Molar excess enthalpy (HmE) for systems of aqueous piperazine derivatives

Molar excess enthalpies (H-m(E)) of aqueous1-methyl piperazine (1-MPZ), 4-(2-hydroxy ethyl) morpholine (4,2-HEMO), 1,4-dimethyl piperazine (1,4-DMPZ), 1-(2-hydroxyethyl) piperazine (1,2-HEPZ), 3-morpholinopropyl amine (3-MOPA), morpholine (MO) were reported at three different temperatures T = (298.15, 313.15, and 323.15) K and over the entire range of mole fractions. The Redlich-Kister (RK) equation was used to correlate the experimentally measured H-m(E) values as a function of mole fractions. The molar enthalpies of amines and water at infinite dilutions were determined from the RK coefficients. Among the studied solution theory models to correlate the experimental data, the modified UNIFAC (UNIversal Functional groups Activity Coefficient, Dortmund) model exhibited the lowest percentage of average absolute deviations from the experimental data, followed by the NRTL (Non-Random Two Liquid) model and the UNIQUAC (UNIversal QUAsi Chemical) model. Among the six amines studied, the {1-MPZ + water} system exhibited the highest values of molar excess negative enthalpies followed by {3-MOPA + H2O}, {1,2-HEPZ + H2O}, {MO + H2O}, {1,4-DMPZ + H2O} and {4,2-HEMO + H2O} systems. (C) 2015 Elsevier Ltd. All rights reserved.