取代脂环烃物理化学性质的拓扑化学研究

为了探讨有机化合物的分子结构与理化性质的关系,作者在以前的工作基础上,基于一阶分子连通性拓扑指数构建了一个信息拓扑指数.将拓扑指数与取代脂环烃系列分子的气态标准生成热、气态标准熵、气态标准生成自由能、沸点、临界温度、临界压力、临界体积、汽化热、密度、热容及表面张力等十一种热力学性质及物理化学性质相关联,用一个通用公式对各类性质进行概括,然后用已有的实验数据与拓扑指数进行回归分析,得到一系列计算各性质的经验公式.回归结果发现,分子的理化性质与拓扑指数有较好的相关性,有5类性质的复相关系数大于0.99.用经验公式对各类性质进行重新计算,其结果与实验值比较符合,用实验值对计算值作图,发现各数据点紧靠对角线,说明误差较小.残差分布呈正态分布.     

改进的分子连接性方法

通过用Mulliken键级来加权分子连接性指数中的点价,使分子轨道理论与分子连接性指数有机地结合起来,将分子连接性指数改进成为一种量子拓扑指数。对比发现,分子连接性指数的点价与Mulliken键级具有相近的物理意义,而Mulliken键级更具有独特的优越性。利用改进的分子连接性指数对几种具有代表性的烃类与其体积、疏水常数以及热力学性质进行了关联,得到了满意的结果。     

一种新的分子拓扑指数及其在QSPR/QSAR研究中的应用

通过引入量子数、键参数,认为分子的性质与其中各原子的电负性、价电子数、成键电子数、价层主量子数及各化学键的键长有关,提出了一种新的分子拓扑指数mAY.采用该拓扑指数对饱和烷烃、烷基苯、烷氧氯硅烷、卤代苯、含氮杂环化合物、碱金属卤化物及卤化锡的性质/活性进行了相关关系的研究.结果表明,mAY与有机物和无机物的性质/活性间具有良好的相关性.     

一个新的拓扑指数用于有机化合物的QSPR/QSAR研究

在分子图的邻接矩阵和距离矩阵的基础上提出了一个新的拓扑指数Xu,该拓扑指数易于计算,对C~2-C~1~6饱和烷烃有较高的结构区分能力,通过适当的处理可方便地推广到含多重键杂原子体系。该指数与饱和烷烃的正常沸点等理化性质,不饱和链烃类化合物的热容以及某些脂肪醇的毒性和疏水性参数均具有较好的性质相关性。绝大多数理化性质与Xu指数均能建立简单线性模型,且相关系数均大于0.99,表明该指数有望在QSPR/QSAR研究中作为一个新的参数而获得推广应用。     

分子连接性指数(mZh)与烷基苯理化性质的相关性研究

定义有机物分子中成键原子点价δiz.基于δiz和分子图的邻接矩阵,建构一种新的分子连接性指数mZh(m=0,1),并研究了0Zh,1Zh与烷基苯的燃烧热、等张比容、沸点、汽化热、标准生成自由能、标准熵、摩尔体积、溶解度、正辛醇/水分配系数等10种物理化学性质的相关性.结果表明:0Zh,1Zh与烷基苯的物理化学性质具有优良的性质相关性,二元相关系数均在0.99以上;以0Zh,1Zh和分子中C原子数NC为自变量的三元线性回归方程对烷基苯理化性质的预测结果相当令人满意.     

