The Thermokinetics of the Formation Reactions of Cerium(III) n-dodecylbenzene Sulfonate and Cerium(III) Stearate

The thermokinetics of the formation reactions of cerium(III) n-dodecylbenzene sulfonate and cerium(III) stearate are studied by using a microcalorimeter. On the basis of experimental and calculated results, three thermodynamics parameters (the activation enthalpies, the activation entropies, the activation free energies), the rate constant, three kinetic parameters (the activation energies, the pre-exponential constant and the reaction order) and the enthalpies of the reaction of preparing cerium(III) n-dodecylbenzene sulfonate in the temperature range of 20–35°C and cerium(III) stearate in the temperature range of44.6–62.8°C are obtained. The results showed that the title reactions easily took place in the studied temperature. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

Study on Coordination Behaviour of Manganese Chloride with L-a-Histidine

The reaction thermodynamic and kinetic equations for the non-reversible reactions are established. The enthalpy change of formation reaction of manganese(II) histidine (His) complex in water has been determined by microcalorimetry, using manganese chloride with L-a-histidine at 298.15-323.15 K. The standard enthalpy of formation of Mn(His)₂ ²⁺(aq) has been calculated. On the basis of experimental and calculated results, three thermodynamics parameters (the activation enthalpy, the activation entropy and the activation free energy), the rate constants, along with three kinetic parameters (the apparent activation energies, the pre-exponential constant and the reaction order) are obtained. The results show that the reaction easily takes place over the studied temperature range. The solid complex Mn(His)₂Cl₂·4H₂O was prepared and characterized by IR and TG-DTG. This revised version was published online in August 2006 with corrections to the Cover Date.     

Activation energy of electrochemical reaction at a constant value of electrode potential

Equations were derived interrelating ideal activation energy W (determined at the constant Galvani potential value), real activation energy A (determined at a constant overpotential), and the so called formal activation energy Ω (calculated at a constant electrode potential vs. an arbitrarily chosen reference electrode). The obtained equations include only the parameters of the studied reaction and no characteristics of the reaction occurring on the reference electrode. The type of the Ω dependence on the electrode potential is established. Conditions are found, under which the real and formal activation energies of the electrochemical reactions can simultaneously remain constant in the given temperature range and it becomes possible to use them in the integral forms of the Arrhenius equation.     

硫酸锌与组氨酸固液反应的热动力学研究

用微热量计对硫酸锌与组氨酸在水中的固液反应进行了热动力学研究。通过实验和计算得出了该反应的热动力学参数（活化焓,活化熵及活化自由能）,速率常数和动力学参数（活化能,指前因子及反应级数）,并对温度改变对该反应的影响及配合物的合成条件进行了讨论。     

“First‐Principles” kinetic monte carlo simulations revisited: CO oxidation over RuO2(110)

First principles‐based kinetic Monte Carlo (kMC) simulations are performed for the CO oxidation on RuO₂(110) under steady‐state reaction conditions. The simulations include a set of elementary reaction steps with activation energies taken from three different ab initio density functional theory studies. Critical comparison of the simulation results reveals that already small variations in the activation energies lead to distinctly different reaction scenarios on the surface, even to the point where the dominating elementary reaction step is substituted by another one. For a critical assessment of the chosen energy parameters, it is not sufficient to compare kMC simulations only to experimental turnover frequency (TOF) as a function of the reactant feed ratio. More appropriate benchmarks for kMC simulations are the actual distribution of reactants on the catalyst's surface during steady‐state reaction, as determined by in situ infrared spectroscopy and in situ scanning tunneling microscopy, and the temperature dependence of TOF in the from of Arrhenius plots. © 2012 Wiley Periodicals, Inc.     

硝酸钐/硝酸镝/硝酸铒与组氨酸液-液反应的热动力学

稀土氨基酸配合物具有消炎、杀菌、降血糖等作用犤１犦。它们的晶体结构和相化学已有报道犤２，３犦。前报犤４犦曾详细报道了稀土硝酸盐与组氨酸配合行为的溶解度图和制备与表征。但文献中未见有关该类配合反应热动力学研究的报道。本文用微量热法对硝酸钐／硝酸镝／硝酸铒与组氨酸的液－液反应进行了热动力学研究。其结果可为这类配合物的反应机理研究和制备提供必要的技术参数。１实验部分１．１试剂RE（NO３）３·６H２O（RE＝Sm，Dy，Er）按文献犤５犦的方法制备。L－α－组氨酸为B．R．（上海康达氨基酸厂）；纯度＞９９．５％…     

Synthesis,characterization, pyrolysis kinetics and conductivity studies of chloro substituted cobalt phthalocyanines

