AskDefine | Define ether

Dictionary Definition

ether

Noun

1 a colorless volatile highly inflammable liquid formerly used as an inhalation anesthetic [syn: ethoxyethane, divinyl ether, vinyl ether, diethyl ether, ethyl ether]
2 the fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies [syn: quintessence]
3 any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom
4 a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves [syn: aether]

User Contributed Dictionary

see Ether

English

Alternative spellings

Pronunciation

  • a UK /ˈiːθə/
  • a US /ˈiːθəɻ/
  • a WEAE /ˈiː.θɚ/
Rhymes with: -iːθə(r)

Etymology

From aether < sc=polytonic < sc=polytonic.

Noun

  1. organic compound countable A compound containing an oxygen atom bonded to two hydrocarbon groups.
  2. organic compound uncountable Diethyl ether (C4H10O), a compound used as an early anaesthetic.
  3. In the context of "ancient philosophy|and|alchemy|uncountable": A classical physical element, considered as prevalent in the heavens and inaccessible to humans. In some versions of alchemy, this was the fifth element in addition to air, earth, fire and water.
  4. A substance (aether) once thought to fill all space that allowed Electromagnetic waves to pass through it and interact with matter, without exerting any resistance to matter or energy (disproved by Einstein in his Theory of Relativity).
  5. The sky or heavens; the upper air.

Quotations

Translations

organic chemistry: a compound containing an oxygen atom bonded to two hydrocarbon groups
  • German: Äther, Ether
  • Greek: αιθέρας
  • Icelandic: ljósvaki
  • Japanese: エーテル
  • Russian: эфир
  • Scottish Gaelic: adhar fìnealta
  • Swedish: eter
organic chemistry: diethyl ether, C4H10O
the fifth classic physical element
  • German: Äther, Ether
  • Greek: αιθέρας
  • Icelandic: ljósvaki
  • Japanese: エーテル
  • Russian: эфир
  • Scottish Gaelic: adhar fìnealta
  • Swedish: eter
archaic: space filling substance
  • Chinese: 以太
  • German: Äther
  • Greek: αιθέρας
  • Icelandic: ljósvaki
  • Japanese: エーテル, イーサー
  • Portuguese: éter
  • Russian: эфир
  • Scottish Gaelic: adhar fìnealta
  • Spanish: éter
  • Swedish: eter
poetic and literary: the sky or heavens; the upper air
  • Portuguese: éter

Extensive Definition

Ether is a class of organic compounds which contain an ether group — an oxygen atom connected to two (substituted) alkyl or aryl groups — of general formula R–O–R. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (ethoxyethane, CH3-CH2-O-CH2-CH3).

Physical properties

Ether molecules cannot form hydrogen bonds among each other, resulting in a relatively low boiling point comparable to that of the analogous alcohols. However, the differences in the boiling points of the ethers and their isometric alcohols become smaller as the carbon chains become longer, as the hydrophobic nature of the carbon chain becomes more predominant over the presence of hydrogen bonding.
Ethers are slightly polar as the R - C - O - C - Z bond angle in the functional group is about 110 degrees, and the C - O dipole does cancel out. Ethers are more polar than alkenes but not as polar as alcohols, esters or amides of comparable structure. However, the presence of two lone pairs of electrons on the oxygen atoms makes hydrogen bonding with water molecules possible, causing the solubility of alcohols (for instance, butan-1-ol) and ethers (ethoxyethane) to be quite dissimilar.
Cyclic ethers such as tetrahydrofuran and 1,4-dioxane are totally miscible in water because of the more exposed oxygen atom for hydrogen bonding as compared to aliphatic ethers.
Ethers can act as Lewis bases. For instance, diethyl ether forms a complex with boron compounds, such as boron trifluoride diethyl etherate (BF3.OEt2). Ethers also coordinate to magnesium in Grignard reagents (RMgBr).

Nomenclature

In the IUPAC nomenclature system, ethers are named using the general formula "alkoxyalkane", for example CH3-CH2-O-CH3 is methoxyethane. If the ether is part of a more complex molecule, it is described as an alkoxy substituent, so -OCH3 would be considered a "methoxy-" group. The simpler alkyl radical is written in front, so CH3-O-CH2CH3 would be given as methoxy(CH3O)ethane(CH2CH3). The nomenclature of describing the two alkyl groups and appending "ether", e.g. "ethyl methyl ether" in the example above, is a trivial usage.

Similar structures

Ethers are not to be confused with the following classes of compounds with the same general structure R-O-R.
  • Aromatic compounds like furan where the oxygen is part of the aromatic system.
  • Compounds where one of the carbon atoms next to the oxygen is connected to oxygen, nitrogen, or sulfur:

Primary, secondary, and tertiary ethers

The terms "primary ether", "secondary ether", and "tertiary ether" are occasionally used and refer to the carbon atom next to the ether oxygen. In a primary ether this carbon is connected to only one other carbon as in diethyl ether CH3-CH2-O-CH2-CH3. An example of a secondary ether is diisopropyl ether (CH3)2CH-O-CH(CH3)2 and that of a tertiary ether is di-tert-butyl ether (CH3)3C-O-C(CH3)3.
Dimethyl ether, a primary, a secondary, and a tertiary ether.

Polyethers

Polyethers are compounds with more than one ether group. While the term generally refers to polymers like polyethylene glycol and polypropylene glycol, low molecular compounds such as the crown ethers may sometimes be included.

