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    Equilibrium solubility of 6-methylcoumarin in some (ethanol plus water) mixtures: determination, correlation, thermodynamics and preferential solvation
    (Taylor & Francis, 2022) Akay, Sema; Kayan, Berkant; Coşkun, Savaş; Jouyban, Abolghasem; Martinez, Fleming; Acree, William E.
    The solubility of 6-methylcoumarin in water, ethanol and nine aqueous ethanol mixtures was determined from 293.15 to 323.15 K. 6-Methylcoumarin solubility expressed in mole fraction was correlated with some well-known correlation/prediction models. Gibbs energy, enthalpy and entropy, for dissolution and mixing processes, were computed using van't Hoff and Gibbs equations. The plot of enthalpy vs. Gibbs energy of dissolution exhibited negative slopes from water to w(1) = 0.20 and from w(1) = 0.90 to ethanol but positive slopes in the interval 0.20 w(1) w(1) = 0.20 is entropy-driven that could be attributed to water molecules releasing originally bounded as 'icebergs' around the drug-non-polar groups. In mixtures of 0.20 w(1) < 0.90, enthalpy-driving mechanism for drug transfer from more-polar to less-polar systems is observed, probably owing to better solvation by ethanol. Inverse Kirkwood-Buff integrals show that 6-methylcoumarin is preferentially solvated by water in water-rich mixtures but preferentially solvated by ethanol in 0.24 x(1) < 1.00.
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    Equilibrium solubility of vanillin in some (ethanol plus water) mixtures: determination, correlation, thermodynamics and preferential solvation
    (Elsevier, 2021) Akay, Sema; Kayan, Berkant; Jouyban, Abolghasem; Martinez, Fleming; Acree, William E., Jr.
    Equilibrium mole fraction solubility of vanillin in nine aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from T = 293.15 to T = 323.15 K. Vanillin solubility in these mixtures was adequately correlated with several well-known correlation models with the mean percentage deviations of 5.9 to 18.3%. Respective apparent thermodynamic functions, i.e. Gibbs energy, enthalpy, and entropy, for the dissolution, mixing and solvation processes, were computed using the van't Hoff and Gibbs equations. The enthalpy-entropy relationship for vanillin was non-linear in the plot of enthalpy vs. Gibbs energy of dissolution with positive slopes from neat water to the mixture of w(1) = 0.10 and the interval 0.50 < w(1) < 0.90 but negative in the interval 0.10 < w(1) < 0.50 and from w(1) = 0.90 to neat ethanol. Accordingly, in the first cases the vanillin transfer from more polar to less polar solvent systems is enthalpy-driven but entropy-driven for the last ones. Moreover, by means of the inverse Kirkwood-Buff integrals is observed that vanillin is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in mixtures of 0.23 < x(1) < 1.00.
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    Solubility of coumarin in (ethanol plus water) mixtures: Determination, correlation, thermodynamics and preferential solvation
    (Elsevier, 2021) Akay, Sema; Kayan, Berkant; Jouyban, Abolghasem; Martinez, Fleming; Acree, William E.
    Equilibrium mole fraction solubility of coumarin in nine aqueous-ethanolic mixtures, as well as in neat water and neat ethanol, was determined at seven temperatures from (293.15 to 323.15) K. Coumarin solubility in was adequately correlated with several well-known correlation models with the mean percentage deviations of 5.1-10.8%. The respective apparent thermodynamic functions (Gibbs energy, enthalpy, and entropy) for the dissolution, mixing and solvation processes were computed using the van't Hoff and Gibbs equations. The enthalpy-entropy relationship for coumarin was non-linear in the plot of enthalpy vs. Gibbs energy of dissolution with negative slope from neat water to the mixture of w(1) = 0.10 but positive from this mixture to neat ethanol. Accordingly, in the first case the coumarin transfer from neat water to the mixture of w(1) = 0.10 is entropy-driven, which could be attributed to water molecules release originally bounded as "icebergs" around the non-polar groups of this drug. Otherwise, in mixtures of w(1) >= 0.10 the driving mechanism for the transfer of coumarin from the more polar solvent systems to those less polar is the enthalpy, probably owing the better drug solvation. Moreover, by means of the inverse Kirkwood-Buff integrals is observed that apparently coumarin is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in mixtures of 0.23 < x(1) < 1.00. (C) 2021 Elsevier B.V. All rights reserved.
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    Solubility, dissolution thermodynamics and preferential solvation of 4-nitroaniline in (ethanol plus water) mixtures
    (Taylor & Francis, 2021) Akay, Sema; Kayan, Berkant; Martinez, Fleming
    In this research, the equilibrium mole fraction solubility of 4-nitroaniline (4-NA) in some aqueous-ethanolic mixtures was determined at seven temperatures from (293.15 to 323.15) K. The respective apparent thermodynamic functions (Gibbs energy, enthalpy, and entropy) of the dissolution processes were computed using the van't Hoff and Gibbs equations. The enthalpy-entropy relationship for 4-NA was non-linear in the plot of enthalpy vs. Gibbs energy of solution with negative slopes from neat water to the mixture w (1) = 0.10 and from w (1) = 0.20 to neat ethanol but positive slope from w (1) = 0.10 to w (1) = 0.20. Therefore, the driving mechanism for 4-NA transfer processes is the entropy in water-rich mixtures. Additionally, by means of the inverse Kirkwood-Buff integrals is observed that 4-NA is preferentially solvated by water molecules in water-rich mixtures but preferentially solvated by ethanol molecules in the mixtures of 0.23 <= x (1) <= 1.00.