天然产物的绝对构型研究(Ⅰ)——通过比较旋光和碳谱的实验值与计算值确定酮类、内酯类和醇类化合物的绝对构型

在研究天然产物绝对构型的过程中, 筛选了系列绝对构型未鉴定的化合物, 在B3LYP/aug-cc-pVDZ//B3LYP/6-31G(d)水平上计算了它们的旋光和碳谱数据. 结果表明, 计算结果与实验数值十分符合, 从而鉴定出了这些化合物的绝对构型. 另外, 根据计算结果和早期实验报告更正了1个化合物的碳谱化学位移.     

绝对硬度的量化探究——介绍一个计算化学实验

介绍了利用Gaussian软件定量研究软硬酸碱中化合物硬度的实验设计,涉及化合物的构型优化和高精度单点能计算。旨在通过本实验,学生能够初步掌握运用量子化学计算绝对硬度的基本步骤,加深对软硬酸碱理论的理解,为今后从事相关科研工作打下基础。     

四层过渡金属夹心化合物的电子构型

本文利用共点稠合型硼烷的拓扑结构规则和EHMO量子化学计算方法, 讨论了四层过渡金属夹心化合物的电子构型, 以及它与几何结构之间的关系. 用于解释实际化合物的电子构型. 继而, 对四层、三层和双层夹心化合物的电子构型与几何结构之间的关系进行了比较和讨论.     

光谱法鉴定手性化合物的绝对构型——从仪器表征到理论计算

手性化合物的结构确定,尤其是新型手性化合物的绝对构型测定一直是不对称研究的重要工作.除单晶测试外,光谱学方法近年来被广泛应用于手性分子结构鉴定,主要包括电子和振动圆二色谱、旋光光谱、旋光拉曼谱等.本文对上述测试方法的原理、应用范围和相关理论计算方法做了介绍.把谱学测试与理论计算相结合,将成为手性分子结构鉴定的重要发展方向.     

有机硅活性中间体的研究 Ⅱ.一些含环丙基的有机硅化合物的合成及其结构

用锂有机物的方法合成了四种含有环丙基的有机硅化合物,对上述每种化合物中可能存在着的立体异构体进行了分离和构型测定.     

难熔固体MX(M=Sc,Ti,V;X=C,N,O)电子结构和力学性质的密度泛函研究

采用密度泛函方法对MX(M=Sc,Ti,V;X=C,N,O)固体的体相电子结构和力学性质进行了系统研究.计算结果表明,对于金属原子相同的同一系列化合物,氮化物具有最大的体模量;进一步的研究可知,随着外界压力的增大,化合物由NaCl构型向CsCl构型转变由易到难的顺序依次是氧化物、氮化物和碳化物.本文还首次用密度泛函方法系统地计算了各化合物的能带结构和态密度,并对该类型化合物的导电性能进行了探讨.     

用^1H NMR法研究以CpTiCl3-LiAlH4为还原剂的pinacol反应的立体选择性

Corey 等人曾以CpTiCl_3-LiAlH_4(cp≡■)为还原剂成功地进行了一些Pinacol反应,并对该法做了较深入的研究,但对醛类化合物分子间反应产物的立体选择没有做详尽的讨论。这样,存一些要求有一定空间构型的邻二仲醇化合物的合成中,可否利用该方法就难以确定。为此,我们研究了一些醛类化合物     

激子手性方法用于多氧取代环己烯类化合物的研究

多氧取代环己烯是一类比较独特的天然产物,分子中多具有四个手性中心,立体化学多变,尽管用化学衍生物方法确定了部分化合物的绝对构型,但对已报道的化合物中仍有大部分未能确定其构型。在阐明分子相对构型的基础上,应用激子手性方法确定此类化合物的绝对构型,并利用Alchemy程序进行了分子动力学计算,对此类化合物的圆二色性规律进行了总结。     

