Thermodynamic and structural characteristics of aqueous alkanolamine solutions

Journal of Structural Chemistry - Thermodynamic characteristics are calculated for aqueous alkanolamine solutions that are obtained by substituting alkyl radicals for the protons in the amino group...     

Thermodynamic parameters of intermolecular interaction in strongly associated solvents and their mixtures with dimethylformamide

The specific and nonspecific constituents of the total energy of intermolecular interasction in ethylene glycol, diethylene glycol, and formamide were determined for the range 288.15–323.15 K using a simulation approach. Diethylene glycol, like formamide and ethylene glycol, forms networks of hydrogen bonds. In ethylene glycol and formamide, the hydrogen bonds make a predominant contribution to the total interaction energy. The specific and nonspecific contributions in mixtures of the above solvents with dimethyl-formamide were calculated, and the results were discussed in combination with the data for aqueous dimethyl-formamide solutions.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 11, 2004, pp. 1789–1796.Original Russian Text Copyright © 2004 by Zaichikov, KrestyaninovThis revised version was published online in April 2005 with a corrected cover date.     

Thermodynamic characteristics of self-associated aminoalcohols

Thermodynamic characteristics of aminoalcohols self-associated by hydrogen bonds have been calculated. Specific and nonspecific components of the total energy of intermolecular interactions have been determined within the model approach. Main goal of this work is the search of thermodynamic characteristics of the liquid-phase systems effectively reflecting both features of intermolecular interactions, and structural changes of individual aminoalcohols. It is established that the most part of the studied aminoalcohols belongs to solvents with H-bonds networks in which there is an intensifying of nonspecific interactions with the temperature rise, and to solvents with chained self-association where the contribution of these interactions practically do not depend on temperature. The aminoalcohols obtained by the substitution of nitrogen atom protons of monoethanolamine by alkyl radicals belong to group of solvents similar aprotic ones at which nonspecific interactions are weakened with the temperature rise. The reasons of it have been discussed by comparison of the data with results for diols, oxyethylated glycols, monoalcohols, and aprotic amides obtained by us earlier.     

Thermodynamic parameters of solvation of nonelectrolytes in aqueous solutions with hydrogen bond networks

The contributions from interaction and reorganization to the enthaplies of solvation of polar and nonpolar nonelectrolytes in aqueous solutions of formamide, ethanediol, and 1,2-propanediol, forming 3D-associated structures in the entire composition range, were calculated. The enthalpy terms of the solvation of nonelectrolytes in aqueous solutions of methyl-and dimethylformamide were estimated. The data were compared considering the thermodynamic characteristics of these aqueous systems that we determined previously. It was found that the shape of the concentration dependences of the enthalpies of solvation of nonelectrolytes in all the examined solutions is determined by the reorganization term. The fact that the solvation of nonelectrolytes in water is the most exothermic compared to the aqueous-organic systems under consideration is due to the lowest value of the reorganization term in water, despite the fact that nonelectrolytes interact with water more weakly than with the nonaqueous components.     

Group Contributions to the Enthalpy Characteristics of Solutions of Formic and Acetic Acid Amides in Water-1,2-Propanediol Mixtures

Enthalpies of solution of formamide and of dimethyl and diethyl derivatives of formamide and acetamide in mixtures of water with 1,2-propanediol at 298.15 K were determined thermochemically. The contributions of hydrocarbon radicals and polar groups to the enthalpies of solution, vaporization, and solvation of the amides were determined. The influence exerted by the structure of molecules and the composition of mixtures on the enthalpy characteristics was considered.     

Thermochemical Study of Ethylene Glycol Mixtures with N,N-Disubstituted Amides of Carboxylic Acids

The enthalpies of mixing of N'N-disubstituted amides of formic, acetic acids with ethyleneglycol were considered in view of the data on the enthalpies of mixing of the same compounds with form-amide and water. The exothermicity of amide-ethylene glycol interactions results from the formation of heterocomponent H bonds stronger than the H bonds in ethylene glycol. Solvophilic solvation and solvophobic effects are much weaker in nonaqueous solutions with low concentrations of amides than in water.     

Solvation and Enthalpy Coefficients of Interaction of Carboxylic Acid Amides with 1,2-Diols in Water

The enthalpies of solution of formamides, acetamides, and propionamides with various extents of N-substitution in aqueous solutions of propylene glycol and 1,2-butanediol (concentration 4 mol kg^{- 1}) at 298.15 K were measured. The enthalpies of transfer of the amides from water to mixed aqueous-organic solvents were determined and discussed in combination with data on the enthalpies of transfer of amides from water to aqueous ethylene glycol solutions. The enthalpy coefficients of pair interactions of amides with 1,2-diols in water were calculated and used for evaluating the group components on the basis of the principle of group additivity of contributions. As the hydrophobic properties of polyfunctional nonelectrolytes are enhanced, the coefficients increase, which is due to the growth of the hydrophobic component of the interaction.     

Excess Enthalpies of Binary Mixtures of Formamide with Secondary Amides

The excess molar enthalpies H^E of binary mixtures of formamide with N-methylformamide, N-ethylformamide, N-methylacetamide, N-ethylacetamide and N-methylpropion-amide have been measured as functions of the mole fraction at 308.15 K, using an isoperibol rotating calorimeter. The experimental values of H^E are negative for all mixtures over the whole composition range. Intermolecular interactions in these mixtures are discussed through comparison of the results with those for corresponding binary mixtures of water. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrochemical Characteristics of the Negative Electrode in Lithium-Ion Batteries: Effect of Structure and Surface Properties of the Carbon Material

Dependence of charge-discharge characteristics of the carbon electrode of a lithium-ion battery on crystallographic and macrostructural parameters of the carbon material and the on conditions of a preliminary treatment of this material are studied. The conclusion is drawn that, in order to obtain a carbon material that would be optimum for the negative electrodes of lithium-ion batteries, it is necessary to couple technological expedients of various types that would take into account the opposite, by the results, action of various factors (in the first place, dispersion of carbon and an increase in the temperature of its thermal treatment) on such electrochemical characteristics of electrodes as the rate of a charge-discharge process and value of its coulombic efficiency. Characteristics of carbon materials, obtained on the basis of domestic raw materials, which ensure efficient operation of such electrodes, are presented.     

Hydrogen bonds in ethylene glycol,monoethanolamine, and ethylenediamine complexes with water

Russian Journal of Physical Chemistry A - The structures of ethylene glycol, aminoethanol, and ethylenediamine complexes with water and the formation of hydrogen bonds of different types are...