Solubility of anthracene in binary alkane + ethanol solvent mixtures at 298.15 K

Experimental solubilities are reported for anthracene in six binary alkane?+?ethanol solvent mixtures at 298.15?K. The alkane solvents studied were hexane, heptane, octane, cyclohexane, methylcyclohexane and 2,2,4-trimethylpentane. Results of these measurements were used to test a mathematical representation based on the combined nearly ideal binary solvent (NIBS)/Redlich–Kister equation. For the six systems studied, the combined NIBS/Redlich–Kister equation was found to accurately describe the experimental data, with an average absolute deviation between measured and back-calculated values being approximately ±0.5%.     

Preferential solvation of etoricoxib in some aqueous binary cosolvent mixtures at 298.15 K

Preferential solvation parameters of etoricoxib in several aqueous cosolvent mixtures were calculated from solubilities and other thermodynamic properties by using the IKBI method. Cosolvents studied were as follows: 1,4-dioxane, N,N-dimethylacetamide, 1,4-butanediol, N,N-dimethylformamide, ethanol and dimethyl sulfoxide. Etoricoxib exhibits solvation effects, being the preferential solvation parameter δx_1,3, negative in water-rich and cosolvent-rich mixtures but positive in mixtures with similar proportions of both solvents. It is conjecturable that the hydrophobic hydration in water-rich mixtures plays a relevant role in drug solvation. In mixtures of similar solvent proportions where etoricoxib is preferentially solvated by the cosolvents, the drug could be acting as Lewis acid with the more basic cosolvents. Finally, in cosolvent-rich mixtures the preferential solvation by water could be due to the more acidic behaviour of water. Nevertheless, the specific solute–solvent interactions in the different binary systems remain unclear because no relation between preferential solvation magnitude and cosolvent polarities has been observed.     

Hetero-molecular association in binary mixtures of solvent extractants and diluents at temperature 303.15 K

Ultrasonic velocity and viscosity measurements have been made for binary liquid mixtures of solvent extractants, LIX reagents such as LIX 84 and LIX 984 in benzene, amyl alcohol and tri-n-butyl phosphate (TBP) at temperature 303.15?K and at atmospheric pressure. The measured values of ultrasonic velocity, density and viscosity have been utilised to compute various thermo-acoustic parameters and their excess functions, which provide information about the nature and strength of intermolecular interactions present in the systems.     

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

The mole fraction solubility of phenacetin (PNC) in methanol + water binary solvent mixtures at 298.15 K was determined along with density of the saturated solutions. All these solubility values were correlated with the Jouyban–Acree model. Preferential solvation parameters of PNC by methanol (δx_1,3) were derived from their thermodynamic solution properties using the inverse Kirkwood–Buff integrals (IKBI) method. δx_1,3 values are negative in water-rich mixtures but positive in methanol mole fraction of >0.32. It is conjecturable that in the former case the hydrophobic hydration around non-polar groups of PNC 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 behaviour of methanol.     

Excess enthalpies of binary mixtures of butylamines + propanols at 298.15 K

The molar excess enthalpies of eight systems of butylamines + propanols were determined at 298.15 K using a twin-microcalorimeter. All excess enthalpies were exothermic and large. An equilibrium constant K ₁ expressed in terms of mole fractions and standard thermodynamic properties of formation (Δ_f H, Δ_f G, Δ_f S) of 1:1 complex were evaluated by ideal mixtures of monomeric molecules and their associated complexes. Concentration dependence of the FT-Raman spectrum showed systematic changes of bands. Spectroscopic considerations based on this and ab initio calculations on molecules were performed at the Mp2/6-311G(d,p) level of theory. Interaction energies between butylamine and propanol were calculated by the supermolecular and NBO methods. The results were discussed with previous results to clarify the steric and positional effect of the amino and hydroxyl group.     

