anhydrideja

Anhydrides are chemical compounds derived from acids by the removal of water. In organic chemistry, the term typically refers to carboxylic acid anhydrides, which have the general structure R-CO-O-CO-R'. They are formed by the dehydration of two carboxylic acid molecules or by alternative routes such as reaction of an acid chloride with a carboxylate, and they readily hydrolyze in water to yield the corresponding carboxylic acids.

Organic acid anhydrides include acetic anhydride (two acetyl groups), phthalic anhydride, succinic anhydride, and maleic anhydride. They are widely used as acylating agents in organic synthesis and as reactive intermediates for polymers and pharmaceuticals. Their reactivity is governed by the two adjacent acyl groups linked through an anhydride bond, making them highly susceptible to nucleophilic attack by alcohols, amines, and water.

Inorganic anhydrides are oxides of elements that form acids on hydrolysis. Examples include sulfur trioxide, which forms sulfuric acid; phosphorus pentoxide, which forms phosphoric acid; and carbon dioxide, the anhydride of carbonic acid. Basic oxides such as sodium oxide and calcium oxide are also described as basic anhydrides because they form bases on contact with water. The term highlights a relationship to the corresponding oxyacids produced upon hydration.

Preparation and handling: Many organic anhydrides are prepared from corresponding carboxylic acids by dehydration with reagents or through condensation of acid chlorides with carboxylic acids. They react with water to regenerate the acids, and with alcohols or amines to give esters or amides, respectively.

Applications and safety: Anhydrides are important reagents in synthesis, coatings, and polymer chemistry. They are typically moisture sensitive and can be corrosive or irritant. They should be stored under dry conditions and handled with appropriate protective equipment in well-ventilated spaces.