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Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH 3 CO) 2 O. Commonly abbreviated Ac 2 O , it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis .
Hippuric acid, the benzamide derivative of glycine, cyclizes in the presence of acetic anhydride, condensing to give 2-phenyl-oxazolone. [3] This intermediate also has two acidic protons and reacts with benzaldehyde, acetic anhydride and sodium acetate to a so-called azlactone. This compound on reduction gives access to phenylalanine. [4]
The Perkin reaction is an organic reaction developed by English chemist William Henry Perkin in 1868 that is used to make cinnamic acids.It gives an α,β-unsaturated aromatic acid or α-substituted β-aryl acrylic acid by the aldol condensation of an aromatic aldehyde and an acid anhydride, in the presence of an alkali salt of the acid.
The product of the condensation of two molecules of acetic acid is acetic anhydride. The worldwide production of acetic anhydride is a major application, and uses approximately 25% to 30% of the global production of acetic acid. The main process involves dehydration of acetic acid to give ketene at 700–750 °C. Ketene is thereafter reacted ...
The following figure shows the reaction mechanism: [2] Reaktionsmechanismus Albright-Goldman-Oxidation. First, dimethyl sulfoxide (1) reacts with acetic anhydride to form a sulfonium ion. It reacts with the primary alcohol in an addition reaction. Furthermore, acetic acid is cleaved, so that intermediate 2 is formed. The latter reacts upon ...
Modern variations on the Dakin–West reaction permit many enolizable carboxylic acids – not merely amino acids – to be converted to their corresponding methyl ketones. For example, β-aryl carboxylic acids can be efficiently converted to β-aryl ketones by treatment of an acetic anhydride solution of the acid with catalytic N-methylimidazole.
The name "Schotten–Baumann reaction conditions" often indicate the use of a two-phase solvent system, consisting of water and an organic solvent. The base within the water phase neutralizes the acid, generated in the reaction, while the starting materials and product remain in the organic phase, often dichloromethane or diethyl ether.
A common type of organic acid anhydride is a carboxylic anhydride, where the parent acid is a carboxylic acid, the formula of the anhydride being (RC(O)) 2 O. Symmetrical acid anhydrides of this type are named by replacing the word acid in the name of the parent carboxylic acid by the word anhydride. [2] Thus, (CH 3 CO) 2 O is called acetic ...