Solubility determination and thermodynamic modelling for 2-amino-4-chlorobenzoic acid in eleven organic solvents from T = (278.15 to 313.15) K and mixing properties of solutions

Abstract

The solubility of 2-amino-4-chlorobenzoic acid in eleven organic solvents including N-methyl-2-pyrrolidone, ethanol, n-propanol, isopropanol, ethyl benzene, toluene, n-butanol, acetonitrile, ethyl acetate, 1,4-dioxane and acetone were determined experimentally using the isothermal saturation method over a temperature range from (278.15 to 313.15) K under 101.2kPa. Within the temperature range studied, the mole fraction solubility of 2-amino-4-chlorobenzoic acid in the solvents increased with a rise of temperature. On the whole, they obeyed the following order from high to low in the selected solvents: N-methyl-2-pyrrolidone>acetone>1, 4-dioxane>ethyl acetate>ethanol>isopropanol>n-propanol>n-butanol>acetonitrile>toluene>ethyl benzene. The solubility values obtained for 2-amino-4-chlorobenzoic acid were correlated with the modified Apelblat equation, λh equation, Wilson model and NRTL model. The largest values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 8.25×10−4 and 3.35%, respectively. The modified Apelblat equation correlated the experimental solubility best on the basis of the result of AIC analysis. Furthermore, the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient (γ1∞) and reduced excess enthalpy (H1E,∞) at infinitesimal concentration were determined. Solubility and thermodynamic studies are very important for optimizing the purification process of 2-amino-4-chlorobenzoic acid.