共查询到19条相似文献,搜索用时 125 毫秒
1.
分子价连接性指数中杂原子价点价计算新方法及应用 总被引:29,自引:0,他引:29
对分子价连接性指数中杂原子点价δ^v~i的计算方法进行了改进,提出了一种计算杂原子价点价δ^h~i的新方法,认为分子中某一杂原子i的价点价δ^h~i值不仅与它的价层电子数Z~i、最高主量子数n~i以及结合的氢原子数目h~i有关,还与它所在的族烽N~i、陷氢图中连接的其他原子的数目m~i以及杂化方式L~p有关。杂原子i的δ^h~i值与原子i的Pauling电负性具有相近的物理意义。用由δ^h~i构成的分子价连接性指数^nχ^h(n=0,1,2)研究了取代芳烃和烃衍生物的物理化学性质和生物活性,结果表明,^1χ^h比^1χ^v有显著的改善,计算值与实验值接近的程度更高。 相似文献
2.
3.
4.
硫醇的分子连接性指数与气相色谱保留值 总被引:1,自引:0,他引:1
硫醇的分子连接性指数与气相色谱保留值赵邦屯王利亚(洛阳师专化学系洛阳471022)关键词硫醇分子连接性指数气相色谱保留值中图分类号O657.71有机化合物的色谱保留行为与其结构之间的定量关系研究一直是物理化学、分析化学和生物化学的研究对象之一。长期以... 相似文献
5.
原子连接性指数与对镧系元素理化性质的预测 总被引:8,自引:1,他引:7
以原子为研究对象的原子连接性指数( mAt)被定义为:mAt=Σ(Ei×Ej×Ek×…)-0.5,E为价电子的能级值。其中:0At=Σ(Ei)-0.5, 1At=Σ 相似文献
6.
价连接性指数mX与有机污染物lgKsw的相关性 总被引:6,自引:0,他引:6
定义新的价连接性指数^mXA、^mXB用于有机污染物的定量结构-活性相关性研究中,发现^mX与138种6个系列的有机污染物的分配系数具有良好的线性关系,相关方程为:1gKsw=0.1342^0XA-0.1172^1XA 0.1191^0XB 0.0396^1XB1.6366,相关系数为0.9713。使用相关模型对1gKsw的估算结果,非常接近或优于文献方法。本法还具有计算简单,物理意义明确等优点. 相似文献
7.
烷基苯标准生成焓与分子价连接性指数mX*的关系 总被引:8,自引:0,他引:8
提出了一个计算不饱和烃分子中碳原子价点价δi^*的新方法,以δi^*为核心建构了分子价连接性指数mx*(M=0,1),并研究了烷基苯标推生成焓与mX*指数的相关性。结果表明,mX^*指数对烷基苯的结构选择性和性质相关性均优于mX^*指数和F’指数。以0Xn,1X1和碳原子数N为自变量的三元线性回归方程为:—ΔfHm=38.079^0X^n 5.0911X^* 954.991N-1501.639,该方程对烷基苯标推生成焓的预测结果相当准确。 相似文献
8.
9.
分子连接性指数与溶液吸附自由能的相关性 总被引:2,自引:0,他引:2
测定了硅胶自四氯化碳中吸附脂肪醇及活性炭自水中吸附芳香化合物的吸附等温线, 等温线均可用Langmuir方程描述。利用Langmuir参数计算了各体系的吸附标准自由能变化。计算了各种吸附质的分子连接性指数。各种分子的分子连接性指数与吸附标准自由能变化间有相关性, 并给出了相关方程, 同时作了初步的讨论。 相似文献
10.
原子配分参数、配分连接性指数及其应用 总被引:9,自引:0,他引:9
结构决定性质,性质反映结构,这是化学、生物学等学科的一条基本规律。因此,分子的微观结构与性质之间存在着密切关系。物质的理化性质、生物活性等数据的获取,迄今主要来自于实验。如能建立结构与性能之间的数量关系用以估算与预测分子的性质,这无疑是一项十分有意义的工作。拓扑指数法以其计算简单、准确性高、应用范围广而在上述领域中发挥重要作用犤1~4犦。拓扑指数是对分子结构进行的定量描述,使分子之间的结构差异定量化。自Wiener提出第一个拓扑指数(W)犤5犦以来,迄今已有200余种拓扑指数问世。其中一部分能够有效地… 相似文献
11.
Through modification of the delta values of the molecular connectivity indexes, and connecting the quantum chemistry with topology method effectively, the molecular connectivity indexes are converted into quantum-topology indexes. The modified indexes not only keep all information obtained from the original molecular connectivity method but also have their own virtue in application, and at the same time make up some disadvantages of the quantum and molecular connectivity methods. 相似文献
12.
