Temperature Dependence of Solubility for Ibuprofen in Some Organic and Aqueous Solvents

The thermodynamic functions—Gibbs energy, enthalpy, and entropy of solution—were evaluated from the solubilities of ibuprofen determined at several temperatures in the pure solvents: octanol, isopropyl myristate, chloroform, cyclohexane, and water. The organic solvent-saturated aqueous media and water-saturated organic solvents were also studied, except for cyclohexane. In aqueous media, the solubility was determined at pH = 7.4 and an ionic strength 0.15 mol-L^–1 (physiological values). The excess Gibbs energy and the activity coefficients of the solutes were also determined. The solubilities are higher in organic media such as chloroform and octanol than in aqueous media and cyclohexane.     

Temperature-dependence of the solubility of some acetanilide derivatives in several organic and aqueous solvents

The thermodynamic functions free energy, enthalpy, and entropy of solution, were evaluated from the solubility data of acetanilide, acetaminophen, and phenacetin, determined at several temperatures in water, octanol, isopropyl myristate, and chloroform. These three organic solvents mutually saturated with water, and finally, in cyclohexane. In the aqueous media, the solubility was determined at pH 7.4 and ionic strength 0.15?mol?L^?1. The excess free energy and the activity coefficients of the solutes were also determined. The solubility for acetanilide and phenacetin was higher in organic media such as octanol and chloroform than is those obtained in the aqueous media and cyclohexane, while for acetaminophen the solubility was higher in octanol than those obtained in the other solvents.     

Thermodynamic Study of the Solubility of Benzocaine in some Organic and Aqueous Solvents

The thermodynamic functions free energy, enthalpy, and entropy of solution, were evaluated from solubility data of benzocaine determined at several temperatures in octanol, water, and the mutually saturated solvents, in isopropyl myristate, water, and the mutually saturated solvents, and in cyclohexane. In aqueous media the solubility was determined at pH 7.4 and ionic strength 0.15 mol-L^–1. The excess free energy and the activity coefficients of the solutes also were determined. The solubility was higher in organic media, such as octanol and isopropyl myristate, than in aqueous media and cyclohexane.     

Solution Thermodynamics of Triclocarban in Organic Solvents of Different Hydrogen Bonding Capability

The thermodynamic functions Gibbs energy, enthalpy and entropy for the solution of triclocarban (TCC) in four organic solvents were calculated from solubility values obtained at temperatures from 293.15 up to 313.15 K. The solubility of TCC was determined in octanol (ROH), isopropyl myristate (IPM), chloroform (CLF), and heptane (HPT). The excess Gibbs energy and the activity coefficients of the solutes were also calculated. The solubilities of TCC are higher in ROH and IPM relative to those obtained in CLF and HPT. In addition, thermodynamic quantities for the transfer of this drug from HPT to the other organic solvents were calculated in order to estimate the hydrogen-bonding contributions.     

Thermodynamic quantities relative to solution processes of Naproxen in aqueous media at pH 1.2 and 7.4

Based on van’t Hoff and Gibbs equations, the thermodynamic functions Gibbs free energy, enthalpy, and entropy of solution, mixing and solvation of naproxen (NAP) in water at pH 1.2 and 7.4, were evaluated from solubility values determined at several temperatures. The solubility at pH 7.4 and 25.0°C was almost 150 times higher with respect to pH 1.2. The enthalpies of solution were positive and greater for pH 1.2, while the entropies of solution were both negative, thereby implying a greater molecular organization at pH 7.4. The results were discussed in terms of solute–solvent interactions.     

Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography

The partial molar volumes, V1(M), and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1 + solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, omega2(infinity) and the Flory-Huggins thermodynamic interaction parameters, chi21(infinity), between polymer and solvents were determined. The partial molar free energy, deltaG2(infinity), the partial molar heat of mixing, deltaH2(infinity), at infinite dilution and the polymer solubility parameter, delta1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons (n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T-x phase diagrams of the polymer-solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The omega2(infinity) were determined from the solubility measurements and were predicted by using the UNIFAC FV model.     

Solution Thermodynamics of Piroxicam in some Ethanol + Water Mixtures and Correlation with the Jouyban–Acree Model

The solubility of piroxicam (PIR) in several ethanol + water mixtures was determined at five temperatures from 293.15 to 313.15 K. The thermodynamic functions; Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these solubility data and the drug properties of fusion by using the van’t Hoff and Gibbs equations. The greatest solubility value was obtained in pure ethanol. A non-linear enthalpy–entropy relationship was observed from a plot of enthalpy versus Gibbs energy of solution. Accordingly, the driving mechanism for PIR solubility in water-rich mixtures is the entropy, probably due to water-structure loss around the drug’s non-polar moieties by ethanol, whereas, in ethanol-rich mixtures the driving mechanism is the enthalpy, probably due to better PIR solvation by the co-solvent molecules. The solubilities and the derived thermodynamic properties in mixed solvents were correlated using the Jouyban–Acree model.     

