链烷烃的热力学性质与分子拓扑指数的关系

THE CORRELATION BETWEEN THERMODYNAMIC PROPERTIES AND MOLECULAR TOPOLOGICAL INDEX OF ALKANES

引言 在物质的结构与性能关系研究中,拓扑化学以其方法简单、准确性高、运用方便等优点受到了广泛的关注,Wiener最早提出了烷烃的拓扑指数,并用它研究了烷烃的沸点、生成热、表面张力、蒸汽压等性质。Platt等人用Wiener指数研究过分子的折射率、摩尔体积。本文作者也曾用Wiener指数研究过烷烃分子的密度变化规律,在已经问世的一百多种拓扑指数中,最成功及应用最广的要算是分子的连通性指数,它可用于烷烃的沸点及在水中的溶解度、药物设计、卤代烃的麻醉性、物质的气相色谱停留指数等研究。 本工作考虑到分子的连通性指数特别有利于描述分子的分支情况,求算了支链烷烃分子的连通性指数,并将指数与分子的标准生成热、标准熵、标准生成自由能相关联,取得满意结果。

Connectivity indices of 85 alkanes were calculated based on the definition of M. Randic. The properties such as the standard enthalpies of formation, the standard entropies and the standard free energies of formation of these alkanes were correlated with the connectivity indices and the number of carbon atoms. A general equation was proposed as follows; P = a X + bN + c. The thermodynamic properties calculated for both gasous and liquid states of the 85 alkanes are in excellent agreement with the experimental values through regression analysis.