The enthalpies of solution of L-α-alanyl-L-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution (T = 298.15 K) of L-α-alanyl-L-α-alanine in aqueous-organic solvents (acetonitrile, 1,4-dioxane, acetone, formamide, N-methylformamide, N,N-dimethylformamide, N,N-diethylformamide, and N,N-dimethylsulfoxide) were measured at organic component concentrations x ₂ = 0–0.3 mole fractions. The standard enthalpies of solution (Δ_sol H ^o) and transfer (Δ_tr H ^o) of the peptide from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on solute thermochemical characteristics is considered. The enthalpy pair interaction coefficients h _xy between L-α-alanyl-L-α-alanine and organic solvent molecules were calculated. The linear Kamlet-Taft four-parameter equation was used to reveal correlation between the h _xy values and the properties of organic solvents.     

Studies on solution properties of ternary mixture of acetophenone + n-amyl alcohol + dichloromethane and its corresponding binaries at 298.15 K

The excess values of molar volume (V ^E), viscosity deviation (Δη), deviation in isentropic compressibility (ΔK_S ), excess molar refraction (ΔR) and excess Gibbs energy of activation (ΔG^*E ) of viscous flow have been investigated from the experimentally measured densities, viscosities, sound speeds and refractive indices for three binary mixtures of acetophenone?+?n-amyl alcohol, acetophenone?+?dichloromethane and n-amyl alcohol?+?dichloromethane and their corresponding ternary mixtures at 298.15?K over the entire composition range. The calculated quantities are further fitted to the Redlich–Kister equation to estimate the binary fitting parameters and standard deviations from the regression lines. The excess or deviation properties were found to be either negative or positive depending on the molecular interactions and the nature of liquid mixtures and have been discussed in terms of molecular interactions and structural changes.     

Solubility behavior,dissolution thermodynamics and solute–solvent intermolecular interactions of a solid antioxidant product in water + isopropanol liquid mixtures from 298.15 to 320.15 K

The solid–liquid equilibria of a poorly water-soluble antioxidant agent namely naringoside were assayed to determine solubility in binary liquid mixtures of water?+?isopropanol (iso-PrOH) between 298.15 K and 320.15 K under atmospheric pressure. The mole fraction solubilities of naringoside in the saturated solution were determined using a combination of static shake-flask and ultraviolet spectrophotometry techniques. The dissolution behavior of naringoside was correlated with three solution models consisting of the van’t Hoff equation, the modified Apelblat equation and the Buchowski-Ksiazczak λH equation. The modified Apelblat equation was more consistent than the two other correlation models. Apparent thermodynamic analysis of naringoside dissolution was also performed at the mean harmonic temperature using the model parameters of the modified Apelblat equation. Furthermore, the Kamlet, Abboud and Taft Linear Solvation Energy Relationship (KAT-LSER) model was applied to analyze the effect of the solute–solvent intermolecular interactions on the solubility of this natural bioactive product.     

Thermodynamics of binary mixtures of aliphatic linear alkanes (C6–C12) at 298.15 K

This article reports experimental values of speeds of sound, densities and refractive indices on mixing of the binary mixtures n-hexane + (n-heptane, n-octane, n-nonane, n-decane, n-undecane, or n-dodecane) at 298.15?K and atmospheric pressure, over the whole concentration range. The corresponding excess and derived properties were computed from the experimental data. The results were fitted by means of the Redlich–Kister equation, such parameters being gathered. Different estimation methods (equations of state, mixing rules, Collision Factor and Free Length Theory) were applied, qualitative agreement between the experimental and theoretical values both in magnitude and sign being obtained.     

Reduced Redlich–Kister functions and interaction studies of Dehpa + Petrofin binary mixtures at 298.15 K

In order to understand the effect of different types of interactions in liquid mixtures by applying the correlative reduced Redlich–Kister equation, excess molar volume, excess dielectric constant, deviation in refractive index, deviation in molar refraction and molar polarisation were calculated at the temperature 298.15 K and atmospheric pressure P = 101.325 kPa for the binary mixture Petrofin (1) + Dehpa (2). The experimentally determined data of density and refractive index which were published earlier were used for these calculations. The results were interpreted in terms of structural effects of the solvents.     

