Kinetics of hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution as a function of temperature near the temperature of maximum density,and the isochoric controversy

At temperatures above and below the temperature of maximum density, TMD, for water at ambient pressure, pairs of temperatures exist at which the molar volumes of water are equal. First-order rate constants for the pH-independent hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution at pairs of such isochoric temperatures show no unique features. Taken together with previously published kinetic data for the hydrolysis of a range of simple organic solutes in both water and D2O near their respective TMDs, we conclude that special significance in the context of rates of chemical reactions in aqueous solutions should not be attached to the isochoric condition.     

Kinetics of alkaline hydrolysis of organic esters and amides in neutrally-buffered solution

Reaction rate constants for the hydrolysis of organic esters and amides were determined at temperatures of 100–240°C in aqueous solutions buffered at pH values between 5.5 and 7.3. Experiments are modeled assuming alkaline hydrolysis with a thermodynamic solution model included to account for the temperature dependence of hydroxide ion concentration. In most cases, the ester hydrolysis second order rate constants agree well with published values from experiments in strongly basic solutions at pH values from 11 to 14 and temperatures from 25–80°C, despite the large extrapolations required to compare the data sets. The amide hydrolysis rate constants are about one order of magnitude higher than the extrapolated results from other investigators, but the reaction rate increased proportionally with hydroxide ion concentration, suggesting that an alkaline hydrolysis mechanism is also appropriate. These data establish the validity of the alkaline hydrolysis mechanism and can be used to predict hydrolysis reaction rates in neutrally-buffered solutions such as many groundwater and geothermal fluids.     

Complexes of nickel(II) withS-carboxyalkyl-L-cysteines in aqueous medium. Determination of enthalpies by thermometric titrimetry

Summary Molar heats for the reaction of nickel(II) with sulphur-containing amino acids,S-carboxymethyl-L-cysteine andS-carboxyethyl-L-cysteine, have been determined by thermometric titrimetry. The data refer to aqueous solutions at 25°C andI=2.0m. From these enthalpies and equilibrium constants, the corresponding entropies have been calculated. The present thermodynamic data are complementary to previous spectrophotometric data in explaining the structures of the complexes. In particular, the importance of solute-solvent external factors in determining different stabilities for successive steps of complex-formation is stressed.     

Speciation studies in aqueous HCO3(-)-CO3(2-) solutions. A combined Raman spectroscopic and thermodynamic study

Raman (and a few additional FT-IR) spectroscopic measurements of sodium and potassium carbonate and hydrogencarbonate in aqueous solution have been carried out over wide concentration ranges at room temperature and at elevated temperatures. The bands of the CO3(2-)(aq) and HCO3(-)(aq) species, which possess pseudo D3h and C1 symmetry respectively, have been assigned and discussed. Quantitative Raman measurements and thermodynamic calculations on KHCO3 solutions show that the salt does not dissolve congruently in aqueous solutions but forms small amounts of CO3(2-). Quantitative Raman spectroscopic measurements have also been carried out on K2CO3 solutions and the hydrolysis of the carbonate ion has been determined as a function of concentration at room temperature and as a function of temperature up to 219 degrees C. The pK2 value of carbonic acid at 23 degrees C has been established as 10.35 by Raman spectroscopy, a value that compares favourably with published thermodynamic values.     

Reactivity Trends and Kinetic Inspection of Hydroxide Ion Attack and DNA Interaction on Some Pharmacologically Active Agents of Fe(II) Amino Acid Schiff Base Complexes at Different Temperatures

The reactivity of few novel high‐spin Fe(II) complexes of Schiff base ligands derived from 2‐hydroxynaphthaldehyde and some variety of amino acids with the OH^? ion has been examined in an aqueous mixture at the temperature range from 10 to 40°C. Based on the kinetic investigations, the rate law and a plausible mechanism were proposed and discussed. The general rate equation was suggested as follows: rate = k_obs[complex], where k_obs. = k₁ + k₂[OH^?]. Base‐catalyzed hydrolysis kinetic measurements imply pseudo–first‐order doubly stage rates due the presence of mer‐ and fac‐isomers. The observed rate constants k_obs are correlated with the effect of substituent R in the structure of the ligands. From the effect of temperature on the rate base hydrolysis reaction, various thermodynamic parameters were evaluated. The evaluated rate constants and activation parameters are in a good agreement with the stability constants of the investigated complexes. Moreover, the reactivity of the investigated complexes toward DNA was examined and found to be in a good agreement with the reported binding constants.     

