Mechanism and Kinetics of Thermal Dissociation of Inclusion Complex of β-Cyclodextrin and 1-Methylcyclopropene

The inclusion-complex of CD-MCP （β-cyclodextrin （β-CD） including 1-methylcyclopropene （1-MCP）） was prepared and characterized. Basing on programmed-heating procedure and weight-temperature analysis, as well as the application of Satava-Sestak＇s, Ozawa＇s and Kissinger＇s methods, the mechanism and kinetics of thermal dissociation of this inclusion complex were studied. An additional mass loss is found at 170-180℃. The mechanism of thermal dissociation of CD-MCP is dominated by a one-dimensional random nucleation and subsequent growth process （A2/3）. The activation energy Es and the pre-exponential factor AS for the process are 102.14 kJ/mol and 3.63×10^10s^-1, respectively. This ES value shows that there is no strong chemical intere, ctions between β-CD and 1-MC;P,

THE STUDY OF THE REACTION OF THE QUASI-AROMATIC COMPLEX [Ni(PnAO)-6H]^(?)WITH FORMALDEHYDE: KINETICS AND MECHANISM

The kinetics of the reaction of [Ni(PnAO)—6H]° with formaldehyde was studied in H_2O—CH_3OH solution under neutral condition and a complicated mechanism with three steps including competitive, consecutive and reverse reactions was proposed.

Insights into kinetics and reaction mechanism of acid-catalyzed transesterification synthesis of diethyl oxalate

The catalytic performance of different acidic catalysts for diethyl oxalate synthesis from the one-step transesterification of dimethyl oxalate and ethanol was evaluated.The effects of different factors(e.g.,acidity,electron accepting capacity,cations type and crystalline water)on the catalytic activity of acidic catalysts were investigated respectively.It was proposed and confirmed that the transesterification reaction catalyzed by a Lewis acid(FeCl3)and a Bronsted acid(H2SO4)follows a first-order kinetic reaction process.In addition,the Lewis acid-catalyzed transesterification processes with different ester structures were used to further explore and understand the speculated reaction mechanism.This work enriches the theoretical understanding of acid-catalyzed transesterification reactions and is of great significance for the development of highly active catalysts for diethyl oxalate synthesis,diminishing the industrial production cost of diethyl oxalate,and developing downstream bulk or high-value-added industrial products.

The reaction of the iron thiosulfate-nitrosyl complex with adenosine triphosphoric acid

Iron tetranitrosyl complex bearing the thiosulfate ligand (TNIC) is an efficient nitrogen monoxide donor (NO). He shows antitumor properties and may be used as an original drug for the therapy of acute coronary syndrome. In this work, the reaction of the TNIC with adenosine triphosphoric acid (ATP) was studied. Formation of the products for the reaction of ATP with TNIC was shown by electronic microscopy. The kinetics of the reaction was controlled by spectrofluorometric method, and the complexation constant was measured. The mechanism of interaction of ATP with TNIC was proposed, and the relevant kinetic model satisfactorily described the experimental data, which permitted to calculate the rate constants for these process stages. NMR, IR, and M?ssbauer studies were used for determination of the reaction product structure. NMR study showed TNIC interaction only with adenine part of ATP. The method of IR spectroscopy identified both the absence NO in the reaction products and the occurrence of new Fe-S and Fe-N bonds. M?ssbauer study showed that iron in the reaction products was presented by two forms: Fe(II) and Fe(III). Thus, the structures for the [ATP-Fe2+S] and [ATP-Fe3+S] complexes were proposed.

Synthesis, Characterization, Thermal Decomposition Mechanism and Non-Isothermal Kinetics of the Pyruvic Acid-Salicylhydrazone and Its Complex of Praseodymium(III)

The pyruvic acid salicylhydrazone and its new complex of Pr(III) were synthesized. The formulae C 10 H 10 N 2O 4 (mark as H 3L) and [Pr 2(L) 2(H 2O) 2]·3H 2O (L=the triad form of the pyruvic acid salicylhydrazone [C 10 H 7N 2O 4] 3- ) were determined by elemental and EDTA volumetric analysis. Molar conductance, IR, UV, X ray and 1H NMR were carried out for the characterizations of the complex and the ligand. The thermal decompositions of the ligand and the complex with the kinetic study were carried out by non isothermal thermogravimetry. The Kissinger's method and Ozawa's method are used to calculate the activation energy value of the main step decomposition. The stages of the decompositions were identified by TG DTG DSC curve. The non isothermal kinetic data were analyzed by means of integral and differential methods. The possible reaction mechanism and the kinetic equation were investigated by comparing the kinetic parameters.

