Kinetic studies on the formation of N-nitroso compounds IX. Nitrosyl acetate as a nitrosating agent

A study of the nitrosation of N-methylaniline and piperazine by nitrous acid in acetate buffer supports a mechanism covering both reactions, whose effective pathway depends on the relationship between the concentrations of nitrite ion, acetate ion, and nitrosatable substrate. In the case of N-methylaniline the only nitrosating agent is nitrosyl acetate, whereas in the nitrosation of piperazine the nitrous acidium ion and dinitrogen trioxide are also involved.The results obtained seem to show that nitrosation by nitrosyl acetate is diffusion controlled. On this assumption, the equilibrium constant of the reactionAcOH + HNO₂ AcONO + H₂O has been estimated from kinetic measurements as approximately 1.4 · 10^–8 M ^–1. This means that the concentration of nitrosyl acetate in the medium must be extremely small, which explains the virtual impossibility of detecting it in aqueous solution except by kinetic methods.

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Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 9. Mitt.: Nitrosylacetat als Nitrosierungsreagens

Zusammenfassung Die Untersuchung der Nitrosierung von N-Methylanilin und Piperazin mit Salpetriger Säure in Acetat-Puffer unterstützt einen für beide Fälle geltenden Mechanismus, dessen effektiver Ablauf von den Konzentrationsverhältnissen des Nitritions, des Acetations und der nitrosierbaren Substanz abhängt. Im Fall des N-Methylanilins ist das einzige Nitrosierungsagens Nitrosylacetat, während bei der Nitrosierung von Piperazin das Nitrit-Acidium-Ion und Distickstofftrioxid ebenfalls beteiligt sind.Die erhaltenen Resultate scheinen zu zeigen, daß die Nitrosierung durch Nitrosylacetat diffusionskontrolliert ist. Unter dieser Annahme kann die Gleichgewichtskonstante der ReaktionAcOH + HNO₂ AcONO + H₂O aus kinetischen Messungen zu etwa 1,4 · 10^–8 M ^–1 abgeschätzt werden. Das bedeutet, daß die Konzentration von Nitrosylacetat im Medium extrem gering sein muß; das erklärt die praktische Undetektierbarkeit dieser Spezies in wäßriger Lösung, ausgenommen mit kinetischen Methoden.

     

Kinetic studies on the formation of N-nitroso compounds X. The nitrosation ofN-methylacetamide and its differences with respect to the nitrosation of amines

The kinetics of the nitrosation ofN-methylacetamide have been studied using spectrophotometry. Significant differences with respect to the mechanism of nitrosation of amines were observed: the absence of catalysis by halides, the existence of general basic catalysis by acetate and its chlorated derivatives obeyingBrønsted's law (with =0.49), and the primary isotopic effect (with a ratio of 7.9 between the rate constants for the elementary process in H₂O and D₂O). All this indicates that the slow step of the mechanism must be the transfer of a proton from the protonated nitrosamide to the reaction medium.

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Kinetische Untersuchungen zur Bildung von N-Nitroso-Verbindungen, 10. Mitt.: Die Nitrosierung vonN-Methylacetamid und die Unterschiede in bezug auf die Nitrosierung von Aminen

Zusammenfassung Die Kinetik der Nitrosierung vonN-Methylacetamid wurde mittels Spektrophotometrie untersucht. Es wurden signifikante Unterschiede zum Mechanismus der Nitrosierung von Aminen beobachtet: die Abwesenheit einer Katalyse durch Halogenide, die Existenz einer generellen basischen Katalyse durch Acetat und dessen chlorierten Derivaten unter Übereinstimmung mit demBrønstedschen Gesetz (mit =0,49) und einem beobachtbaren Isotopeneffekt (mit einem Verhältnis von 7,9 zwischen den Geschwindigkeitskonstanten in H₂O und D₂O). All das zeigt an, daß der geschwindigkeitsbestimmende Schritt im Mechanismus der Transfer eines Protons vom protonierten Nitrosamid zum Reaktionsmedium sein muß.

     

Salt effects in the mercuration of unsaturated compounds. Kinetic evidence for the formation of ion pairs and a solvated ion

The kinetics of mercuration of bornylene and cyclohexene in different solvents in the presence of NaOAc and LiClO₄ has been investigated. Addition of NaOAc sharply decreases the rate of addition reactions of mercuric acetate to bornylene and cyclohexene in alcohols; the main direction of the mercuration of bornylene is the formation of acetoxy-adducts, and the yield of solvo-adducts decreases from 76 % in the absence of NaOAc, to 19 % in the presence of the salt (4·10^–3 mol L^–1). A reaction scheme involving the participation of intermediate ion pairs and a solvated mercurinium ion is suggested and confirmed by a steady-state concentration method. The influence of NaOAc on the rate of the reaction and on product formation is realized through the common ion effect.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 819–826, May, 1994.     

