The thermodynamic properties and solvation of lithium halides in N-methylpyrrolidone at 298.15 K

The heat capacity and density of solutions of lithium chloride, bromide, and iodide in N-methylpyrrolidone (I) were determined by calorimetry and densimetry techniques. The standard partial molar heat capacities and volumes ( $\overline {C^\circ _{p2} } $ and $\overline {V^\circ _2 } $ ) of lithium halides in I were calculated. The $\overline {C^\circ _{pi} } $ and $\overline {V^\circ _i } $ values for halogen and lithium ions in I were determined. The coordination numbers of the Li⁺, Cl^?, Br^?, and I^? ions in solutions in I at 298.15 K were calculated.     

The thermodynamic properties of acetals+heptane mixtures at 298.15 K

Excess enthalpies and excess volumes were determined at 298.15 K for: dimethoxymethane+heptane, diethoxymethane+heptane, 1,1-dimethoxyethane+heptane, 1,1-diethoxyethane+heptane, 2,2-dimethoxypropane+heptane and 1,1-diethoxypropane+heptane.     

The heat capacity of singly charged inorganic ions in methylpyrrolidone at 298.15 K

The standard partial molar heat capacities of singly charged ions in methylpyrrolidone (MP) at 298.15 K are reported. Heat capacity changes caused by the solvation of ions in MP and water are used to analyze the influence of various effects on ion-solvent interactions.     

The heat capacity and density of solutions of cadmium and mercury diiodides in methylpyrrolidone at 298.15 K

The heat capacity and density of solutions of cadmium and mercury diiodides in methylpyrrolidone (MP) at 298.15 K were studied by calorimetry and densimetry. The data obtained are discussed in relation to the special features of solvation and complex formation in solutions of the salts. The standard partial molar heat capacities and volumes (

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and

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) of the electrolytes in MP were calculated. The standard heat capacities

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and volumes

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of the Cd²⁺ and Hg²⁺ ions in solutions in MP at 298.15 K were determined.

     

Physicochemical investigation on interactions of some amino acids with aqueous tetra-butyl ammonium bromide solution at 298.15 K

Apparent molar volumes, viscosity B-coefficients, and apparent molar isentropic compressibilities of glycine, L-alanine, L-valine and L-leucine in 0.062, 0.125 and 0.256 mol kg^?1 aqueous tetra-butyl ammonium bromide (TBAB) solution have been determined at 298.15 K from their experimental density, flow time and sound speed measurements, respectively. The standard partial molar volumes and compressibilities are used to calculate the corresponding volume of transfer at infinite dilution, from water to aqueous TBAB solutions. The linear correlation of partial molar volumes for a homologous series of amino acids has been utilised to calculate the contribution of charged end groups and other alkyl chains of the amino acids to partial molar volumes. The hydration numbers of amino acids have also been determined. Viscosity B-coefficients have been calculated using the Jones–Dole equation. The values of the charged end groups contribution to the viscosity B-coefficients of the amino acids are calculated.     

The enthalpies of solution and solvation of glycine in mixed water-formamide solvents at 298.15 K

The enthalpies of solution (ΔH _sol ^o ) of glycine in aqueous formamide, N-methylformamide, N,N-dimethylformamide, and N,N-diethylformamide were determined by calorimetry at 298.15 K over the concentration range x ₂=0–0.3 mole fractions. The enthalpies of glycine solvation (ΔH _solv ^o ) and transfer from water to mixed solvents (ΔH _tr ^o ) were calculated. The ΔH _sol ^o =f(x ₂) dependences for glycine in water-N-and water-N,N-substituted amide mixtures had extrema and, in water-formamide mixtures, this dependence was a smooth function, whose values changed in the opposite direction. The enthalpy coefficients of pair glycine-amide interactions were calculated. The interrelation between the enthalpy characteristics of solution, transfer, and solvation of glycine and the structure and physicochemical characteristics of solvents, on the one hand, and the composition of mixtures, on the other, was revealed.     