键参数拓扑指数与常用元素的标准电极电位

采用元素键参数拓扑指数关联了第一、二和七主族元素的标准电极电位;采用无机化合物键参数拓扑指数关联了第四周期过渡元素和标准电极电位,结果显示,键参数拓扑指数与元素的标准电极电位之间有较好的线性相关性。     

扩展的距离矩阵指数W~*及其应用研究

重新定义了距离矩阵及距离矩阵拓扑指数W~*，该定义考虑分子中每一原子的 性质和成键情况以及分子中每一原子与所有其它原子的结合情况。拓扑指数W~*对 于饱和碳氢体系可还原为Wiener的距离矩阵指数W，同时，W~*还可一般地应用于含 多重键及杂质原子的有机体系和无机体系。本研究用W~*相关的卤代甲烷标准生成 焓、SiX_n（X = F，Cl，Br，I，n = 1～4）体系的标准生成焓，相关系数均在0. 99以上，置信度大于99.9%。并用W~*研究了含苯环的碳氢体系气相色谱保留指数， 含氧原子的醛酮体系的标准生成焓以及卤代苯体系的辛醇/水分配系数。对饱和碳 氢体，W为W~*的特殊形式。     

晶格能的键参数拓扑指数关联

拓扑指数或分子连通性指数法在研究有机化合物结构与性能关系方面,已作了大量工作,并得到了广泛的应用。拓扑指数只与分子的几何结构有关,而不考虑原子的性质;键参数法虽然研究无机化合物结构与性能方面已获得了巨大的成功,但键参数法只考虑原子的性质,而不考虑分子的几何结构,使它们的应用受到了一定的限制。Berysz,张宏光和辛厚文等在将键参数和拓扑指数结合起来方面和了有益的尝试。本文提出了一种将分子的几何结构与组成分子的原子性质较好结合起来的键参数拓扑指数。     

烯烃的热力学性质与价键拓扑指数的关系研究

烯烃的热力学性质与价键拓扑指数的关系研究倪才华冯志云＊（荆州师专化学系４３４１００）在有机化合物结构与性能研究中，用拓扑指数研究饱和烷烃的物理化学性质已有了较多尝试。因为饱和烷烃分子中键的类型只有Ｃ－Ｃσ单键和Ｃ－Ｈσ单键，在省氢分子图上，任意一根化...     

多溴代芴热力学性质的理论预测研究

为了预测环境污染物多溴代芴的热力学性质,计算了60种多溴代芴的分子连接性指数、电性距离矢量指数、电性拓扑状态指数以及分子形状指数.采用多元线性回归的方法建立了多溴代芴化合物的标准生成焓(Δ_fH~0)、标准熵(S~0)、标准生成吉布斯自由能(Δ_fG~0)及等容热容等热力学性质的QSPR相关性模型,方程的相关系数值均在0.99以上.与相关文献的相关系数R和标准误差S进行比较,该模型具有良好的预测能力和稳定性.     

Using variable and fixed topological indices for the prediction of reaction rate constants of volatile unsaturated hydrocarbons with OH radicals

Volatile organic compounds (VOCs) play an important role in different photochemical processes in the troposphere. In order to predict their impact on ozone formation processes a detailed knowledge about their abundance in the atmosphere as well as their reaction rate constants is required. The QSPR models were developed for the prediction of reaction rate constants of volatile unsaturated hydrocarbons. The chemical structure was encoded by constitutional and topological indices. Multiple linear regression models using CODESSA software was developed with the RMS(CV) error of 0.119 log units.The chemical structure was encoded by six topological indices. Additionally, a regression model using a variable connectivity index was developed. It provided worse cross-validation results with an RMS(CV) error of 0.16 log units, but enabled a structural interpretation of the obtained model. We differentiated between three classes of carbon atoms: sp2-hybridized, non-allylic sp3-hybridized and allylic sp3-hybridized. The structural interpretation of the developed model shows that most probably the most important mechanisms are the addition to multiple bonds and the hydrogen atom abstraction at allylic sites.     

The study of the relationship between the new topological index A(m) and the gas chromatographic retention indices of hydrocarbons by artificial neural networks

The newly developed topological indices A_m1-A_m3 and the molecular connectivity indices ^mX were applied to multivariate analysis in structure-property correlation studies. The topological indices calculated from the chemical structures of some hydrocarbons were used to represent the molecular structures. The prediction of the retention indices of the hydrocarbons on three different kinds of stationary phase in gas chromatography can be achieved applying artificial neural networks and multiple linear regression models. The results from the artificial neural networks approach were compared with those of multiple linear regression models. It is shown that the predictive ability of artificial neural networks is superior to that of multiple linear regression method under the experimental conditions in this paper. Both the topological indices ²X and A_m1 can improve the predicted results of the retention indices of the hydrocarbons on the stationary phase studied.     