硝酸铀酰—硝酸—磷酸三丁酯体系的反萃取动力学研究

本文采用恒界面池法和上升单液滴法研究了UO_2(NO_3)_2/HNO_3/TBP-环己烷体系的反萃取动力学。得出扩散控制下的反萃速率方程为R=k_1[U]_(O)[TBP]_(O)~(-1.17)[HNO_3]~(-1.70;在恒定硝酸浓度下化学反应控制的反萃速率方程为R=k_2[U]_(O)[TBP]_(O)~0,并对二种速控类型下的反萃机制进行了讨论。     

Kinetic studies on the addition of dipropylamine to starch acrylate

Summary The kinetics of nucleophilic addition of dipropylamine to vinyl groups of starch acrylate has been investigated. The reactions were carried out under pseudo-first order conditions in tetrahydrofuran with excess amine within the temperature range from 25 to 45^oC. Pseudo-first-order rate constants for addition and the activation energy have been determined.     

Kinetic studies on the addition of dipropylamine to glucose acrylate

The kinetics of the nucleophilic addition reaction of dipropylamine to the vinyl double bonds of glucose acrylate (GA) has been investigated. The reactions were carried out under pseudo first-order conditions in tetrahydrofuran with excess amine within the temperature range from 25 to 45 °C. The activation energy of dipropylamine addition to the vinyl groups of GA is 21.1 kJ/mol.     

Kinetic studies on the formation ofN-nitroso compounds VII. Nitrosation of morpholine in acetate buffer

The kinetics of the nitrosation of morpholine in acetate buffer have been studied. It was found that in the experimental conditions used the effective nitrosating agent is dinitrogen trioxide, whose formation is promoted by the acetate ion in accordance with the scheme: No reaction between nitrosyl acetate and the a mine was observed, probably owing to the low concentration of the former. The proposed mechanism explains the experimental facts that no catalysis by the buffer is observed in conditions in which the rate controlling step is the reaction of N₂O₃ with the amine, and that the catalytic effect has only been observed when the formation of the nitrosating agent is also rate controlling. Values have been calculated for several equilibrium and kinetic constants involved in the mechanism proposed.     

Salt effects and the mechanism of electrophilic mercuration of unsaturated compounds

The reaction of Hg(OAc)₂ with bornylene in THF-H₂O and CH₃CN-H₂O mixed solvents (75 25, v/v) was studied. The effects of the addition of NaOAc on the reaction rate and the composition of products were investigated. In the CH₃CN-H₂O mixture, the addition of NaOAc decreases the amount of the rearranged product, fundamentally changes the ratio between the regioisomeric solvoadducts, and promotes the formation of products of Hg(OAc)₂ addition. The reaction proceedsvia an ion pair and free mercurinium ion; the cation of the ion pair and the free mercurinium ion have dissimilar structures.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 544–548, March, 1995.     

动力学分光光度法测定微量草酸的研究

本文详细讨论了草酸对锡－苯基荧光酮－溴化十六烷基三甲基铵三元络合物显色反应的催化动力学条件，建立了动力学光度法测定微量草酸的新方法，本法Ｓａｎｄｅｌｌ灵敏度为７．４ｎｇ／ｃｍ＾２，草酸浓度在０－１．０μｇ／ｍＬ范围有良好线性关系，方法可直接用于菠菜中草酸含量的测定。     

Kinetic studies for sorption of amino acids using a strong anion-exchange resin. Effect of ionic strength

This work deals with the influence of the ionic strength on the sorption of L-phenylalanine and L-tyrosine by a strong basic anion-exchange resin, converted to the hydroxide form with sodium hydroxide. Equilibrium uptake isotherms were obtained for phenylalanine and tyrosine by carrying out batch experiments at different ionic strength values of the solution. The model used to correlate these results is the modified Langmuir equation which has been applied with success to biological systems. Batch kinetic experiments were performed using a packed bed of differential length inserted in a liquid circulation loop and in which the ionic strength of the solution was varied. Moreover, an experiment at variable pH for tyrosine was also performed. Experimental transient concentration profiles were compared to those predicted by the pore diffusion model and enabled the estimation of the intraparticle diffusivities for phenylalanine and tyrosine.     

