18-Crown-6

Chembox new
Name = 18-Crown-6
ImageFile = 18-crown-6.svg
ImageName = 18-Crown-6
IUPACName = 1,4,7,10,13,16-hexaoxacyclooctadecane
Section1 = Chembox Identifiers
CASOther = {CAS|17455-13-9}
SMILES = C1OCCOCCOCCOCCOCCOC1
Section2 = Chembox Properties
Formula = C₁₂H₂₄O₆
MolarMass = 264.122 g/mol
Density = 1.237 g/cm³
MeltingPt = 37-40 °C
BoilingPt = 116 °C (0.2 Torr)
Section8 = Chembox Related
OtherCpds = Dibenzo-18-crown-6
Triglyme

18-Crown-6 is an organic compound with the formula [C₂H₄O] ₆ and the IUPAC name of 1,4,7,10,13,16-hexaoxacyclooctadecane. The compound is a crown ether. Crown ethers coordinate some metal ions in their central cavity; 18-crown-6 displays a particular affinity for potassium cations. The synthesis of the crown ethers led to the Nobel Prize in Chemistry to Charles J. Pedersen.

Applications

Crown ethers are useful as phase transfer catalysts. [Liotta, C. L.; Berknerin, J. "18-Crown-6" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi|10.1002/047084289X.rc261] In the presence of 18-crown-6 potassium permanganate dissolves in benzene, although this application is eclipsed by the use of quaternary ammonium/phosphonium salts.:Crown ethers can also be used to change the properties of inorganic compounds in organic solution. For example, in the presence of 18-crown-6, potassium acetate is a more powerful nucleophile in organic solvents than potassium acetate alone.

It can be purified by distillation, where its tendency to supercool becomes evident. Rigorously dry material can be made by dissolving the compound in THF followed by the addition of NaK to give [K(18-crown-6)] Na, an alkalide. Other ligands for alkali metal cations include cryptands and acyclic polyethers.

ynthesis

It can be prepared by a modified Williamson ether synthesis or the oligomerization of ethylene oxide in the presence of a template. The more accessible dibenzo crown-18-Crown-6 is prepared in one-pot from catechol and bis(chloroethyl)ether. [OrgSynth | author = Charles J. Pedersen | title = Macrocyclic Polyethers:Dibenzo-18-Crown-6 Polyether and Dicyclohexyl-18-Crown-6 Polyether | collvol = 6 | collvolpages = 395| year = 1988 | prep = CV6P0008]

Related compounds

A related and generally superior complexant for alkali metal cations is dibenzo-18-crown-6.:

References

External links

* [http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIAL/274984 Sigma Aldrich chemical profile]