ether: Definition and Much More from Answers.com

n.

1. Any of a class of organic compounds in which two hydrocarbon groups are linked by an oxygen atom.
2. A volatile, highly flammable liquid, C₂H₅OC₂H₅, derived from the distillation of ethyl alcohol with sulfuric acid and used as a reagent and solvent. It was formerly used as an anesthetic. Also called diethyl ether, ethyl ether.
3. The regions of space beyond the earth's atmosphere; the heavens.
4. The element believed in ancient and medieval civilizations to fill all space above the sphere of the moon and to compose the stars and planets.
5. Physics. An all-pervading, infinitely elastic, massless medium formerly postulated as the medium of propagation of electromagnetic waves.

[Middle English, upper air, from Latin aethēr, from Greek aithēr.]

etheric e·ther'ic (ĭ-thĕr'ĭk, ĭ-thîr'-) adj.

(1) An invisible medium through which all light, heat and electromagnetic waves propagate. Pronounced "eether" with the "th" as in the word "thought," ether was postulated from the 1600s to the 1800s. The word was inspiration for Ethernet. See Ethernet.

(2) A group of chemical compounds, the most popular of which is the colorless and transparent diethyl ether, used as a solvent and anesthetic. Diethyl ether was synthesized in the 1500s and named "ether" in the 1700s.

Any of a class of organic compounds whose molecular structure has an oxygen atom interposed between two carbon atoms that are part of hydrocarbon molecules. Ethers have the general chemical formula ROR¢, in which R and R¢ represent the hydrocarbons. They resemble alcohols but generally are less dense, less soluble in water, more volatile, and more inert. They are used in chemical processing, for extraction and separation of chemicals, and as solvents. Some are used as insecticides and soil fumigants. They are also used in medicine and pharmacology. Codeine is the methyl ether of morphine. The term ether often refers to ethyl ether (C₂H₅OC₂H₅), best known as an anesthetic but also used as a solvent, an extractant, and a reaction medium.

For more information on ether, visit Britannica.com.

in chemistry
in physics and astronomy

any of a number of organic compounds whose molecules contain two hydrocarbon groups joined by single bonds to an oxygen atom. The most common of these compounds is ethyl ether, CH₃CH₂OCH₂CH₃, often called simply ether, a colorless, volatile liquid with a distinctive odor; its IUPAC name is ethoxyethane. Ethyl ether boils at 34.5°C and is extremely flammable. It is insoluble in water but mixes with many organic solvents and is widely used as a solvent itself, e.g., for fats and oils. Its most familiar historical application is as an anesthetic. An ether such as ethyl ether in which both hydrocarbon groups are identical is said to be a simple, or symmetrical, ether. An ether in which the two groups differ (e.g., methyl ethyl ether, CH₃OCH₂CH₃) is said to be a mixed, or unsymmetrical, ether. Ethers are often prepared commercially by heating an alcohol with sulfuric acid; the reaction is one of dehydration. In the laboratory ethers are often prepared by reaction of an alkyl halide with a sodium alkoxide (a method called the Williamson synthesis). Ethers are usually chemically unreactive but can be cleaved (broken apart) at high temperatures by concentrated hydrogen halides; initially an alkyl halide and an alcohol are formed. Epoxides are a special class of cyclic ethers.

ether or aether, in physics and astronomy, a hypothetical medium for transmitting light and heat (radiation), filling all unoccupied space; it is also called luminiferous ether. In Newtonian physics all waves are propagated through a medium, e.g., water waves through water, sound waves through air. When James Clerk Maxwell developed his electromagnetic theory of light, Newtonian physicists postulated ether as the medium that transmitted electromagnetic waves. Ether was held to be invisible, without odor, and of such a nature that it did not interfere with the motions of bodies through space. The concept was intended to connect the Newtonian mechanistic wave theory with Maxwell's field theory. However, all attempts to demonstrate its existence, most notably the Michelson-Morley experiment of 1887, produced negative results and stimulated a vigorous debate among physicists that was not ended until the special theory of relativity, proposed by Albert Einstein in 1905, became accepted. The theory of relativity eliminated the need for a light-transmitting medium, so that today the term ether is used only in a historical context.

1. diethyl ether: a colorless, transparent, very volatile, highly inflammable liquid with a characteristic odor; given by inhalation to produce general anesthesia.
2. any organic compound containing an oxygen atom bonded to two carbon atoms.

• spiritus e. nit. — used as a stimulant for depressed animals, both as an inhalant and in oral drenches.
• vinyl e. — a clear colorless liquid used as an inhalation anesthetic.

Essay: Does the ether exist?

In 1881 Albert A. Michelson and Edward Morley tried to measure the absolute velocity of Earth with respect to the rest of the universe. The result of their measurement showed that Earth is at rest in space, but no one believed that that could be true. The idea of a motionless Earth had been given up 300 years earlier. Something had to be wrong with the experiment.

The problem at first glance seemed to be with light. Ever since Thomas Young had demonstrated in 1803 that light produces interference patterns, it was assumed that light must be waves, a view previously held by Christiaan Huygens and others. All those who espoused the wave theory--the alternative theory was that light consisted of particles--assumed that light must be waves in something. When Augustin-Jean Fresnel began to work on the wave theory of light, he named the something ether, after Aristotle's fifth element. Fresnel was able to show that light waves are more like water waves (but in three dimensions instead of just up and down) than they are like sound waves (which are back and forth instead of up and down).

Michelson had taken a suggestion of James Clerk Maxwell, made in 1875, to develop a sensitive measuring tool based on the interference patterns of waves of light. The Michelson-Morley experiment was designed to use the interferometer, Michelson's new tool, to measure how Earth moves through the ether, which was assumed to be stationary. Michelson and Morley measured the speed of light in two perpendicular directions. The speed was found to be the same, implying that Earth stands still.

