Standard enthalpies of formation and thermodynamic cycle values of crystal lattice energies of methylammonium halides

The standard enthalpies of formation of the methylammonium halides [NMenH4–n]X(n= 1–3; X = Cl, Br, or I) have been derived from calorimetric studies. These values lead to the crystal lattice energies of the salts. Linear relations permit the calculation of ΔHf⊖([NMe4]X,c) which are in fair agreement with derived literature values. The values obtained for the crystal lattice energies of the tetramethylammonium halides, however, are in poor agreement with those obtained by extended-calculation procedures.