Activities of the components of glycerol-water binary solutions at 298.15 K

Based on the assumption that there exists a distribution of hydrates over the hydration number, expressions for the hydration number, activity coefficients of the components, and excess Gibbs energy were obtained. It was demonstrated that the van Laar formula for the activity coefficients corresponds to the Poisson distribution of hydrates. It was established that, at a constant ratio of the variance to the mathematical expectation of the distribution of hydrate, the model’s equations adequately describe the available experimental data on the vapor pressure and water activity for the glycerol-water system over the entire concentration range.     

Reactions of Methyl 4-Aminofurazan-3-carboximidate with Nitrogen-Containing Nucleophiles

Methyl 4-aminofurazan-3-carboximidate reacts with aromatic amines and hydrazines to give the corresponding amidines and amidrazones. The reaction of the title compound with o-phenylenediamine yields 3-amino-4-(2-benzimidazolyl)furazan, and with acylhydrazines N²-acyl-4-aminofurazan-3-carbohydrazides are formed. The latter undergo thermal intramolecular cyclization with formation of 3-amino-4-(1,2,4-triazol-3-yl)furazan derivatives containing various substituents in position 5 of the triazole ring.     

On the adequacy of modeling the concentration dependences of the activity coefficients for the components of solutions

An analysis of the accepted methods for calculating the activity coefficients for the components of binary aqueous solutions was performed. It was demonstrated that the use of the osmotic coefficients in auxiliary calculations decreases the accuracy of estimates of the activity coefficients. The possibility of calculating the activity coefficient of the solute from the concentration dependence of the water activity was examined. It was established that, for weak electrolytes, the interpretation of data on heterogeneous equilibria within the framework of the standard assumption that the dissociation is complete encounters serious difficulties.     

New Heterocycles with a 3-Aminofurazanyl Substituent

New 3-aminofurazans containing 1,2,4- and 1,3,4-oxadiazole, pyridine, and 1,2,4-triazole substituents in the 4-position were synthesized.     

Dependences of the osmotic coefficients of aqueous calcium chloride solutions on concentration at different temperatures

A model that considers the contributions from hydration, ion association, and electrostatic interactions to the nonideality of 2?1 electrolyte solutions is substantiated. The parameters of the model’s equations are the mean ion hydration number, the spread of the distribution of hydrated ion stoichiometric coefficients in the standard state, and the number of association. The model is successfully used to describe literature experimental data on the concentration dependence of osmotic coefficients of aqueous CaCl₂ solutions at temperatures ranging from 0 to 100°C. The modeling of the above systems shows that as the temperature rises, the hydration number falls slightly, the distribution of the hydration number broadens, and the ion paring of the salt rises by the first degree.     

Reactivity of 3,5-bis-(4-amino-1,2,5-oxadiazol-3-yl)-1,2,4-triazole

Alkylation of 3,5-bis(4-amino-1,2,5-oxadiazol-3-yl)-1,2,4-triazole with haloalkanes afforded N-CH₂R derivatives, and nitration furnished the corresponding bis-N-nitramine isolated as a trisodium salt. Treatment of the latter with CH₃I resulted in denitration. Diazotization and oxidation of 3,5-bis(4-amino-1,2,5-oxadiazol-3-yl)-1,2,4- triazole, its N-methyl and N-carboxy derivatives gave rise to the corresponding azido and nitro derivatives. Salts of 3,5-bis(4-amino-1,2,5-oxadiazol-3-yl)-1,2,4-triazol-5-acetic acid with nitrogen-containing bases were synthesized. It was established that the character of reaction products of 3,5-bis(4-amino-1,2,5-oxadiazol-3-yl)-1,2,4-triazole with formaldehyde depended on the acid-base properties of the medium.__________Translated from Zhurnal Organicheskoi Khirmii, Vol. 41, No. 2, 2005, pp. 270–276.Original Russian Text Copyright © 2005 by Sergievskii, Romanova, Mel’nikova, Tselinskii.     

Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

A modified Robinson-Stokes equation with terms that consider the formation of ionic hydrates and associates is used to describe thermodynamic properties of aqueous solutions of electrolytes. The model is used to describe data on the osmotic coefficients of aqueous solutions of alkali metal carboxylates, and to calculate the mean ionic activity coefficients of salts and excess Gibbs energies. The key contributions from ionic hydration and association to the nonideality of solutions is determined by analyzing the contributions of various factors. Relations that connect the hydration numbers of electrolytes with the parameters of the Pitzer-Mayorga equation and a modified Hückel equation are developed.