Experimental Study on Binary (Solid + Liquid) Equilibrium and Solubility Analysis of 2-Aminopyrimidine in 17 Organic Solvents at Temperatures Ranging from 272.65 to 323.35 K

In this work, the solid–liquid equilibrium solubility and the impact of different solvents on 2-aminopyrimidine were explored across 17 distinct single-solvent systems, including methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-pentanol, isopentanol, ethyl acetate, butanone, 2-pentanone, acetone, acetonitrile, ethyl formate, methyl acetate, cyclopentanone, and cyclohexanone, at atmospheric pressure and temperatures ranging from 272.65 to 323.35 K. It was observed that in all these solvents, solubility increases as the temperature rises. At 298.15 K, the molar solubility sequence in the solvents is as follows: cyclopentanone > cyclohexanone > ethyl formate > methanol > ethyl acetate > butanone > methyl acetate > acetone > n-propanol > ethanol > 2-pentanone > n-butanol > isobutanol > isopropanol > isopentanol > n-pentanol > acetonitrile. The solubility data obtained from experiments were fitted using four models: the modified Apelblat model, the Buchowski–Ksiazaczak λh model, the NRTL model, and the Wilson model, all of which demonstrated a good fit. The modified Apelblat model yielded the most accurate correlations, as indicated by the lowest average ARD and RMSD values. Furthermore, using the Wilson model, the thermodynamic properties of the mixing process of 2-aminopyrimidine in the chosen solvents were calculated, revealing that the mixing was spontaneous and primarily driven by entropy. The results of this study provide valuable insights for the purification, crystallization, and industrial application of 2-aminopyrimidine and similar compounds.