In organic chemistry , ethers are a class of compounds that contain an ether group —an oxygen atom bonded to two organyl groups (e.g., alkyl or aryl ). They have the general formula R−O−R′ , where R and R′ represent the organyl groups. Ethers can again be classified into two varieties: if the organyl groups are the same on both sides of the oxygen atom, then it is a simple or symmetrical ether, whereas if they are different, the ethers are called mixed or unsymmetrical ethers. A typical example of the first group is the solvent and anaesthetic diethyl ether , commonly referred to simply as "ether" ( CH 3 −CH 2 −O−CH 2 −CH 3 ). Ethers are common in organic chemistry and even more prevalent in biochemistry , as they are common linkages in carbohydrates and lignin .
37-640: Ethers feature bent C−O−C linkages. In dimethyl ether , the bond angle is 111° and C–O distances are 141 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 sp. Oxygen is more electronegative than carbon, thus the alpha hydrogens of ethers are more acidic than those of simple hydrocarbons. They are far less acidic than alpha hydrogens of carbonyl groups (such as in ketones or aldehydes ), however. Ethers can be symmetrical of
74-682: A complex with boron trifluoride , i.e. borane diethyl etherate ( BF 3 ·O(CH 2 CH 3 ) 2 ). Ethers also coordinate to the Mg center in Grignard reagents . Tetrahydrofuran is more basic than acyclic ethers. It forms with many complexes . This reactivity is similar to the tendency of ethers with alpha hydrogen atoms to form peroxides. Reaction with chlorine produces alpha-chloroethers. The dehydration of alcohols affords ethers: This direct nucleophilic substitution reaction requires elevated temperatures (about 125 °C). The reaction
111-736: A hydroxyl group. The term "oxide" or other terms are used for high molar mass polymer when end-groups no longer affect polymer properties. Crown ethers are cyclic polyethers. Some toxins produced by dinoflagellates such as brevetoxin and ciguatoxin are extremely large and are known as cyclic or ladder polyethers. The phenyl ether polymers are a class of aromatic 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′). There are compounds which, instead of C in
148-526: A blendstock in propane autogas . It is also a promising fuel in diesel engines , and gas turbines . For diesel engines, an advantage is the high cetane number of 55, compared to that of diesel fuel from petroleum, which is 40–53. Only moderate modifications are needed to convert a diesel engine to burn dimethyl ether. The simplicity of this short carbon chain compound leads to very low emissions of particulate matter during combustion. For these reasons as well as being sulfur-free, dimethyl ether meets even
185-762: A composite of the two substituents followed by "ether". For example, ethyl methyl ether (CH 3 OC 2 H 5 ), diphenylether (C 6 H 5 OC 6 H 5 ). 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. Polyethers are generally polymers containing ether linkages in their main chain. The term polyol generally refers to polyether polyols with one or more functional end-groups such as
222-415: A ferrous sulfate followed by addition of KSCN. Appearance of blood red color indicates presence of peroxides. The dangerous properties of ether peroxides are the reason that diethyl ether and other peroxide forming ethers like tetrahydrofuran (THF) or ethylene glycol dimethyl ether (1,2-dimethoxyethane) are avoided in industrial processes. Ethers serve as Lewis bases . For instance, diethyl ether forms
259-432: A silyl electrophile and a base , or just reacting an enolate with a silyl electrophile. Since silyl electrophiles are hard and silicon-oxygen bonds are very strong, the oxygen (of the carbonyl compound or enolate) acts as the nucleophile to form a Si-O single bond. The most commonly used silyl electrophile is trimethylsilyl chloride . To increase the rate of reaction, trimethylsilyl triflate may also be used in
296-524: A silyl enol ether with PhSCl, a good and soft electrophile, provides a carbonyl compound sulfenylated at an alpha carbon . In this reaction, the trimethylsilyl group of the silyl enol ether is removed by the chloride ion released from the PhSCl upon attack of its electrophilic sulfur atom. Hydrolysis of a silyl enol ether results in the formation of a carbonyl compound and a disiloxane . In this reaction, water acts as an oxygen nucleophile and attacks
