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, in chemistry

ether, 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℃ 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.


, in physics and astronomy
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.
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(ee -th'er) An extremely elastic medium of negligible density that was thought in the 19th century to permeate all space and thus provided a medium through which light and other electromagnetic waves from celestial bodies could travel. (At that time all waves were considered to require a medium for their propagation). The speed of travel of the electromagnetic waves, i.e. the speed of light, was assumed to be fixed with respect to the ether. The Earth, however, should move with respect to the ether and so, from considerations of relative motion, the speed of light should vary very slightly when measured in different directions.

Experiments were set up in the late 19th century to detect and measure the motion of the Earth relative to the ether. The most notable experiment was carried out in 1887 by A.A. Michelson and E.W. Morley (the Michelson–Morley experiment). No such motion was found, indicating both that the ether did not exist and that electromagnetic waves did not require any medium for their propagation. The concept of the ether was thus discarded. The result of these experiments was later explained by Einstein's special theory of relativity (1905) in which it was stated that the speed of light was independent of the velocity of the observer and was therefore invariant.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



any of a number of organic compounds having the general formula R—O—R, that is, consisting of two hydrocarbon radicals linked by an oxygen atom.

Symmetric ethers are ethers with identical R groups—for example, CH3OCH3 (dimethyl ether) and C6H5OC6H5 (diphenyl ether). Mixed ethers are those with different R groups—for example, C5H11OCH2C6H5 (amyl benzyl ether). Some ethers have trivial names, such as anisole (CH3OC6H5, the methyl ether of phenol) and cellosolves (the monoethers of ethylene glycol).

As a rule, ethers are poorly soluble in water but readily soluble in organic solvents. Many ethers take the form of liquids with a pleasant odor. Ethers are chemically inert toward most substances, especially bases and alkali metals. Because of their weak basicity, which results from the presence of unbonded electron pairs on the oxygen atom, they form oxonium compounds when reacted with mineral acids and Lewis acids; two such compounds are (C2H5)2O+HCl and C2H5)2O + BF3. When ethers are saturated with hydrogen iodide, one of the C—O bonds is broken according to the reaction

C2H5OC2H5 + HI → C2H5I + C2H5OH

Ethers can also be cleaved by heating them with metallic sodium. This reaction is used in chemical analysis for detecting methoxy groups (CH3O—) and ethoxy groups (C2H5O—).

Upon prolonged exposure to atmospheric oxygen, ethers form explosive peroxides; for this reason and because they are highly flammable, their use in industry as solvents and extraction agents is limited. Aliphatic ethers are produced by the catalytic dehydration of alcohols or by the Williamson synthesis—that is, the alkylation of alcoholates. The Williamson synthesis serves as the basis for an industrial method of producing ethyl cellulose. Aliphatic-aromatic ethers may be produced directly by reacting phenols with diazomethane or by alkylating phenolates with such reagents as dialkyl sulfates. Such ethers as nerolin and iara-iara are used for fragrances. Diethyl ether is inhaled as an anesthetic, and diphenyl ether is used as a conductor of heat.

Also categorized as ethers are heterocyclic compounds containing an oxygen atom in the ring (such as ethylene oxide and tetrahydrofuran). Polyethers, ethers of the hydrated forms of aldehydes and ketones, and ethers of ortho acids with the general formula RC(OR)3 also belong to the class of ethers.


Nesmeianov, A. N., and N. A. Nesmeianov. Nachala organicheskoi khimii, books 1–2. Moscow, 1969–70.



(also luminiferous ether), a hypothetical all-pervasive medium, which, according to past scientific notions, acted as the carrier of light and of electromagnetic interactions in general.

Originally the ether was thought to be a mechanical medium similar to an elastic body. Accordingly, the propagation of light waves was likened to the propagation of sound in an elastic medium, and electric and magnetic field strengths were identified with mechanical tensions of the ether. The hypothesis of a mechanical ether met with serious difficulties; in particular, it was unable to reconcile the transverse nature of light waves, which requires that the ether be an absolutely rigid body, with the lack of resistance of the ether to the motion of heavenly bodies. (It is now clear that this hypothesis is inconsistent simply because the forces of elasticity, tension, and the like are themselves electromagnetic in nature.) The difficulties of the mechanical interpretation of the ether led in the late 19th century to abandonment of attempts to develop mechanical models of the medium. The only remaining unsolved problem was how the ether took part in the motion of bodies. The difficulties and contradictions that arose in this connection were overcome in the special theory of relativity created by A. Einstein, which did away completely with the ether problem by simply excluding the ether from theory (seeRELATIVITY, THEORY OF).

From the contemporary viewpoint, a physical vacuum has some properties of an ordinary material medium. However, it should not be confused with the ether, from which it is different in principle simply because the electromagnetic field is an independent physical object that does not require a special carrier.


Born, M. Einshteinovskaia teoriia otnositel’nosti. Moscow, 1964. (Translated from English.)


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


The medium postulated to carry electromagnetic waves, similar to the way a gas carries sound waves.
(organic chemistry)
One of a class of organic compounds characterized by the structural feature of an oxygen linking two hydrocarbon groups (such as R-O-R).
(C2H5)2O A colorless liquid, slightly soluble in water; used as a reagent, intermediate, anesthetic, and solvent. Also known as ethyl ether.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1. a colourless volatile highly flammable liquid with a characteristic sweetish odour, made by the reaction of sulphuric acid with ethanol: used as a solvent and anaesthetic. Formula: C2H5OC2H5
2. any of a class of organic compounds with the general formula RORʹ where R and Rʹ are alkyl groups, as in diethyl ether C2H5OC2H5
3. the ether the hypothetical medium formerly believed to fill all space and to support the propagation of electromagnetic waves
4. Greek myth the upper regions of the atmosphere; clear sky or heaven
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005


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(1) (Ether) The native Ethereum cryptocurrency. See Ethereum.

(2) An invisible medium through which all light, heat and electromagnetic waves propagate. Pronounced "ee-ther" with the "th" as in the word "thought," ether was postulated from the 1600s to the 1800s. The word inspired the name Ethernet.

(3) 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.
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