Kinetics of Hydrolysis of Inosine in Aqueous Solutions

The kinetics of hydrolysis of inosine was studied in aqueous solution at 353 K over a pH range of 0.45 - 12.13. The decomposition was followed by HPLC. The pH - profile was accounted for by assuming spontaneous water-catalyzed decomposition of the inosine molecules at various degrees of dissociation.     

Kinetics of Glucose Mutarotation in Aqueous Urea Solutions

Kinetics of glucose mutarotation in water-urea mixtures with urea concentrations of 0-15 mol % was studied in the temperature range 283-308 K. It was found for the first time that the rate of mutarotation increases with increasing concentration of urea in water. It was established that urea molecules along with water molecules affect directly the reaction rate via specific solvation. The fact that the activation parameters are almost independent of the concentration of urea was explained in terms of preservation of the structure of the solutions in the composition range studied.     

Kinetics of the Catalytic Oxidation Reactions of Thiol Compounds in Aqueous Solutions in the Presence of Copper Ions

The kinetics of the catalytic oxidation reactions of thiol compounds with molecular oxygen in aqueous solutions in the presence of copper ions was studied in relation to the structures of oxidized thiols and the pH of the solution. A modified procedure used for the determination of [O₂] allowed us to obtain the kinetic characteristics of more than 30 thiols over a wide pH range. We found that weakly chelating thiols exhibited a first order of reaction with respect to [Cu⁺] and [O₂] under conditions when the [(Cu⁺)(RS^–)₂] complex occurred. In the oxidation of strongly chelating thiols in an alkaline medium, the order of reaction with respect to [Cu⁺] was equal to 2, and the rate of reaction was independent of [O₂]. We found that the introduction of small amounts of strongly chelating thiols into Cu⁺ solutions containing difficult-to-oxidize mercaptans resulted in a dramatic acceleration of mercaptan oxidation. We hypothesized that O₂ was effectively bound to the [(Cu⁺)(RS^–)₂] complexes in an alkaline medium in the case of strongly chelating thiols, and this was not the case with the complexes of weakly chelating thiols.     

Radiation-Stimulated Oxidation Reactions of Oxo Anions in Aqueous Solutions

The common features of oxidation processes for inorganic oxo anions under the action of ionizing radiation are considered. The radiation-stimulated oxidation reactions of lower nitrogen, phosphorus, arsenic, and sulfur oxo anions occur via a chain mechanism. The kinetics of these processes can be explained in terms of the peroxide oxidation theory. A correlation between the kinetic and thermodynamic characteristics of the assumed rate-determining step is observed, thus proving the uniformity of oxidation mechanisms. Ways to use the processes of interest in practice are proposed.     

Kinetics of Polyol Oxidation by Ozone in Aqueous Solutions

Spectrophotometry is applied to study the oxidation of ethylene glycol, triethylene glycol, glycerol, etriol, pentaerithritol and mannitol by ozone in aqueous solutions at 277–304 K. Rate constants and activation parameters of the reaction are measured. It is proposed that the oxidation of these alcohols by ozone occurs via the same mechanism. The formation of an intermediate complex is a rate-limiting step in the case of diols; the decomposition of the complex is a rate-limiting step for tri- to hexatomic alcohols.     

Kinetics of Cathodic Reduction of Hypophosphite Anions in Aqueous Solutions

The kinetics of the cathodic reduction of hypophosphite anions in aqueous solutions is studied as a function of the electrode nature, the sodium hypophosphite concentration, and the solution pH. It is shown that the product of the reduction of hypophosphite anions is phosphorus. A scheme is proposed for the reduction process, according to which the phosphorus formation can proceed via two parallel routes—electrochemical and chemical—whose realization depends on the nature of the metal catalyst.     

Kinetics of Hydrolysis of Bisoprolol Hemifumarate in Aqueous Acidic Solutions

The kinetics of hydrolysis of bisoprolol hemifumarate in acidic conditions was studied using high‐performance liquid chromatography. For this purpose, different hydrohalic acids and one weak carboxylic acid were used. The rate constants, the order of the reaction, and the activation parameters: enthalpy, entropy, and energy of activation were calculated. A proposition for the mechanism of degradation was provided.     