硫辛酸在金电极上自组装成膜动力学研究

自组装单层膜 (ＳＡＭ)应用广泛[1～ 3] 。但对于硫辛酸 (ＴＡ)自组装成膜动力学过程的研究尚未见报道。本研究利用石英晶体微天平 (ＱＣＭ)对ＴＡ自组装成膜过程进行在线监测 ,研究成膜动力学特征 ,并探讨浓度、温度对成膜过程的影响 ,以及在不同ｐＨ值下 ,ＳＡＭ的稳定性 ,推算了不同温度下的速率常数及成膜的活化能。1　实验部分1 1　基本原理通过监测成膜过程中石英晶体微天平 (ＱＣＭ)的振荡频率的变化 ,据Ｓａｕｅｒｂｒｅｙ方程 ,可推知在石英谐振器 (ＱＣＭ)的金电极表面 ,ＴＡ的吸附质量Γ(Γ =Δｍ Ａ ,ｇ ｃｍ2 )与ＱＣＭ的频率…     

Kinetic studies on the aminolysis of someO-aryl oximes in benzene

Pyrrolidinolysis and piperidinolysis ofO-aryl oximes show third order dependence on amine with no uncatalytic route. The effect of temperature on separate routes and overall rate is reported and explained.     

Kinetic study of the formation reaction of colloidal silica spheres by transmitted-light-intensity and dynamic light-scattering measurements

Kinetic analyses of the formation reaction of colloidal silica spheres which are synthesized from ethyl silicate (EtSi), ammonia and a trace of water in ethanol are made by the transmitted-light-intensity and dynamic light-scattering methods. Sphere size versus time profiles from the two methods agree well especially at the beginning of the reaction. The polymerization starts after a certain induction time (t _i) ranging from several tens of seconds to several minutes. t _i increases as the concentrations of NH₃, EtSi and/or H₂O decrease. The apparent rates of the reaction, v ^′ are estimated from the reciprocal periods between the intersections of the linear line with the initial and final horizontal lines in the cube root of the absorbance versus time plots. Log v ^′ increases linearly with slopes of 1, 2 and 0.5 as the logarithms of the concentrations of EtSi, NH₃ and/or H₂O increase, respectively. These results are consistent with the assumption proposed earlier that the polymerization mechanism of the formation of the small preliminary particles is followed by their coalescence to form large silica spheres. Received: 10 November 1998 Accepted in revised form: 12 January 1999     

吡啶甲酸锂-铑(Ⅰ)配合物催化甲醇羰基化反应

本文采用吡啶甲酸或吡啶二甲酸锂盐为配体,与铑形成顺二羰基配合物,用于催化甲醇羰基化制乙酸。研究表明,与通常的铑配合物相比,该类双金属配合物无论在催化活性或乙酸生成的选择性方面均有明显的提高。     

聚丙烯酰胺胶凝动力学的研究

聚丙烯酰胺(PA)水溶液的胶凝作用已成功地应用于油井堵水及二、三次采油的压裂工艺~[1].1979年Hessert等~[2]用Cr(Ⅵ)还原生成的Cr(Ⅲ)使PA交联成三维凝胶并用于采油,Terry等~[3]用稳态剪切粘度法对影响该过程动力学的因素作过研究.Prud'hornme等~[4]用流变模数随时间的变化来表征胶凝的速率.Sydansk~[5,6]对Cr(Ⅲ)使PA水溶液发生胶凝的速率及     

Kinetic studies of the polymerization of an epoxy resin modified with rhodamine B

Novel fluorescent materials were satisfactorily synthesized. With this aim, an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) was reacted with a laser dye, rhodamine B (RB), to achieve an epoxy-based prepolymer. Then, a diamine, m-xylylenediamine (MXDA), was used as hardener with the purpose of obtaining a crosslinked polymer. The curing conditions strongly influence the intended final properties and the optimization of the curing requires a reliable kinetic model. For that reason, this work presents the kinetic study of the polymerization of the epoxy resin by differential scanning calorimetry (DSC) in isothermal mode as well as by Fourier transform infrared spectroscopy (FTIR). DSC data were fitted using a Kamal autocatalytic equation. Conversion as a function of reaction time curves obtained by means of both techniques agreed well. In addition, the synthesized epoxy-based materials were characterized by proton nuclear magnetic resonance spectroscopy (¹H NMR) and their fluorescent properties were also analysed.     

动力学参数数目与法方程条件数的关系

多相催化反应动力学研究的基本问题是动力学方程中的参数估计，它一直是动力学研究中的活跃领域·在参数估计中最常用的方法是最小二乘法．早在1947年［刘开始用线性最小二乘法处理动力学模型的数据．1958年在线性最小二乘法中应用置信区间问题［21．1959年MarguardM出非线性最小二乘法问．前人提出如何求非线性最小二乘法的初值［4］，及加权最小二乘法的重要性问，并对最小二乘法在动力学中的应用做了综述卜］．在多相催化动力学研究中，关干线性最小二乘法遇到根本性困难的问题前人未涉及．我们曾在动力学研究中发现线性最小二乘法的法…