18-Crown-6
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| 18-Crown-6 | |
|---|---|
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| IUPAC name | 1,4,7,10,13,16-hexaoxacyclooctadecane |
| Identifiers | |
| CAS number | 17455-13-9 |
| SMILES | C1OCCOCCOCCOCCOCCOC1 |
| Properties | |
| Molecular formula | C12H24O6 |
| Molar mass | 264.122 g/mol |
| Density | 1.237 g/cm³ |
| Melting point |
37-40 °C |
| Boiling point |
116 °C (0.2 Torr) |
| Related compounds | |
| Related compounds | Dibenzo-18-crown-6 Triglyme |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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.
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[edit] Applications
Crown ethers are useful as phase transfer catalysts.[1] 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.
[edit] Synthesis
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.[2]
[edit] Related compounds
A related and generally superior complexant for alkali metal cations is dibenzo-18-crown-6.
[edit] References
- ^ 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
- ^ Charles J. Pedersen (1988). "Macrocyclic Polyethers:Dibenzo-18-Crown-6 Polyether and Dicyclohexyl-18-Crown-6 Polyether". Org. Synth.; Coll. Vol. 6: 395.
