Products
Acetic anhydride is available in specialized stores.
Structure and properties
Acetic anhydride (C4H6O3, Mr = 102.09 g/mol) is the condensation product of two acetic acid molecules. It exists as a colorless liquid with a pungent odor of acetic acid. This is a result of hydrolysis with water:
- C4H6O3 (acetic anhydride) + H2O (water) 2 C2H4O2 (acetic acid)
Fields of application
Acetic anhydride is mainly used for acetylations in organic chemistry, for example for alcohols and amines. In this reaction, acetic acid is produced as a by-product:
- Alcohol + acetic anhydride ester + acetic acid.
With amines, an amide is formed:
- Amine + acetic anhydride amide + acetic acid
Finally, aromatics can also be acetylated with acetic anhydride.
Synthesis of acetylsalicylic acid (aspirin).
For the synthesis of acetylsalicylic acid (aspirin, generic), salicylic acid is acetylated with acetic anhydride. Little sulfuric acid or phosphoric acid serves as catalyst. The salicylic acid acts as a nucleophile, and the acetic anhydride acts as an electrophile.
Abuse
Acetic anhydride can be misused for the synthesis of the narcotic heroin (diacetylmorphine).
Adverse effects
Both the vapor and the liquid are flammable. Acetic anhydride is harmful if swallowed and causes burns to the skin and eyes on direct contact. The appropriate precautions in the Material Safety Data Sheet must be observed.
