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Deracemization extended to racemic‐compound‐forming systems is demonstrated. We present here the first results of an alternative for the resolution of systems that exhibit a stable racemic compound but also a closely related conglomerate‐forming system. If the couples of enantiomers forming the racemic compound and the enantiomers of the stable conglomerate can syncrystallize in mirror‐related partial solid solutions, it is possible to deracemize the racemic mixture of mixed crystals to access to a single handedness. The evidence for this possibility is given in three examples by using temperature‐cycling‐induced deracemization. [ABSTRACT FROM AUTHOR]

New values for the standard enthalpies of formation of titanium fluorides at 0 K have been obtained by revisiting data on homogeneous and heterogeneous equilibria with their participation (kJ/mol): –1403.2 ± 2.7 for TiF3(c), –1144.2 ± 3.3 for TiF3, –2349.4 ± 6.3 for Ti2F5(c); –933.7 ± 6.8 for TiF2(c), and –650.4 ± 2.4 TiF2. The thermodynamic metastability of TiF2(c) has been shown. [ABSTRACT FROM AUTHOR]

The experimental data on the joint fluorination of metallic iridium and platinum with molecular fluorine in the temperature range 654–880 K have been analyzed. The reasons for the decrease in the thermodynamic activity of metals and the possibility of the formation of new phases on their surfaces have been quantitatively considered. The ΔrH°(0) of reactions, kJ/mol, have been determined: Ir(c) + PtF4(g) = IrF4(g) + Pt(c), 23.0 ± 4.5; Ir(c) + 2IrF6(g) = 3IrF4(g), 217.7 ± 8.6; Ir2F6(c) + IrF6(g) = 3IrF4(g), 396.2 ± 21.3. The standard enthalpies of formation of the following iridium fluorides have been recommended: ΔfH°(Ir2F6, c, 0) = ‒1012.6 ± 15.5 kJ/mol, ΔfH°(IrF4, g, 0) = –482.3 ± 7.7 kJ/mol, and ΔfH°(IrF6, g, 0) = –832.3 ± 12.7 kJ/mol. [ABSTRACT FROM AUTHOR]

The goals of this work are as follows: (а) searching for a method of study of the In – Se system taking into account the specified problems and difficulties, (b) choosing a way for the instrumental implementation of this method, and (c) obtaining experimental evidence that this method and its implementation are promising. The choice of the In – Se system is related to the fact that indium selenides, layered structures and semiconductor phases with stoichiometric vacancies, are promising from the point of view of materials science. This choice is also related to the use of binary precursors for the synthesis of heterostructures based on CIS compounds. We studied the possibility of applying the auxiliary component method using the equilibrium with the participation of indium chloride vapours which were made to contact the condensed phases of the In – Se system. Equilibrium was achieved using high-temperature spectrophotometry of the vapour phase. The experiment had two stages. During the first stage we determined the absorption characteristics of the InCl3 vapour. During the second stage we studied the heterogeneous equilibrium of the unsaturated indium chloride vapour with several phases of the In – Se system. Over the course of the study, we determined the molar attenuation coefficients of the InCl3 vapour and plotted the temperature dependences of the value KP. It was found that the phase composition of the alloys significantly influences the position of the corresponding lines on the KP–T diagram, which proves the possibility of using the suggested auxiliary component method in its specific instrumental (spectrophotometric) implementation in order to study the In – Se system. We also showed the additional possibilities of using this method for plotting T-x diagrams of binary systems in such high-temperature areas where the binary solid phase is in equilibrium with the melt. This application of the method is related to the solubility of a vapour of an auxiliary component (chlorine in the form of indium chlorides) in the melts of binary phases (indium selenides).