Cobalt(II) phthalocyanine (CoPc), cobalt(II) tetrachloro phthalocyanine (CoPcCl₄), cobalt(II) octachloro phthalocyanine (CoPcCl₈) and cobalt(II) hexadecachloro phthalocyanine (CoPcCl₁₆) are synthesized pure and characterized using elemental analysis, UV-visible, IR-spectroscopy, magnetic susceptibility, X-ray crystallography, and thermogravimetry. All four complexes have monoclinic structure with different crystal lattice constants. Broido's, Coats-Redfern and Horowitz-Metzger relations were employed to calculate the kinetic and activation parameters associated with thermal decomposition of the above complexes. The compounds are analyzed for kinetic parameters, activation energies for decomposition and the Arrhenious pre-exponential factors, in their pyrolysis. Using these factors and standard equations, thermodynamic parameters such as enthalpy, entropy and free energies are calculated. The activation energies are evaluated based on their electrical conductivity conducted over the temperature range 30–200°C. The electrical conductivities observed at 30°C are in the order CoPcCl₁₆?>?CoPcCl₄?>?CoPcCl₈?>?CoPc. The relevant electrical conductivity data are reported.     

Theoretical studies of the reactions of O(3P) with halogenated methyl (I)

The reaction of o(³P) with CH₂C1 radical has been studied usingab initio molecular orbital theory. G2 (MP.2) method is used to calculate the geometrical parameters, vibrational frequencies and energies of various stationary points on the potential energy surface. The reaction mechanism is revealed. The addition of o(³P) with CH₂Cl leads to the formation of an energy rich intermediate OCH₂Cl^* which can subsequently undergo decomposition or isomerization to the final products. The calculated heat of reaction for each channel is in agreement with the experimental value. The production of H+CHClO and C1+CH₂O are predicted to be the major channels. The overall rate constants are calculated using transition state theory on the basis ofab initio data. The rate constant is pressure independent and exhibits negative temperature dependence at lower temperatures, in accordance with the experimental results.     

Composites based on phenyl substituted cobalt porphyrins with Nafion as catalysts for oxygen electroreduction

The electrochemical behavior of composite materials based on phenyl substituted cobalt porphyrins and Nafion is studied. Several cobalt porphyrins with presumably predictable variation of their hydrophilic/hydrophobic properties due to different donor and acceptor substituents in the para position of phenyl rings are synthesized and studied. It is shown that introduction of Nafion into a system with acceptor substituents results in a significant acceleration of the model oxygen reduction reaction. This allows assuming that a bond between a proton of the Nafion sulfogroup with the porphyrin active center is most probable in this very group of porphyrins, which facilitates the protonation step required for activation of the oxygen molecule. A certain correlation is found between the model reaction of oxygen electroreduction (halfwave potential, reaction rate constant) and Hammett constant varying as dependent on the nature of peripheric substituents.     

Vacuum and oxidative pyrolysis of poly-p-xylylene. II. Chromatographic analysis and kinetics of reaction products

Reaction products of vacuum and oxidative degradation of poly-p-xylylene have been quantitatively determined by chromatographic analysis as function of time, temperature and oxygen pressure. Respective Arrhenius parameters were also ascertained for some of the reaction products and for the sums of all products. The energies of activation for the sums agree quite satisfactorily with the energies of activation obtained previously by uninterrupted experiments in quartz-spoon reaction vessels. The results found here can be described in terms of mechanisms previously postulated on the basis of the total loss in weight (or volatile production) data. Scission of “weak” links (due to abnormal structures) takes place followed by formation of various products. The whole process is governed by the initial chain scission reaction; however, the energies of activation for each of the products do not need to be identical with that of the chain scission reaction. Each product is formed by a reaction which has its own characteristic number average kinetic chain lengths; the latter have their specific energy of activation values. Oxidative degradation produces the same organic compounds as vacuum degradation and in addition CO, CO₂, and H₂O. Oxidized intermediate compounds are apparently fairly rapidly decarboxylated and decarbonylated. Oxidative chain scission is appreciably faster than that in vacuum. Almost simultaneous “weak” link and “normal” chain scission are taking place initiating the formation of a number of products.     

Kinetics of Fe(II) reduction of cis‐halogeno(dodecylamine) bis(ethylenediamine)‐ cobalt(III) complex ion in aqueous solutions

Kinetics of reduction of the surfactant complex ions, cis‐chloro/bromo (dodecylamine)bis(ethylenediamine)cobalt(III) by iron(II) in aqueous solution was studied at 303, 308, and 313 K by spectrophotometry method under pseudo‐first‐order conditions, using an excess of the reductant. The second‐order rate constant remains constant below critical micelle concentration (cmc), but increases with cobalt(III) concentration above cmc, and the presence of aggregation of the complex itself alters the reaction rate. The rate of reaction was not affected by the added [H⁺]. Variation of ionic strength (μ) influences the reaction rate. Activation and thermodynamic parameters have been computed. It is suggested that the reaction of Fe²⁺ (aq) with cobalt(III) complex proceeds by the inner‐sphere mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 98–105, 2006     

A Thermochemical Study on Complex Nickel(Ⅱ) L-α-Histidine

IntroductionNickel is an essential trace biological element.L-α- Amino acids are the structural units of pro-teins.L- α- Histidine is one of the eight species ofamino acids which have to be absorbed from foodbecause they are not synthesized by organism.Thus,the investigation on the complexation ofnickel and L -α- histidine is of considerable practicaland fundamental importance.For the nickel com-plexes of amino acids,more extensive work hasbeen carried out[1— 3 ] . However,the thermochem…     

