Calculation of retention indices by molecular topology. Chlorinated benzenes

A comparative study was undertaken to test the ability of several different topological indices to predict the retention indices of chlorinated benzenes on polar and non-polar stationary phases using both correlation coefficients and correctly predicted elution sequences as criteria of fit. The test was performed on three topological indices: connectivity indices, Wiener numbers, and Balaban indices. The regression analyses showed that the molecular connectivity model predicted the retention indices of chlorinated benzenes more successfully than either Wiener numbers or Balaban indices. The results also demonstrated that the major structural property controlling chromatographic behavior was the size of the chlorinated benzene. In addition, the use of the new non-empirical heteroatom parameterization scheme in the calculation of Wiener numbers and Balaban indices was successfully tested for the first time.     

芳烃化合物结构参数与色谱保留值关系的探讨

在自制的十六烷基磷酸锡固定相、甲醇－水流动相的色谱体系中，建立了烷基取代苯、不同数目的甲基取代苯、稠环芳烃等溶质的色谱保留值与其分子结构参数（分子连接性指数、范德华体积）之间的回归方程，并用疏溶剂理论予以解释，同时探讨了结构参数与色谱热力学的关系。     

HPLC separations of some substituted benzenes on thermally treated clays

HPLC columns were packed with quasi-spherical montmorillonite particles which were prepared by spray-drying and then thermally treated. Separations of phenylureas (linuron, neburon, diuron and monuron), phosphothioate phenyl esters (parathion, methyl parathion and paraoxon) and other smaller substituted benzenes were performed on the columns. The relative retention of the substituted phenyl pesticides demonstrated the important role polar substituents play in the eluate-surface interactions and the strong influence of steric factors on these interactions. The retention of the pesticides decreased sharply as the polarity of the mobile phase increased. The retention of the smaller substituted benzenes showed a similar trend, but for these smaller molecules this trend was partially counteracted by the increased accessibility of interlayer spaces due to swelling as the polarity of the liquid phase increased. The role of the exchangeable cation (Na⁺, Co²⁺ and Cu²⁺) in the adsorption was found to be complex. The cations determine both the strength of interaction, which increases with the valence of the cation, and the accessibility of the interlayer adsorption sites which decreased with the valence.     

氯代苯、醇、酯气相色谱保留指数与其正辛醇-水分配系数相关性

报道了氯代苯、醇、酯类化合物气相色谱保留指数与其正辛醇－水分配系数的相关性，研究了固定相极性对相关性影响，得出弱极性柱上测得的化合物保留指数能更准确地预测其分配系数，从而为极性化合物氯代苯、醇、酯分配系数的测定和预测提供了一种简便易行的新方法。     

Incorporation of solvent effects into density functional predictions of molecular polarizabilities and hyperpolarizabilities

A study of the effect of the field, the basis set, the functional, and the cavity size on molecular polarizabilities and hyperpolarizabilities of substituted benzenes in liquid or solution is reported. The calculations have been performed using the density functional theory (DFT) within the conductor‐like screening model (COSMO). The optimized computational parameters are adopted to calculate molecular polarizabilities and hyperpolarizabilities of substituted benzenes in liquid or solution. The results show good agreement with the experimental values. From comparison of the different theoretical results, it is found that at the same theoretical level, the selection of the different solvation models may play an important role in the calculations of molecular solvation polarizability, and using the same solvation model, the effects of the different theoretical methods are relatively small. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001     

Study on the relationship between retention behavior and molecular structure parameters of substituted benzene derivatives in RPLC

Summary A quantitative structure-retention model derived from the concept of hydrophobic substituent constant () and the total solubility parameter (_T) has been established. It has been used to predict successfully the retention behavior of a number of solutes on various columns in several different eluents. The experimental results indicate that the model can be employed for the prediction of retention of substituted benzenes in a large volume fraction range of mobile phase. In addition, the physical meaning of the sign and the influence of the coefficients of the model on the retention process had been discussed together with the dependence of these coefficients on the composition of mobile phase.     

烷基苯凝聚型性能与分子结构之间关系的探讨

本文根据分子结构的特点，用图论方法探讨了烷基苯的凝聚型性能与其分子结构之间的关系，用四个结构信息指数描述了分子的大小和形状、烷基的大小和数目及烷基在苯环上的位置对凝聚型性能的影响，据此提出一个具有一定结构基础的定量关系式。应用这一定量关系，不仅能够预测烷基苯的沸点、密度和折光指数，而且有助于揭示物质结构与性能之间的奥秘。计算结果表明计算值与实验值的一致性令人满意。     

Studies on ferrocene derivatives. Part XVI: steric effects on the ligand exchange reactions of alkylferrocenes

Ligand exchange reactions of alkylferrocenes with substituted benzenes were carried out. The steric effects of substituents on the reaction were almost equal irrespective of the site of the substituents, either on the cyclopentadienyl – or the benzene ring. For benzene ring substituents, the effect on the symmetrically substituted benzenes was greater than that on the unsymmetrically substituted benzenes.     

取代苯体系的二阶非线性光学性质:动力学李代数方法

提出了一种动力学李代数方法来研究取代苯体系的非线性光学性质. 对于给定的PPP模型(Pariser-Parr-Pople)哈密顿量, 生成了一个动力学李代数. 依据这些代数元构造出演化算子作为群参数的函数, 通过求解一组非线性微分方程能够得到这些群参数. 再按照统计力学中的密度算子公式给出取代苯分子体系偶极矩的统计平均值. 于是导出二阶极化率的表达式. 与其他量子力学计算结果比较, 表明这种动力学李代数方法在预言有机共轭分子的非线性光学性质上同样有用.     

