2.2.2-Cryptand
-Cryptand is the organic compound with the formula. This bicyclic molecule is the most studied member of the cryptand family of chelating agents. It is a white solid. Many analogous compounds are known. Their high affinity for alkali metal cations illustrates the advantages of "preorganization", a concept within the area of supramolecular chemistry.
For the design and synthesiis of cryptand, Jean-Marie Lehn shared the Nobel Prize in Chemistry. The compound was originally prepared starting with the diacylation of the diamine-diether:
The resulting macrocyclic diamide is reduced by lithium aluminium hydride. The resulting macrocyclic diamine tetraether reacts with a second equivalent of 2 to produce the macrobicyclic diamide. This diamide is reduced to the diamine by diborane.
Cryptand binds K+ as an octadentate N2O6 ligand. The resulting cation + is lipophilic.
Image:Cryptate of potassium cation.jpg|thumbnail|left|Structure of -cryptand encapsulating a potassium cation as determined by X-ray crystallography.