Others had different explanations. Both George Francis Fitzgerald and Hendrik Antoon Lorentz suggested that the problem could be resolved by assuming that objects contract when they move. By assigning the correct value to the contraction, the speed of light could be made to appear the same in two different directions, since the apparatus used to measure it would contract in the direction in which Earth is moving.

In 1905 Albert Einstein resolved the issue in a different way. Einstein perceived that the same physical laws must be true in all frames of reference in steady motion with respect to each other. But this requirement also means that light must have the same speed no matter how a body is moving. There can be no fixed frame of reference against which Earth moves, so Michelson and Morley got the correct result. In addition, the Fitzgerald-Lorentz contraction is a real effect, explained by Einstein's theory. Furthermore, in a separate paper, Einstein showed that light behaves like a particle as well as like a wave. Although this wave-particle duality remains difficult to picture, it has become quite clear since 1905 that light has both wave and particle properties. A particle does not require a medium the way that a wave does.

Does the ether exist? Einstein's theory of special relativity suggests that the question is irrelevant. Certainly no one thinks today that a solid medium pervades space. On the other hand, it is widely believed that there is no real vacuum. Arno Penzias and Robert Wilson detected in 1964 the cosmic background radiation, a leftover of the big bang. This radiation is pervasive and basically the same in all directions. It is possible to measure Earth's movement against this background radiation. As it turns out, Earth moves.

IN BRIEF: n. - A colorless volatile highly inflammable liquid formerly used as an inhalation anesthetic; A medium that was once supposed to fill all space and to support the propagation of electromagnetic waves.

Tutor's tip: The doctor told her patient she could have "either" (one of two) no anesthetic or "ether" (a chemical) .

This article is about a general class of chemical compounds. For other uses, see Aether.

Ether is the general name for a class of chemical compounds which contain an ether group — an oxygen atom connected to two (substituted) 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" (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 C - O - C bond angle in the functional group is about 110 degrees, and the C - O dipole does 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, 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(CH₃)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

Not all compounds of the formula R-O-R are ethers

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:
  • Esters R-C(=O)-O-R
  • Acetals R-CH(-O-R)-O-R
  • Aminals R-CH(-NH-R)-O-R
  • Anhydrides R-C(=O)-O-C(=O)-R

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.

• Intermolecular Dehydration of alcohols:

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 sulphuric 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.

• Nucleophilic displacement of alkyl halides by alkoxides

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 procede (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

• Electrophilic addition of alcohols to alkenes.

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

Structure of the polymeric diethyl ether peroxide

Ethers in general are of very low chemical reactivity. Organic reactions are:

• Hydrolysis.

Ethers are hydrolyzed only under drastic conditions like heating with boron tribromide or boiling in hydrobromic acid. Lower mineral acids containing a halogen, such as hydrochloric acid will cleave ethers, but very slowly. Hydrobromic acid and hydroiodic acid are the only two that do so at an appreciable rate. Certain aryl ethers can be cleaved by aluminium chloride.

• Nucleophilic displacement.

Epoxides, or cyclic ethers in three-membered rings, are highly susceptible to nucleophilic attack and are reactive in this fashion.

• Peroxide formation.

Primary and secondary ethers with a CH group next to the ether oxygen easily form highly explosive organic peroxides (e.g. diethyl ether peroxide) in the presence of oxygen, light, and metal and aldehyde impurities. For this reason ethers like diethyl ether and THF are usually avoided as solvents in industrial processes.

Important ethers

	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

• Functional group
• Methoxy
• Petroleum ether, not an ether but a low boiling alkane mixture.
• Thioether, analogs of ethers with the oxygen replaced by sulfur.
• Luminiferous ether

References

1. ^ International Union of Pure and Applied Chemistry. "ethers". Compendium of Chemical Terminology Internet edition.

External links

• ILPI page about ethers.
• An Account of the Extraordinary Medicinal Fluid, called Aether, by M. Turner, circa 1788, from Project Gutenberg
• The Ether Monument at Boston Public Gardens

Functional groups
Chemical class: Alcohol • Aldehyde • Alkane • Alkene • Alkyne • Amide • Amine • Azo compound • Benzene derivative • Carboxylic acid • Cyanate • Disulfide • Ester • Ether • Haloalkane • Imine • Isocyanide • Isocyanate • Ketone • Nitrile • Nitro compound • Nitroso compound • Peroxide • Phosphoric acid • Pyridine derivative • Sulfone • Sulfonic acid • Sulfoxide • Thioester • Thioether • Thiol

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Dansk (Danish)
n. - æter

Nederlands (Dutch)
ether, opperste hemelsfeer, stof dat opperste hemelsfeer vult (filosofie)

Français (French)
n. - (Chim, Phys) éther, les éthers, les espaces célestes (littér)

Deutsch (German)
n. - Äther

Ελληνική (Greek)
n. - (χημ.) αιθήρ. αιθέρας

Italiano (Italian)
etere

Português (Portuguese)
n. - éter (m) (Quím.)

Русский (Russian)
эфир, небесное пространство

Español (Spanish)
n. - éter

Svenska (Swedish)
n. - eter

中文（简体） (Chinese (Simplified))
乙醚, 以太, 醚, 太空, 苍穹

中文（繁體） (Chinese (Traditional))
n. - 乙醚, 以太, 醚, 太空, 蒼穹

한국어 (Korean)
n. - 하늘, 빛, 열, 전자기의 복사 현상의 가상적 매체

日本語 (Japanese)
n. - エーテル, 天空上層の空間, ラジオ

العربيه (Arabic)
‏(الاسم) السماء, الأثير‏

עברית (Hebrew)
n. - ‮אתר, סם הרדמה‬

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