Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Knowledge of solubility for 2-methyl-6-nitroaniline in different solvents is essential for its purification and further theoretical studies. In this paper, the solid-liquid equilibrium for 2-methyl-6-nitroaniline in ten pure organic solvents (methanol, ethanol, n-propanol, isopropanol, toluene, ethyl acetate, acetonitrile, acetone, cyclohexane and 1,4-dioxane) was established using the isothermal saturation method at temperatures T = (278.15 313.15) K under pressure of 101.2 kPa, and the solubility of 2-methyl-6- nitroaniline in these solvents were determined by a high-performance liquid chromatography (HPLC). In general, the mole fraction solubility followed the following order from high to low in different solvents: 1,4-dioxane (0.1799 0.3390) greater than acetone (0.1128 0.3010) greater than ethyl acetate (0.08414 0.2654) greater than acetonitrile (0.04179 0.2027) greater than toluene (0.02367 0.1104) greater than n-propanol (0.01080 0.04514) greater than ethanol (0.01020 0.04202) greater than isopropanol (0.008595 0.03763) greater than methanol (0.007391 0.03198) greater than cyclohexane (0.001027 0.005617). The modified Apelblat equation, kh equation, Wilson model and NRTL model were employed to correlate the measured solubility data of 2-methyl-6-nitroaniline in the selected solvents. Results indicated that the largest values of RAD and RMSD acquired by the four models were less than 0.76% and 9.13 10 4, respectively. The modified Apelblat equation provided better results than the other three models. Furthermore, the standard dissolution enthalpy and excess enthalpy of the solutions were computed from the solubility values. The standard dissolution enthalpies vary within the range from (14.88 to 45.57) kJ mol 1 and are all positive, the dissolution process of 2-methyl-6-nitroaniline is endothermic. The solubility data and models would be very useful for optimizing the separation process of the isomeric mixtures of 2-methyl-6-nitroaniline and 2-methyl-4-nitroaniline.