Calculation of the free energy of solvation for neutral analogs of amino acid side chains

The ability of the GROMOS96 force field to reproduce partition constants between water and two less polar solvents (cyclohexane and chloroform) for analogs of 18 of the 20 naturally occurring amino acids has been investigated. The estimations of the solvation free energies in water, in cyclohexane solution, and chloroform solution are based on thermodynamic integration free energy calculations using molecular dynamics simulations. The calculations show that while the force field reproduces the experimental solvation free energies of nonpolar analogs with reasonable accuracy the solvation free energies of polar analogs in water are systematically overestimated (too positive). The dependence of the calculated free energies on the atomic partial charges was also studied.     

Thermodynamic Study of the Solubility of Some Sulfonamides in Octanol, Water, and the Mutually Saturated Solvents

The free energy, enthalpy and entropy of solution, were evaluated from solubility data for a group of sulfonamides from 25 to 40°C in octanol, water, and the mutually saturated solvents. In aqueous media, the solubility was determined at the isoelectric point and ionic strength 0.15 mol-L^–1. The excess free energy and the activity coefficients of the solutes also were determined. The results are discussed in terms of solute–solvent interactions.     

Thermodynamics of 4’-bromomethyl-2-cyanobiphenyl in different solvents

The melting properties and the heat capacity of the solid state and the melt state 4’-bromomethyl-2-cyanobiphenyl (OTBNBr) were determined. The enthalpy, entropy and Gibbs free energy of fusion were also calculated. The solubility of OTBNBr in eight organic solvents was experimentally measured at temperatures from (283.15 to 323.15) K by using a static method. The reasons for the differences of the solubility of OTBNBr in various solvents are discussed by using the intermolecular interaction. Furthermore, the experimental solubility values were well correlated by the modified Apelblat equation, the λh equation, the Wilson model and the van’t Hoff equation. Finally, the temperature dependence of the activity coefficient and the van’t Hoff enthalpy in the tested solutions was investigated and is discussed.     

Solubility of budesonide in {ethanol + water} mixtures from T = (293.2 to 313.2) K: Experimental measurement and mathematical modelling

The solubility of budesonide (BDS) in binary mixtures of ethanol and water at T = (293.2–313.2) K is determined and mathematically represented using two cosolvency models, i.e. Jouyban–Acree model and Jouyban–Acree–van’t Hoff model. The mean relative deviations for fitting the solubility data of BDS in binary mixtures of ethanol + water are 6.6% and 6.5%, respectively. Furthermore, the apparent thermodynamic properties, dissolution enthalpy, dissolution entropy, and Gibbs free energy change of dissolution process of BDS in all the mixed solvents were calculated according to van’t Hoff and Gibbs equations. Dissolution of BDS in these mixed solvents is an endothermic process.     

Thermodynamic interactions and characterisation of naphthenic oil by inverse gas chromatography

The thermodynamic properties of naphthenic oil, a plasticiser, were investigated by means of inverse gas chromatography (IGC) using 10 different kinds of solvents as probes. Some thermodynamic parameters, such as specific retention volume, weight fraction activity coefficient, Flory–Huggins interaction parameter, partial molar heats of mixing and solubility parameter were obtained to judge the interactions between oil and solvents and the solubility of oil in these solvents. The results indicated that n-heptane, n-hexane, cyclohexane, chloroform, benzene and diethyl ether are good solvents for oil at experimental temperatures. The solubility parameters of oil varied from 13.94 to 13.21?(J?cm^?3)^1/2 at temperature range 323–353?K. The solubility parameter of oil was calculated to be 14.38?(J?cm^?3)^1/2 at room temperature, which is consistent with that obtained using surface tension–solubility parameter relation method.     

Solution thermodynamics of nimodipine in some PEG 400 + ethanol mixtures

The solubility of nimodipine (NMD) in several PEG 400 + ethanol mixtures was determined at five temperatures from 293.15 to 313.15 K. The thermodynamic functions of Gibbs energy, enthalpy and entropy of solution and of mixing were obtained by using the van't Hoff and Gibbs equations from these solubility data and drug properties of fusion. The highest solubility value was obtained in PEG 400 and the lowest in ethanol at all temperatures. A non-linear enthalpy–entropy relationship was observed from a plotof enthalpy vs. Gibbs energy of solution. Accordingly, the driving mechanism for NMD solubility in ethanol-rich mixtures is the enthalpy, whereas in PEG 400-rich mixtures thedriving mechanism is the entropy, although the molecular events involved are unclear.     

