卤代烷第一电离能的变化规律研究

卤代烷RX的第一电离能[WTBX]Ip的变化规律可用如下方程表示：Ip(eV)=3.3380+0.7344Ep(X)+2.7424[(1/ax)qx-1.4302PEI其中,Ep(X)、x分别为卤素原子最外层P电子的电离能和原子极化度,qx是卤代烷RX分子中卤原子X所带的部分电荷,PEI是RX分子中烷基R的极化效应指数。研究结果表明用上式估算卤代烷的第一电离能与实验值符合的比较好。     

单取代烷烃电离能的估算

根据量子力学微扰理论,将单官能团取代甲烷(MeZ)和单官能团取代烷烃(RZ)分别当作未微扰体系和同扰体系,则后者的第一电离能Ip~1~(~R~Z~)可由下式估算：Ip~1~(~R~Z~)＝Ip~1~(~M~e~Z~)＋7.1702△qz－1.3949△PEI。其中Ip~1~(~M~e~Z~)为取代甲烷的第一电离能,△qz为RZ和MeZ分子中Z上面的部分电荷之差,△PEI为基团R和Me的极化效应指数(PEI)之差。对10类单官能团取代烷烃的61个化合物计算结果表明,计算值和实验值之间的平均相对误差仅为0.20%。     

胺、醇和醚类化合物电离能的估算

脂肪族胺、醇、醚、硫醇和硫醚的第一电离能Ip与N、O、S原子的电负性X~Z^O、分子中N、O、S原子的部分电荷q~z以及烷基的极化效应指数PEI的关系可以表示为:Ip(eV)=4.4851+3.0727X~Z~O+7.1702q~z-1.3949∑PEI上式较好地表达了脂肪族胺、醇、醚、硫醇和硫醚的第一电离能变化的共同规律。     

烷烃与羟基自由基反应速率常数的估算

Activation energy of hydroxyl radical OH reacting with alkanes was estimated from the quantitative relation between the bond dissociation energy (BDE) of Ri-H and the polarizability effect index (PEI) of alkyl radical Ri. Preexponential factor A in Arrhenius expression quantitatively was related to the topological steric effect index (TSEI) of alkyl radical Ri. The research results show that three parameters, PEI, TSEI and temperature T, can be used to quantify the activity of hydroxyl radical reacting with primary, secondary and tertiary carbon hydrogen bonds in alkane. The expression can accuratly evaluate the activity of C-H bonds. Moreover, the PEI and TSEI of alkyl radical Ri can be correlated quantitatively with the reaction absolute and relative rates of alkanes and cyclanes with hydroxyl radicals at various temperatures. The predicted rate constants are in good agreement with the experimental ones.     

On molecular polarizability. 4. Evaluation of the ionization potential for alkanes and alkenes with polarizability

To express the influence of polarizability effect on ionization potential (Ip), the Geometric Mean Polarizability Effect Index (GMPEI) and Geometric Mean Polarizability Effect Index of pi Bond (GMPEIpi) were proposed for alkanes and alkenes, respectively. Taking a few of the compounds as a model, we obtained the correlation equations between the experimental Ip and GMPEI or GMPEI pi and then, with the obtained equations, we evaluated the Ip for the title compounds. The estimated Ip values by this work are in good agreement with the measured ones. Furthermore, the ab initio (#HF/6-31G** OPT, Gaussian 98 program) and semiempirical (AM1) Ip computation are finished, and other topological index correlations with the Ip of alkane are discussed.     

分子拓扑学方法估算多环芳香烃类化合物的电离能

It was found that the ionization potentials (Ip) is related with the polarizability effect index (PEI) for the fragments CH, CH2, and CH3 of polycyclic aromatic hydrocarbon. Therefore a kind of adjacent matrix of molecular graph was constructed, in which the characteristics of the diagonal elements were expressed with the PEI of the fragments C, CH, CH2, and CH3 in molecular graph. The research result shows that there is a good correlation between the eigenvalue of the matrix and the ionization potential for the title compounds: Ipi=4.756+2.870OMOi, R=0.9853, s=0.1765, n=446. This new calculation method has only one parameter for calculating ionization potentials of polycyclic aromatic hydrocarbon. The obtained result shows that the topologic molecular method is convenient and reliable.     

