Lattice potential energies and thermochemical properties of triethylammonium halides (Et3NHX) (X = Cl, Br, and I)

A series of triethylammonium halides (Et3NHCl, Et3NHBr, and Et(3)NH1) was synthesized. The crystal structures of the three compounds were characterized by X-ray crystallography. The lattice potential energies and ionic radius of the common cation of the three compounds were obtained from crystallographic data. Molar enthalpies of dissolution of the compounds at various values of molality were measured in the double-distilled water at T = 298.150 K by means of an isoperibol solution-reaction calorimeter. According to Pitzer's theory, the values of molar enthalpies of dissolution at infinite dilution and Pitzer's parameters of the compounds were obtained. The values of apparent relative molar enthalpies, relative partial molar enthalpies of the solvent and the compounds at different molalities were derived from the experimental values of molar enthalpies of dissolution of the compounds. Finally, hydration enthalpy of the common cation Et3NH+ was calculated to be Delta H+ = (150.386 +/- 4.071) kJ . mol(-1) by designing a thermochemical cycle. (C) 2011 Elsevier Ltd. All rights reserved.