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ether (n.)
1.a colorless volatile highly inflammable liquid formerly used as an inhalation anesthetic
2.a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves
3.any of a class of organic compounds that have two hydrocarbon groups linked by an oxygen atom
4.the fifth and highest element after air and earth and fire and water; was believed to be the substance composing all heavenly bodies
Ether (n.)
1.(MeSH)A mobile, very volatile, highly flammable liquid used as an inhalation anesthetic and as a solvent for waxes, fats, oils, perfumes, alkaloids, and gums. It is mildly irritating to skin and mucous membranes.
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Merriam Webster
EtherE"ther (ē"thẽr), n. [L. aether, Gr. a'iqh`r, fr. a'i`qein to light up, kindle, burn, blaze; akin to Skr. idh, indh, and prob. to E. idle: cf. F. éther.] [Written also æther.]
1. (Physics) A medium of great elasticity and extreme tenuity, once supposed to pervade all space, the interior of solid bodies not excepted, and to be the medium of transmission of light and heat; hence often called luminiferous ether. It is no longer believed that such a medium is required for the transmission of electromagnetic waves; the modern use of the term is mostly a figurative term for empty space, or for literary effect, and not intended to imply the actual existence of a physical medium. However. modern cosmological theories based on quantum field theory do not rule out the possibility that the inherent energy of the vacuum is greater than zero, in which case the concept of an ether pervading the vacuum may have more than metaphoric meaning.
2. Supposed matter above the air; the air itself.
3. (Chem.) (a) A light, volatile, mobile, inflammable liquid, (C2H5)2O, of a characteristic aromatic odor, obtained by the distillation of alcohol with sulphuric acid, and hence called also sulphuric ether. It is a powerful solvent of fats, resins, and pyroxylin, but finds its chief use as an anæsthetic. Commonly called ethyl ether to distinguish it from other ethers, and also ethyl oxide. (b) Any similar compound in which an oxygen atom is bound to two different carbon atoms, each of which is part of an organic radical; as, amyl ether; valeric ether; methyl ethyl ether. The general formular for an ether is ROR′, in which R and R′ are organic radicals which may be of similar or different structure. If R and R′ are different parts of the same organic radical, the structure forms a cyclic ether.
Complex ether, Mixed ether (Chem.), an ether in which the ether oxygen is attached to two radicals having different structures; as, ethyl methyl ether, C2H5.O.CH3. -- Compound ether (Chem.), an ethereal salt or a salt of some hydrocarbon as the base; an ester. -- Ether engine (Mach.), a condensing engine like a steam engine, but operated by the vapor of ether instead of by steam.
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⇨ voir la définition de Wikipedia
Ether (n.) (MeSH)
Diethyl Ether (MeSH), Ether, Ethyl (MeSH), Ethyl Ether (MeSH)
ether (n.)
aether, diethyl ether, divinyl ether, ethoxyethane, ethyl ether, quintessence, vinyl ether
⇨ Acetyl Glyceryl Ether Phosphorylcholine • Alkenyl Ether Phospholipids • Bis(Chloromethyl) Ether • Bis(Chloromethyl)Ether • Chloromethyl Ether • DHP Ether • Dichloromethyl Ether • Diethyl Ether • Dihematoporphyrin Ether • Divinyl Ether Maleic Anhydride Copolymer • Ether Phosphatidates • Ether, Ethyl • Ether-A-Go-Go Potassium Channels • Ether-A-Go-Go Related Potassium Channels • Ethyl Ether • Guaiacol Glyceryl Ether • Hoffmann's ether spirit • Maleic Anhydride Divinyl Ether • Maleic Anhydride Vinyl Ether • Petroleum ether • Vinyl Ether Maleic Anhydride Polymer • addiction to ether • diethyl ether • divinyl ether • ether addict • ethyl ether • vinyl ether
⇨ 2-Arachidonyl glyceryl ether • Acetyl glyceryl ether phosphorylcholine • Acetyl-glyceryl-ether-phosphorylcholine • Bis(chloromethyl) ether • Bisphenol A diglycidyl ether • Book of Ether • Chloroalkyl ether • Chloromethyl methyl ether • Compound spirit of ether • Crashing the Ether • Crown ether • Decabromodiphenyl ether • Deithyl ether • Di-tert-butyl ether • Diaryl ether • Dibutyl ether • Diethyl Ether • Diethyl ether • Diethyl ether (data page) • Diethyl ether (drug) • Diethyl ether peroxide • Diisopropyl ether • Dimethyl ether • Dimethyl ether (data page) • Diphenyl ether • Enol ether • Ether (Book of Mormon prophet) • Ether (Encantadia deity) • Ether (Fischer-Z album) • Ether (Fischer-Z) • Ether (album) • Ether (disambiguation) • Ether (song) • Ether Dome • Ether Dome, Massachusetts General Hospital • Ether File Transfer Protocol • Ether Monument • Ether Ore • Ether Saga Online • Ether Shepley • Ether Ship • Ether Song • Ether Way • Ether lipid • Ether, North Carolina • Ethyl ether • Ethyl phenyl ether • Ethyl tert-butyl ether • Ethylene glycol dimethyl ether • From the Ether • Glycerol ether • Glyceryl-ether monooxygenase • Halogenated ether • Isopropyl ether • Jim Ether • Methyl t-butyl ether • Methyl tert-butyl ether • Methyl tertiary butyl ether • Methyl tertiary-butyl ether • Methylthiomethyl ether • Muriatic ether • Nitric ether • Nitrophenyl octyl ether • Nitrous ether • Octabromodiphenyl ether • Octaethylene glycol monododecyl ether • Organic ether • Patrolling the Ether • Pentabromodiphenyl ether • Pentaethylene glycol monododecyl ether • Petrol ether • Petroleum ether • Poly(tetramethylene ether) glycol • Polyphenyl ether • Silyl enol ether • Silyl ether • Sulfuric ether • Sulphuric ether • Tert-Amyl methyl ether • Tetrahydropyranyl ether • Thanks for the Ether • Vinyl ether • When Under Ether • Williamson ether synthesis
Ether (n.) [MeSH]
Ethoxy Compounds, Ethyl Ethers[Hyper.]
