从分子构造到分子构型和分子构象（中）

我们从(上)文看到,化学家们最初认为物质的性质只决定于物质的分子组成,后来逐渐认识到物质的性质除决定于物质的分子组成外,还决定于分子构造.     

从分子构造到分子构型和分子构象（下）

范特霍夫和列贝尔分别各自提出碳原子的四个价键指向一个正四面体的四个顶点概念确立后,1885年德国化学家拜尔(Baeyer,Adolphvon 1835-1917)发表价键的张力学说。他根据碳原子四个价键的正四面体模型,任何两个价键之间的正常角度应当是109o28',如图I所示。     

从分子构造到分子构型和分子构象（上）

分子构造(constitution)是指分子中原子相互联结的方式和次序,过去长期以来称为分子结构((structure),根据国际纯粹和应用化学联合会的建议,改为“构造”。“结构”一词应用在广泛的范围,例如物质结构、原子的电子结构等等。     

卟啉超分子化合物在分子器件中的应用

分子电子器件已成为近年来的一个研究热点，卟啉类化合物因为光敏性好、性能稳定、易于修饰等优点成为分子器件研究的理想模型化合物。本文着重介绍了它在分子器件中的最新应用进展。     

分子识别在分析化学中的应用

本文概述了分子模板理论的产生和发展，总结了分子模板技术在分析化学领域中的应用和发展趋势，同时对分子印渍技术的理论进行概述，并指出分子印渍技术在分析化学领域中的应用和发展情况，阐述了分子模板和分子印渍技在分子识别分析方面的应用前景，其将为各种物质的超微量分析提供更加讯捷，准确，方便的分析方法。     

药物头孢氨苄分子模板聚合物水中结合性质的研究

采用分子模板技术合成了以头孢氨苄为模板分子以三氟甲基丙烯酸和４－乙烯基吡啶同时为功能单体的分子模板聚合物。将得到的棒状聚合物研磨过筛后,运用平衡结合实验研究了头孢氨苄分子模板聚合物的结合性质,Ｓｃａｔｃｈａｒｄ分析表明,在所研究的浓度范围内,在聚合物中形成了两类不同的结合位点。头孢氨苄分子模板聚合物与其化学组成相同的非模板聚合物相比,有很高的结合容量。底物选择性实验表明,与其它结构相似的药物相比,     

分子陀螺的设计、合成与组装

近来,科学家设计和合成了系列分子水平的陀螺。类似于儿童的玩具陀螺仪,这种分子陀螺由一个转子、一个定子框架和连接定子和转子的轴组成。定子框架通过自身的刚性结构为中心转子的转动提供足够的内在自由度,得以对内部的转子实施保护。并使得分子陀螺成为一个理想的分子转子。当转子上有偶极距时,则可能在外来电、磁、光的刺激下进行定向转动,成为分子马达。化学家们通过X射线晶体衍射技术、动态核磁技术、理论计算化学、热力学分析等方法表征了分子陀螺的各种特征,并积极探索其潜在的应用价值。本文着重介绍分子陀螺,以及超分子陀螺仪的发展历史以及研究进展。     

发光性受体的分子设计与分子识别

介绍了发光受体的几种典型分子识别模型。从分子识别与超分子化学的角度综述了它们在分子离子识别中的应用。对近几年发展较快的分子印迹技术及其应用进行了综述。引用文献71篇。     

基于C=O…HN分子间氢键的超分子液晶研究进展

基于C=O…HN的分子间氢键能够自组装形成具有精确分子排列和很好稳定性的有序结构,在设计构造液晶功能材料方面具有重要的不可替代的地位.分子形状是设计小分子热致液晶的一个主要考虑因素,它对液晶态的结构有至关重要的影响.以分子形状与液晶态相互关系为主线,重点介绍了目前文献报道的基于C=O…HN分子间氢键的盘状和楔形分子形成液晶的研究进展,以期为新型液晶材料的分子设计提供一些借鉴.     

