水及有机溶剂中离子溶剂化焓的理论计算

In the light of the interactions between particles, this paper is a calculation of the standard solvation enthalpies for ions Li~+, Na~+, K~+, Rb~+, Cs~+, Ag~+, Cl~-, Br~- and I~- in solvents as H_2O, MeOH, FA, DMF, DMSO, MeCN, PC and SL. The contributions from the cavity formation process, electrostatic attraction, electrostatic repulsion and those from nonelectrostatic interactions are considered. The accordance between the calculated values and those from literature is good except Li~+.     

STUDY ON IMMOBILIZED PORCINE PANCREATIC LIPASE CATALYZING TRANSESTERIFICATION BETWEEN METHYL－BUTYRATE AND 1－BUTANOL IN NONAQUEOUS SYSTEMS

ＳＴＵＤＹＯＮＩＭＭＯＢＩＬＩＺＥＤＰＯＲＣＩＮＥＰＡＮＣＲＥＡＴＩＣＬＩＰＡＳＥＣＡＴＡＬＹＺＩＮＧＴＲＡＮＳＥＳＴＥＲＩＦＩＣＡＴＩＯＮＢＥＴＷＥＥＮＭＥＴＨＹＬ－ＢＵＴＹＲＡＴＥＡＮＤ１－ＢＵＴＡＮＯＬＩＮＮＯＮＡＱＵＥＯＵＳＳＹＳＴＥＭＳＸｉ...     

非水介质毛细管电泳电化学检测日夜百服宁中的有效成分

用非水毛细管电泳电化学检测法分离检测了日夜百服宁中的有效成分，研究了电极电位，不同浓度的甲酰胺（FA），电解液浓度和酸度，电泳电压及进样时间对电泳分离的影响，得到了较为优化的测定条件。实验结果表明，在25mmol/L Tris-25mmol/L H3BO3(表观pH=8.5)运行介质中，日夜百服宁中的4种有效成分即扑热息痛（AP），盐酸伪麻黄碱（PH），氢溴酸右美沙芬（DM）和扑尔敏（CM）在12min内完全分离，检测电位为＋0．9V(vs.SCE)。线性范围分别为AP 0．5－200mg/L;PH 0.8-300mg/L;DM2.5-350mg/L;CM0.5-330mg/L；检测限分别为AP0.1mg/L;PH0.55mg/L;DM1mg/L;CM0.2mg/L。     

示波非水电位滴定法及其在药物分析上的应用

本文介绍一种非水电位滴定指示终点的新方法,即用阴极射线示波器取代常用的测量电压的装置。将样品溶于含适量醋酐的冰醋酸中,加入适量的醋酸汞,用微铂球电极作指示电极,甘汞电极作参比电极,它们直接与阴极射线示波器的y轴和接地相连,两电极间无任何外加电压,滴定终点时两电极间电位差(△E)产生瞬时突变,示波器荧光屏上荧光点的跳移指示滴定终点。用本法测定了11种有机碱药物,和法定方法作了比较,结果无显著性差异。     

Redox kinetics of metal complexes in nonaqueous solutions: Oxidation of a series of tris(1,10-phenanthroline)iron(II) ions by hexakis(trimethylphosphate)iron(III) in acetonitrile — A reactivity-selectivity relationship

Summary The kinetics of outer-sphere oxidation of Fe(Xphen) ₃ ²⁺ ions (X=H or several methyl substituents) in acetonitrile (MeCN) solution by iron(III), introduced as Fe(tmp)₆(ClO₄)₃ (tmp=trimethylphosphate), have been investigated at 25°C. The reactions are very complex because of solvation equilibria betweentmp andMeCN coordinated at Fe³⁺, with a reduction potential difference of 0.20 V for the replacement of onetmp byMeCN. This makes the various solvate species highly different in driving force. The second essential feature is the high charge-type of +2/+3. This brings about strong acceleration by salt because of ion association reducing the work necessary to overcome the Coulombic repulsion in forming the precursor complex.The task was to deconvolute two kinds of speciation: the ionic and the solvate speciations. The analysis suggests the concurrent existence of five Fe(tmp) _n ³⁺ (n=2–6) species among which four species (n=2–5) are reacting, with an additional mono and bis perchlorate ion pair for eachn. Extra complications arise as some of the solvation equilibria are not always fast compared to the redox reactions, leading to non-first order rate constants.Although the rate constants could not be defined with the desired precision, at least two results are worth noting: (i) The relative effects of driving force and charge are highlighted in controlling overall reactivity. (ii) The stronger the reducing power of the Fe(Xphen) ₃ ²⁺ moiety, the less it can distinguish between the various solvate species (reactivity-selectivity relationship).

