Thermokinetics of the Formation Reaction of Zinc Histidine Complex

The enthalph change of reaction of zinc chloride with L-α-histidine in the temperature range of 25-50℃ has been determined by a microcalorimeter.On the basis of experimental and calculated results,three thermodynamics parameters (the activation enthalpy,the activation entropy,the activation free energy),the rate constant and three kinetic parameters (the activation energy,the pre-exponential constant and the reaction order) of the reaction,and the standard enthalpy of formation of Zn(His)^2 (aq.) are obtained.The results showed that the title reaction easily took place at the studied temperature.     

Zn(NO3)2-Leu-H2O体系(25℃)的相平衡及新相配合物的合成与性质

用半微量相平衡方法研究了硝酸锌-亮氨酸-水体系在25℃及全浓度范围内的溶度性质,绘制了体系的相图和饱和溶液折光率曲线,发现并制备了未见报道的非一致溶解配合物[Zn(Leu)(NO3)2(H20)]·H20(A)和Zn(Leu)2(NO3)2·H20(B),通过化学分析、元素分析、IR和TG-DTG等对其组成、结构及热稳定性进行了研究.用精密转动弹热量计测定配合物的标准燃烧能分别为(-12692.80±5.83)和(-15345.71±9.11)J/g,求得它们的标准燃烧焓分别为(-4523.22±2.08)和(-7208.86±4.28)kJ/mol,标准生成焓分别为(-615.67±2.27)和(-1863.16±4.60)kJ/mol     

ZnSO~4-Thr-H~2O体系(25℃)的相平衡及配合物的合 成与性质

用半微量相平衡方法研究了硫酸锌-苏氨酸-水体系在25℃及全浓度范围内的溶度性质,绘制了体系的相图和饱和溶液折光率曲线,体系中不存在新化合物。在水-丙酮混合溶剂中合成了未见文献报道的Zn(Thr)SO~4·H~2O三元固态化合物,通过化学分析、元素分析、IR,XRD,XPS和TG-DTG等对其组成、结构及热稳定性进行了研究。用精密转动弹热量计测定了配合物的标准燃烧能(-11848.76±17.76)J·g^-^1,求得它的标准燃烧焓(-3534.82±5.30)kJ·mol^-^1,标准生成焓(-256.37±5.69)kJ·mol^-^1.     

Interactions of hexamethyltetrabutyl-substituted biladiene-a,c with cobalt(II) and zinc(II) acetates

The thermodynamics of the reaction of 1,3,7,13,17,19-hexamethyl-2,8,12,18-tetrabutylbiladiene-a,c (H₂L) with cobalt(II) and zinc(II) acetates in dimethylformamide (298.15 K) was studied by spectrophotometric and calorimetric titration. It was found that H2L and Zn(II) form a mononuclear complex ZnL, and in the case of Co(II), a binuclear biligand complex Co₂L₂ is formed. Thermodynamic characteristics of the formation of Co(II) and Zn(II) complexes with biladiene-a,c in DMF at 298.15 K were determined.     

Coordination behavior of erbium chloride hydrate with diethylammonium diethyldithiocarbamate

The complex of erbium chloride lower hydrate with diethylammonium diethyldithiocarbamate (D-DDC) has been synthesized conveniently in absolute alcohol and dry N₂ atmosphere. The title complex was identified as Et₂NH₂[Er(S₂CNEt₂)₄] by chemical and elemental analyses, the bonding characteristics of which was characterized by IR. The enthalpies of solution of erbium chloride hydrate and D-DDC in absolute alcohol at 298.15 K and the enthalpies change of liquid-phase reaction of formation for Et₂NH₂[Er(S₂CNEt₂)₄] at different temperatures were determined by microcalorimetry. On the basis of experimental and calculated results, three thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constant and three kinetic parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of liquid phase reaction of formation were obtained. The enthalpy change of the solid-phase title reaction at 298.15 K was calculated by a thermochemical cycle. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of constant‐volume combustion energy for the complexes of zinc nitrate with three amino acids

