Enthalpic pair-interaction coefficients between electrolytes and non-electrolytes in water and N N-dimethylformamide

Abstract

From the enthalpies of solution of various electrolytes and some non-electrolytes in binary solvent systems containing water and different amides, several enthalpic pair-interaction coefficients have been evaluated. They refer to the interactions of different quarternary ammonium bromides, some trialkyl-phosphates and triethylamine with formamide, N-methylformamide, N N-dimethylformamide and N N-dimethylacetamide in aqueous solution and with water in the non-aqueous solvent N N-dimethylformamide. In aqueous solution a much larger variety of values for pair-interaction coefficients is found than in the non-aqueous systems. The different pair-interaction coefficients in water can be related to the structure of the solutes. A functional group additivity concept, introduced by Savage and Wood for non-ionic solutes, is also applicable to the interactions between electrolytes and non-electrolytes. The values of the functional-group parameters for the electrolytes in water are in reasonable agreement with those obtained from non-electrolytic interactions. In non-aqueous solutions the additivity concept gives a better correlation of the experimental values than in aqueous systems.