Solid–liquid equilibrium of diphenyl anilinophosphonate in the different organic solvents

A phosphorus flame retardant named diphenyl anilinophosphonate (DPAP) was synthesized using diphenyl chlorophosphate and aniline. Its structural features and purity were investigated by mass spectrometry (MS), infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and high-performance liquid chromatography (HPLC). The thermal properties of DPAP were evaluated using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A static-analytic method was used to measure the solubilities of DPAP in acetonitrile, methanol, chloroform, ethanol, acetone, toluene, i -propanol, n -propanol, methyl acetate, ethyl acetate, 1,2-dichloroethane, and tetrahydrofuran from 293.15 to 333.15   K. Several thermodynamic models were used to correlate the experimental solubility data, such as the van’t Hoff equation, Buchowski–Ksiazczak ( λh ), Scatchard–Hildebrand, Wilson, nonrandom two-liquid (NRTL), and UNIQUAC. The calculated results showed that these models can reproduce the experimental data well, and that the NRTL equation gives the best correlation. The activity coefficients and solubility parameters of the solute were calculated using the Scatchard–Hildebrand methodology.