crown ether


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crown ether

[′krau̇n ‚ē·thər]
(organic chemistry)
A macrocyclic polyether whose structure exhibits a conformation with a so-called hole capable of trapping cations by coordination with a lone pair of electrons on the oxygen atoms.
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was dispersed in distilled water (~1 / 100, by weight) by stirring overnight in a beaker; then a 1 ~3 % by volume solution of crown ether in acetone (~150 mmol/ 100 g, crown ether/clay) was added slowly to the suspension.
The sodium clay was dispersed in distilled water (~1/100, wt/wt) by stirring overnight in a beaker, then an 1-3% solution of potassium iodide-crown ether complex in water (the complex was prepared by mixing KI with crown ether in water) was added drop-wise to the suspension.
The complexation constant reflects the binding ability between the cation and the crown ether.
This clearly indicates that the crown ether or cryptand does complex with both potassium or sodium ion and effect an expansion of the d-spacing.
The intercalation of PS into the clay may be explained by the complexation constant between the crown ether and the cation.
Photo: A crown ether unfolds to grab a potassium ion.
Cram and his group have concentrated on building rigid molecules that, unlike crown ethers, have a permanent cavity.
Synergistic solvent extraction and separation of lanthanoids with mixtures of 1-phenyl -3-methyl -4-benzoyl-5-pyrazolone and crown ethers.
Crown ethers as synergistic agents in the solvent extraction of trivalent lanthanoids with thenoyltrifluoroacetone.
Part F includes Chapters on a New General Method for the Synthesis of O- and S-Glucosides; Chiral Crown Ethers Incorporating D-Glucose; Biomass Production of Industrial Sweet Potato as Influenced by Vesicular Arbuscular Mycorrhizal Fungal Inoculation; Mesta as a Potential Source of Carbohydrate via Organosolv Delignification; Scanning Electron Microscopic Studies of the Surface Texture of Controlled Release Matrices of Carboxymethylcellulose; Study on Thermal Degradation of Ispaghula Esters; Synthesis of Quaternary Ammonium Compounds of Hydroxyethyl Guar Gum as Catalysts for Curing of Epoxy Resins.
These consisted of helixes with polar crown ethers to act as the "jumping points" for the ions.
After dealing with preliminaries he presents a section on moieties within molecules, discussing crown ethers, cryptands, and related molecules as hosts; cyclodextrins and some analogs as hosts; and crystal chemistry of some DNA oligonucleotides and their complexes.