Calcium carbonate solubility: a reappraisal of scale formation and inhibition

Considerable disparity exists in the published thermodynamic data for selected species in the Ca(2+) /CO(2)/H(2)O system near 25 degrees C and 1 atm pressure. Some authors doubt the significance of CaCO(3)(0)aq) complexes although there is experimental evidence of their occurrence. Evaluation of all the published experimental and estimated data for aqueous calcium carbonate species confirms that the consistent set of constants given by Plummer and Busenberg in 1982 is the best available, and suggests a formation constant log beta = 3.22 for CaCO(3)(0)(aq). This value was confirmed by additional experimental data and calculations using a specially developed computer program. The solubility s and solubility product K(s) are critically evaluated for each solid polymorph (amorphous CaCO(3), ikaite, vaterite, aragonite and calcite) using a hydrated ion pair model and we give coherent explanations for the calcium carbonate precipitation/dissolution process and the existence of supersaturated waters. The practical cases of scale formation and its inhibition by phosphonate-type compounds are discussed and explained with the same model, taking into account the CaCO(3)(0)(aq) species.     

Prediction of microscopic protonation constants of polybasic molecules via computational methods: A complete microequilibrium analysis of spermine

For the first time, a simple methodology is reported for theoretical calculation of microscopic protonation constants of polybasic molecules in solution. Density functional theory study was used for complete microequilibrium analysis of spermine, H₂N(CH₂)₃NH(CH₂)₄NH(CH₂)₃NH₂, a linear tetraamine with 16 known microspecies. A general thermodynamic cycle is proposed to calculate protonation microconstants of polybasic molecules using calculated micro‐ΔG values in aqueous solution. The microscopic protonation constants were determined with considering both the most abundant and most stable conformers for all microspecies. The results show that the microscopic protonation constants derived from the most abundant conformers (i.e., linear conformers in which the intramolecular hydrogen bonding does not exist) are in good agreement with the corresponding available experimental data. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Utilization of cellulose nitrate waste

A two-step procedure for utilization of cellulose nitrate waste accumulated at industrial enterprises of the Russian Federation was suggested and experimentally checked. The procedure involves hydrolysis of cellulose nitrate in alkaline medium and incineration of hydrolysis products. The best reagents for complete hydrolysis of cellulose nitrate are aqueous solutions of sodium hydroxide and sodium carbonate. As demonstrated by thermal analysis and thermodynamic calculations, incineration of cellulose nitrate base hydrolysis products can be performed without using hydrocarbon fuel.     

A Reexamination of Inductive Substituent Constants Derived from pKa Values of 4-Substituted Quinuclidines. Polar effects. Part VIII

pK_a Values of 42 quinuclidinium perchlorates I have been measured in 0.1 M aqueous KCl-solution. In a few cases small corrections of earlier thermodynamic pK_a values are indicated. These measurements, in conjunction with recent X-ray structure determinations, confirm the reliability of the inductive substituent constants σ_I^q derived from them.     