Linear free energy relationships between reaction rate constants and equilibrium constants of complex compounds——III. Kinetics and mechanisms of ternary complex formation between (5-X-1, 10-phenanthroline)copper(II) and threonine

The kinetics of ternary complex formation involving Cu(5-X-1, 10-phen) and threonine (CuAL, A=5-X-1, 10-phen; L=threonine or represented by O-N; X=NO_2, Cl, H, CH_3) has been studied by temperature-jump and stopped-flow methods. The formation rate constants, k_f(M^(-1).s^(-1)), for the complexation reaction, CuA + LCuAL, are as follows; X=NO_2, 8.68×10~8; X=Cl, 7.13×10~8; X=H, 6.12×10~8; X=CH_3, 5.42×10~8. The rate constants for zwitterion attack are nil within experimental error. It has been found that a linear free energy relationship exists between the stability(logK_(CuAL)^(CuA) of the complexes CuAL and log kf as follows: IogK_(CuAL)^(CuA)=0.13 + 0.83 logk_f, r=0.99. It suggested that the formation rate governed the stability of the ternary complexes. The rates of formation of the ternary complexes increased with decreasing electron-donating property of the substituents. A linear relationship was found to exist as expressed by the following equation: log(k_f^R/k_F^O) = 0.097σ, r=0.96. A mechanism involves a rapid equilibrium between CuA and L followed by a slow ring closure of L.

Kinetics and Mechanism of Oxidation of Lactic Acid by Dihydroxyditelluratoargentate(Ⅲ) in Alkaline Medium

The kinetics of the oxidation of lactic acid(Lac) by dihydroxyditelluratoargentate(Ⅲ)[abbreviated as DDA of Ag(Ⅲ)] anions was studied in an aqueous alkaline medium by conventional spectrophotometry in a temperature range of 25- 40 ℃ . The order of the redox reaction of lactic acid and DDA was found to be first order. The rates increased with the increase in and decreased with the increase in . No free radical was detected. In the view of this the dihydroxymonotelluratoargentate(Ⅲ) species(DMA) is assumed to be the active species. A plausible mechanism involving a two electron transfer is proposed, and the rate \{equation\} derived from the mechanism can be used to explain all the experimental results. The activation parameters(25 ℃) and the rate constants of the rate determining step along with the preequilibrium constants at different temperatures were evaluated.

Kinetics of Reaction Bisphenol-S Epoxy Resin with Methylacrylic Acid

The reaction kinetics of bisphenol-S epoxy resin with methyl-acrylic acid in the presence of quaternary ammonium salt catalyst was studied. The reaction rate constants at different temperatures were determined. The reaction is first order with respect to epoxy group, zero order with respect to methylacrylic acid and 0.71 order with respect to quaternary ammonium salt catalyst, respectively. The mechanism of this reaction was discussed.

Planarization mechanism of alkaline copper CMP slurry based on chemical mechanical kinetics

The planarization mechanism of alkaline copper slurry is studied in the chemical mechanical polishing （CMP） process from the perspective of chemical mechanical kinetics.Different from the international dominant acidic copper slurry,the copper slurry used in this research adopted the way of alkaline technology based on complexation. According to the passivation property of copper in alkaline conditions,the protection of copper film at the concave position on a copper pattern wafer surface can be achieved without the corrosion inhibitors such as benzotriazole（BTA）,by which the problems caused by BTA can be avoided.Through the experiments and theories research,the chemical mechanical kinetics theory of copper removal in alkaline CMP conditions was proposed. Based on the chemical mechanical kinetics theory,the planarization mechanism of alkaline copper slurry was established. In alkaline CMP conditions,the complexation reaction between chelating agent and copper ions needs to break through the reaction barrier.The kinetic energy at the concave position should be lower than the complexation reaction barrier,which is the key to achieve planarization.

Redox reactions of iron and manganese oxides in complex systems

Conspectus:Redox reactions of Fe-and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments.Due to experimental and analytical challenges associated with complex environments,there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems,and most of the studies so far have only focused on simple model systems.To bridge the gap between simple model systems and complex environmental systems,it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation.In this Account,we primarily focused on(1)the oxidative reactivity of Mn-and Fe-oxides and(2)the reductive reactivity of Fe(Ⅱ)/iron oxides in comolex model systems toward contaminant degradation.The effects of common metal ions such as Mn2+,Ca2+,Ni2+,Cr3+and Cu2+,ligands such as small anionic ligands and natural organic matter(NOM),and second metal oxides such as A1,Si and Ti oxides on the redox reactivity of the systems are briefly summarized.

