⅲ, Z=4, V=2.3010(nm)^3, μ (MoKα)=0.853cm^-^1, D~c=1.260g/cm^3, final R=0.0413 for 2488 observed reflections. meos-2, C~2~4H~2~4N~2O~4, space group P1, a=0.9315(1), b=0.9390(1), c=1.3241(2)(nm); α=84.39(1); β=99.38(1); γ=105.46(1)ⅲ ; Z=2, V=1.0995(nm)^3, μ(CuKα)=6.439cm^-^1, D~c=1.222g/cm^3, final R=0.0501 for 2191 observed reflections. dl-2', C~2~4H~2~4N~2O~4, space group P1, a=0.9006(1), b=1.1763(1), c=1.4179(2)(nm); α=111.51 (1), β=95.07(1), γ=100.37(1)ⅲ, Z=2, V=1.3549(nm)^3, μ(CuKα)=43. 565cm^-^1, D~c=1.442g/cm^3, final R=0.0804 for 3049 observed reflections. meso-3, C~2~2H~1~8Cl~2N~2O~4, space group P2~1/c, a=0. 8035(1), b=1.0004(1), c=1.3216(1)(nm); β =85.01(1)ⅲ; Z=2, V=1.0583 (nm)^3, μ(CuKα)=30.662cm^-^1, D~c=1.397g/cm^3, final R=0.0585 for 1460 observed reflections. dl-3', C~2~2H~1~8Cl~2N~2O~4, space group P2~1/c, a=1.3901(1), b=1.8152(1), c=0.8824(1)(nm); β =100.33(1)ⅲ, Z=4, V=2.1905(nm)^3, μ(CuKα)=29.629cm^-^1, D~c=1.350g/cm^3, final R=0.0521 for 2347 observed reflections. The most important information obtained is that, in comparsion with normal C-C single bond (0.1544nm), the bond length for the central C-C bond in all of the diastereoisomers shows a remarkable lengthening effect of 0.0023- 0.0052(nm) (1.4-3.4%). The bond length for the central bonds in all of meso-isomers is longer than that in corresponding dl-isomers. It is also observed that, among the substituted groups attached to the two central carbon atoms in the molecules of all of the diastereoisomers respectively, the interatomic distance between nonbonded atoms is smaller than the sum of Van der Waals radii, indi2, 3-二氰基-2, 3-二 (p-取代苯基)丁二酸二乙酯的分子结构和 晶体结构

Key words: CRYSTAL STRUCTURE, MOLECULAR STRUCTURE, DIETHYL SUCCINATE, DIPHENYL GROUP, CRYSTAL STRUCTURE DETERMINATION