<i>N</i> -Acetyl- <scp>l</scp> -alanine Solubility and Correlation in 16 Monosolvents: Solvent Effects, Molecular Simulation, and Comparison with Structurally Similar Substance

The mole fraction solubility of N-acetyl-l-alanine in 16 pure solvents was determined by the static gravimetric method at a temperature range of 283.15–323.15 K under a pressure of 101.2 kPa, and the solubility of N-acetyl-l-alanine was positively correlated with temperature. Whether N-acetyl-l-alanine produced a polycrystalline form in the solvent system was investigated by powder X-ray diffraction. The results showed that N-acetyl-l-alanine did not undergo crystalline transformation during solubility determination. The solubility data were fitted using the modified Apelblat, NRTL, UNIQUAC, and Margules models, and the model parameters and errors were estimated. The interactions of N-acetyl-l-alanine in solvent systems were studied using molecular electrostatic potential surfaces (MEPS). Hansen solubility parameters (HSPs) were used to evaluate the nature of the solvent and its solubility properties for N-acetyl-l-alanine. In addition, thermodynamic properties of the mixing for N-acetyl-l-alanine in solvent systems were investigated using the NRTL model, and the mixing process was found to be entropic and spontaneous. Furthermore, the difference in solubility between N-acetyl-l-alanine and l-alanine in the same solvent was analyzed, where N-acetyl-l-alanine > l-alanine, which may be due to intermolecular forces and the influence of the acetyl group.