Acetic Anhydride

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Infobox on Acetic Anhydride
Example of Acetic Anhydride
Origin -
Stowage factor (in m3/t) Drums: 1,78/1,92 m3/t, 63/68 ft3
Humidity / moisture Density: 1.082 g/cm 3. Solubility in water: 2.6 g/100 ml
Ventilation -
Risk factors IMDG Class 8 Corrosive, also flammable

Acetic Anhydride


Colourless, flammable liquid with an irritating odour. Normally carried in glass carboys in an outer covering of box or crate, also in metal or plastic drums.

Corrosive to most metals when moisture is present. Flammable when heated above 50°C. Any vapour given out is strongly irritant to eyes and mucous membranes. Decomposes in hot water to Acetic Acid.

Acetic anhydride, or Ethanoic Anhydride, is a chemical compound. Commonly abbreviated Ac2O, it is the simplest isolatable acid anhydride and is a widely used reagent in organic synthesis. It is a colourless liquid that smells strongly of Acetic Acid, formed by its reaction with the moisture in the air.


Acetic anhydride is mainly used for acetylations leading to commercially significant materials. Its largest application is for the conversion of cellulose to cellulose acetate, which is a component of photographic film and other coated materials. Similarly it is used in the production of aspirin (acetylsalicylic acid), which is prepared by the acetylation of salicylic acid. It is also used as a wood preservative via autoclave impregnation to make a longer lasting timber.

In starch industry, acetic anhydride is a common acetylation compound, used for the production of modified starches (E1414, E1420, E1422)

Because of its use for the synthesis of heroin by the diacetylation of morphine, acetic anhydride is listed as a U.S. DEA List II precursor, and restricted in many other countries.

Risk factors

Hazard IMDG Class 8 Corrosive, also flammable

Acetic anhydride is an irritant and flammable. Because of its reactivity toward water, alcohol foam or carbon dioxide are preferred for fire suppression. The vapour of acetic anhydride is harmful. When mixed with Hydrogen Peroxide, an excess of acetic anhydride reacts with one of the reaction products peracetic acid and forms highly shock sensitive and explosive diacetyl peroxide.

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