凝胶色谱和紫外光谱法对煤四氢呋喃抽提物的分析

本实验选取大同、铁法大兴、义马和神府4种煤样,用乙腈、四氢呋喃、吡啶作溶剂连续抽提后,对其中的四氢呋喃抽提物进行了凝胶色谱及二极管阵列检测分析,以确定煤抽提物中中等极性化合物的分子量分布和结构特征。通过对样品的凝胶色谱及紫外光谱分析发现,煤四氢呋喃抽提物的分子量小于840 amu,分子量分布在840~340 amu(组分1)、340~175 amu(组分2)及175~110 amu(组分3)间的组分均为芳香族化合物。但由于芳环上有不同分子量的取代基存在,使分子量分布相差极大;分子量在110 amu以下(位于标定曲线以外)的(组分4)为小分子量的链烃或脂环烃类化合物;1、2、4组分是煤四氢呋喃抽提物主要组分;而组分3在抽提物样品中含量极少。分子量在110 amu以下的小分子化合物(组分4)除大同样品中含量(8.68%)较少外,在其余3个样品中占的比例很大(神府72.96%,义马54.05%,铁法大兴51.74%)。组分1随煤变质程度增加,相对含量增加,其它组分相对含量与煤变质程度没有直接关系。     

Nonlinear Dielectric Effect Study of Tetrahydrofuran Association in Benzene and Cyclohexane Solutions

The nonlinear dielectric effect (NDE) has been applied to study the molecular association in tetrahydrofuran (THF) solutions in benzene and in cyclohexane. On the basis of the experimental values of the NDE parameter, electric permittivity, and density, determined as a function of temperature and concentration, and applying the general, statistical theory of NDE, the association constants and dipole moments of the associates were determined. The molecular orbital PM3 method has been applied to calculate the dipole moments and energy of molecular clusters. The results of NDE and PM3 studies are fairly consistent and reveal that a weak dipolar association takes place in the cyclohexane solutions. In the benzene solutions the association, if any, is much weaker probably due to competitive interactions between the solute and the solvent.     

Quasichemical interpretation of the ultrasonic velocity in ternary aqueous systems

The quasichemical model of hydration have been used to calculate the speed of ultrasound in binary solutions of water and nonelectrolyte. The model has been confined to systems that exhibit a maximum in the ultrasonic velocity vs. nonelectrolyte concentration. The parameters of the model are the hydration equilibrium constant, the nonelectrolyte hydration number, and the molar volume and compressibility of the hydrated nonelectrolyte. These have been fitted to experimental results by the method of least squares. The model calculations reproduce qualitatively the ultrasonic velocity as a function of nonelectrolyte concentration. The calculated maximum of the ultrasonic velocity is generally too low, but the nonelectrolyte concentration at which this maximum occurs agrees well with experiment.Addition of a third component shift the velocity maximum. The quasichemical model has also been used to calculate this shift. These calculations have been based on the parameters developed for the binary system. The shift on the nonelectrolyte concentration scale is reproduced satisfactorily, but the shift of the maximal value of the ultrasonic velocity is less accurately predicted by the model.     

Cyclodehydration of 1,4-butanediol to tetrahydro- furan catalyzed by supported silicotungstic acid

Summary Acid strength, acid density and the combination ability between silicotungstic acid and support were investigated when supported silicotungstic acid was used as a catalyst for cyclodehydration of 1,4-butanediol to tetrahydrofuran. The interaction between heteropoly acid and support influenced the catalytic activity. TiO2-supported silicotungstic acid catalyst exhibited higher activity than the other catalysts supported on kaolin, kieselguhr, and activated charcoal.     

环氧乙烷-四氢呋喃共聚醚中环状齐聚物的气相色谱/质谱分析

首先将环氧乙烷（EO）-四氢呋喃（THF）共聚醚与二异氰酸酯反应，然后将未反应的环状齐聚醚（OCE）用乙醚萃取出来。经气相色谱/质谱（GC/MS）联机分析，鉴定出12个主要峰的结构组成，占总峰面积的96.42%。其中环状四聚体和环状五聚体的含量较高。     

Interactions Between Tetra(trifluoromethylsulfonyl)-1,4,8,11-tetraazocyclotetradecane and Perchlorate Anion in Propylene Carbonate, Nitromethane, Acetonitrile, and Tetrahydrofuran

Electrical conductance measurements are reported for lithium perchlorate andthe anion receptor tetra(trifluoromethylsulfonyl)-1,4,8,11-tetraazocyclotetradecane(TTCD) in different aprotic solvents (propylene carbonate, nitromethane,acetonitrile, and tetrahydrofuran). The data have been analyzed by a suitablemethod based on the Lee-Wheaton theory on mixed electrolytes in order to obtainthe true thermodynamic formation constants of macrocyclic-anion complexes andthe ion pairs of both the uncomplexed (ClO₄ ^–)and complexed (TTCD-ClO₄ ^–)anions. The results show that the anion-ligand formation constants increase withdecreasing dielectric constant and that the presence of the ligand increases theionization of lithium perchlorate and enhances the transference number of lithiumion. These findings are of particular interest in view of the technologicalapplication of anion receptors in electrolyte solutions for lithium batteries.     

催化剂量甘油对THF-FER沸石结晶过程的加速作用

The hydrothermal crystallization of THF-FER zeolite was investigated in the reactant system of Na2O-SiO2-Al2O3-H2O with tetrahydrofuran （THF） as the template in the presence of various catalytic amount of glycerol [CH2（OH）CH（OH）CH2（OH）, Glyc] in the temperature range of 413--473 K. Powder X-ray diffraction （XRD） was used to observe the crystallization process, and scanning electron microscope （SEM）, ^13C cross polarization （CP） and ^27Al magic angle spinning nuclear magnetic resonance （MAS NMR）, X-ray fluorescence scattering spectroscopy （XRF）, thermal analysis and nitrogen sorption were used to characterize the zeolite synthesized in the reactant system with Glyc. The catalytic amount of Glyc could promote the crystallization of FER zeolite, to result in lowering the reaction temperature, shortening the period of the zeolite crystallization and effectively restraining cocrystallization of MOR zeolite as an impure phase especially at low reaction temperature, and possess a significant effect on the morphology and the crystal size of TI-IF-FER zeolite.     

Temporary Generation of a Cyclopropyl Oxocarbenium Ion Enables Highly Diastereoselective Donor–Acceptor Cyclopropane Cycloaddition

A novel formal [3+2] cycloaddition of cyclopropylacetals and aldehydes was developed, and the resulting trisubstituted tetrahydrofurans display three new chiral centers formed with highly diastereoselectivity. This method is stereocomplementary to most previously reported cycloadditions of malonate diesters, relies on the transient generation of cyclopropyl oxocarbenium ions, proceeds under mild conditions, and is based on the concept of temporary activation of an otherwise inert protecting group.     

Nucleophilic substitution at phosphorus: stereochemistry and mechanisms

This review is devoted to the stereochemistry of nucleophilic substitution reactions at phosphorus. The study of the reactions of phosphoryl group transfer is important for biological and molecular chemistry. The stereochemistry and mechanisms of S_N1(P) monomolecular and S_N2(P) bimolecular nucleophilic substitution reactions of organophosphorus compounds are discussed. It has been shown that hydrolysis of many natural phosphates proceeds according to the monomolecular S_N1(P) mechanism via the formation of metaphosphate intermediate (PO₃^?). S_N2(P) nucleophilic substitution at chiral trivalent or pentavalent phosphorus compounds proceeds via the formation of penta-coordinated transition state or pentacoordinate intermediate.