Interaction of Molybdenum(VI) with Methyliminodiacetic Acid at Different Ionic Strengths by Using Parabolic,Extended Debye-Hückel and Specific Ion Interaction Models

The main aim of this research is to study the complexation of molybdenum(VI) with methyliminodiacetic acid in NaClO₄ aqueous solutions at pH = 6.00 and ionic strengths (0.1<I/mol⋅dm⁻³<1.0) at 25 °C by using potentiometric and UV spectrophotometric measurements in order to obtain thermodynamic stability constants at I=0 mol⋅dm⁻³. A comparison with previous literature data was made for the stability constants, though few data were available. The stability constants data have been analyzed and interpreted by using extended Debye-Hückel theory, specific ion interaction theory and parabolic model. Finally it might be concluded that parabolic model applies better for this complexation reaction.     

A study on hydrolytic polymerization of lanthanide ions

Experimental data of hydrolytic polymerization of lanthanide ions in aqueous solution were treated by graphic method, computer fitting and pq analysis, species present were ascertained and hydrolysis constants obtained. Ln (OH)²⁺ and Ln₂ (OH)₂⁴⁺ predominated in the species of all hydrolysis products. When the first and the second hydrolysis constants were plotted against radii and effective nuclear charge of lanthanide ions, the curves obtained conformed with the “three-division groups” rule. Correlation between hydrolysis constants of Ln₂ (OH)₂⁴⁺ and other hydrolysis constants is linear. Using the above empirical correlations we calculated hydrolysis constants of all lanthanide ions and obtained satisfactory results which showed good regularity for hydrolysis of lanthanide ions and thus systematized all data of the reaction.     

Dissociation constants of protolytic dissociation of glutamyl-glutamic and glycyl-glutamic acids in aqueous solution at 298 K

Protolytic dissociation constants of stepwise dissociation of glutamyl-glutamic and glycyl-glutamic acids in aqueous solutions at 298.15 K at ionic strengths of 0.1, 0.5, and 1.0 M on the NaCl background were measured by potentiometric titration. The thermodynamic dissociation constants were calculated. Using the obtained and published data, we discuss the effect of additional carboxy groups in the side chains of the molecule on the protolytic dissociation constants of peptides.     

Kinetics of the reaction between [chloro(phenyl)arsanyl]acetic and chloroacetic acids

The reaction between [chloro(phenyl)arsanyl]acetic and chloroacetic acids proceeds in alkaline aqueous medium by the Sn2 mechanism and is accompanied by alkaline hydrolysis of chloroacetic acid. Mean rate constants and thermodynamic parameters of the reaction are evaluated.     

On triazoles. XL [1]. Non catalytic dehalogenation of some 5-chloro-1,2,4-triazolo[1,5-a]pyrimidine derivatives

A non catalytic dehalogenation method of type 4 5-chloro- 1 ,2,4-triazolo[1,5-a]pyrimidine derivatives based on the hydrolysis of the corresponding type 5 p-toluenesulphonyl hydrazones with diluted aqueous sodium carbonate solution was elaborated. The method provides the required 5-unsubstituted derivatives 6 also in those cases when the simple hydrogenation is not possible. Using deuterium oxide as the solvent of the hydrolysis, deuterium atoms also could be inserted into position 5 of derivatives 6 . Different by-products of the reactions were also isolated, and a possible explanation was given for their formation.     

Solubility and phase behavior of nickel oxide in aqueous sodium phosphate solutions at elevated temperatures

A platinum-lined, flowing autoclave facility was used to investigate the solubility/phase behavior of nickel oxide (NiO) in aqueous sodium phosphate solutions between 290 and 560 K. A layer of hydrous nickel oxide was concluded to exist on the nickel oxide surface below 468 K; only at higher temperatures did the anhydrous nickel oxide phase control the nickel ion solubility behavior. The measured solubility behavior was examined via a nickel(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from a least-squares analysis of the data. The existence of two new nickel ion complexes are reported for the first time: Ni(OH)₂(HPO₄)⁼ and Ni(OH)₃(H₂PO₄)⁼. The positive entropy change associated with the formation of Ni(OH)₃(H₂PO₄)⁼ leads to its dominance in alkaline phosphate solutions at elevated temperatures.     

