Solubility of imidazoles in alcohols

The solid-liquid equilibrium (SLE) has been measured from 270 K to the melting temperature of the solid for 24 binary mixtures of an imidazole (1H-imidazole, 2-methyl-1-H-imidazole, and 1,2-dimethyl-imidazole) with an alcohol (ethanol, propan-1-ol, propan-2-ol, butan-1-ol, butan-2-ol, 2-methylpropan-2ol, hexan-1-ol, and dodecan-1-ol) using a dynamic method. The melting point, enthalpy of fusion, and heat capacity change at the melting temperature were determined by differential scanning calorimetry. The solubility of imidazoles in alcohol is lower than in water and generally decreases with increasing molecular weight of the alcohol. The intermolecular solute-solvent interaction for 2,3-dimethylimidazole is higher for secondary and tertiary alcohols. Experimental results of solubility are compared with values calculated by means of the Wilson, UNIQUAC ASM, and NRTL 1 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 for three imidazoles is 0.89.