A quantum chemical definition of valency proposed in Part I is used to calculate the valency of carbon, nitrogen, oxygen,
lithium, beryllium and boron in a number of compounds with the SINDO1 method. It is demonstrated that consistency of the basis
set is necessary for comparable results. The general features of valency and bonding in these molecules are discussed. The
π-electron concept of free valence is generalised to sigma systems and atoms in molecules are classified as subvalent, normal
or hypervalent. The relation between valency and natural hybrid occupancy is illustrated. The symmetry properties of natural
hybrid orbitals are discussed by means of group theory. A preliminary attempt is made to relate covalency and covalent reactivity.
Bond indices and the σ, π character of bonds are obtained by a suitable partitioning and projection of valency into bonding
and antibonding contributions.
Alexander von Humboldt Fellow 1982–83. 相似文献
13.
The effect of replacing the hydrogen atoms in thioformaldehyde by halogen atoms (F, Cl) on the ionisation potential of the
non-bonding electron is analysed by using the Hellman-Feynman theorem, regarding the nuclear charge of the substituent as
a parameter in the many-electron Hamiltonian. The trends predicted by our theory nicely agree with the relevant ionisation
potentials computed either by applying Koopmans’ theorem or by the ΔE
SCF method. For the carbonyls, avaible experimental data indicate the reliability of our prediction. 相似文献
14.
We present a novel matrix representation of graphs based on the count of equal‐distance common vertices to each pair of vertices in a graph. The element (i, j) of this matrix is defined as the number of vertices at the same distance from vertices (i, j). As illustrated on smaller alkanes, these novel matrices are very sensitive to molecular branching and the distribution of vertices in a graph. In particular, we show that ordered row sums of these novel matrices can facilitate solving graph isomorphism for acyclic graphs. This has been illustrated on all undecane isomers C11H24 having the same path counts (total of 25 molecules), on pair of graphs on 18 vertices having the same distance degree sequences (Slater's graphs), as well as two graphs on 21 vertices having identical several topological indices derived from information on distances between vertices. © 2013 Wiley Periodicals, Inc. 相似文献
15.
The second version of the program package AIM2000 is presented. AIM2000 makes use of the well established theory of atoms in molecules. AIM2000 analyzes the molecular structure and calculates properties of atoms in molecules as well as properties of interatomic surfaces. The program has an interactive, context-sensitive help component and extensive 2D and 3D visualization components. 相似文献
16.
改进的连接性指数用于链烷烃热力学性质与沸点研究 总被引:4,自引:1,他引:4
基于邻接矩阵和原子特征值qi,建立邻接指数^mQ,用^0Qr,^1Q与85种链烷烃的标准生成焓、标准生成自由能、标准熵和沸点关联,相关系数均在0.99以上,属于良好模型,与Randic指数的^mX比较,^mQ具有良好的性质相关性。 相似文献
17.
V. D. Ignatiev 《Journal of Structural Chemistry》2005,46(4):744-751
A new system of atomic radii for the elements up to barium inclusive is constructed. Values of the radii are chosen so as the dependence between the dissociation energy of diatomic homonuclear molecules and a depth of atom overlapping is monotonous, and the scatter of data is minimal. The depth of overlapping is calculated as a difference between the sum of atomic radii and an experimental interatomic distance. Conclusions are made that: the radii of free atoms and ions are determined by the value of the electron density equal to 0.01 au; they considerably change in molecules and crystals only as a result of the charge transfer from cation to anion; covalent bonding is well described by the overlapping of free atoms (ions), confined by the surface of the given radius, and its energy depends upon the depth of overlapping of valence electron densities of atoms. A method of overlapping atoms is proposed for the approximate estimation of ionic sizes and charges in bound systems. 相似文献
18.
The conformational preferences of two model compounds for the O--CH2--O anomeric unit: methanediol and dimethoxymethane analyzed within the framework of the QTAIM theory provide a new interpretation of the anomeric effect. The characteristic stabilization of the gauche conformers of these compounds is accompanied by a progressive reduction of the electron population of the hydrogens of the central methylene as the number of their gauche interactions to lone pairs rises. The electron population removed from these atoms during the conformational change is gained in the gauche conformers by atoms of larger atomic number, which results in a more negative molecular energy. Also, the variations displayed by atomic populations and the QTAIM delocalization indexes are not keeping in line with the hyperconjugative model of the anomeric effect. 相似文献