Enthalpy characteristics of L-proline dissolution in certain water–organic mixtures at 298.15 K

A thermochemical study of the processes of L-proline dissolution in aqueous solutions of acetonitrile, 1,4-dioxane, acetone, dimethyl sulfoxide, nitromethane and tetrahydrofuran at Т = 298.15 K in the range of organic solvent concentrations x₂ = 0–0.25 mole fractions is performed. Standard values of the enthalpies of solution and transfer of L-proline from water to mixed solvent, and the enthalpy coefficients of pairwise interactions between L-proline and molecules of organic solvents, are calculated. The effect the composition of a water–organic mixture and the structure of organic solvents have on the enthalpy characteristics of L-proline dissolution and transfer is examined. The effect the energy properties of intermolecular interactions between components of a mixed solvent has on the intermolecular interactions between L-proline and molecules of cosolvent is estimated. The correlation between the enthalpy characteristics of L-proline dissolution and electron-donor properties of organic cosolvent in aqueous solutions is determined.     

Micellisation thermodynamics of sodium lauroylsarcosinate in water–alcohol binary mixtures

Aggregation of sodium lauroylsarcosinate (SLS) in aqueous solutions of methanol, ethanol, propanol and ethylene glycol at 288–313 K has been determined from conductivity measurement in the range 0–20% v/v of additives. The precise values of the critical micelle concentration (CMC) and the degree of counter-ion dissociation of micelles were obtained at each temperature by fitting the specific conductivity-surfactant concentration curve to the integrated form of the Boltzmann-sigmoid equation. The CMC was found to increase with increase in additive concentrations in the case of methanol and ethylene glycol, while it decreases with increase in ethanol and propanol concentration. The equilibrium model of micelle formation was applied to obtain the thermodynamic parameters of micellisation. The Gibbs free energies were observed to vary only slightly with temperature and additive concentrations. Enthalpy–entropy compensation was observed for all the systems with a constant compensation temperature of ≈300 K and negative compensation enthalpy.     

The thermochemical characteristics of solution of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine in water-organic solvent mixtures at 298.15 K

The integral enthalpies of solution of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine in water-organic solvent (acetonitrile, 1,4-dioxane, acetone, N,N-dimethylformamide, and N,N-dimethylsulfoxide) mixtures were measured at organic component concentrations x ₂ = 0–0.4 mole fractions and T = 298.15 K. The standard enthalpies of solution (Δ_sol H°) and transfer (Δ_tr H°) of the peptides from water into mixed solvents were calculated. The influence of the structure and properties of solutes and mixture composition on the thermochemical characteristics of the peptides was considered. The enthalpy coefficients of pair interactions (h _xy ) of DL-α-alanylglycine and DL-α-alanyl-DL-α-alanine with organic solvent molecules were calculated. The h _xy values were correlated with the properties of organic solvents using the Kamlet-Taft equation.     

The thermochemistry of solution of L-α-alanyl-L-α-alanine in water-alcohol mixtures at 298.15 K

The integral enthalpies of solution of L-α-alanyl-L-α-alanine in water-ethanol, water-n-propanol, and water-isopropanol mixtures were measured calorimetrically at alcohol concentrations x ₂ ranging from 0 to 0.4 mole fractions. The standard enthalpy of peptide solution Δ_sol H ^o and transfer Δ_tr H ^o from water into a mixed solvent were calculated. The effect of the structure and properties of peptides and mixture composition on the enthalpy characteristics is discussed. The enthalpy coefficients of pair interactions h _xy between L-α-alanyl-L-α-alanine and alcohol molecules were calculated; these coefficients were positive and increased in the series ethanol, n-propanol, isopropanol. The analysis performed allowed the differences in the thermodynamic characteristics of solution of L-α-alanyl-L-α-alanine and DL-α-alanyl-DL-α-alanine in water-alcohol mixtures to be determined.     

Thermodynamic aspects of phase equilibrium in binary water–organic solvent mixtures

It is shown that the boundary curves of liquid equilibria in binary systems characterize the temperature–concentration boundary of the existence of homogeneous mixtures whose formation is not accompanied by changes in the Gibbs energy of the system and are a combination of two branches that do not convert into each other but intersect at the temperature of homogenization of a mixture of critical composition. The phase diagrams of a number of water–organic solvent systems are analyzed to determine the thermodynamic particularities of the latter.

