Abstract: 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 trans-isomers of alkenes. Multiple linear regression analysis was carried out on these descriptors and a series of physico-chemical properties for cis- and trans-isomers of alkenes, such as boiling point (b. p.), refractive index (n_D²⁰), density (D²⁰), and molar refractive index (nM). 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.

Key words: Alkene, Cis/trans- isomerism, Topological index, Physicochemical property, QSPR