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Crown Ethers

Crown Ethers. Crown Ethers. structure cyclic polyethers derived from repeating —OCH 2 CH 2 — units properties form stable complexes with metal ions applications synthetic reactions involving anions. O. O. O. O. O. O. 18-Crown-6.

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Crown Ethers

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  1. Crown Ethers

  2. Crown Ethers structurecyclic polyethers derived from repeating —OCH2CH2— units propertiesform stable complexes with metal ions applicationssynthetic reactions involving anions

  3. O O O O O O 18-Crown-6 negative charge concentrated in cavity inside the molecule

  4. O O O O O O 18-Crown-6 negative charge concentrated in cavity inside the molecule

  5. O O O O O O 18-Crown-6 forms stable Lewis acid/Lewis base complex with K+ K+

  6. O O O O O O 18-Crown-6 forms stable Lewis acid/Lewis base complex with K+ K+

  7. Ion-Complexing and Solubility K+F– not soluble in benzene

  8. O O O O O O Ion-Complexing and Solubility K+F– benzene add 18-crown-6

  9. O O O O O O O O O O O O Ion-Complexing and Solubility F– K+ benzene 18-crown-6 complex of K+ dissolves in benzene

  10. O O O O O O O O O O O O + F– Ion-Complexing and Solubility K+ benzene F– carried into benzene to preserve electroneutrality

  11. Application to organic synthesis Complexaton of K+ by 18-crown-6 "solubilizes" salt in benzene Anion of salt is in a relatively unsolvated state in benzene (sometimes referred to as a "naked anion") Unsolvated anion is very reactive Only catalytic quantities of 18-crown-6 are needed

  12. Polyether Antibiotics

  13. Example KF CH3(CH2)6CH2Br CH3(CH2)6CH2F 18-crown-6 (92%) benzene

  14. Polyether Antibiotics Monensin

  15. Polyether Antibiotics Monensin

  16. Polyether Antibiotics

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