The chemical stability of uranyl arsenates of rare-earth elements with the general formula MIII(AsUO6)3⋅16H2O (MIII–La–Lu) in aqueous solutions has been studied in a wide range of acidity. The acid–base ranges of the existence of these compounds in aqueous solutions were established, the transformation products formed outside these ranges were identified, and the solubility of MIII(AsUO6)3⋅16H2O was determined. Based on the experimental data obtained, the solubility products, Gibbs free energies of the formation of the rare-earth elements uranyl arsenates were calculated, the solubility curves of the studied compounds were computed, and the speciation diagrams of uranium(VI), arsenic(V), and rare-earth elements in saturated aqueous solutions and equilibrium solid phases were constructed. [ABSTRACT FROM AUTHOR]

Literature data on the existence of mixed fluorides of 3d elements M(II)M(III)F5 (M = Mn, Fe, Co, Ni) were analyzed. Heterogeneous equilibria in MF2–MF3 systems were considered, and equilibrium constants and enthalpies were calculated for the reactions with participation of M2F5(c). The FeF2 sublimation enthalpy of 268.7 ± 1.9 kJ/mol was confirmed, and the FeF3(c) sublimation enthalpy was essentially refined, equal to 264.5 ± 2.2 kJ/mol. For crystalline fluorides Mn2F5, Fe2F5, Co2F5, and Ni2F5, the standard formation enthalpies were determined as equal to –1909.0 ± 7.8, –1716.3 ± 4.4, ≥–1554.2 ± 11, and –1370.5 ± 8.0 kJ/mol, respectively, at 0 K. The enthalpies and Gibbs energies of formation of these compounds from crystalline MF2 and MF3 were within a range of values typical for the solid solutions with weak interaction. [ABSTRACT FROM AUTHOR]

A mathematical model of the Cu(II)–H2O–OH––NH3 system is developed using experimental data obtained by analyzing data on the residual concentration and pH, allowing determination of the conditions for the formation of copper compounds in a solution and in precipitated form. The solubility with respect to the intermediate and the rule for choosing the preferred precipitate are used in the model along with the rules of the product of solubility and molecular solubility to calculate regions of the formation of a solid phase. The values of the effective equilibrium constants of homogeneous and heterogeneous processes are calculated, using the proposed model for forty compounds formed in the system. In a number of cases, the compositions of the compounds are confirmed via X-ray fluorescence, X-ray diffraction, and differential thermographic analysis. It is established that in light of new theoretical concepts, the model allows the conditions for the hydrochemical synthesis of different target compounds to be optimized and provides a more efficient way of creating a database using the final experimental results. [ABSTRACT FROM AUTHOR]

The state of uranyl arsenates with general formula MIAsUO6·nH2O, MI = H+, Li+, Na+, K+, Rb+, Cs+, NH4+ have been investigated in aqueous solutions. The pH ranges of existence of these compounds in aqueous solutions, transformation products and solubility of MIAsUO6·nH2O have been established. Solubility products, standard Gibbs free energies of the uranyl arsenates formation, speciation diagrams for uranium (VI) and arsenic (V) in saturated aqueous solutions and equilibrium solids have been calculated on the basis of the experimental data. [ABSTRACT FROM AUTHOR]

The fluorination of metallic platinum and of cobalt(II) and nickel(II) fluorides with nonequilibrium mixtures of F2 containing high percentages of F is considered in terms of the acquisition of thermodynamic equilibrium. The enthalpy of the reaction Ni2F5(cr) = 2NiF2(cr) + 1/2F2(g) was determined by an independent method to be ΔrH°(0) = –59.9 ± 1.5 kJ/mol, and the enthalpy of formation was verified: ΔfH°(Ni2F5(cr), 0 K). A correlation was shown between the experimentally determined sequences of reactions that occur inside a nickel effusion cell and their enthalpies. [ABSTRACT FROM AUTHOR]

The quantitative basis of the theory of buffer properties for two-phase acid-base buffer systems and for multicomponent heterogeneous systems has been derived. The analytical equations with respect to all components for diverse multicomponent systems were deduced. It has been established, that the buffer capacities of components are mutually proportional.

