Thermodynamic and structural characteristics of aqueous diamine solutions

Thermodynamic characteristics are calculated for aqueous diamine solutions prepared by substituting an amino group for the hydroxyl group of amino alcohols. Patterns are revealed in the change of the structural properties of the mixtures. The correlation between the entropy and enthalpy characteristics of the water–diamine systems and the excess packing coefficients suggests that the universal interactions determine the structural and energy properties of aqueous solutions of the studied diamines. The form of the concentration dependences of the structural and thermodynamic characteristics in the studied systems is found to be symbatic with the data for the mixtures of water with aprotic amides. The reasons for this are discussed by comparing the results with our previously published data for aqueous solutions of aprotic amides.     

Structural-thermodynamic characteristics and intermolecular interactions in mixtures of strongly associated solvents with aprotic amides

Thermodynamic characteristics of mixtures of aprotic amides with water and organic solvents with hydrogen bond networks are calculated. Within a model approach the specific and non-specific components of the total energy of the intermolecular interaction are determined, based on which the corresponding contributions to the enthalpies of component mixing are calculated. It is found that negative enthalpies of mixing in the mixtures under study are due to non-specific interactions rather than heterocomponent specific ones. It is shown that the difference in the structural-thermodynamic characteristics of aqueous and nonaqueous mixtures of aprotic amides is mainly caused by packing features of solutions and the behavior of hydrogen bond networks of water and organic solvents.     

Structural and thermodynamic characteristics of amide solvents

The structural and thermodynamic characteristics of amide solvents are calculated with different types of molecular self-assembly through hydrogen bonding. Under a model-based approach, the specific and nonspecific components of the total energy of intermolecular interactions are identified for primary, secondary, and tertiary amides of carboxylic acids. It is found that similarly to water, primary amides have a network of hydrogen bonds and belong to the class of liquids characterized by an increase in nonspecific interactions with temperature. In secondary amides with the chain self-assembly, the contribution of these interactions is practically independent of temperature, and in tertiary amides it decreases with an increase in temperature. The molar values of the specific and nonspecific components are used to analyze the intermolecular interactions and the structural properties of amides with different degrees of N-substitution.     

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 Study of Oxyethylated Glycols and Their Mixtures with Tertiary Carboxamides

The contributions into the total energy of intermolecular interactions in oxyethylated ethylene glycol derivatives were estimated in terms of a model approach that uses inner pressure as a measure of nonspecific interactions in a liquid. Increased number of ether groups in ethylene glycols increases the nonspecific contribution and decreases specific contributions. Unlike diethylene glycol, triethylene glycol and tetraethylene glycol contain H-bond networks in the range 298.15–308.15 K. The enthalpies of mixing of tertiary amides with tetraethylene glycol were measured and compared with those for ethylene glycol, diethylene glycol, and triethylene glycol. The effect of the structural and thermodynamic properties of the components on the integral and differential thermochemical characteristics of mixtures of glycols with N,N-disubstituted amides was discussed.     

Solvation of amides of formic and acetic acids in water-glycerol mixture. Additivity of thermochemical characteristics of solutions

Values of the solution enthalpy of are measured and values of solvation enthalpy are calculated for formamide and N,N-two-substituted methyl-and ethylamides of formic and acetic acids in the mixed solvent: water-glycerol. Enthalpy coefficients of pair interactions between amides and glycerol in aqueous solutions are calculated. The influence of mixture composition and also of a structure and properties of the dissolved compounds on enthalpy characteristics is considered. Within the frames of the offered additive scheme the contributions from the structural fragments of molecules of amides to enthalpy characteristics of solutions are established. It has allowed us to analyze quantitatively the role of nonspecific and specific solvation of amides in solution, to predict the enthalpy of evaporation, solution, solvation, the enthalpy coefficients of pair interactions of experimentally unstudied N-methylformamide, N-ethylformamide, N-methyl-N-ethylformamide, N-methylacetamide, N-ethylacetamide, and N-methyl-N-ethylacetamide in the mixtures of water-glycerol, and also to evaluate the donor numbers of these specified amides.     