Five solid complexes of zinc with L‐α‐methionine, L‐α‐phenylalanine and L‐α‐histidine were prepared. The constant‐volume combustion energies of the complexes, ΔE_c (coordination), were determined by a precise rotating bomb calorimeter at 298.15 K. They were ‐ 2969.03 ± 0.34, ‐2929.46 ± 1.59, ‐9597.13 ± 6.12, ‐4378.98 ± 3.27 and ‐14047 ± 6.75 kJ/mol, respectively. Their standard enthalpies of combustion, ΔH^θ_m,c(coordination, s, 298.15 K), and standard enthalpies of formation, ΔH^θ_m,f (coordination, s, 298.15 K), were calculated. They were ‐2959.73 ± 0.34, ‐2923.88 ± 1.59, ‐9649.18 ± 6.12, ‐4373.40 ± 3.27, ‐14048.53 ± 6.75 kj/mol and ‐1180.94 ± 0.92, ‐1401.26 ± 1.77, ‐2501.69 ± 6.50, ‐1381.47 ± 3.49, ‐1950.19 ± 7.65 kJ/mol, respectively.     

Thermokinetics on the reaction of formation of Dy[(C<Subscript>5</Subscript>H<Subscript>8</Subscript>NS<Subscript>2</Subscript>)<Subscript>3</Subscript>(C<Subscript>12</Subscript>H<Subscript>8</Subscript>N<Subscript>2</Subscript>)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen?H₂O) in absolute ethanol at 298.15 K has been determined as (-16.12 ± 0.05) kJ?mol^-1 by a microcalormeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59 ± 0.29) kJ?mol^t-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.     

Thermokinetics on the reaction of formation of Dy[(C5H8NS2)3(C12H8N2)]

The enthalpy change of formation of the reaction of hydrous dysprosium chloride with ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phen•H₂O) in absolute ethanol at 298.15 K has been determined as (-16.12 ± 0.05) kJ•mol^-1 by a microcalormeter. Thermodynamic parameters (the activation enthalpy, the activation entropy and the activation free energy), rate constant and kinetics parameters (the apparent activation energy, the pre-exponential constant and the reaction order) of the reaction have also been calculated. The enthalpy change of the solid-phase reaction at 298.15 K has been obtained as (53.59 ± 0.29) kJ•mol^t-1 by a thermochemistry cycle. The values of the enthalpy change of formation both in liquid-phase and solid-phase reaction indicated that the complex could only be synthesized in liquid-phase reaction.

     

Mechanistic Investigations of Oxidation of Some Dipeptides by Sodium N‐chloro‐p‐toluenesulfonamide in Alkaline Medium:A Kinetic Study

The kinetics of oxidation of five dipeptides (DPP) viz., glycylglycine (Gly-Gly), L-alanyl-L-alanine (Ala-Ala), L-valyl-L-valine (Val-Val), L-leucyl-L-leucine (Leu-Leu) and phenylglycyl-phenylglycine (Phg-Phg) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT) in NaOH medium was studied at 308 K. The reactions follow identical kinetics for all the dipeptides, being first-order dependence each on [CAT]_o, [DPP]_o and fractional-order on [OH^－]. Addition of p-toluenesulfonamide or halide ions (Cl^－ or Br^－) has no significant effect on the rate of reaction. The reaction rate was found to increase with increase in ionic strength of the medium. The solvent isotope effect was studied using D₂O. The activation parameters for the reaction were computed from Arrhenius plots. Equilibrium and decomposition constants were evaluated. The oxidation products of the dipeptides were identified as their corresponding aldehydes. An isokinetic relationship was observed with β＝352 K, indicating that enthalpy factors control the reaction rate. CH₃C₆H₄SO₂NCl^－ of the oxidant has been postulated as the reactive oxidizing species. Under comparable experimental conditions, the rate of oxidation of the dipeptides increases in the order: Phg-Phg＞Ala-Ala＞Val-Val＞Leu-Leu＞Gly-Gly. The kinetics of oxidation of the dipeptides have also been compared with those of their corresponding monomer amino acids. The observed results have been explained by a plausible mechanism and the related rate law has been deduced.     

五-和六配位的三核锌配合物{[ZnL(OAc)]2Zn}∙CH3COCH3的合成，晶体结构及荧光性质

合成并结构表征了一种新型的线性三核锌(II)配合物,{[ZnL(OAc)]2Zn}∙CH3COCH3（H2L：乙二氧双(5-溴-2-羟基苯亚甲基胺)）。X-射线结构表明配合物中三个锌(II)离子配位到了两个四齿的L2-单元和两个桥联的的乙酸根基团。围绕两端的Zn(1) 或 Zn(1)#1原子形成了扭曲的四方锥配位几何体,围绕中心Zn(2) 原子构成了一个稍微扭曲的八面体配位结构。同时,观察到锌(II)配合物能发出蓝绿色荧光,其最大发射波长为464 nm。     