Decomposition Kinetics of Alkali Metal Gallams in Hydroxide Aqueous Solutions

The decomposition kinetics of alkali metal gallams in LiGa-LiOH, NaGa-NaOH, KGa-KOH, LiGa-NaOH, LiGa-KOH, and KGa-NaOH systems in the 40-80°C range was studied. The rate constant and current density of decomposition were determined. The rate equation of gallam decomposition under the given experimental conditions was obtained.     

凝聚液态水溶液中的化学反应

液态水是进行化学反应的最重要介质与溶剂之一,也是研究在凝聚(液)态中进行化学反应的主要对象。在不同的外界条件下(特别是极端条件下),液态水的组成、结构与性能会发生很大的变化,促使在其中进行的化学反应呈现不同的特点,因而形成了温和条件下、水热条件下(Hydrothermal condition)与超临界水热条件下(Supercritical water codition)三大类型反应的凝聚态化学。本文立足凝聚态,讨论了在温和(一般)条件下,液态水与水溶液的组成、结构与性能对发生于其中的化学反应(包括溶解与结晶反应、盐类复分解反应、酸碱反应、沉淀反应、成胶与晶化反应、水解反应、氧化-还原反应以及配位化学反应)的影响,包括对反应物存在状态与化学活性,化学反应的过程与机理,反应的中间与最后产物的组成、结构等造成的影响,以及产生的结果与规律等有关的反应化学。通过这些讨论我们提出应从凝聚态的角度看待发生于液态水溶液中的化学反应,并希望这种新视角对研究在其他类型液体(诸如有机溶剂、离子液体、分子熔体等)中进行的化学反应时有所帮助,同时能加强彼此间的交流、讨论与批判,协力为推动以液态为主要研究对象的凝聚态化学的研究与学科建设提供有益的基础。     

葡萄糖水溶液氢键结构和动力分析

利用分子动力学模拟方法研究了不同浓度下葡萄糖水溶液的氢键结构和氢键生存周期. 分析了参与i个氢键(分子内、分子间、所有类型)的葡萄糖分子和水分子的百分比分布. 研究发现存在一个特征数N, 参与N个氢键的分子的比例最高, 当iN时, 参与i个氢键的分子的比例随着浓度的增加而减小. 还分析了不同类型氢键(葡萄糖分子内、葡萄糖分子间、水分子间、葡萄糖分子与水分子间、所有类型)的连续和截断自相关函数, 并计算了对应的氢键生存周期.     

Kinetics of Cadmium Sulfide Precipitation from Aqueous Thiourea Solutions

Kinetics of cadmium sulfide precipitation with thiourea from solutions of cadmium(II) ammine complexes under conditions of spontaneous nucleation of the solid phase in the bulk of solution was studied.     

Iron Hydroxides—New Catalysts for Oxidation Reactions in Aqueous Solutions

The catalytic decomposition of H₂O₂ in the presence of SiO₂-supported amorphous and colloidal FeO(OH) is studied. An inactive Fe(IV) compound and a Fe(III) peroxo complex are found in the hydroxide composition. Possible mechanisms are discussed for H₂O₂ decomposition involving no free radicals. It is shown that lower hydrocarbons are oxidized in the systems, and their presence changes both the kinetics of H₂O₂ decomposition and the behavior of Fe(IV) and the peroxo complex.     

Kinetics of Bulk Crystallization of Salts from Aqueous Solutions of Ethanol

The kinetics of crystallization of a number of salts from aqueous solutions of ethanol was studiedunder isothermal conditions on a setup enabling simultaneous automated recording of the electrical conduc-tivity, optical transmission, light scattering (at an angle of 90° to the incident light beam) of a super-saturated solution in salt crystallization. The rate coefficients of crystal growth were determined.     