Kinetics of the reactions of [Chloro(phenyl)arsanyl]acetic acid with bromo- and iodoacetic acids

Quternization of [chloro(phenyl)arsanyl]acetic acid with bromo- and iodoacetic acids in aqueous alkali follows S_N2 mechanism and is accompanied by alkaline hydrolysis of haloacetic acids. The rate constants and thermodynamic parameters of the process were determined     

Quantum-Chemical Calculation of the Mechanism of Gas-Phase Hydrolysis of Benzenesulfonyl Chloride

The potential energy surface of gas-phase hydrolysis of benzenesulfonyl chloride was calculated by PM3 quantum-chemical method. The structural and energy parameters were calculated for all the intermediates and transition states; activation parameters and the thermodynamic functions of the reaction were determined. The axial orientation of the nucleophilic attack is preferred when the reactive center is attacked by the water molecule occurring at the axis of the C-S bond from the sulfonyl group. Gas-phase hydrolysis of benzenesulfonyl chloride is an exothermic process involving formation of an unstable five-coordinate intermediate. The calculated apparent rate constants and activation parameters of the process are compared with the published data on hydrolysis of benzenesulfonyl chloride in water and aqueous-organic solvents.     

Contact angle measurements under thermodynamic equilibrium conditions

The precise control of the ambient humidity during contact angle measurements is needed to obtain stable and valid data. For a such purpose, a simple low-cost device was designed, and several modified surfaces relevant to biosensor design were studied. Static contact angle values for these surfaces are lower than advancing contact angles published for ambient conditions, indicating that thermodynamic equilibrium conditions are needed to avoid drop evaporation during the measurements.     

1,3-THIAZOLIDINIC AND 2,4,5,6-TETRAHYDRO-1,3-THIAZINIC SPIROCHROMENES AND MEROCYANINES. SYNTHESIS,REACTIVITY AND PHOTOCHROMIC PROPERTIES

Abstract

The acid catalyzed rate for hydrolysis of methylphosponfluoridic acid has been determined at several hydrogen ion concentrations and temperatures. The acid hydrolysis is second order (in acid and substrate). Assumed rate expressions, observed rate constants, and hydrogen ion concentrations were used to calculate the thermodynamic equilibrium constant (K _a=0.56) and rate constants for acid catalysis. The activation energy E _a has been determined as 18.3 Kcal/mole. Finally, the acid catalyzed deuterolysis was determined to be about 1.47 times the rate of hydrolysis. The data suggest a two-step mechanism consisting of a rapid proton transfer, followed by slow hydration of the protonated complex.     

Radioactive contaminants in the subsurface: the influence of complexing ligands on trace metal speciation

Equilibrium thermodynamics is one of the pillars which support safety analyses of repositories for radioactive waste. The research summarized in this review deals with approaches to resolve the problems related to thermodynamic equilibrium constants and solubility of solid phases in the field of radioactive waste management. The results have been obtained at the Paul Scherrer Institut between 1995 and 2005 and comprise the scientific basis of the author’s habilitation thesis in the field of nuclear environmental chemistry. The topics are grouped according to three different levels of problem solving strategies: (1) Critical and comprehensive reviews of the available literature, which are necessary in order to establish a reliable chemical thermodynamic database that fulfils the requirements for rigorous modeling of the behavior of the actinides and fission products in the environment. (2) In many case studies involving inorganic and simple organic ligands a serious lack of reliable thermodynamic data is encountered. There, a new modeling approach to estimate the effects of these missing data was applied. This so called “backdoor approach” begins with the question, “What total concentration of a ligand is necessary to significantly influence the speciation, and hence the solubility, of a given trace metal?” (3) In the field of natural organics, mainly humic and fulvic acids, we face an ill-defined problem concerning the molecular structure of the ligands. There, a pragmatic approach for performance assessment purposes was applied, the “conservative roof” approach, which does not aim to accurately model all experimental data, but allows estimates of maximum effects on metal complexation by humic substances to be calculated.