anidridos

Anidridos is a term used in some Romance-language traditions to refer to chemical compounds known in English as anhydrides. In English, anhydride is the standard term, but anidrido serves as a direct linguistic counterpart in other languages. Anidridos, or anhydrides, are compounds formed by the removal of water from an acid or by the combination of two acyl groups with loss of H2O. They are broadly classified into organic and inorganic varieties.

Organic anidridos are typically formed from carboxylic acids by dehydration and act as reactive intermediates in organic synthesis. They often contain two acyl groups linked by an anhydride bond, as in acetic anhydride (two acetyl groups connected by an O–C(O)–O linkage) and phthalic anhydride (a cyclic diacid anhydride). Mixed anhydrides, where two different acyl groups are present (RCO–O–COR'), are also recognized. These compounds are widely used as acylating agents, enabling the introduction of acyl groups into substrates.

Inorganic anidridos arise from the dehydration of oxides of nonmetals and metals, forming acid anhydrides such as sulfur trioxide (SO3) from sulfuric acid and phosphorus pentoxide (P4O10) from phosphoric acid. These species are typically highly reactive with water, producing corresponding acids, and play central roles in industrial processes, such as the production of sulfuric and phosphoric acids.

Preparation and properties: organic anidridos are commonly synthesized by dehydrating corresponding carboxylic acids or by coupling reactions that eject water. Inorganic anidridos form through dehydration of oxides and acids. They generally hydrolyze readily in water, releasing the parent acids and often requiring careful handling due to reactivity and corrosivity.

See also: anhydride, acylation, organic synthesis, inorganic oxides.