计算烷烃异构体生成焓的新方法

基于作者提出的诱导极性叠加原理,设计了包括与诱导极性叠加总量要关的能量项的烷烃异构体的标准生成焓估算的新方法。与前人方法比较,它具有较高的计算精度,较少的参数,各参数物理意义明确,而且理论上可以推广到含多种杂原子的衍生物的标准生成焓的计算。     

计算饱和醇异构体标准生成焓的新方法

基于极性叠加原理,在成功设计烷烃异构体和多氯代烷烃生成焓计算新方法的基础上,设计了一种计算多元醇异构体生成焓的新方法,并合理地假定任一异构体的原子化焓等于三种键(C-C、C-H和C-O-H键)的键能、极性叠加能项以及氢键能项的加和.用这一模型拟合24种原子化焓数据,得到了标准生成焓的估算公式.为了检验预测的精确性,又设计了一种预测方法,使用在排除被预测的化合物条件下回归得到的参数,预测该化合物的生成焓.按这种方法,预测了24种异构体的生成焓.通过该5参数预测的相对于实验值的各种误差(平均绝对误差、均方根误差和最大绝对误差)不仅比7参数的基团法预测的对应误差小得多,而且比相应实验数据的误差还要小.与键加和法比较,该方法的模型包含了极性叠加能和氢键能量,该两项代表了主要的非键相互作用能,表征了不同异构体的结构差异,并大大减少了参数.     

异构现象与最大硬度原理

利用原子-键电负性均衡方法计算了700多个异构体的硬度, 通过与标准生成焓所确定的相对稳定性比较后发现, 多数异构体并不遵守最大硬度原理.     

新型金属-有机框架材料分离性能研究

采用基于1,3,5-三[4-苯甲酸]-均苯三甲酰胺配体构筑的具有一维孔道及酰胺活性基团的金属-有机框架(MOF-Sm-L)作为毛细管固定相,研究其在气相色谱中分离烷烃、醇类和取代芳香烃方面的性能。实验结果表明,烷烃、醇类及酚类异构体在这种MOF上得到了有效分离。这些有机物的分离基于毛细管内壁存在的范德华力,以及有机物内的羟基与MOF材料的活性基团酰胺之间的氢键作用力。分离芳香异构体过程为放热过程,同时受焓和熵的控制。     

多溴吩噻嗪系列化合物的稳定性和热力学性质的密度泛函理论研究

用Gaussian 03程序, 在B3LYP/6-31G*水平上全优化计算了吩噻嗪和135个多溴吩噻嗪系列化合物(PBPTHs)在298.15 K和101.3 kPa状态时的热力学参数. 设计等键反应, 计算了PBPTHs系列化合物的标准生成热( )和标准生成自由能( ). 同时研究了这些参数与溴原子的取代位置及取代数目(NPBS)之间的关系. 结果表明: 多溴吩噻嗪的热能校正值(Eth)、恒容热容( )、标准熵( )、标准焓( )以及标准自由能( )与NPBS之间有很强的相关性(r2≥0.998). 在相关方程中, 溴原子的取代个数对多溴代吩噻嗪热力学数值的大小有很大影响. 根据 的相对大小, 从理论上求得异构体的相对稳定性顺序.     

有机化合物结构的唯一性表征方法研究──一个高选择性的拓扑指数

以扩展连接矩阵EA的幂级数函数为基础,建立了一个新的拓扑指数EATI,该指数对1～22个碳原子的所有3807434个烷烃异构体的指认并不出现简并,且能区分含杂原子的化合物,其唯一性良好。该指数可用于数据库中替代CAS登录号进行结构的编码、管理及检索。     

二氯丁烷标准蒸发焓的测定

用直接量热法测量了五种二氯丁烷位置异构体的标准蒸发焓值,探讨了二氯代烷烃液态蒸发焓的影响规律.     

