Solubility of Indole-3-butyric Acid in 19 Monosolvents: Characterization, Determination, Molecular Simulations, and Model Correlation

Indole-3-butyric acid is a plant growth regulator, and the study of the solubility behavior of indole-3-butyric acid in monosolvents is necessary for its crystallization and isolation process. The solubility data of indole-3-butyric acid in 19 monosolvents (methanol, ethanol, n-propanol, n-butanol, n-pentanol, isopropanol, isobutanol, isopentanol, sec-butanol, methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, isopropyl acetate, dl-ethyl lactate, dimethyl carbonate, acetone, acetonitrile, and 2-butanone) were determined by the static gravimetric method, and the solubility ranged from 283.15 to 323.15 K. Its solubility in all the solvents studied increased with an increase in temperature. In addition, Hansen solubility parameters were employed to assess the solvency of the solvents, while molecular electrostatic potentials, interaction region indicator, and interaction energies were utilized to determine the internal interactions in indole-3-butyric acid solutions. The solvation behavior is primarily influenced by the solvent polarity (E_T(30)) and hydrogen bonding. Furthermore, the modified Apelblat model, Margules model, NRTL model, and UNIQUAC model were employed to correlate the solubility. Furthermore, the thermodynamic properties of the mixing of indole-3-butyric acid in these solvents were calculated by using the NRTL model.