多环芳烃气相色谱保留指数预测与估算

按碳原子的键合特性对其进行分类,定义并计算了多环芳烃的分子距边矢量（VMDE）,在此基础上对94种多环芳烃的气相色谱保留指数（RI）进行定量相关性研究,发现色谱保留指数与分子距边矢量之间存在良好的线性关系,RI．a b VMDE,n=94,相关系数r=0.9946,均方根RMS＝8．15,同时,还进行了留一法交互检验结果为r=0.9928,RMS=9.35。表明了新分子距边矢量的合理性和有效性,可成功地用于多环芳烃气相色谱保留指数的估计与预测,有望在定量构效关系研究中获得广泛的运用。     

Computational Studies on the Reactivity of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment as toxic pollutants. In this study, quantum chemistry methods are used to study reactions of PAHs in both particle and gas phases. Seven theoretical methods are exploited to predict the reactive sites of 15 PAHs in the particle phase. Among these methods, the performance of the condensed Fukui function (CFF) is optimum. The gas-phase reactions of eight PAHs are also investigated. Except for fluorene, CFF predicts correctly the gas-phase mono-nitro products for seven systems. The products of fluorene predicted by CFF are 1-nitrofluorene and 3-nitrofluorene, which is however inconsistent with the experimental results. Transition state theory is then used to investigate the reaction mechanism of fluorene. Calculated rate constants for 3-nitrofluorene and 2-nitrofluorene formation are much bigger than that for 1-nitrofluorene formation, which is in agreement with the experimental results.     

Discrimination and ordering of chemical structures by the number of walks

The use of the number of walks for the discrimination of graphs representing chemical structures is discussed. A highly selective graph-theoretical index based on the number of walks is defined. The index values were calculated for 661 acyclic and 376 cyclic structures. The selectivity of the new index is compared to that of some of the most selective previously defined indexes. The ordering of structures induced by the value of the index is also considered.Presented in part at the 7th International Conference on Computers in Chemical Research and Education, held in Garmisch-Partenkirchen, Germany, June 10–14, 1985     

Analysis of Complex Mixtures of Aromatic Hydrocarbons. Relations between Retention Index and Molecular Structure

Abstract

Relationships between Kovats indices on nonpolar stationary phases and the structure of alkyl- and alkenylbenzenes, defined by the molecular connectivity or connectivity index, have been established.

Almost all components of aromatic naphthas are included in the different linear equations which relate both empirical indices. The constant terms of the straight lines depend on the nature and position of the substituents in the benzene ring. Substituents in para position do not influence each other, allowing the study of the effect of its nature on the ratio δI/Δχ

Equations for different series of compounds, including n-alkyl- and 1,4-di-n-alkylbenzene homologous series, are calculated in order to support its identification in aromatic naphthas.     

分子连接性指数~mX~z与不饱和链烃沸点的定量关系研究

提出了一个计算分子中成键原子点价δ_i~z的新方法，以δ_i~z为基础建构的 新的分子连接性指数为~mX~z = ∑(δ_i~z·δ_j~z·δ_k~z……)~(-0.5)，其中 ~0X~z，~1X~z的定义为：~0X~z = ∑(δ_i~z)~(-0.5), ~1X~z = ∑(δ_i~z·δ _j~z)~(-0.5)，并研究了~0X~z,~1X~z与不饱和链烃沸点的相关性。结果表明，该 拓扑指数具有良好的结构-性质相关性。以~0X~z,~1X~z和碳原子数N为结构参数分 别与80个单烃烃、39个单炔烃、169个不饱和链烃（包括烷烃、炔烃及烯炔）的沸 点进行关联所得到的三元回归方程为：单烯烃，log(779.13-bp) = 2.822433-0. 0133346 ~0X~z - 0.0638379 ~1X~2 + 0.0111229N (R = 0.99895, F = 202783. 65, s = 3.36)；单炔烃，log(797.47-bp) = 2.809912-0.0108374~0X~z - 0. 0864540 ~1X~z + 0.0233028N (R = 0.99935, F = 98657.36, s = 3.65);不饱和 链烃，log(741.26-bp) = 2.779526 + 0.0194388~0X~z - 0.0519158~1X~z - 0. 0211047N (R = 0.99467, F = 82387.26, s = 7.74)。应用这些经验公式可以预测 不饱和链烃的沸点。     