Kinetics and Mechanism of the Uncatalyzed Esterification of Acid-Rich Oil with Glycerol

In this paper, non-catalytic high temperature deacidification process of glycerol rich in acid oil was studied. Through orthogonal experiment, the primary and secondary order of influencing factors was temperature, glycerol dosage and reaction time, and the optimal process conditions were further verified: The ratio of fatty acid to glycerol is 1:1.2, the reaction temperature is 240°C, and the acid value can be reduced to 1.66 mg KOH/g for 2 h. In addition, the activation energy of the reaction was 54.93 kJ/mol by kinetic study. Combined with the K1 value of each reaction, it was confirmed that the temperature rise was conducive to the progress of the reaction. Finally, the high temperature ionization theory of glycerol is put forward, and the mechanism of auto-catalyzed deacidification reaction of glycerol is deduced by using this theory. This theory not only explains this study, but also perfectly explains the slow reaction time of low glycerol dosage.

基于苯磺酸配体构筑的Cu(Ⅱ)配合物的合成、表征及催化性能

以三水合硝酸铜、对甲基苯磺酸钠(p-CH_(3)C_(6)H_(4)SO_(3)Na)和咪唑(Im)为原料,利用溶剂热合成法制备了配合物Cu(Im)_(4)(p-CH_(3)C_(6)H_(4)SO_(3))_(2).通过单晶X射线衍射分析、红外光谱、热重分析、氮气吸附/脱附分析及粉末X射线衍射分析对其进行了表征.由单晶X射线衍射分析可知,该配合物的中心Cu^(2+)与2个对甲基苯磺酸根中的O原子和4个咪唑的N原子配位,通过分子间氢键作用力形成了三维网状结构.以Knoevenagel缩合反应为探针对配合物的催化性能进行了考察,结果表明,该配合物在Knoevenagel缩合反应中具有酸碱协同催化作用,反应时间短,产品产率高,且催化剂可多次重复使用.最后,通过密度泛函理论(DFT)对Cu(Im)_(4)(p-CH_(3)C_(6)H_(4)SO_(3))_(2)、苯甲醛和丙二腈进行了量化计算,预测了活性位点和反应位点;并利用X射线光电子能谱进行了验证,进而推测出可能的催化作用机理.

注塑级聚乳酸热分解动力学分析

目的研究注塑级聚乳酸材料的热分解动力学,准确理解注塑级聚乳酸的耐热稳定性,为开发耐高温阻燃注塑级聚乳酸(PLA)材料提供理论依据。方法通过非等温热重分析法,采用5、10、15、20、25℃/min的升温速率,研究注塑级PLA在氮气气氛中的热分解行为,利用1种微分法和3种积分法进行详细的动力学计算。比较相关系数及标准偏差,选取KAS等温积分法,以相对偏差Ai=|1–αc/αe|为目标函数,利用16种热分解动力学机理模拟计算注塑级PLA热分解最合适的反应机理。结果得到了注塑级PLA热分解所需的活化能和指前因子,其中Kissinger、Madhusudanan-Krishnan-Ninan(MKN)、Kissinger-Akahira-Sunose(KAS)和Flynn-Wall-Ozawa(FWO)法计算所得注塑级PLA活化能分别为177.01、174.43、173.01和173.28 kJ/mol。指前因子分别为25.84、26.69~33.75、25.83~32.89和26.38~32.94。结论确定了随机成核和随后生长反应机理(A1/4),ln(β/T2)=ln[4.75×10^(9)/–ln(1–α)]–2.08×10^(4)/T是描述注塑级PLA热分解最合适的反应机理。

糠酸分解反应动力学与机理研究

己糖二酸脱水环合制备2,5-呋喃二甲酸(2,5-FDCA)是一条有工业发展潜力的工艺。针对该工艺母液循环过程中杂质成分不确定、副产物糠酸分解反应动力学和机理不清楚等问题,在糠酸分解产物明确的基础上,测定了糠酸在4种催化体系中的分解反应动力学和分解产物的生成反应动力学。结果表明,在不同催化体系中糠酸的分解速率由快到慢依次为:10%H_(2)SO_(4)、3%HBr+2%MgBr2、3%HBr、3%HBr+2%LiBr(百分数均为质量分数)。采用1级反应动力学拟合得到糠酸在2%HBr+5%LiBr催化下的分解反应活化能为98.74 kJ·mol^(-1)。提出了糠酸分解的可能路径为糠酸先脱羧生成呋喃,呋喃再通过Diels-Alder反应生成相对稳定的2,3-苯并呋喃,2,3-苯并呋喃可与呋喃通过Diels-Alder反应进一步生成氧芴。

