单取代烷烃液相生成焓估算新方法

ANovel Approach for Estimating the Enthalpies of Formation of Monosubstituted Alkanes RXin Liquid-phase

根据烷基R和取代基X(Cl、Br、I、OH、SH、NO2、CN、NH2、CHO和COOH等)本身的电子效应,应用烷基R的极化效应指数PEI和取代基X的电负性!X定量描述单取代烷烃RX中R和X间的相互作用,再结合已提出的C—C键和C—H键的键连接矩阵的特征根,建立了一个估算单取代烷烃RX液相生成焓的方程:fH0(RX,l)=-39.5001X1CC+33.5508NCC-0.0789X1CH-25.7087NCH+0.1557Sij+0.9976H(X)-27.6642PEI(R)×X+31.5043X此方程用于估算RX的生成焓,不仅结果非常令人满意(其相关系数R达到0.9999,标准偏差SD仅为2.87kJ·mol-1),而且方程中各项参数的物理意义也非常明确,便于人们深入地理解分子结构与性能的关系.应用去一法(leave-one-out)对以上方程进行交叉验证分析表明该方程具有较好的稳定性和较强的预测能力.研究发现,著名的Luo氏方程是上述方程的一种特殊形式,上述方程是对Luo氏方程的一个较大扩展.该方法为研究更复杂体系内基团之间的相互作用提供了一种新的方法和思路.

Based on the electrostatic effects of the alkyl R and the substituent X, combining the polarizability effect index PEI（R） of alkyl R and the electronegativity xx of substituent X, the interaction of R and X in monosubstituted alkane RX was quantified. It was taken as the parameters that the eigenvalues （X1CC and X1CH） of the orbitalconnecting matrices of Ci-Cj and Ci-H bonds together with the interaction of R and X in RX. A general expression to estimate the enthalpies of formation △fH^0（RX, 1） for monosubstituted alkanes RX （where, X=Cl, Br, I, OH, SH, NO2, CN, NH2, CHO and COOH） in liquid-phase was established： △fH^0（RX,1）=-39.5001∑X1CC＋33.5508NCC-0.0789∑X1CH-25.7087NCH＋0.1557∑Sij＋0.9976H（X）-27.6642PEI（R）xxx＋31.5043xx Where the NCC and NCH are the numbers of C-C and C-H bonds in the RX molecule respectively, the H（X） is the contribution of the substituent X to the △fH^0（RX, 1）. The equation can be used to predict the enthalpy of formation well for RX in liquid-phase with a correlation coefficient R=0.9999 and a standard derivation SD=2.87 kJ·mol^-1. What is more, each of the items in the equation has its explicit physical meaning. The obtained equation can help us further understand the correlation between molecular structures and their properties. The stability of the above equation was tested by the leave-one-out cross-validation method. The research result shows that the famous Luo＇s equation is a specific expression of the above equation, which can be regarded as a good progress in this field of Luo＇s research. This work maybe explores a novel way to investigate the interaction of the substituents in more complex compounds.