333-488: A suitable leaving group (R–X). Although popular in textbooks, the method is usually impractical on scale because it cogenerates significant waste. 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
370-470: 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. The presence of peroxide in old samples of ethers may be detected by shaking them with freshly prepared solution of
407-502: Is also a component of certain high temperature "Map-Pro" blowtorch gas blends, supplanting the use of methyl acetylene and propadiene mixtures. Dimethyl ether is also used as a propellant in aerosol products. Such products include hair spray, bug spray and some aerosol glue products. A potentially major use of dimethyl ether is as substitute for propane in LPG used as fuel in household and industry. Dimethyl ether can also be used as
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#1732765186376444-639: Is atom-economical: Acid catalysis is required for this reaction. Commercially important ethers prepared in this way are derived from isobutene or isoamylene , which protonate to give relatively stable carbocations . Using ethanol and methanol with these two alkenes, four fuel-grade ethers are produced: methyl tert-butyl ether (MTBE), methyl tert-amyl ether (TAME), ethyl tert-butyl ether (ETBE), and ethyl tert-amyl ether (TAEE). Solid acid catalysts are typically used to promote this reaction. Epoxides are typically prepared by oxidation of alkenes. The most important epoxide in terms of industrial scale
481-612: Is based on black liquor gasification in Piteå , Sweden . The largest use of dimethyl ether is as the feedstock for the production of the methylating agent, dimethyl sulfate , which entails its reaction with sulfur trioxide : Dimethyl ether can also be converted into acetic acid using carbonylation technology related to the Monsanto acetic acid process : Dimethyl ether is a low-temperature solvent and extraction agent, applicable to specialised laboratory procedures. Its usefulness
518-586: Is catalyzed by acids, usually sulfuric acid. The method is effective for generating symmetrical ethers, but not unsymmetrical ethers, since either OH can be protonated, which would give a mixture of products. Diethyl ether is produced from ethanol by this method. Cyclic ethers are readily generated by this approach. Elimination reactions compete with dehydration of the alcohol: The dehydration route often requires conditions incompatible with delicate molecules. Several milder methods exist to produce ethers. Alcohols add to electrophilically activated alkenes . The method
555-514: Is especially efficient with tertiary alkyl halides, which form stable carbocations in the presence of Lewis acids like TiCl 4 or SnCl 4 . Halogenation of silyl enol ethers gives haloketones . Acyloins form upon organic oxidation with an electrophilic source of oxygen such as an oxaziridine or mCPBA . In the Saegusa–Ito oxidation , certain silyl enol ethers are oxidized to enones with palladium(II) acetate . Reacting
592-526: Is ethylene oxide, which is produced by oxidation of ethylene with oxygen. Other epoxides are produced by one of two routes: Many ethers, ethoxylates and crown ethers , are produced from epoxides. Nucleophilic displacement of alkyl halides by alkoxides This reaction, the Williamson ether synthesis , involves treatment of a parent alcohol with a strong base to form the alkoxide, followed by addition of an appropriate aliphatic compound bearing
629-607: Is in development. Dimethyl ether is a synthetic second generation biofuel (BioDME), which can be produced from lignocellulosic biomass . The EU is considering BioDME in its potential biofuel mix in 2030; It can also be made from biogas or methane from animal, food, and agricultural waste, or even from shale gas or natural gas . The Volvo Group is the coordinator for the European Community Seventh Framework Programme project BioDME where Chemrec 's BioDME pilot plant
666-463: Is limited by its low boiling point (−23 °C (−9 °F)), but the same property facilitates its removal from reaction mixtures. Dimethyl ether is the precursor to the useful alkylating agent , trimethyloxonium tetrafluoroborate . A mixture of dimethyl ether and propane is used in some over-the-counter " freeze spray " products to treat warts by freezing them . In this role, it has supplanted halocarbon compounds ( Freon ). Dimethyl ether
