August 27, 2019

ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CROWN ETHERS, COMPLEXES AND CRYPTANDS


ORGANIC CHEMISTRY- I (NATURE OF BONDING AND STEREOCHEMISTRY)- CROWN ETHERS, COMPLEXES AND CRYPTANDS


** Crypts and crown ethers constitute an important and an interesting class of complexing ligands.

** When the Nobel was conferred upon the three chemists Pederson, Cram and Lehn in 1987, the advances in host guest and supramolecular chemistry gained special attention.

** The crowns and crypts are enormously studied due to their increasing applications varied chemical and physical processes. Their use as biochemical models further draws greater interest towards them.

** Crown ethers (or crowns) are known as a group of macrocyclic polyethers. Many macropolycyclic ligands which are related to each other are also known to us and are called as 'cryptates' (or cryptands or simply, crypts)

** The two rings of cryptand provide extra strength to hold the ion. In case a regular crown ether "surrounds" an ion, a cryptand "locks it up". This ion-capturing capability of a cryptand can reach upto a hundred thousand times more than that of 18-crown-6.

** Crowns and crypts find many important applications and uses. These include preparative organic chemistry, solvent extraction, phase transfer catalysis, stabilisation of uncommon or reactive oxidation states and the promotion of other improbable reactions.