In chemistry, an anhydride is a compound that can be considered as derived from another compound by subtracting the molecules of water.

For example:: 2 NaOH - H2O → Na2O: H2SO4 - H2O → SO3Thus sodium oxide is an anhydride of sodium hydroxide, and sulfur trioxide is an anhydride of sulfuric acid.

In organic chemistry, the compounds most commonly involved are carboxylic acids.: 2 CH3COOH - H2O → (CH3CO)2O

Compounds involved are often acids or bases; in such cases, the anhydrides can be called acid anhydrides or base anhydrides. This does not imply that the anhydrides are not themselves acids or bases; they are. But the more hydrated forms may be more familiar or convenient.

"Anhydride" is sometimes used as a synonym for "acid anhydride".

Following are two reactions, one with a typical acid and base, one with their anhydrides. The first one is more practical.

: 2 NaOH (aq) + H2SO4 (aq) → Na2SO4 + 2H2O (l): Na2O (s) + SO3 (g) → Na2SO4 (aq)

In general, anhydrides are more reactive than their corresponding acids, as they can react with water to form their corresponding acid. They often are good dehydrating agents. Acetic anhydride is useful in the acetylation of salicylic acid, as using acetic acid to perform the reaction leaves water behind, which can destroy the product, acetylsalicylic acid, or aspirin.

In biology, most of the high-energy phosphate compounds are formed from the condensation of the phosphate ion with a phosphorylated sugar. The resulting pyrophosphate bond is a classic anhydride bond.

ee also

* Acid anhydride

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  • Anhydride — Anhydride. Unter Anhydridbildung versteht man in der organischen Chemie eine Reaktion, nach der ein direkter Wasseraustritt zwischen zwei Hydroxylgruppen entweder eines und desselben oder zweier verschiedener Moleküle stattfindet. Im allgemeinen… …   Lexikon der gesamten Technik

  • anhydride — [ anidrid ] n. m. • 1859; de anhydre et (ac)ide ♦ Chim. Composé obtenu par déshydratation totale d un acide; spécialt Composé organique de formule générale R CO O CO R . Anhydride sulfureux. ● anhydride nom masculin Composé dont la formule… …   Encyclopédie Universelle

  • Anhydride — Anhydride,   Singular Anhydrịd das, s, chemische Verbindungen, die aus Säuren oder Basen durch Abspalten von Wasser entstehen und die mit Wasser wieder Säuren oder Basen bilden. Im engeren Sinn versteht man heute unter Anhydride fast… …   Universal-Lexikon

  • Anhydride — An*hy dride, n. [See {Anhydrous}.] (Chem.) An oxide of a nonmetallic body or an organic radical, capable of forming an acid by uniting with the elements of water; so called because it may be formed from an acid by the abstraction of water. [1913… …   The Collaborative International Dictionary of English

  • Anhydrīde — (v. griech. anydros, »wasserlos«), chemische Verbindungen, die aus Hydraten, Säuren oder Basen durch Wasserverlust entstehen. Metalloxyde sind die A. der Metallhydroxyde oder Metalloxydhydrate. Aus Calciumhydroxyd Ca(OH)2 wird durch Erhitzen… …   Meyers Großes Konversations-Lexikon

  • Anhydride — Anhydrīde, die wasserstofffreien Oxyde der Elementarstoffe, aus diesen durch direkte Oxydation, aus den Hydraten durch Abspaltung von Wasser entstehend …   Kleines Konversations-Lexikon

  • anhydride — [an hī′drīd΄] n. [< Gr anydros (see ANHYDROUS) + IDE] 1. an oxide that reacts with water to form an acid or a base 2. any compound formed by the removal of water …   English World dictionary

  • Anhydride — Un anhydride est le produit d un composé qui a perdu une ou plusieurs molécules d eau (H2O) par élimination au cours d une réaction chimique. Ainsi, très généralement, un atome qui portera plusieurs groupes hydroxyle (–OH) et/ou oxo (=O) formera… …   Wikipédia en Français

  • anhydride — /an huy druyd, drid/, n. Chem. 1. a compound formed by removing water from a more complex compound: an oxide of a nonmetal (acid anhydride) or a metal (basic anhydride) that forms an acid or a base, respectively, when united with water. 2. a… …   Universalium

  • anhydride — /ænˈhaɪdraɪd / (say an huydruyd), / drəd/ (say druhd) noun 1. a compound formed by abstraction of water, an oxide of a nonmetal (acid anhydride) or a metal (basic anhydride) which forms an acid or a base, respectively, when united with water. 2.… …   Australian English dictionary