Estimation of Association Constants of Macrocyclic Ethers by Potentiometry. Part V. Naþ Binding in Dioxane/Water (80/20)

The various association constants, bnm and Knm, of NaCl and NaClO4 with [12]crown-4, [15]crown-5, [18]crown-6, benzo[15]crown-5, benzo[12]crown-4, dibenzo[18]crown-6 and dinaphtho[18]crown-6 have been estimated in a mixture of dioxane/water (80/20) using a sodium ion selective electrode (ISE). The constants have been estimated using 1=ðKnm1⁄2Lo n1m21Þ5 ð1 2 nP 0Þn ð1 2 mP 0Þm=P 0; where P 0, the mole fraction of complexed Nain the presence of identical cation/ligand concentrations, is obtained for different aggregation – dissociation possibilities. The association constants of the complexes are reported and discussed in terms of the multiple composition due to strong dioxane/water binding. The binding mechanism is shown to depend on the free cation and counter ion that are formed by different ratio macrocycle –metal complexes in dioxane/water (80/20) solutions.