Enthalpies of interaction of sodium chloride and potassium chloride with some amides in water at 25 °C

Abstract

Enthalpy changes on mixing have been used to investigate the interactions occurring in water at 25 °C between sodium chloride and potassium chloride and the amides N-methylformamide N, N-dimethylformamide, acetamide, N-methylacetamide and N-acetylglycinamide. The results obtained, along with some others obtained from literature sources, have been addressed using a group-additivity approach to salt–solute interactions. It is found that both salts interact with apolar moieties to the same extent, but potassium chloride interacts more favourably with amide groups than does sodium chloride. As in an earlier study on urea–amide interactions it was found that the interactions of tertiary amide groups with the solutes are more favourable than interactions of both primary and secondary amide groups.