ether (n.)
ether[ClasseHyper.]
paregoric; analgesic; anodyne; painkiller; pain pill[Classe]
ether (n.)
medium[Hyper.]
ether (n.)
organic compound[Hyper.]
ethereal[Dérivé]
ether (n.)
alcool non alimentaire (fr)[Classe]
extrait : produit retiré d'une substance (fr)[Classe]
élément minimal de l'être selon les anciens (fr)[Classe]
raffiner (fr)[termes liés]
distillation (fr)[termes liés]
(alchemy), (alchemist)[termes liés]
Wikipedia
Ethers ( /ˈiːθər/) are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'.[1] A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (CH3-CH2-O-CH2-CH3). Ethers are common in organic chemistry and pervasive in biochemistry, as they are common linkages in carbohydrates and lignin.
Contents |
Ethers feature C-O-C linkage defined by a bond angle of about 104.5° and C-O distances of about 140 pm. The barrier to rotation about the C-O bonds is low. The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp3.
Oxygen is more electronegative than carbon, thus the hydrogens alpha to ethers are more acidic than in simple hydrocarbons. They are far less acidic than hydrogens alpha to carbonyl groups (such as in ketones or aldehydes), however.
1) Simple ethers or symmetrical ethers 2) Mixed ethers or asymmetrical ethers
The names for simple ethers (i.e. those with none or few other functional groups) are a composite of the two substituents followed by "ether." Ethyl methyl ether (CH3OC2H5), diphenylether (C6H5OC6H5). IUPAC rules are often not followed for simple ethers. As for other organic compounds, very common ethers acquired names before rules for nomenclature were formalized. Diethyl ether is simply called "ether," but was once called sweet oil of vitriol. Methyl phenyl ether is anisole, because it was originally found in aniseed. The aromatic ethers include furans. Acetals (α-alkoxy ethers R-CH(-OR)-O-R) are another class of ethers with characteristic properties.
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.
Polyethers are compounds with more than one ether group.
The crown ethers are examples of low-molecular weight polyethers. Some toxins produced by dinoflagellates such as brevetoxin and ciguatoxin are in a class known as cyclic or ladder polyethers.
Polyether generally refers to polymers which contain the ether functional group in their main chain. The term glycol is reserved for low to medium range molar mass polymer when the nature of the end-group, which is usually a hydroxyl group, still matters. The term "oxide" or other terms are used for high molar mass polymer when end-groups no longer affect polymer properties.
Aliphatic polyethers
Name of the polymers with low to medium molar mass | Name of the polymers with high molar mass | Preparation | Repeating unit | Examples of trade names |
---|---|---|---|---|
Paraformaldehyde | Polyoxymethylene (POM) or polyacetal or polyformaldehyde | Step-growth polymerisation of formaldehyde | -CH2O- | Delrin from DuPont |
Polyethylene glycol (PEG) | Polyethylene oxide (PEO) or polyoxyethylene (POE) | Ring-opening polymerization of ethylene oxide | -CH2CH2O- | Carbowax from Dow |
Polypropylene glycol (PPG) | Polypropylene oxide (PPO) ou polyoxypropylene) (POP) | Anionic ring-opening polymerization of propylene oxide | -CH2CH(CH3)O- | |
Polytetramethylene glycol (PTMG) or Polytetramethylene ether glycol (PTMEG) | Polytetrahydrofuran (PTHF) | Acid-catalyzed ring-opening polymerization of tetrahydrofuran | -CH2CH2CH2CH2O- | Terathane from Invista and PolyTHF from BASF |
Aromatic polyethers
The phenyl ether polymers are a class of polyethers containing aromatic cycles in their main chain: Polyphenyl ether (PPE) and Poly(p-phenylene oxide) (PPO).
Many classes of compounds with C-O-C linkages are not considered ethers: Esters (R-C(=O)-O-R), hemiacetals (R-CH(-OH)-O-R), carboxylic acid anhydrides (RC(=O)-O-C(=O)R).
