Solubility determination and thermodynamic modeling of 3-methyl-4-nitrobenzoic acid in twelve organic solvents from T = (283.15–318.15) K and mixing properties of solutions

• Solubilities of 3-methyl-4-nitrobenzoic acid in twelve solvents were determined.
• The solubilities were correlated by using four thermodynamic models.
• The mixing properties of solution were computed.

Solubilities of 3-methyl-4-nitrobenzoic acid in twelve organic solvents of ethanol, isopropanol, n-propanol, n-butanol, methanol, ethyl acetate, toluene, acetone, acetonitrile, 1,4-dioxane, N-methyl-2-pyrrolidone and N,N-dimethylformamide were determined experimentally by using the isothermal saturation method over a temperature range from (283.15–318.15) K under 101.1 kPa. The solubilities of 3-methyl-4-nitrobenzoic acid in each solvent increased with the increase in temperature. In general, the solubility obeyed the following order from high to low in different solvents: (N,N-dimethylformamide, N-methyl-2-pyrrolidone) > 1,4-dioxane > acetone > toluene > ethyl acetate > isopropanol > (methanol, ethanol, n-propanol, n-butanol) > acetonitrile. The experimental solubility data of 3-methyl-4-nitrobenzoic acid in the selected solvents were correlated by the modified Apelblat equation, λh equation, Wilson model and NRTL model. The maximum values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 13.69 × 10−4 and 1.18%, respectively. Generally, the four thermodynamic models were all acceptable for the systems of 3-methyl-4-nitrobenzoic acid in these solvents. In addition, the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration (γ1∞) and reduced excess enthalpy (H1E,∞) were calculated. The dissolution process of 3-methyl-4-nitrobenzoic acid in the solvents was spontaneous and endothermic. The obtained solubility and thermodynamic studies would be very helpful for optimizing the purification process of 3-methyl-4-nitrobenzoic acid.

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