脂肪族胺、醇、醚气相碱性的模型研究

以烷基极化效应指数(PEI)和分子中亲合原子的平衡电负性(XE)及亲合原子的Pauling电负性(X)为基本参数,研究了脂肪族胺、醇、醚的气相碱性(PA)的共同变化规律。结果表明,脂肪族胺、醇、醚的气相碱性可用下列通式来定量描述：PA(KJ/mol)=2468.6730+557.3172∑PEI-551.4261XE-1230.5770(∑PEI/XE)-111.5537X用上式预测了64种化合物的气相碱性,平均绝对相对误差仅为0.34%,预测值与文献值的偏差完全落在实验误差的范围内。     

取代基效应定量研究新进展

综述了最近20多年有机化学取代基效应定量研究所取得的诸多新进展.主要内容包括：（1）电负性均衡原理得到普遍认同并用于计算分子中电荷分布和基团的诱导效应,分子电负性计算方法在几何平均法、调和平均法、加权平均法的基础上又提出了价电子均衡方法,进一步扩展了电负性均衡原理的应用范围.（2）试剂亲电、亲核能力的实验测定,提出了以二苯甲基正离子和醌甲基化合物等作为参考化合物的标定方法,其研究范围被扩展到气相条件、有机金属反应和自由基体系,得到一系列试剂的亲核参数N和亲电参数E.理论上提出亲电性指数和亲核性指数的概念及其定量计算公式,并对实验测定参数和理论计算指数之间的关系进行了深入研究.（3）极化效应参数从最初的经验方法,进而采用量子化学方法计算,再用统计方法提出了烷基极化效应指数PEI和基团极化效应参数PEIX,被广泛用于解释和估算有机化合物的气相酸碱性、电离能、生成焓、键能、反应速率、水溶解性和色谱保留值.（4）直接由取代苯的紫外光谱吸收能量计算得到的取代基激发态参数exCC,不同于取代基在分子处于基态的极性参数和自由基状态下的自旋离域效应参数,该参数用于对位二取代苯、取代二苯乙烯、二取代氮苄叉苯胺等多类有机化合物紫外光谱的定量相关,结果良好.（5）立体屏蔽效应的提出区分了传统的三种立体效应.在羰基与亲核试剂加成反应立体选择性定量表示,提出了立体选择性指数Ci;在表示基团对反应中心表面积屏蔽的定量提出了屏蔽参数SR,进一步基于反应中心体积被屏蔽的角度提出了拓扑立体效应指数TSEI,这些参数在分子内二面角、反应的立体选择性、烯烃和烷基苯的生成焓、咪唑离子液体的酸性以及烷烃与羟基自由基的反应速率等方面得到良好的应用.此外,论文还对有机化学取代基效应定量研究中值得进一步深入探索的领域和问题提出了建议和展望.     

Rapid empirical calculation of the first (n or π) ionization potential of organic molecules

The first ionization potential of an organic molecule containing electrons in nonbonding or π-type molecular orbitals can rapidly be calculated using parameters describing physical and chemical effects. These parameters include effective polarizability, resonance stabilization of a cation, π- and σ-charges, and electronegativity and are directly calculated from the structure of the compound. Correlation analyses with the first ionization potentials were carried out on various data sets classified into five groups to cover a wide range of organic molecules. The equations thus obtained were integrated into a system that automatically calculates the ionization potential of an organic compound from a connection table as obtained by a graphic input program. © 1993 John Wiley & Sons, Inc.     

吲哚酚衍生物的结构——式电位关系及电氧化机理

以半经验分子轨道方法计算吲哚酚衍生物的分子结构参数.以主因子分析法和多元线性回归法研究了吲哚酚衍生物的式电位与其分子结构参数间的关系.研究发现,在所选择的19个分子结构参数中,双中心电子交换能(E     