α-取代丙酸酯化合物在全甲基环糊精固定相上的手性拆分

在全甲基β-环糊精(PMBCD)手性固定相上,测定了20对α-取代丙酸酯类化合物对映体的手性分离行为,计算出18对对映体的热力学参数,并利用超热力学方法证明了其中17对对映异构体在PMBCD上的拆分存在焓熵补偿现象,即存在相同或基本一致的拆分机制。结合热力学参数,讨论了衍生基团、取代基团等因素对对映体分离的影响,论述了PMBCD固定相对这20对对映体的分子识别特性和保留机理。     

多氯代二苯并呋喃在不同色谱柱上的气相色谱保留行为——定量结构-色谱保留关系(QSRR)的研究

 以一种拟原子的方式处理多氯代二苯并呋喃 (PCDFs)异构体中的苯环 ,将PCDFs异构体中的原子或基团分为 3类 ,即 :氯原子 (Cl) (记为“1”) ,氧原子 (O) (记为“2”)及拟原子 (B) (记为“3”)。在烷烃分子距边矢量的基础上 ,提出一种以基团为基准的分子距离边数矢量 (μ矢量 ) ,借助多元线性回归方法分别建立了多氯代二苯并呋喃在不同色谱柱上的色谱保留指数与表征其结构的 μ矢量间的定量结构 色谱保留关系 (QSRR)相关模型。各样本总体所建模型的相关系数均在 0 98以上。     

化合物生成焓:一百年和密度泛函基量子机制的原子模型新时代

讨论基于量子理论的密度泛涵基的原子模型在计算化合物生成焓方面的成功应用,并用此方法分析和计算了七个Mn基Laves相金属简化合物RMn2(R=Sc,Y,Lu,Ti,Zr,Hf,Nb)的标准热力学生成焓.同时,也简单地述评了传统的实验方法和计算模型的发展历史和现状,指出其主要不足.通过与可靠实验数据的对比,实现这一新方法的可靠性和准确性.     

Additivity methods for prediction of thermochemical properties. The Laidler method revisited. 2. Hydrocarbons including substituted cyclic compounds

A revised parameterization of the extended Laidler method for predicting standard molar enthalpies of atomization and standard molar enthalpies of formation at T = 298.15 K for several families of hydrocarbons (alkanes, alkenes, alkynes, polyenes, poly-ynes, cycloalkanes, substituted cycloalkanes, cycloalkenes, substituted cycloalkenes, benzene derivatives, and bi and polyphenyls) is presented. Data for a total of 265 gas-phase and 242 liquid-phase compounds were used for the calculation of the parameters. Comparison of the experimental values with those obtained using the additive scheme led to an average absolute difference of 0.73 kJ · mol⁻¹ for the gas-phase standard molar enthalpy of formation and 0.79 kJ · mol⁻¹ for the liquid-phase standard molar enthalpy of formation. The database used to establish the parameters was carefully reviewed by using, whenever possible, the original publications. A worksheet to simplify the calculation of standard molar enthalpies of formation and standard molar enthalpies of atomization at T = 298.15 K based on the extended Laidler parameters defined in this paper is provided as supplementary material.     

烷烃电离能和生成焓的相关性

根据化合物形成过程中价电子能量变化与生成焓之间的关系, 推导出烷烃的生成焓和电离能之间的关系. 以21个烷烃化合物为模型将实验测定的电离能与标准生成焓进行直接关联, 证实了模型方程的适用性, 所得回归方程的相关系数达到0.9999, 估算值与实验值之间的标准偏差仅为0.03 eV. 同时还利用实验测定的标准生成焓对一系列烷烃的电离能作了预测.     

