Thermodynamics of bolaform electrolytes. I. Heat capacities and enthalpies in H2O and D2O

Abstract

The partial molal heats of solution at infinite dilution, ΔH s o , of bolaform salts [Et3N(CH2)nNEt3]Br2 and [allyl3N(CH2)nNallyl3]Br2, have been measured in H2O and D2O at 25°C using a solution calorimeter. The values of ΔH s o were endothermic for almost all of the compounds studied. Values of ΔH s o were obtained as a function of temperature for several homologs in H2O and D2O. Positive ΔC p o values obtained from least-squares analyses of the ΔH s o vs T data show an almost linear dependence on the number of methylene groups between the nitrogen centers. Whereas the enthalpy of transfer from H2O to D2O is small and endothermic, relatively large positive heat capacity of transfer data, increasing with increased hydrocarbon content of the salts, were observed. The ability of the bolaform cation to act as a model for cation-cation pairing in R4NX systems is discussed.