Acid anhydride


An acid anhydride is a type of chemical compound derived by the removal of water molecules from an acid.
In organic chemistry, organic acid anhydrides contain the functional group ROR'. Organic acid anhydrides often form when one equivalent of water is removed from two equivalents of an organic acid in a dehydration reaction.
In inorganic chemistry, an acid anhydride refers to an acidic oxide, an oxide that reacts with water to form an oxyacid, or with a base to form a salt.

Nomenclature

The nomenclature of organic acid anhydrides is derived from the names of the constituent carboxylic acids which underwent dehydration to form the compound. In symmetrical acid anhydrides, where only one constituent carboxylic acid was used to form the compound OC, only the prefix of the original carboxylic acid is used and the suffix "anhydride" is added. In asymmetrical acid anhydrides, where two different carboxylic acids were used to give the anhydride OC, the prefixes from both acids reacted are listed before the suffix, in this case giving benzoic propanoic anhydride, which may alternatively be referred to as benzenecarboxylic ethanoic anhydride.