703-418: Is obtained from synthesis gas ( syngas ). Other possible improvements call for a dual catalyst system that permits both methanol synthesis and dehydration in the same process unit, with no methanol isolation and purification. Both the one-step and two-step processes above are commercially available. The two-step process is relatively simple and start-up costs are relatively low. A one-step liquid-phase process
740-681: Is the organic compound with the formula CH 3 OCH 3 , (sometimes ambiguously simplified to C 2 H 6 O as it is an isomer of ethanol ). The simplest ether , it is a colorless gas that is a useful precursor to other organic compounds and an aerosol propellant that is currently being demonstrated for use in a variety of fuel applications. Dimethyl ether was first synthesised by Jean-Baptiste Dumas and Eugene Péligot in 1835 by distillation of methanol and sulfuric acid. Approximately 50,000 tons were produced in 1985 in Western Europe by dehydration of methanol : The required methanol
777-723: Is the most common example of this rare class of compounds. In the IUPAC Nomenclature system, ethers are named using the general formula "alkoxyalkane" , for example CH 3 –CH 2 –O–CH 3 is methoxyethane . If the ether is part of a more-complex molecule, it is described as an alkoxy substituent, so –OCH 3 would be considered a " methoxy -" group. The simpler alkyl radical is written in front, so CH 3 –O–CH 2 CH 3 would be given as methoxy (CH 3 O) ethane (CH 2 CH 3 ). IUPAC rules are often not followed for simple ethers. The trivial names for simple ethers (i.e., those with none or few other functional groups) are
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#1732765186376814-420: Is used in some cases) to give the alkyl bromide. Depending on the substituents, some ethers can be cleaved with a variety of reagents, e.g. strong base. Despite these difficulties the chemical paper pulping processes are based on cleavage of ether bonds in the lignin . When stored in the presence of air or oxygen, ethers tend to form explosive peroxides , such as diethyl ether hydroperoxide . The reaction
851-574: The C−O−C linkage, contain heavier group 14 chemical elements (e.g., Si , Ge , Sn , Pb ). Such compounds are considered ethers as well. Examples of such ethers are silyl enol ethers R 3 Si−O−CR=CR 2 (containing the Si−O−C linkage), disiloxane H 3 Si−O−SiH 3 (the other name of this compound is disilyl ether, containing the Si−O−Si linkage) and stannoxanes R 3 Sn−O−SnR 3 (containing
888-926: The Sn−O−Sn linkage). Ethers have boiling points similar to those of the analogous alkanes . Simple ethers are generally colorless. The C-O bonds that comprise simple ethers are strong. They are unreactive toward all but the strongest bases. Although generally of low chemical reactivity , they are more reactive than alkanes . Specialized ethers such as epoxides , ketals , and acetals are unrepresentative classes of ethers and are discussed in separate articles. Important reactions are listed below. Although ethers resist hydrolysis, they are cleaved by 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)CH 3 ]Br. Some ethers undergo rapid cleavage with boron tribromide (even aluminium chloride
925-475: The French engineer Charles Tellier bought the ex-Elder-Dempster a 690 tons cargo ship Eboe and fitted a methyl-ether refrigerating plant of his design. The ship was renamed Le Frigorifique and successfully imported a cargo of refrigerated meat from Argentina . However the machinery could be improved and in 1877 another refrigerated ship called Paraguay with a refrigerating plant improved by Ferdinand Carré
962-480: 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
999-734: The kinetic silyl enol ether (with a less substituted double bond) preferentially forms due to sterics. When using triethylamine , a weak base, the thermodynamic silyl enol ether (with a more substituted double bond) is preferred. Alternatively, a rather exotic way of generating silyl enol ethers is via the Brook rearrangement of appropriate substrates. Silyl enol ethers are neutral, mild nucleophiles (milder than enamines ) that react with good electrophiles such as aldehydes (with Lewis acid catalysis ) and carbocations . Silyl enol ethers are stable enough to be isolated, but are usually used immediately after synthesis. Lithium enolates, one of
