Ether is the general name for a class of organic chemical compounds characterized by molecules that contain an ether functional group—an oxygen atom directly bound to two hydrocarbon (alkyl or aryl) groups. A typical example is diethyl ether, commonly known as "ether" (ethoxyethane, CH3-CH2-O-CH2-CH3). Different ethers have diverse uses, but most are useful as solvents. Dimethyl ether is a multi-purpose fuel, refrigerant, aerosol spray propellant, and a medium for chemical reactions. Ethylene glycol is used in the production of various chemicals and to sterilize medical supplies and spices. Diethyl ether has been used as an anesthetic; dimethoxyethane is used in organometallic chemistry; dioxane is a foaming agent; tetrahydrofuran is used to degrease metal parts; anisole is used in perfumes and as an insect pheromone; and crown ethers are used to hold metal cations in solution. Polyethylene glycol, a polymeric ether, is used in laxatives, skin creams, toothpastes, and various medications.
The traditional approach has been to name the two alkyl groups attached to the oxygen atom (of the ether) and to append "ether" at the end. Examples are "ethyl methyl ether" and "diethyl ether." These are called "trivial names."
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 ether may be classified as a "primary ether," "secondary ether," or "tertiary ether," depending on the substituents on the carbon atoms next to the ether oxygen. For example, diethyl ether, CH3-CH2-O-CH2-CH3, is called a primary ether because each carbon atom attached to the ether oxygen atom is directly linked to only one other carbon atom. An example of a secondary ether is diisopropyl ether, (CH3)2CH-O-CH(CH3)2, in which each carbon atom attached to the ether oxygen atom is directly linked to two other carbon atoms. An example of a tertiary ether is di-tert-butyl ether, (CH3)3C-O-C(CH3)3, in which each carbon atom attached to the ether oxygen atom is directly linked to three other carbon atoms.
Top to bottom: Dimethyl ether; a primary ether (diethyl ether); a secondary ether (diisopropyl ether); and a tertiary ether (di-tert-butyl ether).
Polyethers are compounds with more than one ether group. The term is generally used when referring to polymers such as polyethylene glycol and polypropylene glycol. It is also used for low molecular weight compounds such as the crown ethers.
Ethers are not to be confused with other classes of compounds with the same general structure R-O-R'. Some examples are given below.
Ether molecules cannot form hydrogen bonds with 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).
Ethers are generally low in chemical reactivity. Some of their reactions are as follows.
Ethers can be prepared in the laboratory in several different ways.
Cyclic ethers, also known as epoxides, can be prepared by these methods:
|Ethylene oxide||It is the smallest cyclic ether and is mainly used as an intermediate in the production of ethylene glycol and other chemicals. It is also used to sterilize medical supplies and spices.|
|Dimethyl ether||It is useful as a solvent (in liquefied form), multi-purpose fuel, refrigerant, aerosol spray propellant, medium for chemical reactions, and a blowing agent for foam.|
|Diethyl ether||It is a common solvent for organic compounds, and it has been used as a general anesthetic.|
|Dimethoxyethane||It is a good solvent and a higher boiling alternative to diethyl ether and tetrahydrofuran. It is often used in organometallic chemistry and is the low-viscosity component of the solvent for electrolytes in lithium batteries.|
|1,4-Dioxane||This cyclic ether is used mainly as a solvent in industry, but it is also a foaming agent and is present in fumigants and automotive coolants.|
|Tetrahydrofuran (THF)||This cyclic ether is one of the most polar simple ethers used as a solvent. It is also used to degrease metal parts.|
|Anisole (methoxybenzene)||This aryl ether is a major constituent of the essential oil of anise seed. It is used in perfumes and as an insect pheromone.|
|Crown ethers||These cyclic polyethers can form chemical complexes with metal cations (such as lithium, sodium, and potassium cations), thus holding the cations in solution. The size of the interior of the crown ether determines the size of the cation it can solvate.|
|Polyethylene glycol (PEG)||This nontoxic, water-soluble polymer is the basis for a number of laxatives and skin creams, and is a dispersant in various toothpastes. It prolongs the medicinal effect of protein medications, when the proteins are attached to it. In woodworking, it can be used to replace some of the water content in wood, to prevent the wood from warping or shrinking when dried.|
Early science and philosophy:
All links retrieved August 15, 2017.
|Chemical class: Alcohol • Aldehyde • Alkane • Alkene • Alkyne • Amide • Amine • Azo compound • Benzene derivative • Carboxylic acid • Cyanate • Ester • Ether • Haloalkane • Imine • Isocyanide • Isocyanate • Ketone • Nitrile • Nitro compound • Nitroso compound • Peroxide • Phosphoric acid • Pyridine derivative • Sulfone • Sulfonic acid • Sulfoxide • Thioether • Thiol • Toluene derivative|
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