Reaction of Grignard Reagents with CO₂
Reaction of Grignard Reagents with CO₂: A Grignard reagent (R–MgX) reacts with carbon dioxide (CO₂) to form a carboxylic acid after an acidic workup.
What happens
A Grignard reagent (R–MgX) reacts with carbon dioxide (CO₂) to form a carboxylic acid after an acidic workup. The important result is that CO₂ adds one new carbon to the molecule: a new C–C bond forms and the carbon count goes up by one.
Reaction summary
Grignard reagent R–MgX + CO₂, then H₃O⁺ → carboxylic acid R–COOH (+1 carbon)
Reagents and conditions
- Starting material: Phenylmagnesium bromide (Grignard reagent)
- Reagents: CO₂ (carbon dioxide); H₃O⁺ (acidic workup)
- Products: Benzoic acid (carboxylic acid)
Mechanism
- The Carbon Acts as a Nucleophile: The carbon attached to Mg acts as a nucleophile.
- Attack on CO₂: It attacks the carbon of CO₂, forming a new C–C bond.
- Carboxylate Forms: A carboxylate intermediate is formed.
- Acidic Workup: The acidic workup (H₃O⁺) protonates the carboxylate. The final product is a carboxylic acid.