2,3-二氰基-2,3-二(对-硝基苯基)丁二酸二乙酯的分子结构和晶体结构

我们曾报导了2,3-二氰基-2,3-二苯基丁二酸二乙酯的分子结构,并对该化合物对烯烃单体进行自由基聚合的引发作用,热分解动力学和固态变温ESR谱等进行了研究。为了进一步探讨这类新型引发剂的结构与性能间的关系,我们继续用X射线衍射方法研究了2,3-二氰基-2,3-二(对-硝基苯基)丁二酸二乙酯的两种异构体1和2的分子结构和晶体结构。并讨论了分子中空间立体效应和电子效应对该化合物稳定性的影响。实验异构体1从乙酸乙酯和四氯化碳(9∶1,V/V)混合溶剂中重结晶,在空气中基本稳定。

STRUCTURAL STUDIES ON TWO ISOMERS OF DIETHYL 2,3-DICYANO-2,3-DI-p-NITROPHENYLSUCCINATE (Ⅰ)

The title compoud and its related derivatives show a certain degree of thermal lability and were reported as effective carbon-carbon type initiators for the polymerzation of styrene and other monomers.The crystal and molecular structrues of two isimers of the title compoud has been determined. 1, meso-(I), C_(22)H_(18)N_4O_8 space group, p1, a=0.7860(3), b=0.8350(2), c=0.9303(3) nm, a=89.29(2), β=65.49(2), γ=83.27(2), Z=1, V=0.5512 nm, μ(MoKα)=1.02 cm~(-1), D_c=1.405 mg m~(-3), final R=0.064 for 1729 observed reflections.2, racemic-(I), C_(22)H_(18)O_8·C_6H_6, space group C2/C, a=1.8395(5), b=1.102(2), c=1.3865(4) nm, β=92.16(2)°, Z=4, V=2.809(1) nm, μ(MoKα)=0.89 cm~(-1), D_c=1.458 mg m~(-3), final R=0.084 for 2202 observed reflections.There are numerous intramolecular non-bonded atomic eontacts shorter than the expected van der Waals distances. The strong steric interactions of these atomic pairs lead to enormous strain within the molecule and thus to anomalous bond lengths and angles as well as thermal instability The stretching of the centra C—C bonds, 0.1601(4) nm for meso-(I), 0.1587(6) nm for racemic-(I), is particularly remarkable. It was shown the “steric acceleration” plays an important role during the cleavage of the central C—C bonds.