Kinetics and Mechanism Studies on Dispersion of CNT in SDS Aqueous Solutions

The objects of this research are to study the dispersion of CNT (carbon nanotube) in SDS (sodium dodecyl sulfate) aqueous solutions with kinetics approach and to obtain some information about mechanism for this dispersion. Firstly, I measured the UV‐visible absorption at 260 nm of CNT in SDS aqueous solutions after different time of dispersion for different concentrations of CNT and SDS. Then, curves of the time‐dependent absorbance were analyzed by various mathematical models and were found to fit well with equation of A = A∞ exp(‐k_obs t), where A∞ is the absorbance at infinite time and k_obs is the observed rate constant. The values of A∞, k_obs, and, minimum time for dispersion can be obtained. From the effects of concentrations of SDS and CNT on A∞ and k_obs, the dissociation constant for CNT‐SDS complex and the optimum ratio of [CNT]/[SDS] can be estimated. Finally, the mechanism for this dispersion may be proposed as” where b‐CNT, CNT, CNT‐SDS, and, k_i s are bounded CNT, exfoliated CNT, CNT‐SDS complex, and, the rate constants, respectively. In this mechanism, b‐CNT is firstly unbounded by supersonic energy to form CNT intermediate with rate constant of k₁, which is proportional to the supersonic energy per time. The CNT intermediate then recombines to form b‐CNT with rate constant k_?1[CNT] or reacts with SDS to form CNT‐SDS complex, which has absorbance at 260 nm in UV‐visible spectrum, with rate constant of k₂ [SDS]. Details of kinetics and mechanism will be discussed in this paper.     

Dynamic Surface Tension and Adsorption Kinetics of Sodium Lignosulfonate Aqueous Solutions

In the article, the dynamic surface tension of sodium lignosulfonate (SL) aqueous solutions are investigated using an axisymmetric drop shape analysis-profile method. The data are analyzed by the Langmuir, Frumkin, modified Frumkin, and modified Flory-Huggins equations. The results indicate that the Langmuir model's results with two adjustable parameters are comparable to that of other models with three or four adjustable parameters. Based on the simplicity of simulation, the Langmuir adsorption equation is used to correlate the dynamic adsorption processing. The aggregation between SL molecules and the variation of adsorption configuration are proposed to interpret the results of dynamic surface tension.      

Kinetics and Mechanism of Reactions Occurring in Electrodeposition of Silver from Thiosulfate Solutions

The kinetics and mechanism of processes occurring in reduction of silver thiosulfate complexes on stationary and rotating disc electrodes and on fluidized glass-bead electrode were studied voltammetrically.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 86–89.Original Russian Text Copyright © 2005 by Shvab, Gur’yanova, Omel’chuk.     

Thermodynamics and Kinetics of Bacterial Cellulose Adsorbing Persistent Pollutant from Aqueous Solutions

The adsorption capability of bacterial cellulose(BC) for anionic dye acid fuchsine was studied. Meanwhile, the processes of the adsorption were investignted and fitted by adsorption isotherm models, adsorption thermodynamics and adsorption kinetics models, respectively. The changes of BC before and after adsorbing acid fuchsine were investigated via scanning electron microscopy(SEM) and Fourier transform infrared spectroscopy(FTIR) to further explain the adsorption mechanism. The results show that acid fuchsine could be effectively adsorbed by BC. The adsorption process was fitted well by Langmuir equation and the pseudo-second order kinetics, indicating that the adsorption process was monolayer molecule adsorption with the main action of chemical adsorption. The adsorption process was spontaneous and endothermic. Glucuronic acid groups and hydroxyl groups were responsible for the adsorption of acid fuchsine on BC.     

Temperature-dependent Kinetics on Laser Induced Photolysis of Aqueous CS2-HONO Solutions

Considerable quantities of wastewater effluents containing CS2are produced by industries engaged in the manufacture of artificial leather,viscose,and other synthetic fibers.In addition,CS2also naturally occurs in the condensation of water vapor and its precipitation from the atmosphere in the form of rain,snow or hail.The oxidation of CS2is the subject of a number of studies1-4.Nitrous acid is another pollutant which has been the subject of intensive investigation in recent years.The review…