An improved empirical force field for saturated hydrocarbons

A new molecular mechanics force field for alkanes is presented. The force field aims to eliminate some identified failures of the well-known MM2 force field. The new energy function gives an improved prediction of the rotational barriers of highly congested molecules, a better calculation of short nonbonded contacts, and the correct reproduction of bond elongation in small torsion angles. The calculation of sublimation enthalpies is also improved. The standard deviation of the formation enthalpies for a set of 54 compounds is 0.63 kcal/mol; this compares with the reported value of 0.42 calculated with MM2 and MM3 for different sets. The force field parameters were obtained using a least squares method.     

An Electrostatic Bond Energy Model for Enthalpies of Formation of Chloroalkanes in Gaseous States

An electrostatic bond energy model is formulated to fit the enthalpies of formation and dipole moments of the alkanes and chloroalkanes. In this model, the charge distributions are calculated by an electrostatic approach similar to the "MSE" method, and the enthalpy of formation of a molecule is the sum of the bond energy terms plus the electrostatic energy of the interactions between the charges on all atoms. All parameters of this model are obtained by parameterization. The calculated dipole moments for 13 chloroalkanes and enthalpies of formation for 19 alkanes and non-geminal chloroalkanes agree with the determined values very well. To calculate the enthalpies of formation of geminal chloroalkanes, a correction mainly attributed to the van der Waals interactions in the geminal substituted group, about 24 kJ/mol per pair of geminal chlorine atoms, is introduced.     

信息拓扑指数与烷烃分子热力学性质的关系

Two topological information indices were constructed based on Randic and Wiener indices, and the values of topological information indices for 85 alkanes were calculated. The thermodynamic properties such as the standard enthalpies of formation, the standard entropies and the standard free energies of formation for these alkanes were also correlated with these topological and information indices. It is found that the thermodynamic properties calculated for both gaseous and liquid states of the 85 alkanes are in excellent agreement with the experimental values through the regression analysis.     

A Critical Evaluation of Bond Energy/ Group Contribution Methods of Calculating the Heat of Formation: Development of a New Generalized Scheme. Part I. Alkanes∗

Results of application of seven well-known bond energy/group contribution methods to the experimental data on heats of formation of 70 alkanes, including a few polymers, are reported. The earlier claims of accuracy of many of these schemes become untenable with the emergence of new data on nonanes and polymers, calling for more parameters to cope with the steric interaction energy in higher branched alkanes. A new general bond energy scheme is developed with low standard error of ±0.28 kcal/mole which is close to the experimental uncertainty. Heats of formation of some polyolefin structures are predicted for the experimental verification in the future. The energy terms of the new scheme are transferable to other non-hydrocarbon organic compounds for which a general scheme is under way.     

Thermochemical study of the solvation of alkanes in mixtures of methanol with butyl alcohol isomers

A calorimetric method was applied at 25 °C to measure the enthalpies of dissolution of cyclohexane, heptane, and decane in the methanol-n-butanol mixed solvent and hexadecane in mixtures of methanol withn-, iso-, andtert-butyl alcohols. The standard enthalpies of dissolution of alkanes were determined. It was shown that the equation proposed in the literature for calculation of the enthalpies of dissolution of alkanes in mixtures with nonspecific intermolecular solvent-solvent interactions describes satisfactorily the enthalpies of dissolution of alkanes in mixtures of methanol withn- andiso-butyl alcohols. It was suggested that there is no preferential solvation of alkanes by one of the mixed solvent components in the MeOH−BuⁿOH and MeOH−BuⁱOH mixtures; in the MeOH−Bu^tOH system, the composition of alkane solvation shell differs slightly from the solvent composition in the bulk. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 271–274, February, 1999.     

链烷的物理化学性质及其分子参数的相关性研究

用N，N'，P，q,n等分子参数表征链烷的分子大小、取代参量和相邻取代基的 相互作用，并以其为独立参量，通过回归方法建立模型来预测链烷的某些物理化学 性质，对1-9个碳原子链烷的原子化焓、标准生成焓、汽化焓等理化性质的预测表 明该模型的原理简单、方法实用、结果可靠。其预测值民实验值吻合良好，且置信 度高达99.5%。