Anhydride

In chemistry, an anhydride is typically an oxide of a nonmetallic element or an organic radical, capable of forming an acid by uniting with the elements of water. The anhydride is so called because it may be formed from an acid by the removal of water.

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Examples of inorganic anhydrides include dinitrogen pentoxide, which is the anhydride of nitric acid, and sulfur trioxide, which is the anhydride of sulfuric acid. Useful organic anhydrides include acetic anhydride (an acid anhydride), formed by the condensation of acetic acid:

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: 2 CH3COOH → (CH3CO)2O + H2O

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Anhydrides are typically 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 do the reaction leaves water behind that can destroy the product, acetylsalicylic acid, or aspirin.

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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.

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Oxide: An oxide is a chemical compound of oxygen with other chemical elements. In the 18th century, oxides were named calxes or calces after the calcination process used to produce oxides. Calx was later replaced by oxyd....

Element: The term element may mean:...

Radical: Radical is derived from the Latin word radix, which means "root". In various fields of endeavor, it can mean:...