| 18-Crown-6 | |
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1,4,7,10,13,16-hexaoxacyclooctadecane |
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| Identifiers | |
| CAS number | 17455-13-9 |
| PubChem | 28557 |
| ChemSpider | 26563 |
| ChEBI | CHEBI:32397 |
| ChEMBL | CHEMBL155204 |
| Jmol-3D images | Image 1 Image 2 |
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| 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 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
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 cations 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.
Contents |
This compound can be prepared by a modified Williamson ether synthesis[1] as well as the oligomerization of ethylene oxide in the presence of a templating cation.
It can be purified by distillation, where its tendency to supercool becomes evident. 18-Crown-6 can also be purified by precipitation with acetonitrile, with which it initially forms an insoluble complex. The acetonitrile may be removed in vacuo to obtain the desired compound.[1] 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 salt.
Crown ethers are useful as phase transfer catalysts.[2] 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.
Using 18-crown-6, potassium acetate is a more powerful nucleophile in organic solvents.
A related and generally superior complexant for alkali metal cations is dibenzo-18-crown-6.