Thermodynamics of Bolaform Electrolytes. I. Heat Capacities and Enthalpies in H2O and D2O

The partial molal heats of solution at infinite dilution, Delta H-s degrees of bolaform salts [Et3N(CH2)(n)NEt3]Br-2 and [allyl(3)N(CH2)(n)Nallyl(3)]Br-2, have been measured in H2O and D2O at 25 degrees C using a solution calorimeter. The values of Delta H-s degrees were endothermic for almost all of the compounds studied. Values of Delta H-s degrees were obtained as a function of temperature for several homologs in H20 and D2O. Positive Delta C-p degrees values obtained from least-squares analyses of the Delta H-s degrees 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.