Solubility Modeling and Solvent Effects of Allopurinol in 15 Neat Solvents

Experimental allopurinol solubility in water and 14 organic solvents, namely, N,N-dimethylformamide (DMF), isopropanol, ethanol, methanol, acetone, acetonitrile, n-propanol, n-heptanol, 1-hexanol, n-butanol, 2-butanone, N-methyl-2-pyrrolidone (NMP), 1,4-dioxane, and cyclohexane, has been studied by using the shake-flask method. The experiments were carried out over the temperature range from 278.15 to 333.15 K under p = 101.2 kPa. The solubility of allopurinol in selected solvents rose with the rise in temperature. The solubility values of allopurinol were recorded as the maximum in NMP and the minimum in cyclohexane. The obtained solubility data were mathematically described with the lambda h equation, Apelblat equation, and NRTL equation. The maximum percentage of the average relative deviation was 1.73 x 10(-2), and the maximum value of the root-mean-square deviation was 2.416 x 10(-4). Furthermore, the solvent effect was analyzed through the method of SERL (linear solvation energy relationship). The extent and types of solvent-solute and solvent-solvent interactions were recognized.