Structural thermodynamic parameters and intermolecular interactions in aqueous solutions of secondary amides

Structural thermodynamic parameters are calculated for aqueous solutions of secondary amides of carboxylic acids. Specific and nonspecific contributions to the total energy of intermolecular interactions are determined and the boundaries of concentration regions for a various structural organization of solutions are found.     

Structral and thermodynamic characteristics and intermolecular interactions in aqueous solutions of diols

The structural and thermodynamic characteristics of aqueous solutions of ethanediol, 1,2-and 1,3-propanediols, and 1,2-and 1,4-butanediols were calculated over the whole range of the compositions of the mixtures. The specific and nonspecific components of the total energy of intermolecular interactions were determined. The boundaries of the concentration regions with different structural organizations of solutions were established, and the parameters of preferable solvation of the solution components were evaluated.     

Structural thermodynamic characteristics and intermolecular interactions in aqueous solutions of hexamethylphosphorotriamide

Structural thermodynamic parameters of aqueous solutions of hexamethylphosphorotriamide are calculated. They are discussed together with previously obtained data on aqueous solutions of disubstituted amides of carboxylic acids. The specific and non-specific components of the total energy of intermolecular interactions are determined. The boundaries of concentration regions with different structural organizations of solutions are found, and the preferential solvation parameters of solution components are estimated.     

New Screening Protocol for Effective Green Solvents Selection of Benzamide,Salicylamide and Ethenzamide

New protocol for screening efficient and environmentally friendly solvents was proposed and experimentally verified. The guidance for solvent selection comes from computed solubility via COSMO-RS approach. Furthermore, solute-solvent affinities computed using advanced quantum chemistry level were used as a rationale for observed solvents ranking. The screening protocol pointed out that 4-formylomorpholine (4FM) is an attractive solubilizer compared to commonly used aprotic solvents such as DMSO and DMF. This was tested experimentally by measuring the solubility of the title compounds in aqueous binary mixtures in the temperature range between 298.15 K and 313.15 K. Additional measurements were also performed for aqueous binary mixtures of DMSO and DMF. It has been found that the solubility of studied aromatic amides is very high and quite similar in all three aprotic solvents. For most aqueous binary mixtures, a significant decrease in solubility with a decrease in the organic fraction is observed, indicating that all systems can be regarded as efficient solvent-anti-solvent pairs. In the case of salicylamide dissolved in aqueous-4FM binary mixtures, a strong synergistic effect has been found leading to the highest solubility for 0.6 mole fraction of 4-FM.     

Structural and thermodynamic parameters and intermolecular interactions in aqueous dialkylacetamides

The structural and thermodynamic parameters of aqueous dimethylacetamide and diethylacetamide have been calculated; the specific and nonspecific components of the total energy of intermolecular interactions have been determined. As alkyl radicals increase in size, the concentration regions with different structural organizations of solutions undergo transformation.     

Thermodynamic and structural properties of aqueous linear diol solutions

Thermodynamic characteristics of aqueous linear diol solutions are calculated. These data are used to identify regularities in the variations of the structural properties of the mixtures being studied. The correlation between the entropy and enthalpy characteristics of water-diol systems with excess packing coefficients is evidence that the structural and energy properties of aqueous linear diol solutions are determined by universal interactions. The form of the concentration dependences of the solvation enthalpies and entropies of noble gases in water-linear diols mixtures is determined by the reorganization component and is attributed to the destruction of the H bond network of water, which results in the formation of the most densely packed solutions in the medium range of compositions.     

Thermochemistry of Benzene Solution in Alcohols, Aprotic Solvents, and Mixtures of Aprotic Solvents with Methanol

The standard enthalpies of solution of benzene at 25°C in alcohols (methanol, 1-propanol, 1-pentanol, 1-decanol), aprotic solvents (1,4-dioxane, acetone, acetonitrile, dimethyl sulfoxide, dimethylformamide, propylene carbonate), and mixtures of methanol with these aprotic solvents were determined. Multiple regression analysis revealed the role of specific and nonspecific interactions in solvation of benzene in these solvents.     

