论文部分内容阅读
2,3-二氰基-2,3-二苯基丁二酸二乙酯由α-氰基苯乙酸乙酯经Cu~(++)-TMEDA-O_2系统氧化偶联制得。产物经柱层析得到两个结晶化合物1和2.1和2的单晶经X射线晶体结构分析鉴定,分别为内消旋和外消旋2,3-二氰基-2,3-二苯基丁二酸二乙酯。值得注意的是,在化合物1和2的分子中,中心碳—碳单键的键长均有明显的增长效应,前者为1.585(?),后者为1.62(?)。同时,与中心碳—碳键两端碳原子上相连接的取代基之间有明显的空间位阻效应。这些事实和分子中取代基的电子效应结合在一起,为标题化合物很容易分解为自由基,从而可有效地作为聚合引发剂提供了结构上的解释。用CNDO/2方法计算化合物1分子中各原子上的电荷分布和Wiberg键级,结果与晶体结构分析的结果吻合得很好。
Diethyl 2,3-dicyano-2,3-diphenylbutanedioate was prepared by the oxidative coupling of α-cyano-phenyl-phenylacetate with Cu ~ (++) - TMEDA-O_2 system. The product was subjected to column chromatography to obtain two crystalline compound 1 and the single crystals of 2.1 and 2 were identified by X-ray crystal structure analysis as meso and racemic 2,3-dicyano-2,3-diphenyl Diethyl succinate. It is noteworthy that in the compounds 1 and 2 molecules, the central carbon-carbon single bond length have significant growth effects, the former is 1.585 (?), The latter is 1.62 (?). At the same time, there is a significant steric hindrance effect between the substituents attached to the carbon atoms at both ends of the central carbon-carbon bond. These facts, combined with the electronic effects of the substituents in the molecule, provide the structural elucidation that the title compound is readily decomposed into free radicals and thus effectively acts as a polymerization initiator. The CNDO / 2 method was used to calculate the charge distribution and the Wiberg bond order of each atom in compound 1, which was in good agreement with the crystal structure analysis.