PRODUCT IDENTIFICATION

H.S. CODE

TOXICITY

CLASSIFICATION

EXTRANOTES

PHYSICAL AND CHEMICAL PROPERTIES

AUTOIGNITION

NFPA RATINGS

REFRACTIVE INDEX

110 C

GENERAL DESCRIPTION & EXTERNAL LINKS

As an ether, crown ethers are soluble in non-polar solvents. They are capable of strong solvency binding cations in their central cavity. The exterior of the ring is hydrophobic. The size of the interior central cavity, fused ring system, and side chains and functional groups determine the solvency capacity of the cation and the power of hydrophobic.

The main characteristic of crown ether is the complexation of the ether oxygens with various ionic species. If metalic elements pass through the center of the hole, they stick to oxygen atoms. The crown compound is then termed "host-guest" chemistry; Crown Ether acts as the "host" taking ionic species as its "guest". Crown compounds locks guest atoms in a solution and wrap around it. Crown ethers are used in PTC (phase-transfer catalysts) system and in encouraging the solubility of inorganic compounds in organic solvents to promote chemical reaction.  'Host-Guest' chemistry of crown ethers can be a key to identify the  move of essential elements in the body and can play the part of very complicated biological reactions such as enzyme's functions, which can be applied to develop new pharmaceuticals. Other compounds that have host cavity include cyclodextrins, calixarenes, cucurbiturils and porphyrins..

Cyclen (1,4,7,10-tetraazacyclododecane) is the aza analogues of crown ethers with repeating (-CH₂CH₂N) units. Cyclam is 1,4,8,11-Tetraazacyclotetradecane with repeating (-CH₂CH₂CH₂N) units. They are starting materials to produce macrocyclic polyamine metal-complexing agents. They coordinate more than one metal ions in their central cavity. They are used as a ligand in chemistry for the applications of diagnostic imaging technique to identify medical condition or disease and for the development of medication as a therapeutic agent and pharmaceutic aid.

Wikipedia Linking: http://en.wikipedia.org/wiki/Crown_ether

http://www.org-chem.org/
....An interesting thing about a crown ether is that the ring can capture a positively charged ion like a metal ion and an ammonium ion (the sphere shown inside the ring is the positively charged ion). The negatively charged electrons of the oxygen atoms pointing inward are used to attract and catch the ion. This property made some conventionally impossible things possible, including pulling ionic substances into organic solvent. I should emphasize here the importance of the ring structure, as it holds onto an ion ten thousand times more strongly than does the similar open chain structure.
Larger ions fit in larger crown ethers, and smaller ions fit in smaller crown ethers. The ionic radius increases in the order of lithium, sodium, and potassium, and these metal ions are known to be most compatible with twelve-, fifteen-, and eighteen-membered rings, respectively.
It’s also known that two crown ether molecules can sandwich an ion. In these cases, an ion larger than the natural fit can be captured. A crown ether with an interesting “switch” property has been synthesized...........

APPEARANCE

ASSAY