Structure and thermodynamic properties of nitroformic acid,nitroformyl nitrate,and ammonium nitroformate

As part of a series of investigations of molecules with large numbers of nitro groups, the structures and properties of nitroformic acid, NO₂CO₂H, nitroformyl nitrate, NO₂C(O)ONO₂, and the ion pair ammonium nitroformate, NH₄NO₂CO₂, have been determined using GX theories (X = 2, 3, 4). Minimum-energy structures, vibrational frequencies, selected bond energies, and enthalpies of formation were determined. The title substances may not have much application as high energy materials like other high-nitro compounds, but they may act as good nitrating agents since certain bonds in the molecules are of low enough energy to suggest high reactivity.     

Preferential solvation of methocarbamol in aqueous binary co-solvent mixtures at 298.15 K

The preferential solvation parameters of methocarbamol in dioxane + water, ethanol + water, methanol + water and propylene glycol + water mixtures are derived from their thermodynamic properties by using the inverse Kirkwood–Buff integrals (IKBI) method. This drug is sensitive to solvation effects, being the preferential solvation parameter δx_1,3, negative in water-rich and co-solvent-rich mixtures, but positive in mixtures with similar proportions of solvents, except in methanol + water mixtures, where positive values are found in all the methanol-rich mixtures. It is conjecturable that the hydrophobic hydration around the non-polar groups in water-rich mixtures plays a relevant role. Otherwise, in mixtures of similar solvent compositions, the drug is mainly solvated by co-solvent, probably due to the basic behaviour of the co-solvents; whereas, in co-solvent-rich mixtures, the preferential solvation by water could be due to the acidic behaviour of water. Nevertheless, the specific solute–solvent interactions present in the different binary systems remain unclear.     

The solvation of L-serine in mixtures of water with some aprotic solvents at 298.15 K

The integral enthalpies of solution Δ_sol H ^m of L-serine in mixtures of water with acetonitrile, 1,4-dioxane, dimethylsulfoxide (DMSO), and acetone were measured by solution calorimetry at organic component concentrations up to 0.31 mole fractions. The standard enthalpies of solution (Δ_sol H°), transfer (Δ_tr H°), and solvation (Δ_solv H°) of L-serine from water into mixed solvents were calculated. The dependences of Δ_sol H°, Δ_solv H°, and Δ_tr H° on the composition of aqueous-organic solvents contained extrema. The calculated enthalpy coefficients of pair interactions of the amino acid with cosolvent molecules were positive and increased in the series acetonitrile, 1,4-dioxane, DMSO, acetone. The results obtained were interpreted from the point of view of various types of interactions in solutions and the influence of the nature of organic solvents on the thermochemical characteristics of solutions.     

Heat capacity and density of methylpyrrolidone solutions of sodium and potassium perchlorates at different concentrations and 298.15 K

The heat capacity and density of solutions of sodium and potassium perchlorates in N-methylpyrrolidone (MP) at 298.15 K were studied by calorimetry and densimetry. The standard partial molar heat capacities $ \bar C_{p2}^ \circ $ \bar C_{p2}^ \circ and volumes $ \bar V_2^ \circ $ \bar V_2^ \circ of NaClO₄ and KClO₄ in MP were calculated. The standard heat capacities $ \bar C_{pi}^ \circ $ \bar C_{pi}^ \circ and volumes $ \bar V_i^ \circ $ \bar V_i^ \circ of the perchlorate ion in an MP solution at 298.15 K were determined. The results are discussed with allowance for the specifics of solvation in the solutions of the salts under study. The coordination number of the ClO₄⁻ ion in an MP solution at 298.15 K was calculated.     

