Anhydride ammonolysis
Ammonia attacks the anhydride carbonyl to form a tetrahedral intermediate. Carboxylate departure and proton transfer give an amide; excess ammonia also converts the acid co-product into ammonium carboxylate.
- Reagents
- Excess NH3
- Conditions
- Controlled acylation
- Reaction class
- Anhydride ammonolysis
- Equation
- (RCO)2O + 2NH3 -> RCONH2 + RCOO- + NH4+
Overview
Ammonia attacks the anhydride carbonyl to form a tetrahedral intermediate. Carboxylate departure and proton transfer give an amide; excess ammonia also converts the acid co-product into ammonium carboxylate.
Transformation
- Equation
- (RCO)2O + 2NH3 -> RCONH2 + RCOO- + NH4+
- Reagents
- Excess NH3
- Environment
- Controlled acylation
- Reaction class
- Anhydride ammonolysis
- Mechanism
- nucleophilic addition-elimination
- Evidence level
- textbook core
Scope and limitations
- Scope
- Ammonia gives a primary amide and an ammonium carboxylate.
- Limitations
- Primary or secondary amines give N-substituted amides instead.
Related reactions
- Acylation: Acyl chlorides → Amides
Ammonia acylation converts acyl chlorides into amides.
- Anhydride hydrolysis: Acid anhydrides → Carboxylic acids
Water attacks an anhydride carbonyl, and collapse of the tetrahedral intermediate breaks the acyl-oxygen linkage. Proton transfer gives carboxylic-acid products; a mixed anhydride yields two different acids.
- Anhydride alcoholysis: Acid anhydrides → Esters
Alcohol oxygen attacks an anhydride carbonyl and the tetrahedral intermediate expels carboxylate. Proton transfer produces the ester and a carboxylic acid; one acyl fragment transfers to the alcohol.
References
- A-level Chemistry 7405: Organic chemistryAQA · AQA specification
Checked 2026-09-16. Supports A-level topic coverage, including acid anhydrides, acylation and aspirin, amines, amino acids, polymers, synthesis and analysis. Coverage varies by examination board.