     

The relative reduced Redlich–Kister equations for correlating excess properties of N,N-dimethylacetamide + 2-methoxyethanol binary mixtures at temperatures from 298.15 K to 318.15 K

Knowledge and prediction of physicochemical properties of binary mixtures is of great importance for understanding intermolecular interactions. The literature shows that most such systems exhibit non-linear behaviour. Excess molar volumes, viscosity deviations and isentropic compressibility changes in N,N-dimethylacetamide?+?2-methoxyethanol binary mixtures at 298.15, 308.15 and 318.15?K were calculated from experimental density, viscosity and sound velocity data presented in previous work. Here these experimental values were used to test the applicability of the correlative reduced Redlich–Kister equation and the recently proposed Herráez equation as well as their corresponding relative functions. Their correlation ability at different temperatures, and the use of different numbers of parameters, is discussed for the case of limited experimental data. These relative functions are important to reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. Limiting excess partial molar volume at infinite dilution were deduced from different methods, activation parameters and partial molar Gibbs energy of activation of viscous flow against compositions were investigated. The results of these observations have been interpreted in terms of structural effects of the solvents. In this frame, a correlating equation is recently proposed by Belda and in order to assess the validity of the proposed equation, it has also been applied to the present system for molar volume properties.     

The specific feature of photochemical processes in molecules of 3,3′-dialkylthiacarbocyanines in binary solvent mixtures

The effect of the composition of the dimethyl sulfoxide (DMSO)-toluene mixture on the photochemical processes of 3,3′-diethylthiacarbocyanine (DETCC) iodide and 3,3′-dimethylthiacarbocyanine (DMTCC) chloride was studied. In the mixtures with the DMSO content more than 20 vol %, DETCC iodide and DMTCC chloride molecules are characterized by a high efficiency of both trans → cis photoisomerization and fluorescence, in contrast to intersystem crossing to the triplet state. With decreasing the DMSO content to 3 vol %, the relative quantum yield of DETCC iodide intersystem crossing increases by two orders of magnitude, which is accompanied by a decrease in the lifetime of DETCC iodide triplet molecules from 1.1 × 10^?4 to 2.4 × 10^?7 s and a decrease in the yield of the cis-isomers. To explain the results, the concepts of “external heavy atom (iodide) effect” and hyperfine coupling (HFC mechanism) in radical pairs that could be formed via electron transfer between the iodide and an excited dye molecule were used.     

Viscometric and volumetric properties of benzene + methyl acetate,or + methyl propanoate,or + methyl butanoate binary systems at 283.15, 298.15 and 313.15 K

Viscosities and densities of three binary liquid mixtures, benzene?+?methyl acetate, benzene?+?methyl propanoate and benzene?+?methyl butanoate, have been measured at 283.15, 298.15 and 313.15?K, and atmospheric pressure. From experimental data, viscosity deviation, excess energy of activation for viscous flow, and excess molar volume were calculated and satisfactorily correlated with Redlich and Kister equation. Empirical and semiempirical equations and the predicted group-contribution method, universal automatic computer, were applied.     

Solubility of minoxidil in binary mixture of ethanol + water at various temperatures

ABSTRACT

The solubility of minoxidil in the aqueous binary mixtures of ethanol at different temperature are investigated and the obtained solubility data are fitted by using some cosolvency models including van’t Hoff equation, Yalkowsky model, Jouyban–Acree model and Jouyban–Acree–van’t Hoff model. The mean relative deviations (MRD%) are used to illustrate the models performance. Moreover, the apparent entropy, enthalpy, and Gibbs free energy of minoxidil dissolution process in the investigated solvent mixtures are computed using van’t Hoff and Gibbs equations. Finally, by means of the inverse Kirkwood–Buff integrals preferential solvation of minoxidil by water is observed in water-rich and ethanol-rich mixtures.