Heats of solution of some tetraalkylammonium salts in water and in propylene carbonate and ionic enthalpies of transfer from water to propylene carbonate

In an extension of earlier work1 the enthalpies of transfer of several additional ions from water to propylene carbonate at 25° were determined calorimetrically. The results for ΔH° relative to that for Na+ are: Me4N+, -1.45; Et4N+, 2.65; Cl-, 3.83; Br-, 0.85; I-, -3.22 (all in kcal/mole). Apparently these conventional single-ion values and those reported earlier1 are quite close to the real, or absolute, single-ion enthalpies of transfer. Most of the results can be understood in terms of well-known structural effects in the water solutions, but this does not seem to be true of the enthalpy of transfer of B(C6H5)4-.