激子手性方法用于多氧取代环己烯类化合物的研究

多氧取代环己烯是一类比较独特的天然产物,分子中多具有四个手性中心,立体化学多变,尽管用化学衍生物方法确定了部分化合物的绝对构型,但对已报道的化合物中仍有大部分未能确定其构型。在阐明分子相对构型的基础上,应用激子手性方法确定此类化合物的绝对构型,并利用Alchemy程序进行了分子动力学计算,对此类化合物的圆二色性规律进行了总结。     

杂氮硼三环的量子化学方法研究

杂氮M三环类化合物(Atranes)是一类存在分子内部弱相互作用的化合物,它不仅具有特殊的笼状结构和奇特的物理化学性质,而且有很多具有特别的生物化学活性,同时近期研究发现这些化合物及其衍生物具有很多新的性质和用途[1～3].由于这类体系所含原子数多 ,从头进行计算工作量大,故此选择合适的计算方法和适当的基组以便在保证计算精度同时 ,尽量减小耗时就显得十分重要.本文分别采用不同的方法和基组对杂氮硼三环(图1)进行构型优化和单点计算,对计算结果进行分析、比较,并从中优选出计算结果与紫外光电子能谱实验吻合较好且计算量又不是很大的计算方法和基组.     

n元酸溶液pH精确计算的无量纲方程

本文提出一个n元酸溶液H~+离子浓度无量纲方程及其变形迭代公式。利用该公式可以较为方便地进行任何一种多元酸(或碱)溶液的pH精确计算。     

锌族和钛族卤化物振动光谱的理论计算

采用ab initio RHF,MP2和B3LYP方法以及LanL2DZ和SDD基组计算了四面体锌族卤素阴离子化合物(MX₄^2-,M=Zn(Ⅱ),Cd(Ⅱ),Hg(Ⅱ);X=F^-,Cl^-,Br^-,I^-)和钛族卤化物(MX₄,M=Ti(Ⅳ),Zr(Ⅳ),Hf(Ⅳ);X=F^-,Cl^-,Br^-,I^-)的几何构型和振动频率。计算结果表明,LanL2DZ基组是合适的基组,能得到合理的电荷分布,几何参数以及振动频率。在锌族卤化物的计算中发现,角弯曲振动频率与实测值相当一致,键伸缩振动频率略为偏低,这主要是由于计算的键长略为偏长所致。MP2方法计算的振动频率更接近于实测值。在钛族卤化物的计算中,三种计算方法都相当地再现了实测值,而以B3LYP方法更为满意。     

Comparative study of calix[4]arene derivatives: implications for ligand design

The first comparative theoretical study of three parent calix[4]arene analogues (calix[4]arene, thiacalix[4]arene, and homooxacalix[4]arene) has been performed using molecular dynamic simulations and density functional theory (MPWB1K/6-311G^∗∗//B3LYP/6-311G^∗∗) methods. The theoretical observations herein including optimized geometry, polarity, and atomic charge data provide that homooxacalix[4]arene would offer more efficient platform for metal ion recognition compared to thiacalix[4]arene or calix[4]arene.     

ab Initio Calculation on Tautomerism of Pyrazolin—5—ones

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单位改制后的滴定分析计算

主要介绍法定计算单位颁布以后,化学滴定分析的计算方法,同时推荐一种更具实用意义的通用计算方法,并对其推导过程进行了详细的阐述。     

配煤对煤灰熔融特性影响的实验与量化研究

采用量子化学计算方法和实验研究,从微观分子结构和宏观煤灰熔融特性两个层面上,研究了高温下高、低灰熔点煤配煤降低高灰熔点煤煤灰熔融温度的熔融特性和熔融机理。实验和计算结果表明,配煤时,Ca²⁺作为电子受体进入煤灰中莫来石的晶格,使晶格发生重组,易生成熔点较低的钙长石。莫来石的分子结构较钙长石的要稳定得多,Ca²⁺进入莫来石晶格后位于由\[SiO₄\]^4-和\[AlO₄\]^5-两种四面体形成的网络之间,与O配位的Ca原子削弱了莫来石中的Si-O键,使得配煤后的混煤灰熔融温度降低。量子化学计算得到的灰中矿物质分子结构及相应的物理化学特性,如化学状态、表面化学活性及成键特性等,能够很好的从灰中矿物质分子微观结构特性解释高温下煤灰熔融过程中耐熔矿物与助熔矿物间的反应机理。     

