The Interaction of Cations with Cyclic Ethers

Citation

Live, David Harris (1974) The Interaction of Cations with Cyclic Ethers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/kq1b-vg86. https://resolver.caltech.edu/CaltechTHESIS:03222021-225134007

Abstract

Proton and carbon nuclear magnetic resonance (NMR) have been used to aid in the understanding of solution structure, cation, anion and solvent interactions, and structural aspects of cation specificities of "crown" cyclic polyethers. Investigations were made in water, water-acetone, acetone and chloroform as a function of cation concentration and of anion. Using the effects of the aromatic residues on the molecules we have studied, we have been able to assign the proton and carbon spectra. From the vicinal proton-proton coupling, the electrostatic effect of cation and anion on the proton NMR, and the structural sensitivity of the carbon NMR, we have obtained results on the interaction of Na⁺, K⁺, Cs⁺ and Ba⁺² with Benzo 18 Crown 6, Dibenzo 18 Crown 6 and Dibenzo 30 Crown 10. Analysis of the cation induced shifts has enabled us in some cases to examine the cation binding as a function of solvent.

The complexes of Benzo 18 Crown 6 and Dibenzo 18 Crown 6 have the same structures in the various solvents as found in the crystal for DB18CR6. However, the solution conformation of the uncomplexed molecules differs from that in the crystal. The K⁺, Cs⁺ and Ba⁺² complexes of Dibenzo 30 Crown 10 in solution, have the same configuration reported for the K⁺ complex in the crystal. The Na⁺ complex does not, and we have proposed an alternate structure. The solvation sphere of a cation is completely removed when it is complexed to the latter crown ether, which is not the case for the 18 membered rings.

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