Some novel neighborhood degree sum-based versus degree-based topological indices in QSPR analysis of alkanes from n-butane to nonanes

The topological indices are reported to be very useful in various QSPR studies as these indices can be utilized as a tool to predict the physicochemical properties of a diverse set of chemical compounds. The objective of this communication is twofold. First, to introduce some neighborhood degree sum-based topological indices and perform a comparative QSPR analysis of the indices with their corresponding degree-based topological indices to analyze the usefulness of the new indices. Second, to investigate isomer discrimination ability of the newly defined indices on the basis of degeneracy test. Neighborhood degree sum-based topological indices not only consider the degree of each atom in the molecule but also the degrees of its neighboring atoms. Moreover, these indices are expected to provide information about how connected and dense the neighborhoods of atoms are within the molecule. In this study, we observe that the proposed neighborhood degree sum-based topological indices exhibit better correlation with some physicochemical properties of Octane Isomers and 66 alkanes as compared to their corresponding degree-based topological indices. Also, the supremacy in terms of sensitivity of the neighbourhood degree sum-based topological indices as compared to the classical degree-based ones is established.     

Aromaticity of giant polycyclic aromatic hydrocarbons with hollow sites: super ring currents in super-rings

We present a systematic theoretical study based on semi-empirical, Hartree-Fock (HF), and density functional theory (DFT) models of a series of polycyclic aromatic hydrocarbons (PAHs) that exhibit hollow sites. In this study we focus particularly on the magnetic criteria of aromaticity, namely (1)H NMR and nucleus-independent chemical shifts (NICS), and on their relationships with other electronic properties. The computed shifts and NICS indices indicate that an external magnetic field induces exceptionally strong ring currents in even-layered PAH doughnuts, in particular in the layer directly adjacent to the central hole of double-layered compounds. These exceptionally strong ring currents also correlate with particularly small HOMO-LUMO gaps and electronic excitation energies and to abnormally high polarizabilities, indicating in turn that these compounds have a more pronounced metallic character. Comparison is made with further depictions of aromaticity in these systems and in [18]-[66]annulene rings by employing topological, structural, and energetic criteria.     

键连接性指数的建构及其在有机体系中的应用研究

以化学键为基础建构了键连接性指数及分子键连接性指数，该指数同时考虑顶 点原子的化学特征及键的性质．对于任意化学键，键连接性指数Si＝1+△I/R·[（ Z1-h1)m2/n1+(Z2-h2)m1/n2]，分子键连接性指数S为∑i=1^m√Si或∑i=1^m1/√ Si，其中，Z1，Z2为化学键键连原子的价电子数；n1，n2成键原子的价层最高主量 子数；m1，m2为成键原子的氧化数；h1，h2为与成键原子相连的氢原子个数；△I 为成键原子的电负性差(△I≥0)；R为化学键的相对键长．与以顶点为基础的价连 接性指数不同，该指数不仅能方便而有效地应用于饱和碳氢体系亦能有效地应用于 含多重键的不饱和体系及含杂原子的有机体系．研究了饱和碳氢体系标准生成焓， 不饱和碳氢体系和酮、醚、酯体系在水中的溶解度和辛醇/水分配系数，卤代甲烷 体系的标准生成焓，卤代苯体系辛醇/水分配系数，均取得比较满意的结果。     

Ad hoc optimal topological indices for QSPR

Optimal topological indices for particular physicochemical properties can be designed using the chemical structure matrix. Taking the alkane boiling points as examples, the extrapolation properties of some well-known topological indices were compared with those of the optimal topological indices designed ad hoc. The advantages of the new indices are shown. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1454–1461, September, 2006.