Organic reactions

Synthesis

Ethers can be prepared in the laboratory in several different ways.
R-OH + R-OH → R-O-R + H2O
This direct reaction requires drastic conditions (heating to 140 degrees Celsius and an acid catalyst, usually concentrated sulfuric acid). Effective for making symmetrical ethers, but not as useful for synthesising asymmetrical ethers because the reaction will yield a mixture of ethers, making it usually not applicable:
3R-OH + 3R'-OH → R-O-R + R'-O-R + R'-O-R' + 3H2O
Conditions must also be controlled to avoid overheating to 170 degrees which will cause intramolecular dehydration,a reaction that yields alkenes. In addition, the alcohol must be in excess.
R-CH2-CH2(OH) → R-CH=CH2 + H2O
Such conditions can destroy the delicate structures of some functional groups. There exist several milder methods to produce ethers.
R-O- + R-X → R-O-R + X-
This reaction is called the Williamson ether synthesis. It involves treatment of a parent alcohol with a strong base to form the alkoxide anion followed by addition of an appropriate aliphatic compound bearing a suitable leaving group (R-X). Suitable leaving groups (X) include iodide, bromide, or sulfonates. This method does not work if R is aromatic like in bromobenzene (Br-C6H5), however, if the leaving group is separated by at least one carbon from the benzene, the reaction should proceed (as in Br-CH2-C6H5). Likewise, this method only gives the best yields for primary carbons, as secondary and tertiary carbons will undergo E2 elimination on exposure to the basic alkoxide anion used in the reaction due to steric hindrance from the large alkyl groups. Aryl ethers can be prepared in the Ullmann condensation.
  • Nucleophilic Displacement of Alkyl halides by phenoxides
The R-X cannot be used to react with the alcohol. However, phenols can be used to replace the alcohol, while maintaining the alkyl halide. Since phenols are acidic, they readily react with a strong base like sodium hydroxide to form phenoxide ions. The phenoxide ion will then substitute the -X group in the alkyl halide, forming an ether with an aryl group attached to it in a reaction with an SN2 mechanism.
HO-C6H5 + OH- → O--C6H5
O--C6H5 + R-X → R-O-C6H5
R2C=CR2 + R-OH → R2CH-C(-O-R)-R2
Acid catalysis is required for this reaction. Often, Mercury trifluoroacetate (Hg(OCOCF3)2 is used as a catalyst for the reaction, creating an ether with Markovnikov regiochemistry. Tetrahydropyranyl ethers are used as protective groups for alcohols.
Cyclic ethers which are also known as epoxides can be prepared:
  • By the oxidation of alkenes with a peroxyacid such as m-CPBA.
  • By the base intramolecular nuclephilic substitution of a halohydrin.

Reactions

| Ethylene oxide |The smallest cyclic ether. |- | |Dimethyl ether |An aerosol spray propellant. |- ||Diethyl ether |A common low boiling solvent (b.p. 34.6°C). |- | | Dimethoxyethane (DME) | A high boiling solvent (b.p. 85°C): |- | | Dioxane | A cyclic ether and high boiling solvent (b.p. 101.1°C). |- | | Tetrahydrofuran (THF) | A cyclic ether, one of the most polar simple ethers that is used as a solvent. |- | |Anisole (methoxybenzene) |An aryl ether and a major constituent of the essential oil of anise seed. |- | |Crown ethers |Cyclic polyethers that are used as phase transfer catalysts. |- | | Polyethylene glycol (PEG) | A linear polyether, e.g. used in cosmetics: |}

See also

References

External links

ether in Arabic: إيثر
ether in Catalan: Èter
ether in Czech: Ethery
ether in Danish: Æter (kemi)
ether in German: Ether
ether in Estonian: Eetrid
ether in Spanish: Éter (química)
ether in Esperanto: Etero (kemio)
ether in French: Éther-oxyde
ether in Korean: 에테르 (화학)
ether in Italian: Eteri
ether in Hebrew: אתר (כימיה)
ether in Latin: Aether (chemica)
ether in Latvian: Ēteri
ether in Hungarian: Éter (kémia)
ether in Macedonian: Етер
ether in Dutch: Ether (chemie)
ether in Japanese: エーテル (化学)
ether in Norwegian: Eter (kjemi)
ether in Norwegian Nynorsk: Eterar
ether in Polish: Etery
ether in Portuguese: Éter
ether in Romanian: Eter
ether in Russian: Простые эфиры
ether in Slovenian: Eter
ether in Serbian: Етар (хемија)
ether in Finnish: Eetteri
ether in Swedish: Etrar
ether in Vietnamese: Ete
ether in Ukrainian: Прості ефіри
ether in Chinese: 醚

Synonyms, Antonyms and Related Words

Caelus, Dry Ice, Freon, Olympian heights, Pentothal, acme, aerial heights, air, airy nothing, ammonia, apex, azure, blue sky, bubble, caelum, canopy, canopy of heaven, carbon dioxide, cerulean, chaff, chip, chloroform, cobweb, cocaine, coolant, cope, cork, dizzy heights, down, dust, elevation, eminence, empyrean, ethyl chloride, ethylene, fairy, feather, firmament, flue, fluff, foam, freezing mixture, froth, fuzz, gas, gossamer, heaven, heavens, height, heights, hyaline, ice, ice cubes, illusion, lift, lifts, liquid air, liquid helium, liquid oxygen, menthol, mist, mote, nitrous oxide, ozone, phantom, raise, refrigerant, rise, rising ground, shadow, sky, smoke, spirit, sponge, spume, starry heaven, steep, stratosphere, straw, the blue, the blue serene, thin air, thistledown, uprise, vantage ground, vantage point, vapor, vault, vault of heaven, welkin, zenith
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