基于DFT和分子连接性指数方法研究醇类化合物的水溶解度和分配系数

将DFT方法计算得到的量化参数和分子连接性指数联合应用到60个醇类化合物的溶解度和辛醇/水分配系数的QSPR研究中,分别通过逐步回归得到具有显著统计意义的4个参数和5个参数的QSPR方程.以此4个参数和5个参数分别作为输入参数,采用BPNN,RBFNN方法建立了QSPR预测模型,使用Latin-partition交叉验证方法评价模型的预测能力.BPNN,RBFNN模型对溶解度预测的相关系数分别为0.993和0.994,而对辛醇/水分配系数预测的相关系数分别0.990和0.997,结果令人满意.     

A new equation for the thermal conductivity of organic compounds

This work presents a wide literature survey of the available data of the experimental thermal conductivity data of organic liquids. The experimental data were collected for 136 compounds belonging to the following families: refrigerants, alkanes, alkenes, aromatics, cycloalkanes, cycloalkenes, ethers, esters, ketones, carboxylic acids, and alcohols. The experimental data were regressed with the most reliable semi-empirical correlating methods existing in the literature and a reliable set of 4,584 experimental data was finally selected. The influence of several physical parameters on the thermal conductivity calculation is discussed and a new equation to represent the thermal conductivity of organic liquids at atmospheric pressure for temperatures below normal boiling point and at saturation for temperatures above the normal boiling point is presented. To minimize the deviation between the predictions and the experimental data and to find the optimal coefficients for the proposed equation, a statistical analysis was performed. The resulting equation is simple and is able to predict the thermal conductivities with low deviations for the major part of the collected data for the studied families.     

偏最小二乘和量子化学参数预测酯类物质的闪点

基于化合物定量结构与性质的关系,对其中88个酯类化合物进行了B3LYP/6-31G*水平上的结构优化,并在优化结构基础上进行了量子化学结构参数的计算。应用偏最小二乘(PLS)方法对酯类化合物闪点温度这个理化性质与量子化学参数进行了关联。结果表明,分子热力学自由能(ΔG)结合偶极距(μ)可以很好地表达酯类化合物闪点温度与量子化学参数间的定量关系。所建立的QSPR模型具有较强的稳健性和预测能力。     

Equation of state for square-well chain molecules with variable range. I: Application for pure substances

An equation of state (EOS) for square-well chain molecules with variable range developed on the basis of statistical mechanics for chemical association in our previous work is employed for the calculations of pVT properties and vapor–liquid equilibria (VLE) of pure non-associating fluids. The molecular parameters for 73 normal substances and 46 polymers are obtained from saturated vapor pressure and liquid molar volume data for normal fluids or pVT data for polymers. Linear relations are found for the molecular parameters of normal fluids with their molecular weight of homologous compounds. This indicates that the model parameters of homologous series, subsequently pVT and VLE, can be predicted when experimental data are not available. The predicted saturated vapor pressures and/or liquid volumes are satisfactory through the generalized model parameters. The calculated VLE and pVT for normal fluids and polymers by this EOS are compared with those from other engineering models, respectively.     

Making equation of state models predictive: Part 2: An improved PCP-SAFT equation of state

We use the PCP-SAFT equation of state, which is of the Van der Waals type and has a sound physical basis, to predict mixture properties, such as vapor–liquid and liquid–liquid equilibria, as well as excess enthalpies. We use molecular properties, such as dipole moment, quadrupole moment, polarizability and dispersion interaction coefficients, that have been determined quantum mechanically in Part I of this publication and adjust the remaining three pure compound parameters to pure compound data. We finally present a new combination rule for the dispersion energy parameter ? that is based on the quantum mechanically determined data. The predictions based on quantum mechanically determined pure compound properties along with the new combination rule show an improved performance compared to the original PCP-SAFT combination rule.     

A simple accurate model for prediction of flash point temperature of pure compounds

In this study, a simple three-parameter linear model is presented for estimation of flash point (FP) of pure compounds. The parameters of the model contain experimental normal boiling point of the compound and two chemical structure-based parameters. A comprehensive database of FPs containing 1472 pure compounds of various chemical structures was used to develop the model. The squared correlation coefficient and average absolute error of the model calculation results for all of the compounds presented in the database are evaluated to be 0.982 and 7.2?K, respectively.     

Solubility calculation of pharmaceutical compounds – A priori parameter estimation using quantum-chemistry

Pure-component electrostatic properties for pharmaceutical compounds and intermediates (xanthene, ibuprofen, aspirin, p-hydroxyphenylacetic acid, p-toluic acid and o-anisic acid) were obtained by quantum-chemical methods. Afterwards, these properties were used for the a priori determination of the pure-component parameters for the Perturbed-Chain Polar Statistical-Associating Fluid Theory (PCP-SAFT). These parameters were applied to perform solubility calculations for binary solute–solvent mixtures. In these calculations the only parameter fitted was the binary parameter. The results show a good agreement of the modeled solubility and experimental data for the considered solutes in non-polar and polar solvents. Finally, the application of different combination rules to also predict the binary interaction parameter in the mixture was investigated.