Solubility Measurement and Thermodynamic Properties of Pyraflumoxamide in 13 Pure Solvents from 283.15 to 323.15 K

The solubility of pyraflumoxamide was measured in 13 pure solvents (methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, acetonitrile, acetone, and tetrahydrofuran) over the temperature range of 283.15 to 323.15 K at 0.1 MPa using a static equilibrium method. The results demonstrated a monotonic increase in solubility with rising temperature. The experimental data were correlated using five thermodynamic models: the Apelblat equation, λh equation, van’t Hoff equation, Wilson model, and NRTL model, among which the λh equation exhibited the best performance. PXRD analysis confirmed that no polymorphic transformation occurred during the measurements. Thermodynamic analysis indicated that the dissolution process is spontaneous, endothermic, and entropy-driven. Solvent effect analysis revealed that the solubility is governed by the combined effects of polarity, hydrogen bond donor–acceptor interactions, and cohesive energy density. The results provide a thermodynamic basis for the crystallization and purification of pyraflumoxamide.