分子调控的概念及其意义

在分子识别的基础之上提出了分子调控的新概念，指出分子调控是外界因素对分子某些性质的指令性干预，是超分子体系所持有的功能，通过这种调控作用，可以有意识、有目的地控制分子的行为，并列举若干实例加以说明。     

Cun、Agn和Aun(n≤9)团簇的静电极化率

The static polarizabilities and polarizability anisotropies of Cun,Agn and Aun (n≤9)clusters have been calculated by the B3LYP density functional method,which is a three parameter mixture of density functional and"exact" Hartree Fock exchange. The calculated results are compared with experimental polarizabilities of sodium clusters. It is shown that the size dependency of the static polarizabilities per atom of Cun,and Agn clusters possesses the same trend as that observed in sodium clusters exception of the Aunclusters while the polarizability of Au atom is much smaller than these of Cu and Ag.The(α-)of Au atom is the smallest and the(α-)per atom of Au approach to the values of Cu from the dimmer to the hexamer. It indicates that in Au clusters the electrons are more strongly attracted by the nuclei because of the more electrons. However,the absolute polarizabilities of the noble mental clusters are considerably smaller than those of the sodium clusters and the electronic structures of the noblemental are much more compact.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Effect of Ag on the Grain Growth and Dielectric Properties of PbTiO3

A series of Ag-PbTiO3 composites were synthesized, and the effects of silver on the morphological development of hydrothermal synthesized PbTiO3 particles and dielectric properties of PbTiO3 ceramic were investigated. Results show that the introduction of Ag benefits the crystal growth of PbTiO3. The diffusion of Ag+ into the perovskite accelerates the crystal growth of PbTiO3 and leads to large fine PbTiO3 crystal. Furthermore, the dielectric constant of PbTiO3-based ceramic was enhanced greatly by the percolation effect of inner Ag clusters.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

酞菁染料的金属化和溴化与光物理影响的研究

以α位(2,4-二特戊基)苯氧基邻苯二腈作为环合前体,制备了多种金属酞菁,产物经元素分析、紫外、红外、核磁氢谱等分析手段进行表征.并选择了部分酞菁进行溴化,其中着重研究了不同中心金属以及溴化对染料Q带吸收的影响.结果表明,酞菁染料的金属化对于其Q带吸收影响很大,多数染料金属化后会出现蓝移,而选择合适的条件进行溴化,可以使得金属酞菁的Q带吸收出现一定程度的红移,其中部分溴化金属酞菁的吸收波长与光信息产业中使用的近红外激光器很接近,具有潜在的实用价值.     

Development of enzyme technology and enzyme engineering in China

Enzymes have been utilized in China for thousands of years for the production of various foods and alcoholic beverages. Today China manufactures and uses enzymes for not only the traditional areas of application, but is expanding the use of enzymes for a variety of nonfood areas. This report describes the present state of the art of enzyme manufacture and application in China today.     

Thermodynamics of dissolving and solvation processes for benzoic acid and the toluic acids in aqueous solution

Experimental data are presented for the solubility in water of benzoic and toluic acids from 5° to 65°C. From the solubility the molality of the monomeric form of the acid is calculated using literature data for both ionization and dimerization of the acid. These data for the monomer combined with data from the literature for vaporization of the solid and ionization in both the gas phase and the aqueous phase yield entropy and enthalpy changes for the solvation of molecular and anionic forms of the acid. A similar procedure is also applied to literature data for the solubility of benzene in water. It is shown that the hydration entropies of the monomeric forms are a linear function of their partial molar volumes. It is concluded that hydration of the undissociated o-toluic acid may be crucial to the increased acidity of that acid compared to benzoic acid.     

ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE

The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here.     

OPTIMIZATION OF THE SYNTHESIS OF ACRYLAMIDE HYDROGEL BY γ-RAY IRRADIATION

Hydrogels have been synthesized from 10%, 20%, 30%, 40%, 50% and 60% aqueous solutions of acrylamide monomer by gamma radiation employing doses in the range of 0.2-30 kGy from a Co-60 source. The effect of solution concentration, γ-ray dose, pH and time was studied in order to observe the optimizing conditions in the characterization of hydrogels. Gel fraction increases with dose for all concentrations indicating hundred-percentage conversion of gel at doses ≥5 kGy for homogenous solutions in the range of 20%-50% concentration. On the other hand, 10% solution provides conversion less than 86% even at 30 kGy, whereas 60% monomer makes an inhomogeneous solution which stile gives about 100% gel fraction. Swelling of hydrogels under water with respect to time varies with both the doses and concentrations due to the change of crosslinking density in the gels. The maximum volume change of hydrogels during swelling and water desorption mainly occurs within 24 h. Swelling is also enhanced with the rise of pH due to change of ionic content of the solvent. Considering the amount of gel fraction and the properties of hydrogel, the samples prepared from 20% solution at 5kGy show better results. Moreover, the effect of bacteria on hydrogel was found to be nil, suggesting a prohibition of growth of microorganism in it.