The Enthalpies and Entropies of Dilution of Alkali Halides and Tetraalkylammonium Halides in N-Methylacetamide

The enthalpies of dilution of some alkali and tetraalkylammonium halides have been measured in N-methylacetamide at 35 degrees C. The results approach the Debye-Huckel limiting law at low concentrations. Excess free energies and entropies were calculated from the present results and previous freezing point measurements. The excess enthalpies of the alkali halides in N-methylacetamide are in the same range as the excess enthalpies in water. The effect of changing anions is quite small in N-methylacetamide. The cation order is Li(+) similar or equal to Na(+) > Cs(+) > K(+). The excess enthalpies of the tetraalkylammonium halides in N-methylacetamide are very different from the excess enthalpies in water, confirming the conclusion that in water the large excess enthalpies are due to hydrophobic bonding and that in N-methylacetamide this effect is not present.