Solubility of imidazoles in ketones

Solid-liquid equilibria (SLE) have been measured from 270 K to the melting temperature of the solid for 15 binary mixtures of an imidazole (1H-imidazole, 2-methyl-1H-imidazole and 1,2-dimethylimidazole) with ketones (butan-2-one. pentan-2-one, hexan-2-one, 4-methylpentan-2-one, cyclopentanone) using a dynamic method. The solubility of imidazoles in ketones is lower than in alcohols and water, but higher than in ethers and generally decreases with increasing molecular weight of the ketone. The highest intermolecular solute-solvent interaction is observed for the cyclopentanone. Experimental solubility results are compared with values calculated by means of the Wilson, UNIQUAC and NRTL equations utilizing parameters derived from SLE results. The existence of a solid-solid first-order phase transition in 2-methyl-1H-imidazole has been observed and has been taken into consideration in the solubility calculation. The best correlation of the solubility data has been obtained by the Wilson equation, by which the average-root-mean-square deviation of activity for the three imidazoles is 1.21. (C) 2002 Elsevier Science B.V. All rights reserved.