2-Amino-6-chlorobenzoic Acid Dissolved in Numerous Individual Solvents: Equilibrium Solubility, Thermodynamic Modeling, and Mixing Properties

Abstract

The solubility of 2-amino-6-chlorobenzoic acid in several individual solvents acetonitrile, n-propanol, toluene, n-butanol, ethanol, isopropanol, ethylene glycol (EG), cyclohexane, ethyl acetate, 1-octanol, n-heptanol, isobutanol, water, and N-methyl pyrrolidone (NMP) at temperatures from 278.15 to 323.15 K was determined by means of the saturated shake-flask method under a pressure of 101.2 kPa. Several organic solvents presented excellent dissolution capability for 2-amino-6-chlorobenzoic acid. The descending order of mole fraction solubility was NMP > ethanol > ethyl acetate > n-propanol > isopropanol > n-butanol > EG > isobutanol > n-heptanol > 1-octanol > acetonitrile > toluene > water > cyclohexane. The interactions of solute–solvent and solvent–solvent molecules were examined via the method of linear solvation energy relationships. The solids in equilibration with the corresponding liquors were analyzed by X-ray powder diffraction, indicating no solvation or polymorphic transformation for 2-amino-6-chlorobenzoic acid dissolved in different individual solvents. The mathematical correlation of mole fraction solubility was made with the help of the Wilson model, λh equation, nonrandom two-liquid (NRTL) model, and Apelblat equation. The maximum relative average deviation and root-mean-square deviation obtained through equations/models were 5.52% and 66.74 × 10–4, respectively. The Apelblat equation provided better correlating results than the other equations/models. What is more, the thermodynamic mixing properties, activity coefficient at infinitesimal concentration, and reduced excess enthalpy were also derived through the Wilson model.