Degradation of Polycyclic Aromatic Hydrocarbons by <Emphasis Type="Italic">Rigidoporus lignosus</Emphasis> and its Laccase in the Presence of Redox Mediators

The metabolism of polycyclic aromatic hydrocarbons (PAHs) was studied in vivo and in vitro in systems consisting of Rigidoporus lignosus and its laccase, in the presence of so-called “mediator” compounds. The static culture of the native fungal strain was able to metabolize anthracene and 2-methylanthracene, but not 9-nitroanthracene. The addition of redox mediators 2,2’-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1-hydroxybenzotriazole (HBT) or violuric acid (VA) led to a significant increase in the degradation of substrates. The oxidation of PAHs was not significant when purified laccase was used without the addition of mediators. The addition of these compounds increased the oxidation of all substrates by approximately 70–80% after 72 h of incubation. The degradation rate was highest for 2-methylanthracene in the presence of VA.     

分子电性距离矢量用于稠环芳烃液相色谱保留值的QSPR研究

采用分子电性距离矢量(Molecular Electronegativity Distance Vector,MEDV)表征稠环芳烃类化合物的分子结构.分别运用多元线性回归(Multiple Linear Regres-sion,MLR)和偏最小二乘回归(PLS)建立了稠环芳烃类化合物结构与其液相色谱(LC)保留值的定量结构一性质关系(QSPR)模型,同时采用内部及外部双重验证的办法对所建模型稳定性能进行分析和验证,建模计算值、留一法交互检验预测值和外部样本预测值的复相关系数Rcum、RLOO、Qext分别为0.9970,0.9950,0.9925(MLR);0.9930,0.9790,0.9917(PLS).结果表明,MEDV能较好地表征该类分子结构信息,所建QSPR模型具有良好的稳定性和预测能力.为稠环芳烃类化合物分离、纯化、检测等方法的建立,提供有效的理论依据.     

拓扑指数与烷烃色谱保留指数的定量相关研究

基于分子图论, 计算了64个链烷烃的一阶连接性指数(¹χ)和奇偶指数(OEI), 并对气相色谱保留指数进行定量结构-性质相关(QSPR)研究, 得到多元线性回归模型RI＝55.7631＋25.7317OEI＋111.4508¹χ (R²＝0.9960, RMS＝9.36, ARD＝1.02%). 交叉验证和预测结果表明, 所建立的QSPR模型具有良好的稳定性和预测能力. 与文献结果比较, 本文所用的参数少, 且计算简便.     

Herringbone Pattern and CH–π Bonding in the Crystal Architecture of Linear Polycyclic Aromatic Hydrocarbons

The herringbone pattern is a pervasive structural motive found in most molecular crystals involving aromatic compounds. A plot of the experimental sublimation enthalpies of members of increasing size of the acene, phenacene and p‐phenyl families versus the number of carbons uncovers a linear relationship between the two magnitudes, suggesting a major role of CH–π bonding. In this work we undertake the task of evaluating the relevance of the edge‐to‐face interaction (or CH–π bond) in the overall reticular energy of the crystal, to quantitatively assess the importance of this structural element. Following a heuristic approach, we considered the series of acenes, phenacenes and p‐phenyls and analyzed the edge‐to‐face interaction between the molecules as they occur in the experimental crystal network. Isolation of the relevant molecular dimers allows to incorporate some of the most sophisticated tools of quantum chemistry and get a reliable picture of the isolated bond. When compared to the experimental sublimation energy, our results are conclusive: this sole interaction is the largest contribution to the lattice energy, and definitively dictates the crystal architecture in all the studied cases. Elusive enough, the edge‐to‐face interaction is mainly dominated by correlation interactions, specifically in the form of dispersion and, to a less extent, of charge‐transfer terms. A suggestive picture of the bond has been obtained by displaying the differences in local electron densities calculated by either correlated or non‐correlated methods.     

