Ce3+/Ce4+电对在混酸(硫酸和甲磺酸)中的电化学行为

采用循环伏安、线性扫描、交流阻抗等技术研究了Ce³⁺/Ce⁴⁺电对在混酸(硫酸与甲磺酸)中的电化学行为,并对该体系在间接有机电合成中的应用进行了探索.结果表明：当硫酸和甲磺酸(MSA)浓度分别为0.8和1.0 mol·L^-1时,Ce³⁺/Ce⁴⁺电对具有最佳的电化学活性;在上述配比的混酸介质中,铈盐的溶解度得到了大幅提高,同时电解氧化铈(III)离子的电流效率较高（92.1%）,与纯硫酸体系中的电流效率接近（92.8%）,明显高于纯甲磺酸体系（78.5%）;该混酸介质中Ce⁴⁺在氧化茴香醚生成茴香醛这一过程中也表现出很好的氧化能力.     

A simple method for extracting both active oily and water soluble extract (WSE) from Nigella sativa (L.) seeds using a single solvent system

The current study provides a way of extraction for both active NSO and WSE from Nigella sativa seeds using 98% methanol. About 1?kg of ground seeds was macerated by 1:2.5 w/v (g/mL) for 72?hours. After rotary evaporation and 7 days of continuous drying and chilling at 50 and 4?°C, NSO and WSE were obtained at the same instant. Solubility tests of 24 solvents and 11 thin layer chromatographic analyses while 2, 2-diphenyl-1-picrylhydrazyl free radical scavenging assay of NSO (73.66) , WSE (33.32) and NSO?+?WSE (78.22) against ascorbic acid (IC50?=?4.28?mg/mL) was performed. WSE was found to be highly soluble in water and 5% NaOH exhibiting the same Rf value of 0.95 for EtOH:DMSO (9:1) against the honey. WSE has revealed more than twofold higher anti-oxidant activity than others. Formulation of WSE with Tualang honey may provide better targeted hydrophilic drug delivery systems.     

Solubilities of the cyclodextrins in the presence of transition metal salts

The solubilities of -, -, and -cyclodextrin have been measured in the presence of the first row transition metals: Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺; chlorides, nitrates and sulphates (in this case Fe²⁺), and, for companson, with CaCl₂, the corresponding Group IIa salt. Where possible the measurements are reported as a function of the activity of the salts. In general, for the transition metals the sulphates all show a linear decrease in solubility with increasing salt activity: for the nitrates the solubility increases and then reaches a limiting value; and for the chlorides a small decrease in solubility is observed at low activity followed by an increase in solubility at higher salt activity. Circular dichroism measurements confirm that there is no direct complexation at non-basic pH.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August 1995.     

Aqueous Solubilities, Infinite Dilution Activity Coefficients and Octanol–Water Partition Coefficients of Tricyclic Analogs of Acyclovir

Solubilities of tricyclic analogs of acyclovir have been determined in water at 25, 35, and 45°C and in octanol, water-saturated octanol, and octanol-saturated water at 25°C. Octanol-water partition coefficients were determined at 25°C. Melting temperatures and molar enthalpies of fusion were measured. Activity coefficients in water, octanol, and in aqueous octanol solutions were determined and are discussed. The effect of hydrophilic and hydrophobic substituents in the tricyclic analogs on their thermodynamic properties are discussed. The standard Gibbs energy of transfer between the saturated phases were found to correlate with known values of the melting point of the solvents and the solubilities of the solute. For a number of the compounds examined, correlations between the minimum inhibitory concentration against the herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), varicella-zoster virus (VZV), thymidine kinase-deficient (TK^–) strains of VZV and were established. Detailed conclusions have been derived concerning the relationships between the structure and the thermodynamic parameters of the compounds examined.     

Solubilities of benzene, toluene and diphenyl in the t-butyl alcohol+water mixtures and hydrophobic interaction

The solubilitices of benzene, toluene and diphenyl in mixed solvents of t-butyl alcohol (TBA) and water at 283.15, 288.15, 293.15 and 298.15 K have been determined by spectrophotometry. The mole fraction of TBA [x (TBA)] in the mixed solvent are 0.000, 0.010, 0.020, 0.030, 0.040, 0.045, 0.050, 0.060, 0.080 and 0.100, respectively. The standard Gibbs energies of solution of benzene, toluene and diphenyl in the mixed solvent have also been calculated based on the solubility data. The hydrophobic interactions (HI) for the pairs of benzene-benzene, methane-benzene and methane-methane in the mixed solvent were calculated and discussed.     

