Solubility Behavior of α-Aminoisobutyric Acid in 13 Individual Solvents at Temperatures Ranging from 283.15 to 323.15 K

In this study, the solid–liquid equilibrium solubility and solvent effects of α-aminoisobutyric acid in 13 monosolvent systems (water, methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, N,N-dimethylformamide, acetonitrile, acetone, ethyl acetate, 2-butanone, and methyl acetate) were reported at the pressure of 101.2 kPa (at T = 283.15–323.15 K). Among the 13 monosolvents, the solubility increased with the increase of absolute temperature, the order is water > N,N-dimethylformamide > methanol > ethyl acetate >2-butanone > ethanol > n-propanol > n-butanol ≈ n-pentanol > isopropanol > acetone > methyl acetate ≈ acetonitrile. The modified Apelblat model, Yaws model, Margules model, and nonrandom two-liquid (NRTL) model were employed to correlate the experimental solubility, and the OriginPro 2019b software was used for analysis and fitting, and the fitting results of the four models were all satisfactory. In addition, through a comparison of the average ARD and root-mean-square deviation (RMSD) values of the four models, the Yaws model achieved the best correlation result. Hirshfeld surface analysis (HS) and molecular electrostatic potential surface (MEPS) performed by the CrystalExplorer software and Gauss 5.0 program were used to determine the internal interactions within α-aminoisobutyric acid solutions. In addition, Hansen solubility parameters (HSPs) were utilized to analyze the solubility behavior. Furthermore, mixing thermodynamic characteristics of α-aminoisobutyric acid in selected solvents were calculated by the NRTL model, which revealed that the mixing process was spontaneous and entropy-driven. These experimental results could be utilized for the purification, crystallization, and industrial applications of α-aminoisobutyric acid, as well as similar substances.