Estimation of pure component properties. Part 4: Estimation of the saturated liquid viscosity of non-electrolyte organic compounds via group contributions and group interactions

A new group contribution method for the prediction of pure component saturated liquid viscosity has been developed. The method is an extension of the pure component property estimation techniques that we have developed for normal boiling points, critical property data, and vapour pressures. Predictions can be made from simply having knowledge of the molecular structure of the compound. In addition, the structural group definitions for the method are identical to those proposed for estimation of saturated vapour pressures. Structural groups were defined in a standardized form and fragmentation of the molecular structures was performed by an automatic procedure to eliminate any arbitrary assumptions. The new method is based on liquid viscosity data for more than 1600 components. Results of the new method are compared to several other estimation methods published in literature and are found to be significantly better. A relative mean deviation in viscosity of 15.3% was observed for 813 components (12,139 data points). By comparison, the Van Velzen method, the best literature method in our benchmarking exercise produced a relative mean deviation of 92.8% for 670 components (11,115 data points). Estimation results at the normal boiling temperature were also tested against an empirical rule for more than 4000 components. The range of the method is usually from the triple or melting point to a reduced temperature of 0.75–0.8. Larger than average deviations were observed in the case of molecules with higher rotational symmetry, but no specific correction of this effect was included in this method.     

USING MEASURING METHOD TO FIND AREA OF ENCLOSED PLANE REGION AND VOLUME OF ENCLOSED SPACE REGION

Two simple methods to calculate the area and volume called improved square gridmethod and cube cutting method are proposed in this paper. For any plane curve orspace surface satisfying certain conditions, by our method, the error of measurement isof the second infinitive order of measuring unit (the side length of the square grid or theside length of the little cube) when the unit is small enough. And when some properties ofthe curve or the surface can be found or its varying bounds can be evaluated, it is pointedout, in order to make the error smaller than any given value, how small the length of themeasuring unit should be.     

Calculation of affinities of peptides for proteins

Several methodologies were employed to calculate the Gibbs standard free energy of binding for a collection of protein-ligand complexes, where the ligand is a peptide and the protein is representative for various protein families. Almost 40 protein-ligand complexes were employed for a continuum approach, which considers the protein and the peptide at the atomic level, but includes solvent as a polarizable continuum. Five protein-ligand complexes were employed for an all-atom approach that relies on a combination of the double decoupling method with thermodynamic integration and molecular dynamics. These affinities were also computed by means of the linear interaction energy method. Although it generally proved rather difficult to predict the absolute free energies correctly, for some protein families the experimental ranking order was correctly reproduced by the continuum and all-atom approach. Considerable attention has also been given to correctly analyze the affinities of charged peptides, where it is required to judge the effect of one or more ions that are being decoupled in an all-atom approach to preserve electroneutrality. The various methods are further judged upon their merits.     

Using Bayes methods and mixture models in inter-laboratory studies with outliers

Inter-laboratory studies (especially so-called key comparisons) are conducted to evaluate both national and international equivalence of measurement. In these studies, a reference value of some measurand (the quantity intended to be measured) is developed and results for all laboratories are compared to this single value. How to determine the reference value is not completely obvious if there are observations and/or laboratories that could be considered outliers. Since ignoring results from one or more participating laboratories is untenable in practical terms, developing methods that are robust to the possibility that a small fraction of the laboratories produces observations unlike those from the others is critical. This paper outlines two Bayesian methods of analyzing inter-laboratory data that have been proposed in the literature and suggests three modifications of one that are more robust to outliers. A simulation study is conducted to compare the five methods.