A calorimetric study of metal ion cyclic polyether interaction :|bI. Cation binding properties of macrocyclic polyethers in aqueous solution as a function of temperature ; II. Effect of solvent dielectric constant on the binding properties of cyclic polyethers for Na[superscript +] and K[superscript +]
The complexation properties of the two isomers of the cyclic polyether dicyclohexyl-18-crown-6 are examined in aqueous solution for a series of metal ions at various reaction temperatures. The results are discussed in terms of size relationships and salvation characteristics of both polyether and metal ions. ΔCp° values are determined from the temperature dependence of the ΔH° values. A discussion of the errors involved in the determination of ΔH° from the temperature dependence of log K values is also included. Comparisons are made between the results of this study and those of a similar study by H. K. Frensdorff, E. I. duPont de Nemours and Co., Wilmington, Delaware, in press. The complexation reactions of dicyclohexyl- and dibenzo-18-crown-6 and benzo-15-crown-5 with Na^+ and K^+ ions are reported in non-aqueous solvents and methanol-water mixtures. The results are discussed with reference to their application in model systems of ion transport. In general the stabilities of the polyether-cation complexes were found to increase with decreasing dielectric constant of the solvent medium. In the methanol-water mixtures large compensating ΔH° and ΔS° changes were observed above 70 weight percent methanol, while the log K values showed a nearly linear increase with increasing methanol concentration. Salvation of the polyethers and metal ions and complexation of ion pairs in non-aqueous solvents are discussed.
College and Department
Chemistry and Biochemistry
BYU ScholarsArchive Citation
Nelson, Dennis Pershing, "A calorimetric study of metal ion cyclic polyether interaction :|bI. Cation binding properties of macrocyclic polyethers in aqueous solution as a function of temperature ; II. Effect of solvent dielectric constant on the binding properties of cyclic polyethers for Na[superscript +] and K[superscript +]" (1971). Theses and Dissertations. 8315.
Polyethers, Cyclic compounds, Calorimetry, Sodium, Potassium, Ionic solutions