Solubility Measurement,Data Correlation, and SolventEffect of ( <i>E</i> )-4-Methylcinnamic Acid in Pure Solventsand in Two Binary Solvent Mixtures from 293.15 to 333.15 K

Abstract (E)-4-Methylcinnamic acid is an important organic intermediate in the pharmaceutical and fine chemical industries. Investigating its solubility and thermodynamic properties offers essential theoretical support for optimizing crystallization, separation, and purification processes. In this work, a gravimetric method was adopted to measure the solubility of 4-methylcinnamic acid in 14 pure solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, isopentanol, n-hexanol, methyl acetate, ethyl acetate, n-propyl acetate, benzene, ACN, and DMF) and two binary solvent mixtures (ethanol + ethyl acetate, n-butanol + ACN) at atmospheric pressure from 293.15 to 333.15 K. Results show that its solubility increases monotonically with temperature in all tested systems, and its solubility in highly polar alcohol solvents is significantly higher than in less polar ester solvents. The solubility data were correlated with thermodynamic models: the Yaws equation fitted best for pure solvents, while the Jouyban–Acree–Van’t Hoff model performed optimally in binary mixtures. KAT-LSER analysis indicates that solvent parameters β and π* dominate the dissolution behavior. Moreover, electrostatic potential and radial distribution function analysis provide microscopic insights and verify the reliability of the solvent effect evaluation.