Fluorescence quenching, time-resolved fluorescence and chemical modification studies on the tryptophan residues of snake gourd (Trichosanthes anguina) seed lectin

Fluorescence quenching and time-resolved fluorescence studies have been performed on the galactose-specific lectin purified from snake gourd (Trichosanthes anguina) seeds, in order to investigate the tryptophan accessibility and environment in the native protein and in the presence of bound ligand. Estimation of the tryptophan content by N-bromosuccinimide modification in the presence of 8 M urea yields four residues per dimeric molecule. The emission spectrum of native lectin in the absence as well as in the presence of 50 mM methyl--d-galatopyranoside (MeGal) shows a maximum around 331 nm, which shifts to 361.8 nm upon reduction of the disulfide bonds and denaturation with 8 M urea, indicating that all four tryptophan residues in the native state of this protein are in a hydrophobic environment. The extent of quenching that is observed is highest with acrylamide, intermediate with succinimide, and low with Cs⁺ and I⁻, further supporting the idea that the tryptophan residues are predominantly buried in the hydrophobic core of the protein. The presence of MeGal (50 mM) affects the quenching only marginally. Time-resolved fluorescence measurements yield bi-exponential decay curves with lifetimes of 1.45 and 4.99 ns in the absence of sugar, and 1.36 and 4.8 ns in its presence. These results suggest that the tryptophan residues are not directly involved in the saccharide binding activity of the T. anguina lectin. Of the four quenchers employed in this study, the cationic quencher, Cs⁺, is found to be a very sensitive probe for the tryptophan environment of this lectin and may be useful in investigating the environment of partially buried tryptophan residues and unfolding processes in other proteins as well.     

Linear polybiurets: Facile synthesis and characteristic properties

Linear polybiurets have been synthesized by polyaddition of benzyloxyamine and diisocyanates, and properties of the novel polymeric materials have been elucidated. Prior to polymerization, model reactions between benzyloxyamine and phenyl isocyanate were examined in detail and proved to be controlled by the molar ratio of reagents and by catalysts to give the urea (1:1 adduct) and/or biuret (1:2 adduct). Under appropriate conditions, the biuret was synthesized in a quantitative yield. Polymerization of equimolar amounts of benzyloxyamine and diphenylmethane or hexamethylene diisocyanate proceeded smoothly to give polybiurets with inherent viscosities up to 0.52 dL/g. The benzyl group of the model biuret and polybiuret could be removed by catalytic hydrogenation. Both the N-benzyloxy-type and N-hydroxy-type polybiurets showed excellent solubility in common organic solvents. The two kinds of polybiurets as well as model biurets adsorbed metal cations efficiently. The N-hydroxybiuret structure exhibited particularly high affinity for iron(III) and was useful for selective removal of iron from metal cation mixtures. © 1996 John Wiley & Sons, Inc.     

Soluble aromatic polyamide and polyimides derived from di(aminophenyl) acetylenediurea

New aromatic polyamide and polyimides were prepared from di(aminophenyl)acetylenediurea. In addition, model compounds were synthesized and their IR spectra were in agreement with those of the corresponding polymers. The polymers were amorphous and readily soluble in polar aprotic solvents (DMF, NMP, DMSO) and certain acids (H₂SO₄, CCl₃COOH). The hydrophilicity of polyamide was estimated by measuring the isothermal water absorption. The polyamide softened at 260°C but no softening was observed for polyimides. The glass transition temperatures of polymers were determined by the TMA method and they were in the range of 235–310°C. The polymers were stable up to 359–404°C in N₂ or air and afforded char yields of 53–65% at 800°C in N₂. © 1996 John Wiley & Sons, Inc.     

H2 + CN(n=0,1)→H + HCN振动选态反应

用从头算方法获得了Ｈ２＋ＣＮ反应的内禀反应坐标（ＩＲＣ），沿着ＩＲＣ，计算了各垂直于ＩＲＣ的简正模所对应的频率（Ｗ）以及沿ＩＲＣ运动与垂直ＩＲＣ运动的简正模之间的耦合常数（ＢＫＦ），根据传统过渡态，变分过渡态理论和选态公式，计算了ｎＣＮ＝０及ｎＣＮ＝１时反应的速率常数，并得到了实验相一致的结果，还计算了ｎＣＨ＝１及ｎＣＮ＝１的Ｈ＋ＨＣＮ→Ｈ２＋ＣＮ反应速率常数，可供实验工作者参考。     

三嗪类化合物溶解度参数及毒性构—效关系

测定了１２种三嗪类化合物的水溶解度，辛醇水分配系数和对发光菌的毒性，并用分子连结性指数建立了预测三嗪类化合物的溶解度，辛醇水分配系数及对发光菌毒性的定量结构活性相关方程，其中１０种化合物献中未见报道。e