Thermodynamic functions of solvation of 1,4-dioxane in various solvents at 298.15 K

The standard changes in enthalpy during the solvation of 1,4-dioxane in methanol, ethyl acetate, DMF, and acetonitrile were determined from calorimetric data and compared with the literature data for a series of solvents with different polarities. The standard changes in the Gibbs energy during the solvation of 1,4-dioxane in a wide series of solvents were calculated from the activity coefficients reported in the literature. The variation of the solvation functions of low-polar 1,4-dioxane in the series of solvents was found to be consistent with the enthalpy-entropy compensation rule. The results for 1,4-dioxane were compared with those for its open-chain analog and related large cyclic molecules. The electrostatic interactions of the solute with the solvents did not markedly affect the thermodynamic characteristics of ether in media with different polarities, but affected the interaction of the solute with the solvent more significantly. The solvation of the small ring of 1,4-dioxane in aprotic solvents was accompanied by a more significant exothermal effect than in the case of its open-chain analog. The conclusion was drawn that the enthalpies of the formation of hydrogen bonds between 1,4-dioxane and the associated water and chloroform molecules in solution were smaller in magnitude than the bonds of the similar open-chain polyether.     

Re-evaluation of the thermodynamic activity quantities in aqueous alkali metal nitrate solutions at T = 298.15 K

The Hückel equation used in this study to correlate the experimental activities of dilute alkali metal nitrate solutions up to a molality of about 1.5 mol · kg⁻¹ contains two parameters being dependent on the electrolyte: B [that is related closely to the ion-size parameter (a∗) in the Debye–Hückel equation] and b₁ (this parameter is the coefficient of the linear term with respect to the molality and this coefficient is related to hydration numbers of the ions of the electrolyte). In more concentrated solutions up to a molality of 7 mol · kg⁻¹, an extended Hückel equation was used, and it contains additionally a quadratic term with respect to the molality and the coefficient of this term is parameter b₂. All parameter values for the Hückel equations of LiNO₃, NaNO₃, and KNO₃ were determined from the isopiestic data measured by Robinson for solutions of these salts against KCl solutions [J. Am. Chem. Soc. 57 (1935) 1165]. In these estimations, the Hückel parameters determined recently for KCl solutions [J. Chem. Eng. Data 54 (2009) 208] were used. The Hückel parameters for RbNO₃ and CsNO₃ were determined from the reported osmotic coefficients of Robinson [J. Am. Chem. Soc. 59 (1937) 84]. The resulting parameter values were tested with the vapour pressure and isopiestic data existing in the literature for alkali metal nitrate solutions. These data support well the recommended Hückel parameters up to a molality of 7.0 mol · kg⁻¹ for LiNO₃ and NaNO₃, up to 4.5 mol · kg⁻¹ for RbNO₃, up to 3.5 mol · kg⁻¹ for KNO₃, and up to 1.4 mol · kg⁻¹ for CsNO₃ solutions. Reliable activity and osmotic coefficients of alkali metal nitrate solutions can, therefore, be calculated by using the new Hückel equations, and they have been tabulated at rounded molalities. The activity and osmotic coefficients obtained from these equations were compared to the values suggested by Robinson and Stokes [Electrolyte Solutions, second ed., Butterworths Scientific Publications, London, 1959], to those calculated by using the Pitzer equations with the parameter values of Pitzer and Mayorga [J. Phys. Chem. 77 (1973) 2300], and to those calculated by using the extended Hückel equation of Hamer and Wu [J. Phys. Chem. Ref. Data 1 (1972) 1047].     

Solubility and preferential solvation of acetaminophen in methanol + water mixtures at 298.15 K

The equilibrium solubility of acetaminophen in methanol + water binary mixtures at 298.15 K was determined and correlated with the Jouyban–Acree model. Preferential solvation parameters by methanol (δx_1,3) were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals method. δx_1,3 values are negative in water-rich mixtures but positive in compositions from 0.32 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case, the hydrophobic hydration around non-polar groups plays a relevant role in the solvation. The higher solvation by methanol in mixtures of similar cosolvent compositions and methanol-rich mixtures could be explained in terms of the higher basic behavior of this cosolvent.     

Thermochemistry of dissolution,solvation, and hydrogen bonding of anilines in proton-acceptor organic solvents at 298.15 K

Enthalpies of dissolution at infinite dilution (298.15 K) of aniline, N-methylaniline, and N,N-dimethylaniline in a series of proton-acceptor solvents of different classes of compounds have been measured. The solvation enthalpies have been determined, and its relationship with the anilines structure has been analyzed. Enthalpy of hydrogen bonding in the complexes of aniline (1: 2) and N-methylaniline (1: 1) with the solvents has been calculated. In the case of aniline complexes, negative cooperativity of hydrogen bonding has been revealed, the effect enhancing with increasing the solvent proton-acceptor ability.     