THE CALCULATIOM OF CHEMXCAL SHIFTS IN SUBSTITOTED PYRIDINES

<正> The principle and method for the calculation of chemical shifts of substituted benzenes have been extended to calculation of the cheiiical shifts in substituted pyridines. We have set up a series of empirical parameters for calculation of the chemical shifts. The calculated results of 154 δ values frou 54 compounds show that the standard deviation between the calculated and the experimental values is 0 . 09 ppm. The combination of the coupling constants can be used to provide a criterion for the determination of molecular structure in substituted pyridines and to assign NMR parameters for the experiment of proton simulated spectra of substituted pyridines.     

The quadrupole moment of substituted cyclopentadienyl anions

Previous work in our group on the cation binding of substituted cyclopentadienyl anions (Cp) showed the curious result that Cp traceless electric quadrupole moments (Θ(zz)) are almost all positive. Probing this issue further here we show that substituted Cp Θ(zz) values are always significantly more positive than the analogous substituted benzenes. Given the nature of aromatic Θ(zz) values, this is the opposite of what would be predicted. Furthermore, we show that the quadrupole moments of Cp anions do not behave as one would expect based on Cp substitutions. Unlike the quadrupole moments of substituted benzenes, which generally become more negative with the addition of electron-donating groups and more positive with the addition of electron-withdrawing groups, Cp quadrupole moments become more positive when any substituent is added, regardless of the electron-donating/withdrawing nature of the substituent. To explain these results we propose a model where the anionic Cp π-electron density repels the substituent electron density toward the molecular periphery and AIM calculations support this view.     

化合物色谱保留参数与其三维结构关系的研究

利用比较分子场分析(CoMFA)方法,建立了烷基取代苯、氯代苯、多环芳烃和二硝基取代芳烃等4类结构相近的化合物在甲醇／水体系中反相C18柱上的保留参数a,c值与其三维结构之间关系的定量模型。前3类化合物所得到的3个模型的交叉验证相关系数q2均大于0.5,其中针对烷基取代苯、氯代苯所建立的两个模型的非交叉验证相关系数r2大于0.995,表明模型具有较好的预测能力。该研究结果对进一步开展化合物液相色谱保留参数与其三维结构关系的研究提供了思路和方法。     

Synthesis of substituted benzenes and phenols by ring-closing olefin metathesis

New synthetic approaches to substituted aromatic compounds are reported. Ring-closing olefin metathesis (RCM)/dehydration and RCM/tautomerization are the key processes in the synthesis of substituted benzenes 3 and phenols 6, respectively. Readily accessible 1,5,7-trien-4-ols 7, which are the precursors of benzenes, were prepared from beta-halo-alpha,beta-unsaturated aldehydes 11 or beta-halo-alpha,beta-unsaturated esters 19 by utilizing reliable transformations in which cross-coupling with vinylic metal reagents 12 and allylation with allylic metal reagents 13 were employed as carbon-carbon bond forming reactions. RCM of 7, followed by dehydration, afforded a wide variety of substituted benzenes 3. In addition, RCM of 1,5,7-trien-4-ones 9, which were prepared by oxidation of 7, furnished various substituted phenols 6 by automatic tautomerization.     

One‐Pot Synthesis of Polysubstituted Benzenes through a N,N‐dimethyl‐4‐aminopyridine (DMAP)‐Catalyzed [4+2] Benzannulation of 1,3‐Bis(sulfonyl)butadienes and γ‐Substituted Allenoates

A new strategy for the one‐pot synthesis of polysubstituted benzenes through a N,N‐dimethyl‐4‐aminopyridine (DMAP)‐catalyzed [4+2] benzannulation from readily prepared 1,3‐bis(sulfonyl)butadienes and γ‐substituted allenoates is described. This method provides a facile, metal‐free and general route to highly substituted benzenes under mild conditions in moderate‐to‐good yields with complete regioselectivity.     

An interpretation of 1H and 13C chemical shifts in substituted benzenes on the basis of M.O. charge densities

The results of an MOLCAO calculation on both σ and π electron systems of several substituted benzenes are reported. The charge densities obtained reproduce the dipole moments of the molecules examined, provided that substituents with strong mesomeric effects are not present. It is shown that there is a satisfactory agreement between ¹³C and ¹H chemical shifts and the trend of total charge densities for all positions of substituted benzenes.     

Monte Carlo simulations of the hydration of substituted benzenes with OPLS potential functions

Intermolecular potential functions have been developed for use in computer simulations of substituted benzenes. Previously reported optimized potentials for liquid simulations (OPLS) for benzene and organic functional groups were merged and tested by computing free energies of hydration for toluene, p-xylene, phenol, anisole, benzonitrile, p-cresol, hydroquinone, and p-dicyanobenzene. The calculations featured Monte Carlo simulations at 25°C and 1 atm with statistical perturbation theory. The average difference between the computed results and experimental data for the absolute free energies of hydration is 0.5 kcal/mol. The AM1-SM2 method is also found to perform well in predicting the free energies of hydration for the substituted benzenes. In addition, the Monte Carlo simulations provided details on the hydration of the substituted benzenes, in particular for the solute–water hydrogen bonding. © 1993 John Wiley & Sons, Inc.     

Molecular surface electrostatic potentials in the analysis of non-hydrogen-bonding noncovalent interactions

Electrostatic potentials computed on molecular surfaces are used to analyse some noncovalent interactions that are not in the category of hydrogen bonding, e.g. “halogen bonding”. The systems examined include halogenated methanes, substituted benzenes,s-tetrazine and l,3-bisphenylurea. The data were obtained byab initio SCF calculations.