Deferiprone solubility in some non-aqueous mono-solvents at different temperatures: experimental data and thermodynamic modelling

The solubility of deferiprone (DFP) in five organic solvents including ethyl acetate, chloroform, acetonitrile, 1,4-dioxane and dichloromethane was investigated by the flask-shake method under atmospheric pressure at temperatures ranging from 293.15 to 313.15 K. In general, the solubility (mol L^–1) obeyed the following order from high to low in different mono-solvents: dichloromethane > chloroform > acetonitrile > 1,4-dioxane > ethyl acetate. The solubility of DFP in the mono-solvents increased with a rise of temperature. The solubility data were successfully correlated with the van’t Hoff equation. The generated data in this work and the previously published data were used to calculate the thermodynamic parameters of the system using the modified van’t Hoff equation, and the derived thermodynamic properties were correlated using Abraham solvation parameters.     

Experimental determination and correlation of bosentan solubility in (PEG 200 + water) mixtures at T= (293.15–313.15) K

The solubility of bosentan (BST) in the aqueous mixtures of polyethylene glycol 200 (PEG 200) at the temperature range, T = (293.15–313.15) K, has been studied using a shake-flask method. The experimental solubility data were correlated with Jouyban–Acree, Jouyban-Acree-van’t Hoff, modified Wilson and Yalkowsky models. Deviations of the calculated solubility from experimental one were determined by percent average relative deviations and relative deviations. In addition, to represent the thermodynamic behaviour of BST in PEG 200 solutions, the apparent thermodynamic functions, Gibbs energy, enthalpy and entropy of dissolution were obtained by using the van’t Hoff and Gibbs equations.     

Solubility and solution thermodynamics of sorbic acid in eight pure organic solvents

By the gravimetric method, the solubility of sorbic acid in eight solvents including ethanol, 2-propanol, methanol, 1-butanol, ethyl acetate, methyl tert-butyl ether, acetone and acetonitrile was determined over a temperature range from 285.15 to K at atmospheric pressure. For the temperature range investigated, the solubility of sorbic acid in the solvents increased with increasing temperature. The experimental values were correlated with the linear solvation energy relationship, modified Apelblat equation, λh equation, non-random two-liquid (NRTL) model, and Wilson model. On the other hand, the enthalpy, entropy and Gibbs free energy of dissolution were obtained from these solubility values by using the van’t Hoff and Gibbs equations. The excess enthalpy of solution was estimated on the basis of λh equation. Furthermore, the a priori predictive model COSMO-RS was employed to predict the solubility of sorbic acid in selected solvents and reasonable agreement with experimental values is achieved.     

Solution thermodynamics of pyrazinamide,isoniazid, and p-aminobenzoic acid in buffers and octanol

The solubility values of pyrazinamide, isoniazid, and p-aminobenzoic acid in buffers (рН 2.0 and 7.4) and octanol were measured in the temperature range of 293.15 to 313.15 K. The dissolution Gibbs energy, enthalpy, and entropy were calculated. The dissolving process was endothermic and enthalpy-determined. The activity coefficients of the compounds at infinite dilution were determined based on the solubility data and thermophysical parameters. A positive deviation from the ideality was observed in all the solutions. A common tendency of the solubility increase with a decrease in the activity coefficients at T = 298.15 K was revealed for the investigated solute-solvent systems. The excess thermodynamic solubility functions were calculated from the temperature dependences of the activity coefficients. The solvation processes were found to have a considerable influence on the solubility of the substances in solutions studied.     

Thermodynamics of solvent extraction of thorium by solutions of HHTA and mixtures of HHTA and TBP

The changes in free energy, enthalpy and entropy for the extraction of thorium by solutions of thenoyltrifluoroacetone (HTTA) and mixtures of solutions of HTTA and tri-n-butylphosphate (TBP), in three diluents, viz. cyclohexane, benzene and chloroform, were determined using the solvent extraction data obtained at different temperatures. From these data the thermodynamic parameters associated with the formation of Th(TTA)₄ · TBP in the respective organic diluents were evaluated. Trends in the enthalpy changes were attributed to different degrees of association of the diluents with themselves and with the solutes present in them.