The kinetics and mechanism of cyclodimerization of alkylthiopropenals

The kinetics of 2-alkylthiopropenals cyclodimerization was studied in the temperature range from -7 to +42 °C in heptane and at 20 °C in various solvents. The rate constants for cyclodimerization of 2-alkylthiopropenals are four orders of magnitude higher than those for dimerization of the oxygen-containing analogs, 2-alkoxypropenals, and are independent of the solvent polarity and substituent steric constant. The activation parameters for 2-butylthiopropenal cyclodimerization were estimated. The distribution of electron density in the 2-methoxy- and 2-methylthiopropenals molecules was calculated by the ab initio method. From comparison of the HOMO and LUMO energies for these aldehydes it was concluded that the ratio between the cyclodimerization rates for 2-alkylthio-, 2-ethoxypropenals, and propenal is determined by the HOMO–LUMO gap.     

A Thermochemical Study on Complex Nickel（Ⅲ）L—α—Histidine

The formation enthalpy ofcomplex nickel(Ⅱ）-histidine(His)in water was determined by means of microcalorimetry in the temperature range of 298.15-323.15K.The standard enthalpy of the formation of Ni(His)2^2 (aq) was calculated.On the basis of the experimental and the calculated results,three thermodynamic parameters(the activation enthaly,the activation entropy and the activation free energy),the rate constants,three kinetic parameters(the apparent activation energy,the pre-exponential constant and the reaction order)of the formation reaction of the title complex were obtained.     

The decarboxylation of methylmalonic acid and n-octadecylmalonic acid in normal alkanols

Rate constants and activation parameters are reported for the decarboxylation of methylmalonic acid and n-octadecylmalonic acid in three normal alkanols (hexanol-1, octanol-1, and decanol-1). Enthalpies of activation for both substrates in the various solvents are found to be a linear function of the number of carbon atoms or methylene groups in the hydrocarbon chain of the solvent. For both reaction series the isokinetic temperature is found to be equal to the melting point of the substrate. The free energy of activation at the isokinetic temperature in kcal/mole is 29.0 for n-octadecylmalonic acid and 29.4 for methylmalonic acid. Based on the results of the present investigation as well as on previously reported data in the case of malonic acid and n-butylmalonic acid, an empirical method of calculating the rate of reaction for the decarboxylation of malonic acid and its n-alkyl derivatives in normal alkanols is proposed. As a further test of the method of calculation the decarboxylation of n-dodecylmalonic acid in heptanol-1 at 110.30°C was studied. The calculated value of the pseudo-first-order specific reaction velocity constant of the reaction agreed with the experimental value to within about 0.1 percent.     

Dielectric properties of some semiconducting polyazophenylenes

The dielectric properties of a series of semiconducting polyazophenylenes were studied as a function of temperature and molecular weight in the temperature range 293–600°K and for molecular weights between 5,100 and 62,800 at a constant frequency of 1 kHz. The compounds studied included poly-2,4-diaminotoluene, poly-2,4-diaminoanisole, and poly-2,5-diaminotoluene. The dielectric properties are presented in the usual way in terms of a complex dielectric constant ε^* = ε′—jε″. Activation energies of relaxation processes were evaluated from the areas and widths of the dielectric loss factor, ε″, against reciprocal temperature at constant frequency. The dielectric activation energies were found to be roughly equal to the activation energies from the DC conductivity. This indicates that the conduction mechanism is based on rotational movements of molecules or parts of molecules.     

热动力学方法测定端羟基聚丁二烯固化反应动力学参数

用热动力学方法对高分子固化反应动力学进行研究,在RD-Ⅰ型热导式自动量热计的基础上,设计了反应器,测定了端羟基聚丁二烯(HTPB)与甲苯二异氰酸酯(TDI)固化反应的动力学参数(表观活化能和反应速率常数),结果与文献值、粘度法和红外光谱法的结果相符。     

Effect of solvent and structure on the kinetics and mechanism of the aquation of bromopentaamine cobalt(III) complex in binary aqueous mixtures

The kinetics of aquation of bromopentaamine cobalt(III) complex have been investigated spectrophotometrically in aqueous‐organic solvent media using acetonitrile, urea, and dimethyl sulfoxide as co‐solvents at 45 ≤ T (°C) ≤ 65. The logarithms of rate constant of the aquation reaction vary nonlinearly with the reciprocal of the dielectric constant for all cosolvent mixtures, indicating a specific solute–solvent interaction. Also, the rate constants are correlated with the total number of moles of water and the organic solvents. However, the solvent effects on the solvation components of the enthalpy of activation, ΔH^?, and the entropy of activation, ΔS^?, have been studied. Analysis of the solvent effect confirmed a common I_d mechanism for the aquation of the cobalt(III) complex. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:494–499, 2004