硝酸铬与组氨酸配合行为的相化学与热化学研究

用相平衡方法研究了硝酸铬-组氨酸-水体系在298.15K时的溶度,绘制了体系的相图,发现并制备了文献未报道的一致溶解配合物:Cr(His)(NO3)3·3H2O(A),Cr(His)2(NO3)3·3H2O(B)和Cr(His)3(NO3)3·3H2O(C),经分析确定了其组成。用微热量计热测定了硝酸铬和组氨酸在水中的反应焓,计算了这些反应的热动力学参数(活化焓、活化熵及活化自由能)、速率常数和动力学能数(活化能、指前因子及反应级数)。     

Thermodynamics of coordination interactions of cobalt(II) and zinc(II) acetates with hexamethyltetrabutyl-substituted biladiene-<Emphasis Type="Italic">a,c</Emphasis>

The thermodynamics of the reaction of cobalt(II) and zinc(II) acetates with 1,3,7,13,17,19-hexamethyl-2,8,12,18-tetrabutylbiladiene-a,c (H₂L) in dimethylformamide (298.15 K) was studied by spectrophotometric and calorimetric titration. It was found that H₂L and Zn(II) form a mononuclear porphyrine-like complex ZnL, and in the case of Co(II), a binuclear biligand complex Co₂L₂ with a doubly interlaced structure is formed. Thermodynamic characteristics of the formation of Co(II) and Zn(II) complexes with biladiene-a,c in DMF at 298.15 K were determined. In the template synthesis of macrocyclic compounds from H₂L, it is more efficient to use Zn²⁺ than Co²⁺ ion as the template.     

Veronicafolin－β-环糊精的物化表征及Veronicafolin－羟丙基-β-环糊精包合物溶解性的增强

用氢谱、红外光谱、X-射线粉末衍射、热分析、元素分析等测试方法研究了Veronicafolin (3,5,4′-三羟基-6,7,3′-三甲氧基黄酮) 和β-环糊精 (β-CD) 的固体包合物的谱学特征。元素分析结果显示形成Veronicafolin-β-CD·20H2O包合物，其中C：39.58%, H: 5.75%，表明包合物中主客体比为1∶1。该包合类型属于A_L-型。通过紫外-可见分光光度法研究了在羟丙基-β-环糊精（HP-β-CD）的存在下Veronicafolin的相溶解度曲线，测得校正曲线为y = 24148x + 0.0075 (r=0.9999)，相溶解曲线为y=0.4738x-2.0×10^-7 (r=0.9490)，包结平衡常数Ks为4.5×10⁶mol-1。HP-β-CD提高了黄酮醇Veronicafolin的溶解度。     

Thermodynamic properties of citric acid and the system citric acid-water

The binary system citric acid-water has been investigated with static vapour pressure measurements, adiabatic calorimetry, solution calorimetry, solubility measurements and powder X-ray measurements. The data are correlated by thermodynamics and a large part of the phase diagram is given. Molar heat capacities of citric acid are given from 90 to 330 K and for citric acid monohydrate from 120 to 300 K. The enthalpy of compound formation Δ_comH (298.15 K)=(?11.8±1) kJ mole^?1.     

Role of Ligand in the Selective Production of Hydrogen from Formic Acid Catalysed by the Mononuclear Cationic Zinc Complexes [(L)Zn(H)]+ (L=tpy,phen, and bpy)

A series of zinc-based catalysts was evaluated for their efficiency in decomposing formic acid into molecular hydrogen and carbon dioxide in the gas phase using quadrupole ion trap mass spectrometry experiments. The effectiveness of the catalysts in the series [(L)Zn(H)]⁺, where L=2,2′:6′,2′′-terpyridine (tpy), 1,10-phenanthroline (phen) or 2,2′-bipyrydine (bpy), was found to depend on the ligand used, which turned out to be fundamental in tuning the catalytic properties of the zinc complex. Specifically, [(tpy)Zn(H)]⁺ displayed the fastest reaction with formic acid proceeding by dehydrogenation to produce the zinc formate complex [(tpy)Zn(O₂CH)]⁺ and H₂. The catalysts [(L)Zn(H)]⁺ are reformed by decarboxylating the zinc formate complexes [(L)Zn(O₂CH)]⁺ by collision-induced dissociation, which is the only reaction channel for each of the ligands used. The decarboxylation reaction was found to be reversible, since the zinc hydride complexes [(L)Zn(H)]⁺ react with carbon dioxide yielding the zinc formate complex. This reaction was again substantially faster for L=tpy than L=phen or bpy. The energetics and mechanisms of these processes were modelled using several levels of density functional theory (DFT) calculations. Experimental results are fully supported by the computational predictions.     

