/es"teuhr/, n. Chem.a compound produced by the reaction between an acid and an alcohol with the elimination of a molecule of water, as ethyl acetate, C4H8O2, or dimethyl sulfate, C2H6SO4.[1850-55; coined by L. Gmelin (1788-1853), German chemist]
* * *Any of a class of organic compounds that can react with water (see hydrolysis) to produce an alcohol and an organic or inorganic acid.They are formed by the reverse process, esterification, in which acid reacts with alcohol to form an ester and water. Esters of carboxylic acids, the most common esters, contain the acid's carbonyl group (―C=O; see functional group); the carbon's fourth bond is with the alcohol's oxygen atom. Hydrolysis of esters in the presence of an alkali (saponification) is used to make soaps from fats and oils. Carboxylic acid esters of low molecular weight are colourless, volatile liquids with pleasant odours; they give flavour and fragrance to fruits and flowers and are used as synthetic flavours and fragrances. Others, such as ethyl acetate and butyl acetate, are used as solvents for lacquers, paints, and varnishes. Certain polymers are esters, including Lucite (polymethyl methacrylate) and Dacron (polyethylene terephthalate). Esters of alcohols and inorganic acids include nitrate esters (e.g., nitroglycerin), which are explosive; phosphate esters, including such biologically important compounds as nucleic acids; and others that are used as flame retardants, solvents, plasticizers, gasoline and oil additives, and insecticides.
* * *any of a class of organic compounds that react with water to produce alcohols (alcohol) and organic or inorganic acids. Esters derived from carboxylic acids (carboxylic acid) are the most common.Carboxylic acid esters, formula RCOOR′ (R and R′ are any organic combining groups), are commonly prepared by reaction of carboxylic acids and alcohols in the presence of hydrochloric acid or sulfuric acid, a process called esterification. In the reaction the hydroxyl group (OH) of the carboxylic acid is replaced by the alkoxy group (R′O) of the alcohol.The reverse of the esterification reaction is an example of hydrolysis. Esters may also be obtained by reaction of acid halides or acid anhydrides with alcohols or by reaction of salts of carboxylic acids with alkyl halides. One ester may be converted to another ester by reaction (transesterified) with an alcohol, a carboxylic acid, or a third ester in the presence of a catalyst.The hydrolysis of esters in the presence of alkalies, a reaction called saponification, is utilized in the preparation of soaps from fats and oils and is also used for the quantitative estimation of esters.Carboxylic acid esters of low molecular weight are colourless, volatile liquids with pleasant odours, slightly soluble in water. Many are responsible for the fragrance and flavour of flowers and fruits; for example, isopentyl acetate is present in bananas (banana), methyl salicylate in wintergreen, and ethyl butyrate in pineapples (pineapple). These and other volatile esters with characteristic odours are used in synthetic flavours, perfumes, and cosmetics. Certain volatile esters are used as solvents for lacquers, paints, and varnishes; for this purpose, large quantities of ethyl acetate and butyl acetate are commercially produced. Waxes secreted by animals and plants are esters formed from long-chain carboxylic acids and long-chain alcohols. Fats and oils are esters of long-chain carboxylic acids and glycerol.Liquid esters of low volatility serve as softening agents for resins and plastics. Esters also include many industrially important polymers. Polymethyl methacrylate is a glass substitute sold under the names Lucite and Plexiglas; polyethylene terephthalate is used as a film (Mylar) and as textile fibres sold as Terylene, Fortrel, and Dacron.Esters are also formed from alcohols and such inorganic acids as sulfuric, phosphoric, and nitric acids. Nitrate esters (e.g., glyceryl trinitrate, or nitroglycerin) are explosive. Phosphate esters are biologically important (nucleic acids belong to this group) and are used widely in industry as solvents, plasticizers, flame retardants, gasoline and oil additives, and insecticides.Esters of sulfuric (sulfuric acid) and sulfurous acids are used in the manufacture of dyes and pharmaceuticals. Dimethyl sulfate, the best-known ester of sulfuric acid, is a dangerous poison.
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