Determination of <i>N</i>-Acetyl-<scp>l</scp>-methionine Solubility in 12 Solvents and Its Comparison with Structurally Similar Substances: Solvent Effects Analysis, Molecular Simulation, and Model Correlation

The mole fraction solubility of N-acetyl-l-methionine in 12 different pure solvents was determined by the static gravimetric method at 101.2 kPa in the temperature range 283.15–323.15 K. The results show that the solubility of solutes in all 12 single solvents increases with increasing temperature, and at 298.15 K, the order is ethanol > n-propanol > n-butanol > acetone > n-pentanol >2-butanone > acetonitrile > methyl acetate > ethyl acetate > propyl acetate > butyl acetate > dimethyl carbonate. In order to study the equilibrium solid phase of N-acetyl-l-methionine in a solvent system, powder X-ray diffraction (PXRD) was used. Three models were used to fit the solubility data, which were the modified Apelblat model, UNIQUAC model, and Margules model. The relevant model parameters and data deviation values were calculated. It was found that the modified Apelblat model could give better results in correlation analysis. The interaction of N-acetyl-l-methionine in solution was studied by using the molecular electrostatic potential surface (MEPS). Furthermore, the differences in solubility between N-acetyl-l-methionine and N-acetyl-dl-methionine in the same solvent were analyzed. The results could provide a basis for the production and optimization of the crystallization process of N-acetyl-l-methionine.