Thermokinetic Study on the Complexation Reaction of the First-Row Transitional Metal Chlorides with Histidine

Introduction The first-row transitional metals of chromium, man-ganese, iron, cobalt, nickel and copper are essential trace elements to human body, which are connected with hundreds of metalloproteins and metalloenzymes, participating in ferment syntheses and playing an im-portant role in metabolism of nucleic acid, protein, carbohydrate and fat. L--histidine is one of the basic units of proteins and absorbed from food because of not being synthesized in human body. Therefore, it is of practic…     

[(bmpyr)2{Zn(OC6H3(NO2)2)4}]: Influence of an Ionic Liquid on Liquid/Liquid Extraction of Metal Ions in a Biphasic System

The compound [(bmpyr)₂{Zn(OR)₄}] (OR = 2,4‐dinitriphenolate) has been prepared from Zn(NO₃)₂·6H₂O and sodium 2,4‐dinitrophenolate in a biphasic aqueous ionic liquid (Butyl‐methyl‐pyrrolidinium trifluoromethylsulfonate [bmpyr][OTf]) system. The presence of the anionic zinc complex in [bmpyr][OTf] is made possible by the exchange of the ionic liquid anions into the aqueous phase for the zinc complex. [(bmpyr)₂{Zn(OR)₄}] was characterized in solution by ¹³C‐ and ¹H‐NMR spectroscopy and in the solid state by crystal structure determination. The zinc complex represents the first type of a zinc complex with more than two phenolate ligands.     

Polymerization mechanism of trimethylene carbonate carried out with zinc(II) acetylacetonate monohydrate

The proposed mechanism of initiation and course of ring‐opening polymerization of cyclic trimethylene carbonate (TMC) involving zinc(II) acetylacetonate is in accordance with the mechanism of monomer activation. At the first stage of the process, coordination of carbonate to Zn(Acac)₂ · H₂O complex occurs with the release of weakly coordinated water molecules. This free water molecule reacts with active TMC–Zn(Acac)₂ complex. The reaction results in the formation of propanediol and CO₂ emission. During further stages of the investigated process, the formed propanediols, or later the oligomeric diols produced with polymerization, are cocatalysts of the chain propagation reaction. The chain propagation occurs because of repeating activation of the TMC monomer through the creation of an active structure resulting in the exchange/transfer reaction between the zinc complex and the monomer, with its following attachment to the hydroxyl groups, carbonate ring opening, and formation of the carbonic unit of polymer chain. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

D,L‐α‐Tocopherol Synthesis Catalyzed by the Brønsted Acidic Ionic Liquids

Abstract

The synthesis of D,L‐α‐tocopherol from trimethylhydroquinone and isophytol using the Brønsted acidic SO₃H‐functionalized ionic liquids as catalysts was explored. The catalytic activities of the SO₃H‐functionalized ionic liquids were dependent on their anions. The yield of D,L‐α‐tocopherol also depended on the solvent, which was the reaction medium. A yield of 94.3% was obtained using the SO₃H‐functionalized ionic liquid with [BF₄ ^?] anion as catalyst in propylene carbonate/heptane. The reaction mixture exhibited good biphasic behaviors, so that the produced D,L‐α‐tocopherol could be separated by decantation. The SO₃H‐functionalized ionic liquids could be reused after the removal of water.     

Study of Copper Chloride Coordination with L-α-Histidine

Thermochemical and kinetic equations for nonequilibrium reactions that occur at constant pressure and temperature were proposed. Thermodynamic and kinetic characteristics of copper(II) reaction with histidine (His) were obtained. The enthalpy of formation of copper(II) complex with histidine at temperatures from 298.15 to 323.15 K was determined by microcalorimetry. The standard enthalpy of formation of Cu(His)₂ ^{2 +}(aq) was calculated. The enthalpy, entropy, and Gibbs energy of activation, rate constants, activation energies, preexponential factor, and reaction order were obtained on the basis of experimental and calculated data. The resulting data suggest that the title reaction readily proceeds at the indicated temperatures. The Cu(His)₂Cl₂·H₂O complex was isolated in the solid state and characterized by IR spectroscopy and thermal analysis.