Analysis of ;W and O NMR chemical shifts in polyoxometalates by extended Hückel mo calculations

The extended Hückel molecular orbital (EHMO) calculations have been carried out using cluster approach to polyoxo anions, i.e. calculations have been done for a single octahedron MO₆ of different symmetry and results have been used to analyze ¹⁸³ W and ¹⁷ O NMR spectra. Using five d→d* energy differences for the individual WO₆ the sum Σ1/ (E_d→E_d*) have been calculated and plotted against the ¹⁸³ W chemical shift (from +258 to −670 ppm) for corresponding type of tungsten atom and practically a linear correlation between two parameters have been observed. This points out the electronic nature of the ¹⁸³ W chemical shift. Similar correlation have been found for the ¹⁷O NMR chemical shifts (−90 to +800 ppm) when the plotted against product of the R⁻³ Σ1/ (E_p→E_p*) where the R⁻³ bond length of the corresponding W–O bond. Increasing the ¹⁸³ W nuclear magnetic shielding with the calculated electron population on tungsten atom for closely related anions has been observed, but no general tendency between δ and the calculated electronic charge if the symmetry of polyhedron is changed is expected.     

Electronic structure and physicochemical properties of s elements

In group-theoretical analysis of the point and permutable (cyclic) groups and molecular orbital study, we obtained analytical expressions for the electronic structure and physicochemical properties of the M_n clusters (n = 2, 3, 4, 5) of the M s elements (hydrogen; alkali, alkali earth, and noble metals) depending on the number of atoms n and the geometrical structure (one-, two-, and three-dimensional clusters of different conformations). The analytical form of the results allowed us to understand the physical sense of the structure and properties of these clusters and to predict certain regularities and effects.     

A convenient method for the preparation ofN-unsubstituted hydrazones of aromatic ketones and aldehydes

A general and useful method for the synthesis ofN-unsubstituted hydrazones of aromatic ketones and aldehydes in good yields was elaborated. The use of a large excess of hydrazine hydrate and catalytic amounts ofp-toluenesulfonic acid makes it possible to prepare the hydrazones without an admixture of the corresponding azine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2199, November, 1999.     

Magnetic Orbitals and Mechanisms of Exchange I. Direct Exchange

Summary. The problem of direct exchange is examined in the simplest cases (formal coupling of two electrons initially isolated and hydrogen molecule). Then we consider the general case of a solid characterized by weak overlaps between the atomic orbitals of first-nearest neighbours so that the involved electrons are quasi-localized. We recall the physical origin of spin-orbit coupling. Its influence on direct exchange allows one to revisit Hunds rules and to express phenomenological Hamiltonians describing anisotropic couplings as well as the antisymmetrical Dzialoshinski-Moriya coupling.     

A Computational Study of Conformers of 2-Thiaoxacyclohexane (1,2-Oxathiane)

Ab initio molecular orbital theory with the 6-31G(d), 6-31G(2d), 6-31+G(d), 6-31G(d,p), 6-31+G(d,p), and 6-311G(d,p) basis sets and the hybrid density functionals B3LYP, B3P86, and B3PW91 have been used to calculate the optimized geometries and relative energies of the chair, half-chair, sofa, twist, and boat structures of 2-thiaoxacyclohexane (1,2-oxathiane). The values of the energy difference (E, kcal/mol) between the chair and 3,6-twist structures of 1,2-oxathiane were 4.92 (HF), 4.73 (MP2), and 4.66 (DFT). The HF chair–twist energy difference (G _c–t ^o) for 1,2-oxathane was 5.16 kcal/mol. Intrinsic reaction coordinate (IRC) calculations connected a transition state (TS-A) between the chair conformation and the less stable 2,5-twist form and connected two transition states (TS-B, TS-C) between the chair conformation and the more stable 3,6-twist conformer. The DFT energy differences between the chair and TS-A, TS-B, and TS-C were 11.4, 10.8, and 12.6 kcal/mol, respectively. Hyperconjugative stereoelectronic interactions were observed in the chair (n _o and ) and 3,6-twist (n _S and n _O ) conformers of 1,2-oxathiane. The chair conformation of 1,2-oxthiane is 9.6 and 10.0 kcal/mol, respectively, less stable than the chair conformations of 3-thiaoxacyclohexane (1,3-oxathiane) and 4-thiaoxacyclohexane (1,4-oxathiane, thioxane).     