Synthesis and micellar properties of 1-decyl-2,3-dimethylimidazolium bromide surfactant in water and water-ethanolamine mixtures at 298.15 K

1-Decyl-2,3-dimethylimidazolium bromide (ddmimBr) has been synthesized by the reaction of 1,2-dimethylimidazole and 1-bromodecane. Micellization of ddmimBr surfactant in water (W) and water-ethanolamine (W-EA) with the weight percent of EA changing within the range 0-39.79%, has been investigated at 298.15 K. Information about the influence of the added EA on the critical micelle concentration (CMC) was obtained through density and surface tension measurements. This last provides information about the dependence of the surface excess concentration, the minimum area per surfactant molecule and the surface pressure at the CMC on the added weight percentage of organic solvent. The effect of binary aqueous mixtures of W-EA on the apparent molar volume (phi V) of the ddmimBr has been investigated. The apparent molar volume upon aggregation (Delta phi V) shows a maximum at about 15 wt% of EA, this behavior is discussed in terms of the changes of the solvent structure. Partial specific volume data, obtained by density measurements, indicate that the fraction of solvent molecules interact with the surfactant remained roughly constant.     

Heat capacity and density of potassium iodide solutions in mixed N-methylpyrrolidone-water solvent at 298.15 K

The heat capacity and density of potassium iodide solutions in a mixed N-methylpyrrolidone (MP)-water solvent with a low content of the organic component are measured via calorimetry and densimetry at 298.15 K. Standard partial molal heat capacities \(\bar C_{p,2}^ \circ \) and volumes \(\bar V_2^ \circ \) of potassium iodide in MP-water mixtures are calculated. Standard heat capacities \(\bar C_{p,i}^ \circ \) and volumes \(\bar V_i^ \circ \) of potassium and iodide ions are determined. The character of the changes in heat capacity and volume are discussed on the basis of calculating additivity coefficients δ _c and δ _v upon the mixing of isomolal binary solutions KI-MP and KI-water, depending on the composition of the MP-H₂O mixture and the concentration of the electrolyte.     

Enthalpy characteristics of the dissolution and solvation of crystalline L-proline in water-ethanol mixtures at 298.15 K

Heats of solution of L-proline in water-ethanol mixtures at ethanol mole fractions in the range 0.00 < X _EtOH < 0.70 are measured at 298.15 K via calorimetry. Standard enthalpies of solution of proline in water and water-alcohol mixtures are calculated and analyzed. Enthalpy coefficients of pair and triple acid-alcohol interactions in water at low alcohol concentrations are calculated in terms of the McMillan-Mayer theory. The obtained enthalpy characteristics are compared to those for previously investigated proline-containing water-alcohol systems.     

Bulk properties and hydration numbers of ammonium nitrate and ammonium chloride in solution: A structural and thermodynamic analysis

The apparent volumes of the salts in the systems H₂O-NH₄Cl (298 K) and H₂O-NH₄NO₃ (273 K, 298 K, and 323 K) are reproduced with an accuracy of 0.03–0.01 cm³/mol by the equation ? = ?⁰ + Aw ₂ ^0.5 + Bw ₂, where w ₂ is the salt content (mass fractions). The study shows that there is a correspondence between the critical (for determining the hydration number) structural parameters-the intrinsic volume of the electrolyte and the volume of water in ion hydration shells-and the limiting (at w ₂ = 1) partial molar volumes of the components. The hydration numbers at infinite dilution are 6.9 for NH₄Cl at 298 K and 9.1, 6.7, and 6.4 for NH₄NO₃ at 273 K, 298 K, and 323 K. The water volume in ion hydration shells decreases in the sequence: No ₃ ^? , Cl^?, and NH ₄ ⁺ . The hydration numbers decrease with increasing salt concentration. The study shows that within a simpler model ? = ?⁰ + aw ₂ ^0.5 , the hydration numbers are temperature independent.