Phase Diagram of the System NaF-KF-AlF3

The phase diagrams of the binary system KF-AlF₃ as well as the ternary system NaF-KF-AlF₃ in the range up to 50 mol% AlF₃, were measured using the thermal analysis method. In the system KF-AlF₃ the coordinates of the eutectic points are: E ₁: 8.0 mol% AlF₃, 821.2°C, and E ₂: 45.5 mol% AlF₃, 565.0°C. In the investigated concentration range of the ternary system 2 eutectic points have been found with the calculated coordinates: E ₁: 36.3 mol% NaF, 62.7 mol% KF, 1.0 mol% AlF₃; t=711.2°C; and E ₂: 51.9 mol% NaF, 27.4 mol% KF, 20.7 mol% AlF₃; t=734.5°C. Other eutectic points lie most probably beyond the investigated part of the system. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Equilibrium Structure of Methyl Fluoride

The equilibrium structure of CH₃F has been determined using new sets of accurate rotational constants that have been determined by taking into account all the interactions between the excited vibrational states. This experimental structure is in excellent agreement with the equilibrium geometry calculated at the CCSD(T) level of theory with the cc-pV(5, Q)Z basis set (including corrections for the core correlation and for the effect of diffuse functions on fluorine). Finally, the experimental and ab initio structures have been combined by a least-squares analysis. The results are , and L _e(HCH) = 110.2 (1)°, where the uncertainties shown in parentheses correspond to three standard deviations.     

A simple one-pot procedure for the direct conversion of alcohols into azides using TsIm

A facile and efficient method for one-pot conversion of alcohols into azides using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, alcohols are refluxed with a mixture of NaN₃, TsIm and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in DMF affording the corresponding alkyl azides in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.     

Direct measurement of gas solubility and diffusivity in poly(vinylidene fluoride) with a high-pressure microbalance

We present solubility and diffusion data for the gases methane and carbon dioxide in the polymer poly(vinylidene fluoride). The polymer was cut from extruded piping intended for use in offshore oil and gas applications. Measurements were carried out using a purpose-built high-pressure microbalance. These properties were determined in the temperature range 80-120 °C and in the pressure range 50-150 bar for methane and 20-40 bar for carbon dioxide. In general, good agreement was obtained for similar measurements reported in the literature. Solubility follows a Henry’s law (linear) dependence with pressure. Diffusion coefficients for each of the gases in the polymer were also measured using the balance. Activation energies for diffusion and heats of solution for the two gases in the polymer were also determined.     

RExOy.nH2O对氟离子的吸附性能

La、Ce等稀土水含氧化物对阴离子的吸附性早有研究「‘－‘1，但从混合轻稀土氯化物制得的水合氧化物吸附F一的研究报道较少．为探讨难溶金属水合氧化物的除氟性能，本文以混合轻稀土氯化物为原料，制得其水含氧化物（RExOy·nH。O），采用高聚物造粒，研究了粒状RExOy·nH。O对F一的吸附性能及吸附机理．所用混合轻稀土氯化物由包头钢铁稀土公司提供，其主要组成（以氧化物计）为：CeO。（50％）、Nd。O3（25％）、La。O。（15％）、P36Oll（8％）．聚丙烯睛分子量为（2．5～5）X10‘．其它试剂为分析纯．RExO．·nH。O参照文…     

Catalytic enantioselective intermolecular reductive aldol reaction to ketones

We describe the first example of a catalytic enantioselective intermolecular reductive aldol reaction. Three types of reactions were studied: (1) reactions between acetophenone and methyl acrylate; (2) reactions between symmetric ketones and β-substituted α,β-unsaturated esters; and (3) reactions between acetophenone derivatives and an allenic ester. Although only moderate enantioselectivity was obtained in the first reaction type, high to excellent enantioselectivity was realized in the enantio-induction at the α-position in the second reaction type and at the δ-position in the third reaction type. Specifically, the third reaction type afforded the corresponding tertiary alcohols with up to 99% ee. Pre-activation of the nucleophile by silyl enolate formation is not necessary in these one-pot catalytic enantioselective reductive aldol reactions.     

聚偏氟乙烯取向薄膜的结晶形态

本文用小角激光散射法研究了聚偏氟乙烯薄膜在拉伸取向过程中晶体形态及结构的变化。拉伸使球晶形变为椭球,同时伴随着局部熔融与重结晶过程,散射图案由原来的四叶瓣发展为八叶瓣。红外测量及X-射线衍射分析表明,拉伸引起分子链构象改变,使晶型发生了转变。     

Adsorption of the fluoride ion on the surface of various faces of a single crystal of silver: a quantum-chemical study

The fluoride ion adsorption from a gas phase on various faces of a single crystal of silver is studied by a density functional method within a cluster model for metal. The adsorption bond energy is found to increase in the series Ag(100) < Ag(111) < Ag(311) < Ag(110). A substantial structural and energetic heterogeneity of various adsorption sites is revealed. The results are utilized to simulate the electrochemical interface between individual faces of a single crystal of silver and aqueous solutions containing the fluoride ion. It is assumed that the adsorption potential may be represented as the sum of two contributions, one of which describes the metal–ion interaction and the other, the ion solvation energy. The plotted adsorption terms take into account partial degradation of the fluoride ion when adsorbed from an aqueous solution. Estimates of discreteness of the electrical double layer are presented. A conclusion on the maximum manifestation of specific adsorption of the fluoride ion for the Ag(100) face is made.Translated from Elektrokhimiya, Vol. 41, No. 2, 2005, pp. 232–238.Original Russian Text Copyright © 2005 by Nazmutdinov, Zinkicheva.This revised version was published online in April 2005 with corrections to the article note and article title and cover date.     

1-氟代糖在化学-酶法合成糖类中的应用

化学-酶法合成糖类具有立体选择性和区域选择性, 逐渐成为糖类合成的主流. 1-氟代糖作为糖基供体应用于化学-酶法合成反应, 显示出越来越重要的作用, 综述了1-氟代糖在糖基转移酶和糖苷酶催化的糖类合成中的应用.     

On the difference between hydrogen fluoride and hydrogen chloride crystals

The geometrical and energetical parameters of hydrogen fluoride and hydrogen chloride crystals are calculated using the periodic Hartree–Fock method with 6-31G and 6-31G(d,p) basis sets. The comparison of the stabilisation energies reveals that HCl crystals are about 75% less stable than HF crystals. The activation energy for collective proton movements are computed and discussed in view of data of isolated infinite chains. The barriers of 13.1 and 40.0 kcal mol⁻¹ at 6-31G(d,p) level are found for HF and HCl crystals.