Recent progress in quantifying substituent effects

This paper summarizes significant progress in quantifying organic substituent effects in the last 20 years. The main content is as follows: (1) The principle of electronegativity equalization has gained wide acceptance, and has been used to calculate the intramolecular charge distribution and inductive effect of groups. A valence electrons equalization method was proposed to compute the molecular electronegativity on the basis of geometric mean method, harmonic mean method, and weighted mean method. This new calculation method further extended the application of the principle of electronegativity equalization. (2) A scale method was established for experimentally determining the electrophilic and nucleophilic ability of reagents, in which benzhydryliumions and quinone methides were taken as the reference compounds, and the research field was extended to the gas phase conditions, organometallic reaction and radicals system. Moreover, the nucleophilicity parameters N and electrophilicity parameters E for a series of reagents were obtained. The definition and quantitative expression of electrophilicity index and nucleophilicity index were proposed theoretically, and the correlation between the parameters from experimental determination and the indexes from theoretical calculation was also investigated. (3) The polarizability effect parameter was initially calculated by empirical method and further developed by quantum chemistry method. Recently, the polarizability effect index of alkyl (PEI) and groups (PEI X ) were proposed by statistical method, and got wide applications in explaining and estimating gas-phase acidity and basicity, ionization energy, enthalpy of formation, bond energy, reaction rate, water solubility and chromatographic retention for organic compounds. (4) The excited-state substituent constant ex CC obtained directly from the UV absorption energy data of substituted benzenes, is different from the polar constants in molecular ground state and the radical spin-delocalization effects constants in molecular radical state. The proposed constant ex CC correlated well with the UV absorption energy of many kinds of organic compounds, such as 1,4-disubstituted benzenes, substituted stilbenes, and disubstituted N-benzylidenebenzenamine. (5) The establishment of the steric shielding effect distinguished the three traditional steric effects. The stereoselectivity index C i was proposed to quantify the stereoselectivity of the addition reaction of carbonyl with nucleophilic reagent. The shielding parameter S R was defined to quantitatively express the specific surface of the reaction center screened by a group. Further, the Topological Steric Effect Index (TSEI) of a group was proposed on the basis of the relative specific volume of reaction center screened by the atoms of substituents. These parameters can be applied in estimating the intramolecular dihedral angles, stereoselectivity of reaction, enthalpies of formation of alkenes and alkylbenzene, acidity of substitutedimidazolium ionic liquid, and the reaction rate of alkane and hydroxyl radical. In addition, some suggestions and prospects for further studies on quantifying the organic substituent effects were presented in this paper.     

共轭烯烃的共轭极化势

Based on the conjugated polarization theory,it is expressed as the conjugated polarizability potential （CPP）that the discrepancy between the average electrostatic energy of dipolar state and the electrostatic energy of non-polar state in the conjugated polarizability procedure for the conjugated alkenes. The correlation between CPP and the energy of ultraviolet absorption maximum,and the correlation between the energy of frontier molecular orbital obtained by ab initio calculation of quantum chemistry and the energy of ultraviolet absorption maximum have been carried out for the conjugated alkenes. Both correlation equations show a similar estimated precision. Further, the contribution of alkyl polarizability effect to the stability of dipolar state for the alkyl substituted alkenes with the effective polarizability effect index（PEI（ef））was quantified. Relating the above two parameters CPP and PEI（ef）to the energy of ultraviolet absorption maximum of the substituted alkenes in a two-parameter expression with a good prediction ability was obtained:v=1.1746+5.0187CPP-0.43204PEI （ef）,R=0.9995,s=0.0403,F=10853.28,n=23. The investigated results also indicate that it is less effective to reduce the energy of ultraviolet absorption maximum by means of increasing the alkyl substituent groups than lengthening the conjugated backbone chain in the conjugated alkenes.     

有效碳链长度与脂肪醇的沸点

脂肪醇沸点(b.p.)变化规律可用下述关系式表示:ln(800.386-T~b)=6.64919-2.94828×10^-^2N~E~C~C+0.150955ΔPEI。式中N~E~C~C为醇中烷基的有效碳链长度, ΔPEI是具有相同碳原子数目的支链烷基与直链烷基的极化效应指数的差值, 它表示羟基对醇的沸点的影响。     

单取代烷烃定量结构-保留相关研究中的分子结构分区处理方法

将单取代烷烃RX(X=卤素,OH,SH,NH2等)分子结构分为两个区域(R和X)来提取分子结构参数,从三方面影响因素(烷基R、取代基X、R与X的相互作用)来定量关联RX的气相色谱保留时间。实验测定了37种单取代烷烃RX的气相色谱保留时间,并以键连接矩阵特征根之和EVM、烷基极化效应指数PEI、取代基质量分数w和取代基上氢原子所带部分正电荷ΔNH 4个参数为变量,建立了定量结构-保留相关模型。该模型具有良好的预测能力和外推能力,对醇在不同色谱柱上的保留指数进行了预测,结果与测定值符合得较好。     

The importance of the external potential on group electronegativity

The electronegativity of groups placed in a molecular environment is obtained using CCSD calculations of the electron affinity and ionization energy. A point charge model is used as an approximation of the molecular environment. The electronegativity values obtained in the presence of a point charge model are compared to the isolated group property to estimate the importance of the external potential on the group's electronegativity. The validity of the "group in molecule" electronegativities is verified by comparing EEM (electronegativity equalization method) charge transfer values to the explicitly calculated natural population analysis (NPA) ones, as well as by comparing the variation in electronegativity between the isolated functional group and the functional group in the presence of a modeled environment with the variation based on a perturbation expansion of the chemical potential.     

