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I n a recent paper in this journal, Zhou et al. 1 reported the experimental solubility data of (Z)-2-(2-aminothiazol-4-yl)-2-methoxyiminoacetic acid (a pharmaceutical intermediate compound) in water, methanol, ethanol, glycol, and 1-propanol and the binary mixtures of water + methanol, water + ethanol, and water + glycol at different temperatures using a laser monitoring technique. The authors correlated the solubility data in binary solvent mixtures at various temperatures using a modified version of the Jouyban−Acree model and reported the accuracy of calculations using the mean percentage deviation (MPD) values computed by

Equations that can be used for partition coefficients of both neutral molecules and ions have been revised, and the term that is specific to ions has been re-evaluated. A new method has been devised for the determination of partition coefficients from water to organic solvents for carboxylate anions that is based on the variation of pK a for carboxylic acids with solvent. Using these partition coefficients, descriptors for carboxylate anions, on the same scale as descriptors for neutral molecules, have been obtained for 71 such anions. For 13 carboxylate anions in a test set, descriptors could be predicted that in turn led to predictions of 78 log P values over six water-solvent systems with an absolute error of 0.13 and a standard deviation of only 0.55 log units. Descriptors have been obtained for 26 protonated amines as a training set and descriptors predicted for 17 protonated amines as a test set. The predicted descriptors in turn led to the prediction of 18 log P values for protonated amines with an absolute error of 0.09 and a standard deviation of 0.39 log units. The carboxylate anions are the strongest monofunctional hydrogen bond bases, and the protonated amines are the strongest monofunctional hydrogen bond acids that we have studied.

Solubilities of carvedilol (CVD) in binary mixtures of (ethanol + propylene glycol (PG)) at 298.2, 303.2, 308.2, and 313.2 K are reported. The modified versions of the van't Hoff and Gibbs equations were used to calculate the thermodynamic properties (enthalpy (ΔH°), entropy (ΔS°), and Gibbs energy (ΔG°) standard changes of solutions) for CVD dissolved in (ethanol (1) + PG (2)) mixtures from the solubility data. The solubility data of CVD in (ethanol (1) + PG (2)) at different temperatures were correlated using different mathematical models, i.e., the Jouyban−Acree model, a combination of the Jouyban−Acree model with the van't Hoff model, and two modified versions of the Jouyban−Acree model. Solubility data of seven drugs in (ethanol (1) + PG (2)) at different temperatures were used to develop a quantitative structure−property relationship model for predicting solubility in solvent mixtures. In addition, enthalpy−entropy compensation using ΔH°vs ΔG°a nd ΔH°vs TΔS°which explains the mechanism of cosolvency at different temperatures was discussed.

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