石英玻璃与HF酸反应动力学的研究

为控制石英玻璃与HF酸的反应 ,实现石英玻璃精密元件的化学蚀刻 ,系统研究 3类石英玻璃与HF酸反应的动力学过程。研究表明 :石英玻璃与HF酸的反应速度由化学反应控制 ,其中≡Si—O—Si≡网络中Si—O键的断裂决定反应速率 ;影响反应速率的主要因素包括反应温度、HF酸中活性成分与浓度以及石英玻璃结构。Ⅰ类石英玻璃在金属坩埚中熔制 ,金属杂质含量高 ,结构中存在较多缺陷 ,导致反应速率最快 ;而Ⅲ类石英玻璃中羟基含量高是反应速率高于II类石英玻璃的主要原因 ;各类石英玻璃在HF酸中的反应活性依次是Ⅰ >Ⅲ >Ⅱ类。反应过程中 ,HF酸中的活性成分 (HF) 2 或HF- 2 吸附于石英玻璃表面 ,对Si原子产生亲核性侵蚀使Si—O键断裂 ,而H+ 对反应起催化作用。在HF酸高浓度区 (>7mol/L)反应速率快速增长的原因是溶液中生成更多活性较大的 (HF) nF- 离子。

硅酸盐玻璃的化学处理研究进展

氢氟酸溶液常用于硅酸盐玻璃的表面处理,其化学反应机理一直备受关注。本文从氢氟酸电离反应出发,全面归纳氢氟酸稀溶液电离机理、平衡常数以及各电离产物的作用,重点总结了HF-SiO2反应动力学、各研究理论模型、反应速率公式和反应机理。针对目前硅酸盐玻璃的化学处理研究现状,认为硅酸盐玻璃在高浓度氢氟酸溶液和氢氟酸/强酸混合溶液中化学处理的应用将是未来的研究方向。

碱性介质中二(过碲酸)合银(Ⅲ)离子氧化苹果酸的动力学及机理

在 2 5～ 4 0℃区间内用分光光度法在碱性介质中研究了二 (过碲酸 )合银 (Ⅲ )离子氧化苹果酸的动力学及机理 .实验结果表明反应对二 (过碲酸 )合银 (Ⅲ )离子是准一级的 ,对苹果酸是分数级 .准一级速率常数kobs随 [OH- ]及 [TeO2 - 2 ]的增大分别减小 ,且发现有正的盐效应 .根据实验结果 ,提出了包含有双电子转移的反应机理 ,据此导出了一个能解释全部实验事实的速率方程 ,并求出了速控步的速率常数及 2 5℃时的活化参数 .

非等温TG- DTG法确定2,2'- 联吡啶- 对甲氧基苯甲酸铕(Ⅲ)热分解反应的机理函数和动力学参数(英文)

采用TG DTG和DTA技术研究了2,2' 联吡啶 对甲氧基苯甲酸铕(Ⅲ)在静态空气中的非等温热分解过程及动力学 ,根据TG曲线确定了热分解过程中的中间产物及最终产物 ,运用微分法与积分法对非等温动力学数据进行分析 ,推断出第一步的动力学方程为dα/dt=Aexp( E/RT)2(1 α)1/2 。

用二次曲线拟合表征土壤酸中和能力的研究

以我国7个农田长期(15～29年)施肥试验的历史样品为供试土壤,研究了土壤质子化反应的动力学过程、土壤性质(pH值和SOM)和施肥措施对土壤酸中和能力(ANC)的影响。根据土壤酸滴定曲线,采用二次曲线方程拟合,pH=3.5为参考值,图解法求解土壤ANC。结果表明,土壤质子化过程可视作由质子扩散控制的假二级反应动力学过程:在酸添加后的100h内,土壤ANC与反应时间的对数值近似线性相关;机械振荡和提高温度可加快土壤质子化反应的进程。土壤ANC在指示土壤酸碱程度上较pH灵敏,但对SOM的变化较土壤酸缓冲容量(ABC)不敏感;土壤ANC受长期施肥措施(施无机氮组<不施氮肥组≈有机无机氮配施组)的显著影响,影响的程度因各试验点而异。对土壤酸中和能力的研究加深了对农田土壤酸缓冲机制的认识。

铑配合物催化甲醇羰基化反应的性能和机理

本文合成了２－丁酸甲酯吡啶与四羰基二氯二铑形成的螯合形配合物，并用Ｘ射线光电子能谱（ＸＰＳ）、红外光谱（ＩＲ）及核磁共振（ＮＭＲ）研究确定了其配位结构特征．通过甲醇羰基化制备乙酸的反应揭示了其结构特征对催化剂活性及稳定性的影响。