烯烃顺反异构的拓扑方法研究

Study on the Cis/trans-isomerism of Alkenes by Topological Approach

在烯烃的顺式与反式异构体中,处于碳碳双键两端的顶点间的距离是不同的.可根据几何原理计算与双键相连的顶点间的空间距离,并以此构造分子图的修正距离矩阵来区分这种差异.按照我们已报导的顶点度鄄距离指数(VDI)和边度鄄距离指数(EDI)的计算方法,用修正距离矩阵(MD)代替距离矩阵(D),得到修正的顶点度鄄距离指数(MVDI)和修正的边度鄄距离指数(MEDI).这两个参数能较好地区分烯烃顺反异构体的分子结构信息.对烯烃顺反异构体的沸点(b.p.)、折光率(n20D)、密度(D20)及摩尔折光率(nM)等物化性质进行定量相关,得到模型方程的相关系数(R)分别为0.9981、0.9570、0.9884和0.9999.同时,交叉验证和随机抽样预测结果表明模型具有良好的稳定性和较强的预测能力.

The distances among the vertices spaced by the double bond are different in the cis-alkenes from those in its trans-isomers. By the geometric principle, the distances among the vertices adjacent to the double bond were quantified, based on which a modified distance matrix (MD) of the alkene molecular graph was constructed. According to the definition of vertex degree-distance index (VDI) and edge degree-distance index (EDI) in our preceding work, two descriptors,the modified vertex degree-distance index (MVDI) and modified edge degree-distance index(MEDI) were calculated from the modified distance matrix (MD) instead of the distance matrix(D). The MVDI together with MEDI can characterize the molecular structural information well for the cis-and transisomers of alkenes. Multiple linear regression analysis was carried out on these descriptors and a series of physicochemical properties for cis- and trans-isomers of alkenes,such as boiling point(b. p.), refractive index(n(D)(20)), density (D-20), and molar refractive index (n(M)),. The QSPR (quantitative structure-property relationship) models were obtained with correlation coefficients 0.9981, 0.9570, 0.9884, and 0.9999, respectively. Furthermore, leave-one-out cross validation and random sampling prediction were performed, which confirmed the good stability and powerful prediction of these models.