Keywords: chiral resolution; deracemization; heterogeneous equilibria; racemic compounds; solid solutions EN chiral resolution deracemization heterogeneous equilibria racemic compounds solid solutions 1 1 1 05/16/23 20230511 NES 230511 B Starting from a deracemizable conglomerate b (blue and red cubes), it is possible to substitute in the solid-state part of the blue and red enantiomers with chemically related enantiomers (green and yellow cubes) that crystallize as a racemic compound. The mirror-image solid solutions (enriched mixed crystals) could be deracemized by temperature cycling (deracemized mixed crystals). Cover Feature: Use of Conglomerate Mixed Crystals to Deracemize a Stable Racemic-Compound-Forming System (Chem. Eur. J. 27/2023). [Extracted from the article]

The acid-base equilibria of a diprotic, slightly hydrosoluble base ketoconazole were studied in homogeneous and heterogeneous water systems. The determinations were performed at 25 ºC at a constant ionic strength of 0.1M(NaCl). The acidity constant Ka1 was determined by potentiometric (pKa1 3.20) and spectrophotometric (pKa1 3.26) methods. A pKa2 constant of 6.10 was obtained based on the equilibrium constants pKs0 4.84 and pKs1 1.26, determined in a heterogeneous ketoconazole system. The obtained values of the constants served to calculate the solubility and the distribution of the equilibrium forms of ketoconazole as a function of pH. On the basis of the distribution of the equilibrium forms of ketoconazole, a spectrophotometric method for the determination of its content in commercial tablets was developed. The determinations were performed at 225 nm in 0.1 M HCl. The method is simple and rapid and enables the direct spectrophotometric determination of the content of ketoconazole without previous isolation.

The acid-base equilibria of a diprotic, slightly hydrosoluble base ketoconazole were studied in homogeneous and heterogeneous water systems. The determinations were performed at 25ºC at a constant ionic strength of M(NaCl). The acidity constant Ka1 was determined by potentiometric (pKa1 3.20) and spectrophotometric (pKa1 3.26) methods. A pKa2 constant of 6.10 was obtained based on the equilibrium constants pKs0 4.84 and pKs1 -1.26, determined in a heterogeneous ketoconazole system. The obtained values of the constants served to calculate the solubility and the distribution of the equilibrium forms of ketoconazole as a function of pH. On the basis of the distribution of the equilibrium forms of ketoconazole, a spectrophotometric method for the determination of its content in commercial tablets was developed. The determinations were performed at 225 nm in 0.1 M HCl. The method is simple and rapid and enables the direct spectrophotometric determination of the content of ketoconazole without previous isolation.

The protolytic equilibria of bromazepam, an ampholyte sparingly soluble in water, in homogeneous and heterogeneous systems were studied in the pH range 014 at 25 ?C and at ionic strength of 0.1 mol/dm3 (NaCl). On the basis of 13C-NMR spectra, the protonation site was predicted in acidic media the pyridine nitrogen of bormazepam is protonated. The acidity constants of bromazepam were determined spectrophotometrically (pKa1 2.83 and pKa2 11.60) and potentiometrically (pKa1 2.99). In the heterogeneous system the following equilibrium constants were determined: Ks0 = [HA] (pKs0 3.44), Ks1 = [H2A+]/[H3O+] (pKs1 0.61), and Ks2 = [A-][H3O+] (pKs2 15.04).

The quantitative basis of the theory of buffer properties for two-phase acid-base buffer systems was derived. The analytical equations for buffer action with respect to all components βiof acid-base pairs for diverse multicomponent systems were deduced. A remarkable relation of proportionality was found between quantities. In heterogeneous systems the maximum buffer capacityoccurs whenis equal to, (andare the dissociation and repartition constants, respectively). The nature of synergic buffer action in two-phase systems by formation of mixed species in organic phase was explained. Agreement between theoretical and experimental data is excellent for all the studied buffer systems. [ABSTRACT FROM AUTHOR]

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Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)