Solubilities of phosphoric acid, P,P′-1,4-phenylene P,P,P′,P′-tetraphenyl ester in the organic solvents

A phosphorous flame retardant of phosphoric acid, P,P′-1,4-phenylene P,P,P′,P′-tetraphenyl ester (PAPTE) was synthesized by diphenyl chlorophosphate and hydroquinone. The structural features of PAPTE were investigated with mass spectra (MS), infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and high-performance liquid chromatograph (HPLC) methods. The thermal behavior of PAPTE was analyzed with differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA) instruments. A static analytic method was used to measure the solubilities of PAPTE in the several selected pure solvents, which are methanol, ethanol, acetone, ethyl acetate, acetonitrile, methyl acetate, toluene, ether, n-propanol, i-propanol, where the temperatures range is from 288.25 to 333.45 K. The experiments were also performed in the binary mixed solvents of acetone and methanol. Several thermodynamic models were used to correlate the experimental solubility data, such as Wilson, nonrandom two-liquid (NRTL), UNIQUAC equations. The solubility data of PAPTE in binary solvents were correlated with the modified Wilson model. The calculated results showed that those models can excellently reproduce the experimental data and the UNIQUAC equation reveals the better ability in correlation. Using the Scatchard–Hildebrand methodology, the activity coefficients, solubility parameter of the solute and the partial molar excess enthalpies at infinite dilution were calculated.