BRAINCAKEAcid Anhydrides
Acid anhydrides are the other acylating agents in AQA's specification. An acid anhydride can be thought of as two carboxylic acid molecules joined together with the loss of a molecule of water. Its general formula is (RCO)2O, and the functional group is RCO-O-COR.
They are named after the parent acid: (CH3CO)2O, made from two ethanoic acid units, is ethanoic anhydride, and (CH3CH2CO)2O is propanoic anhydride.
Acid anhydrides react with the same nucleophiles as acyl chlorides (water, alcohols, ammonia and primary amines) by nucleophilic addition-elimination, and give the same main organic product. There are two key differences:
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Key terms in this lesson
- nucleophilic addition-elimination
- A two-step mechanism in which a nucleophile first adds to the carbonyl carbon, then a leaving group is eliminated to reform the C=O bond.
More in Carboxylic Acids and Derivatives
- Hydrolysis of Esters
- Vegetable Oils and Fats
- Soap Making
- Biodiesel
- Acyl Chlorides
- Nucleophilic Addition-Elimination Mechanism
- Acylation of Water, Alcohols, Ammonia and Amines
- Manufacture of Aspirin
All 16 lessons in Carboxylic Acids and Derivatives · All AQA A-level Chemistry topics