Anhydride 315237 188222196 2008-01-31T20:26:14Z Mwtoews 711150 distinguish from anhydrite {{Distinguish|anhydrite}} [[Image:Generic_Anhydride.png|thumb|150px|right|Generic example of an anhydride.]] In [[chemistry]], an '''anhydride''' is a [[Compound (chemistry)|compound]] that can be considered as derived from another compound by subtracting the molecules of [[Water (molecule)|water]]. For example: : 2 [[sodium hydroxide|NaOH]] - H<sub>2</sub>O → [[sodium oxide|Na<sub>2</sub>O]] : [[sulfuric acid|H<sub>2</sub>SO<sub>4</sub>]] - H<sub>2</sub>O → [[sulfur trioxide|SO<sub>3</sub>]] Thus [[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 acid]]s. : 2 [[acetic acid|CH<sub>3</sub>COOH]] - H<sub>2</sub>O → [[acetic anhydride|(CH<sub>3</sub>CO)<sub>2</sub>O]] Compounds involved are often [[acid]]s or [[base (chemistry)|base]]s; in such cases, the anhydrides can be called [[acid anhydride]]s or [[base anhydride]]s. 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) + H<sub>2</sub>SO<sub>4</sub> (aq) → Na<sub>2</sub>SO<sub>4</sub> + 2H<sub>2</sub>O (l) : Na<sub>2</sub>O (s) + SO<sub>3</sub> (g) → Na<sub>2</sub>SO<sub>4</sub> (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. ==See also== * [[Acid anhydride]] [[Category:Chemical compounds]] [[cs:Anhydrid]] [[de:Anhydride]] [[es:Anhidruro]] [[eo:Anhidrido]] [[fr:Anhydride]] [[it:Anidride]] [[he:אנהידריד]] [[lv:Anhidrīds]] [[nl:Anhydride]] [[pt:Anidrido]] [[ru:Ангидрид]] [[sr:Анхидрид]] [[fi:Anhydridi]] [[sv:Anhydrid]] [[tg:Анҳидрид]] [[uk:Ангідрид]]