Investigation of the structure and energy of β-diketonates. XIV. Composition of overheated vapors and the molecular structure of monomeric yttrium tris-hexafluoroacetylacetonate Y(C5O2HF6)3

Simultaneous electron diffraction and mass spectrometry along with a quantum chemical (DFT/B3LYP) calculation are applied to study the molecular structure of yttrium tris-hexafluoroacetylacetonate Y(hfa)₃. The superheating of the vapor in a double two-temperature effusion cell shows that up to a temperature of ∼200°C ions containing from one to three metal atoms are formed, and the most intensive ion has the stoichiometry of (Y₂L₅)⁺ at a temperature below ∼120°C. The monomer starts to noticeably decompose at temperatures above 330°C.The electron diffraction patterns of monomers are obtained at T _exp = 208(5)°C. According to the results of theoretical and experimental investigations, Y(hfa)₃ molecule has D ₃-symmetry. The rotation angle of triangular O-O-O faces with respect to their position in the regular prism is equal to 14.4(1)°C. The values of internuclear distances and valence angles (r _h1-geometry) are: r(Y-O) = 2.259(6) Å, r(C-O) = 1.263(6) Å, r(C-C_r) = 1.413(4) Å, r(C-C_F) = 1.531(4) Å, r(C-F) = 1.344(3) Å, O-Y-O = 75.2(2)°, O-C-C_F = 113.8(2)°, C-C_F-F = 112.4(2)°. The results of quantum chemical calculations are well consistent with the experimental data. Original Russian Text Copyright ? 2007 by G. V. Girichev, V. V. Rybkin, N. V. Tverdova, S. A. Shlykov, N. P. Kuz’mina, and I. G. Zaitseva __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 48, No. 5, pp. 871–879, September–October, 2007.     

Bimodality of molecular mass distribution of polydienes obtained under the action of dilithium initiators in hydrocarbon media: the reasons,mathematical simulations,and their experimental testing

Bimodal molecular mass distribution (MWD) of polymers, obtained upon polymerization of hydrocarbon monomers in the nonpolar media under the action of dilithium initiators, is the consequence of separation of the reaction mixture into two phases. Bifunctional /living/ oligomers produce the insoluble sediment due to tetrameric association of the lithium active sites (the swollen gel-fraction). Part of the active site remains in the solution (the solfraction). Difference in the concentrations of the active sites into the phases leads to difference between the propagation rates of the /living/ chains and, as a result, to Bimodal MWD. The mathematical model of polymerization in the two-phase system is proposed. Satisfactory agreement between the calculations and the experiments is shown for butadiene polymerization in heptane under the action of 1,4-dilithiumpentane. Regulation of MWD up to the complete elimination of bimodality is possible via the programmed dosage of monomer and solvent into the reactor.     

Thermal Behaviour of the N-donor Adducts of Metal Saccharinates III. Imidazole saccharinates of Co(II), Ni(II) and Cd(II)

The complexes [M(HIm)₄(H₂O)₂](sac)₂ (M=Co, Ni) and [Cd(HIm)₂(sac)₂]₂ with saccharin (sac) and imidazole (HIm) were synthesized and their thermal (TG, DTG and DTA) behaviour in the interval from room temperature up to 1000°C in a static air atmosphere was investigated. Irrespectively of whether the deprotonated saccharinato residues are present as ligands or ions or both as ligands and ions, the anhydrous complexes regularly decompose in two stages. The thermal data of 16 saccharinato complexes (including the title compounds) were correlated with the respective structural data. The general thermal stability order of the saccharinato complexes can be represented as: Pb(II)<Zn(II)<Co(II)Ni(II)<Cd(II) (the stability of the Cu saccharinates depends on the particular compound) and is dictated by several structural factors, e.g. metal ionic radii, participation of the water in the coordination sphere of the metal and other structural characteristics. This revised version was published online in August 2006 with corrections to the Cover Date.