1036-605: The most stringent emission regulations in Europe ( EURO5 ), U.S. (U.S. 2010), and Japan (2009 Japan). At the European Shell Eco Marathon , an unofficial World Championship for mileage, vehicle running on 100 % dimethyl ether drove 589 km/L (169.8 cm /100 km), fuel equivalent to gasoline with a 50 cm displacement 2-stroke engine. As well as winning they beat the old standing record of 306 km/liter (326.8 cm /100 km), set by
1073-414: The place of trimethylsilyl chloride as a more electrophilic substrate. When using an unsymmetrical enolizable carbonyl compound as a substrate, the choice of reaction conditions can help control whether the kinetic or thermodynamic silyl enol ether is preferentially formed. For instance, when using lithium diisopropylamide (LDA) , a strong and sterically hindered base, at low temperature (e.g., -78°C),
1110-558: The precursors to silyl enol ethers, can also be generated from silyl enol ethers using methyllithium . The reaction occurs via nucleophilic substitution at the silicon of the silyl enol ether, producing the lithium enolate and tetramethylsilane . Silyl enol ethers are used in many reactions resulting in alkylation , e.g., Mukaiyama aldol addition , Michael reactions , and Lewis-acid-catalyzed reactions with S N 1 -reactive electrophiles (e.g., tertiary , allylic , or benzylic alkyl halides ). Alkylation of silyl enol ethers
1147-421: The same team in 2007. To study the dimethyl ether for the combustion process a chemical kinetic mechanism is required which can be used for Computational fluid dynamics calculation. Dimethyl ether is a refrigerant with ASHRAE refrigerant designation R-E170. It is also used in refrigerant blends with e.g. ammonia , carbon dioxide , butane and propene . Dimethyl ether was the first refrigerant. In 1876,
Ether - Misplaced Pages Continue
1184-442: The silicon of the silyl enol ether. This leads to the formation of the carbonyl compound and a trimethylsilanol intermediate that undergoes nucleophilic substitution at silicon (by another trimethylsilanol) to give the disiloxane. Cyclic silyl enol ethers undergo regiocontrolled one-carbon ring contractions. These reactions employ electron-deficient sulfonyl azides, which undergo chemoselective, uncatalyzed [3+2] cycloaddition to
1221-464: The silyl enol ether, followed by loss of dinitrogen, and alkyl migration to give ring-contracted products in good yield. These reactions may be directed by substrate stereochemistry, giving rise to stereoselective ring-contracted product formation. Silyl enol ethers of esters ( −OR ) or carboxylic acids ( −COOH ) are called silyl ketene acetals and have the general structure R 3 Si−O−C(OR)=CR 2 . These compounds are more nucleophilic than
1258-454: The type ROR or unsymmetrical of the type ROR'. Examples of the former are dimethyl ether , diethyl ether , dipropyl ether etc. Illustrative unsymmetrical ethers are anisole (methoxybenzene) and dimethoxyethane . Vinyl- and acetylenic ethers are far less common than alkyl or aryl ethers. Vinylethers, often called enol ethers , are important intermediates in organic synthesis . Acetylenic ethers are especially rare. Di-tert-butoxyacetylene
1295-478: The –X group in the alkyl halide, forming an ether with an aryl group attached to it in a reaction with an S N 2 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. Dimethyl ether Polyethylene glycol Methanol Dimethyl ether ( DME ; also known as methoxymethane )
1332-534: Was destroyed. [REDACTED] Silyl enol ether In organosilicon chemistry , silyl enol ethers are a class of organic compounds that share the common functional group R 3 Si−O−CR=CR 2 , composed of an enolate ( R 3 C−O−R ) bonded to a silane ( SiR 4 ) through its oxygen end and an ethene group ( R 2 C=CR 2 ) as its carbon end. They are important intermediates in organic synthesis . Silyl enol ethers are generally prepared by reacting an enolizable carbonyl compound with
1369-525: Was put into service on the South American run. Unlike other alkyl ethers, dimethyl ether resists autoxidation . Dimethyl ether is also relatively non-toxic, although it is highly flammable. On July 28, 1948, a BASF factory in Ludwigshafen suffered an explosion after 30 tonnes of dimethyl ether leaked from a tank and ignited in the air. 200 people died, and a third of the industrial plant
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