QSPR study on GC relative retention time of organic pesticides on different chromatographic columns

In the present study, Lu index and distance-based atom type topological index (DAI) previously developed in our team, were introduced and combined with molecular electronegativity chi ep to characterize quantitative structure-property relationship of GC relative retention time (RRT) for several types of structurally diverse organic pesticides on the four kinds of chromatographic columns. Using multiple linear regression technique, four several-variable models are obtained with the estimations correlation coefficient (R(2)) being between 0.9655 and 0.9285, and the correlation coefficient (R(2)cv) in the leave-one-out cross-validation procedure are between 0.9560 and 0.9143, respectively. The results in this study indicate that the three topological indices Lu index, DAI, and molecular electronegativity chi ep can predict the gas chromatographic RRT of organic pesticides with diverse hetero-atoms.     

Transition state for alkyl group hydrogenation on Pt(111)

Substituent effects have been used to probe the characteristics of the transition state to hydrogenation of alkyl groups on the Pt(111) surface. Eight different alkyl and fluoroalkyl groups have been formed on the Pt(111) surface by dissociative adsorption of their respective alkyl and fluoroalkyl iodides. Coadsorption of hydrogen and alkyl groups, followed by heating of the surface, results in hydrogenation of the alkyl groups to form alkanes, which then desorb into the gas phase. Temperature-programmed reaction spectroscopy was used to measure the barriers to hydrogenation, DeltaE(H)(double dagger), which are dependent on the size of the alkyl group (polarizability) and the degree of fluorination (field effect). This example is one of only two surface reactions for which the influence of the substituents on DeltaE(H)(double dagger) has been correlated with both the field and the polarizability substituent constants of the alkyl groups in the form of a linear free energy relationship. Increasing both the field and the polarizability constants of the alkyl groups increases the value of DeltaE(H)(double dagger). The substituent effects are quantified by a field reaction constant of rho(F) = 27 +/- 4 kJ/mol and a polarizability reaction constant of rho(alpha) = 19 +/- 3 kJ/mol. These suggest that the transition state for hydrogenation is slightly cationic with respect to the alkyl group on the Pt(111) surface, RC + H <--> {RC(delta+)...H}(double dagger).     

Born-Haber-Fajans cycle generalized: linear energy relation between molecules, crystals, and metals

Classical procedures to calculate ion-based lattice potential energies (U(POT)) assume formal integral charges on the structural units; consequently, poor results are anticipated when significant covalency is present. To generalize the procedures beyond strictly ionic solids, a method is needed for calculating (i) physically reasonable partial charges, delta, and (ii) well-defined and consistent asymptotic reference energies corresponding to the separated structural components. The problem is here treated for groups 1 and 11 monohalides and monohydrides, and for the alkali metal elements (with their metallic bonds), by using the valence-state atoms-in-molecules (VSAM) model of von Szentpály et al. (J. Phys. Chem. A 2001, 105, 9467). In this model, the Born-Haber-Fajans reference energy, U(POT), of free ions, M(+) and Y(-), is replaced by the energy of charged dissociation products, M(delta)(+) and Y(delta)(-), of equalized electronegativity. The partial atomic charge is obtained via the iso-electronegativity principle, and the asymptotic energy reference of separated free ions is lowered by the "ion demotion energy", IDE = -(1)/(2)(1 - delta(VS))(I(VS,M) - A(VS,Y)), where delta(VS) is the valence-state partial charge and (I(VS,M) - A(VS,Y)) is the difference between the valence-state ionization potential and electron affinity of the M and Y atoms producing the charged species. A very close linear relation (R = 0.994) is found between the molecular valence-state dissociation energy, D(VS), of the VSAM model, and our valence-state-based lattice potential energy, U(VS) = U(POT) - (1)/(2)(1 - delta(VS))(I(VS,M) - A(VS,Y)) = 1.230D(VS) + 86.4 kJ mol(-)(1). Predictions are given for the lattice energy of AuF, the coinage metal monohydrides, and the molecular dissociation energy, D(e), of AuI. The coinage metals (Cu, Ag, and Au) do not fit into this linear regression because d orbitals are strongly involved in their metallic bonding, while s orbitals dominate their homonuclear molecular bonding.