Solubilities of Phosphonic Acid, P,P′-(1,4-Piperazinediyl)bis-,P,P,P′,P′-tetraphenyl Ester in Selected Solvents

Phosphonic acid, P,P′-(1,4-piperazinediyl)bis-,P,P,P′,P′-tetraphenyl ester (PAPBE), as a versatile flame retardant, was prepared by a literature method. The solubilities of PAPBE in selected solvents have been measured under a range of temperatures from 283.15 K to 343.15 K. The experimental data were correlated with the Buchowski–Ksiazczak (λh), Scatchard–Hildebrand, Wilson, nonrandom two liquid (NRTL), and universal quasichemical (UNIQUAC) equations. The calculated results showed good agreement with the experimental data. The differential values of enthalpy and entropy of dissolution at saturation were also calculated by the van’t Hoff equation. Toluene and acetone are shown to be good candidates as reaction solvents that can be applied to optimize the reactive crystallization process.