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Redox-Kinetik von Metallkomplexe in nicht-wäßrigen Lösungsmitteln: Oxidation einer Serie von Tris(1,10-phenanthrolin)eisen(II)-Ionen mit Hexakis(trimethylphosphat)eisen(III) in Acetonitril-eine Reaktivitäts-Selektivitäts-Beziehung

Zusammenfassung Es wurde die Kinetik der Outer-sphere Oxidation einer Reihe von Fe(Xphen) ₃ ²⁺ Ionen (X=H oder verschiedene Methylsubstituenten) mit Eisen(III), eingeführt als Fe(tmp)₆(ClO₄)₃ (tmp=Trimethylphosphat), bei 25°C in Acetonitril (MeCN) untersucht. Diese Reaktionen sind sehr komplex, da gebundenestmp teilweise durchMeCN ausgetauscht wird, wobei der Ersatz einestmp-Moleküls durchMeCN das Redoxpotential um 0.2 V verschiebt. Deshalb sind die verschiedenen Solvatkomplexe in ihrer Reaktivität sehr unterschiedlich. Ein zweites wesentliches Merkmal der untersuchten Reaktionen ist der hohe Ladungstyp von +2/+3. Das bringt eine starke Erhöhung der Reaktionsgeschwindigkeit durch Elektrolytzusatz infolge von Ionenassoziation mit sich, die die Coulombsche Arbeit für die Bildung des Precursorkomplexes reduziert. Die Aufgabe bestand demnach in der Aufklärung von zwei Speziationsarten, der Solvations- und Ionenassoziationsgleichgewichte. Die Analyse weist auf das gleichzeitige Vorliegen von fünf Fe(tmp) _n ³⁺ Species (n=2–6) hin, wobei vier von ihnen (n=2–5) reagieren. Zusätzlich gibt es für jedesn noch Ionenpaare und Ionentriplets mit Perchlorat. Eine zusätzliche Komplizierung ergibt sich, weil bestimmte Solvationsgleichgewichte nicht immer schnell sind im Vergleich zu den Redoxreaktionen, die dann nicht mehr pseudo-erster-Ordnung sind.Wenn auch die Geschwindigkeitskonstanten nicht mit der üblicherweise gewünschten Präzision angegeben werden können, sind zumindest zwei Ergebnisse nennenswert: (a) Es wird die relative Bedeutung der driving force und der Reaktantenladung für die Gesamtreaktivität hervorgehoben und (b) Je stärker die Reduktionskraft des Fe(Xphen) ₃ ²⁺ Ions, desto weniger kann es die verschiedenen Solvatspezies unterscheiden (Reaktivitäts-Selektivitäts-Beziehung).

     

Non-thermal effects of microwaves on protease-catalyzed esterification and transesterification

The non-thermal effects of microwave irradiation on enzyme-catalyzed reactions have been evaluated by keeping the reaction temperature constant during irradiation. Subtilisin-catalyzed transesterification and α-chymotrypsin-catalyzed esterification have been carried out in six solvents of differing polarities and at three different temperatures. In all cases, microwave irradiation was found to increase the initial reaction rates by 2.1-4.7 times at all hydration levels. It is also shown that microwave irradiation can be used in conjunction with other strategies (like pH tuning and salt activation) for enhancing initial reaction rates.     

Ionic Solvation in Aqueous and Nonaqueous Solutions

Summary.  The history of studies on ionic solvation is briefly reviewed, and structural and dynamic properties of solvated ions in aqueous and nonaqueous solutions are discussed. An emphasis is placed on ionic solvation in nonaqueous mixed solvents in which preferential solvation of ions takes place. A new parameter for expressing the degree of preferential solvation of an ion is proposed. Received January 16, 2001. Accepted January 31, 2001     

Micellar enzymology: methodology and technique

The methodological procedures employed both for serving investigations in the field of micellar enzymology and developed directly in micellar enzymology and being of general significance, such as an estimation of molecular masses and sizes of biocatalysts, titration of active sites of enzymes, chemical modification of proteins (enzymes), conjugation and nanogranulation, are reviewed. Potentialities of using and informativity of various techniques are analyzed.     

Synthesis,characterization, and electrophoretic concentration of titanium dioxide nanoparticles in AOT microemulsions

Stable organosols of TiO₂ nanoparticles were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) in microemulsions of sodium bis(2‐ethylhexyl)sulfoxynate (АОТ) in n‐decane with increasing the content of aqueous pseudophase from 0.15 to 0.85 vol.%. As the water content increased, the hydrodynamic diameter of nanoparticles grew from 10 to 225 nm, and the  ζ‐potential, from ‐6 to 18 mV (the surface of TiO₂ nanoparticles was recharged when the water content was 0.45 vol.%). Nonaqueous electrophoresis in a capacitor‐type cell made it possible to concentrate nanoparticles with a diameter of 60 to 225 nm (concentration factor was 10), separate 20 nm and 225 nm particles, and decrease the content of АОТ in organosol by an order of magnitude. Preparation of a concentrate of nanoparticles with a low content (0.015 M) of AOT included the following stages: (i) electrophoresis after synthesis; (ii) sampling of the concentrate and its twenty‐fold dilution with pure n‐decane; and (iii) repeated electrophoresis. In situ laser and spectrophotometric scanning of the interelectrode space showed the formation of a sharp boundary between the raffinate and the layer of moving nanoparticles during electrophoresis.