Ether molecules cannot form hydrogen bonds with each other, resulting in a relatively low boiling points compared to those of the analogous alcohols. The difference, however, in the boiling points of the ethers and their isometric alcohols becomes lower as the carbon chains become longer, as the van der Waals interactions of the extended carbon chain dominates over the presence of hydrogen bonding.
Ethers are slightly polar. The C-O-C bond angle in the functional group is about 110°, and the C-O dipoles do not 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.
Cyclic ethers such as tetrahydrofuran and 1,4-dioxane are miscible in water because of the more exposed oxygen atom for hydrogen bonding as compared to aliphatic ethers.
Selected data about some alkyl ethers | |||||
---|---|---|---|---|---|
Ether | Structure | m.p. (°C) | b.p. (°C) | Solubility in 1 liter of H2O | Dipole moment (D) |
Dimethyl ether | CH3-O-CH3 | -138.5 | -23.0 | 70 g | 1.30 |
Diethyl ether | CH3CH2-O-CH2CH3 | -116.3 | 34.4 | 69 g | 1.14 |
Tetrahydrofuran | O(CH2)4 | -108.4 | 66.0 | Miscible | 1.74 |
Dioxane | O(C2H4)2O | 11.8 | 101.3 | Miscible | 0.45 |
Ethers in general are of low chemical reactivity, but they are more reactive than alkanes (epoxides, ketals, and acetals are unrepresentative classes of ethers and are discussed in separate articles). Important reactions are listed below.[2]
Although ethers resist hydrolysis, they are cleaved by mineral acids such as hydrobromic acid and hydroiodic acid. Hydrogen chloride cleaves ethers only slowly. Methyl ethers typically afford methyl halides:
These reactions proceed via onium intermediates, i.e. [RO(H)CH3]+Br-.
Some ethers rapidly cleave with boron tribromide (even aluminium chloride is used in some cases) to give the alkyl bromide.[3] Depending on the substituents, some ethers can be cleaved with a variety of reagents, e.g. strong base.
When stored in the presence of air or oxygen, ethers tend to form explosive peroxides, such as diethyl ether peroxide. The reaction is accelerated by light, metal catalysts, and aldehydes. In addition to avoiding storage conditions likely to form peroxides, it is recommended, when an ether is used as a solvent, not to distill it to dryness, as any peroxides that may have formed, being less volatile than the original ether, will become concentrated in the last few drops of liquid.
Ethers serve as Lewis bases and Bronsted bases. Strong acids protonate the oxygen to give "onium ions." For instance, diethyl ether forms a complex with boron trifluoride, i.e. diethyl etherate (BF3.OEt2). Ethers also coordinate to Mg(II) center in Grignard reagents. Polyethers, including many antibiotics, cryptands, and crown ethers, bind alkali metal cations strongly.
This reactivity is akin to the tendency of ethers with alpha hydrogen atoms to form peroxides. Chlorine gives alpha-chloroethers.
Ethers can be prepared in the laboratory in several different ways.
The Dehydration of alcohols affords ethers:
This direct reaction requires elevated temperatures (about 125 °C). The reaction is catalyzed by acids, usually sulfuric acid. The method is effective for generating symmetrical ethers, but not unsymmetrical ethers. Diethyl ether is produced from ethanol by this method. Cyclic ethers are readily generated by this approach. Such reactions must compete with dehydration of the alcohol:
The dehydration route often requires conditions incompatible with delicate molecules. Several milder methods exist to produce ethers.
Nucleophilic displacement of alkyl halides by alkoxides
This reaction is called the Williamson ether synthesis. It involves treatment of a parent alcohol with a strong base to form the alkoxide, 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 usually does not work well for aryl halides (e.g. bromobenzene (see Ullmann condensation below). Likewise, this method only gives the best yields for primary halides. Secondary and tertiary halides are prone to undergo E2 elimination on exposure to the basic alkoxide anion used in the reaction due to steric hindrance from the large alkyl groups.
In a related reaction, alkyl halides undergo nucleophilic displacement 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.
The Ullmann condensation is similar to the Williamson method except that the substrate is an aryl halide. Such reactions generally require a catalyst, such as copper.
Alcohols add to electrophilically activated alkenes.
Acid catalysis is required for this reaction. Often, mercury trifluoroacetate (Hg(OCOCF3)2) is used as a catalyst for the reaction, geneating an ether with Markovnikov regiochemistry. Using similar reactions, tetrahydropyranyl ethers are used as protective groups for alcohols.
Epoxides are typically prepared by oxidation of alkenes. The most important epoxide in terms of industrial scale is ethylene oxide, which is produced by oxidation of ethylene with oxygen. Other epoxides are produced by one of two routes:
Ethylene oxide | The smallest cyclic ether. | |
Dimethyl ether | An aerosol spray propellant. A potential renewable alternative fuel for diesel engines with a cetane rating as high as 56-57. | |
Diethyl ether | A common low boiling solvent (b.p. 34.6 °C), and an early anaesthetic. Used as starting fluid for diesel engines. | |
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 and pharmaceuticals. |
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2007) |
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