Solubility and solution thermodynamics of 2-methyl-4-nitroaniline in eleven organic solvents at elevated temperatures

The knowledge of solubility and solution thermodynamics for 2-methyl-4-nitroaniline in different solvents is essential for its purification and further theoretical studies. In this work, the solid-liquid equilibrium for 2-methyl-4-nitroaniline in eleven pure organic solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, toluene, ethyl acetate, acetonitrile, 2-butanone, acetone and cyclohexane) was established with the isothermal saturation method at temperatures T= (278.15-313.15) K under pressure of 101.2 kPa, and the solubility of 2-methyl-4-nitroaniline in these solvents were determined by a high-performance liquid chromatography (HPLC). In general, the mole fraction solubility obeyed the following order from high to low in different solvents: 2-butanone > acetone > ethyl acetate > acetonitrile > methanol > ethanol > n-propanol > n-butanol > isopropanol > toluene > cyclohexane. The modified Apelblat equation, lambda h equation, Wilson model and NRTL model were employed to correlate the measured solubility values of 2-methyl-4-nitroaniline in the selected solvents. Results show that the largest values of RAD and RMSD obtained with the four models are no greater than 0.71% and 3.27 x 10(-4), respectively. The modified Apelblat equation provided better results than the other three models. Furthermore, the mixing properties, including Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (gamma(infinity)(1)) and reduced excess enthalpy (H-1(E.infinity)) were computed. The dissolution process of 2-methyl-4-nitroaniline is spontaneous and favourable in the selected solvents. The solubility and associated models would be very useful for optimizing the separation process of the isomeric mixtures of 2-methyl-4-nitroaniline and 2-methyl-6-nitroaniline. (C) 2016 Elsevier Ltd.