Thermodynamic characteristics and intermolecular interactions in aqueous solutions of oxyethylated glycols

The thermodynamic characteristics of aqueous solutions of mono-, di-, tri-, and tetraethylene glycols were calculated in the entire range of compositions of the mixtures for various temperatures. The specific and nonspecific terms of the total energy of intermolecular interaction were determined within the framework of a model approach using the internal pressure as a measure of nonspecific interactions in a liquid. The concentration ranges with different types of intercomponent association and of structural organization of solutions depend on the temperature and number of ether groups in the glycol molecules.     

Binary Mixtures of Aprotic and Protic Ionic Liquids Demonstrate Synergistic Polarity Effect: An Unusual Observation

In this communication, we demonstrate the solute–solvent and solvent–solvent interactions in the binary mixtures of two aprotic ionic liquids, namely 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, with the protic ionic liquid 1-methylimidazolium acetate. The synergistic effects as expressed by the solvatochromic parameter are noted. This observation is in contrast to the mixing of protic ionic liquids 1-methylpyrrolidium acetate and 4-methylmorpholine acetate with 1-methylimidazolium acetate, respectively. It appears that the synergistic effects in the binary mixtures of aprotic and protic ionic liquids are caused by the formation of hydrogen bonds, since cations are dominant H-bond donors while anions are dominant H-bond acceptors. Preferential solvation models are used to describe the solute–solvent interactions in the binary ionic liquid mixtures.     

Dispersions of nanoclays of different shapes into aqueous and solid biopolymeric matrices. Extended physicochemical study

Dispersions of nanofillers into aqueous and solid biopolymeric matrices were studied from the physicochemical viewpoint. This work was carried out based on the idea that the combination of biopolymers, derived from renewable resources, and nanofiller, environmentally friendly, may form a new generation of nanomaterials with excellent and unique properties at low cost. To this purpose, two pectins with different degrees of methyl esterification and nanoclays like halloysite and laponite RD were selected. The thermodynamic and structural studies on the aqueous mixtures of pectin and nanoclay were able to discriminate the interactions, which control the adsorption of pectin onto the filler and the aggregation of both pectin and clay particles. The gained insights were useful to interpret the mesoscopic structure of the nanocomposites (prepared from the aqueous mixtures by means of the casting method) evidenced by SEM, thermal stability, tensile properties, and transparency investigations. The attained knowledge represents a basic point for designing new hybrid nanostructures in both the aqueous and the solid phase for specific purposes.     

Thermodynamic Characteristics of Phenacetin in Solid State and Saturated Solutions in Several Neat and Binary Solvents

The thermodynamic properties of phenacetin in solid state and in saturated conditions in neat and binary solvents were characterized based on differential scanning calorimetry and spectroscopic solubility measurements. The temperature-related heat capacity values measured for both the solid and melt states were provided and used for precise determination of the values for ideal solubility, fusion thermodynamic functions, and activity coefficients in the studied solutions. Factors affecting the accuracy of these values were discussed in terms of various models of specific heat capacity difference for phenacetin in crystal and super-cooled liquid states. It was concluded that different properties have varying sensitivity in relation to the accuracy of heat capacity values. The values of temperature-related excess solubility in aqueous binary mixtures were interpreted using the Jouyban–Acree solubility equation for aqueous binary mixtures of methanol, DMSO, DMF, 1,4-dioxane, and acetonitrile. All binary solvent systems studied exhibited strong positive non-ideal deviations from an algebraic rule of mixing. Additionally, an interesting co-solvency phenomenon was observed with phenacetin solubility in aqueous mixtures with acetonitrile or 1,4-dioxane. The remaining three solvents acted as strong co-solvents.     

Structural and thermodynamic parameters and intermolecular interactions in aqueous formic acid amides

The structural and thermodynamic characteristics of aqueous solutions of formamide, N-methylformamide, N,N-dimethylformamide, and N,N-diethylformamide were calculated. The specific and nonspecific components of the total energy of intermolecular interactions were determined. The limits of the concentration regions with differently arranged structures of solutions were established, and the preferable solvation parameters of the solution components were evaluated.