Acetic anhydride is the chemical compound with the formula (CH₃CO)₂O. Commonly abbreviated Ac₂O, it is the simplest acid anhydride and is a widely used reagent in organic synthesis.

An acid anhydride is an organic compound that has two acyl groups bound to the same oxygen atom.[1] Most commonly, the acyl groups are derived from the same carboxylic acid, the formula of the anhydride being (RC(O))₂O.

Maleic anhydride (cis-butenedioic anhydride, toxilic anhydride, dihydro-2,5-dioxofuran) is an organic compound with the formula C₂H₂(CO)₂O. In its pure state it is a colourless or white solid with an acrid odour.

Phthalic anhydride is the organic compound with the formula C₆H₄(CO)₂O. This anhydride of phthalic acid, a colourless solid, is an important industrial chemical, especially for the large-scale production of plasticizers for plastics.

Triflic anhydride is the chemical compound with the formula (CF₃SO₂)₂O. This compound is a particularly strong electrophile, useful for introducing the CF₃SO₂ group. Triflic anhydride is the acid anhydride of the strong acid triflic acid, CF3SO2OH.

Succinic anhydride, also called dihydro-2,5-furandione, is an organic compound with the molecular formula C₄H₄O₃. It is the acid anhydride of succinic acid.

Triflic anhydride is the chemical compound with the formula (CF₃SO₂)₂O. This compound is a particularly strong electrophile, useful for introducing the CF₃SO₂ group. Triflic anhydride is the acid anhydride of the strong acid triflic acid, CF₃SO₂OH.