Answer
Grignard Reaction with a Ketone and Nitrile Group
A compound containing both a ketone and a nitrile group reacts with methylmagnesium bromide (CH₃MgBr), followed by acidic hydrolysis, forming a β-hydroxy ketone.
Step 1: Nucleophilic Addition to the Nitrile
The Grignard reagent CH₃MgBr acts as a nucleophile and attacks the nitrile (–CN), forming an imine magnesium salt intermediate:
R–CN + CH₃MgBr → R–C(=N⁻MgBr⁺)–CH₃
Step 2: Addition to the Ketone
Another equivalent of CH₃MgBr adds to the ketone group, forming an alkoxide intermediate.
Step 3: Acidic Workup
Treatment with aqueous acid (H₃O⁺) leads to:
- Hydrolysis of the imine to a ketone
- Protonation of the alkoxide to form a secondary alcohol
Final Product:
The product is a compound containing:
- A secondary alcohol
- A ketone
- A quaternary carbon center
IUPAC name: 1-phenyl-1-hydroxy-2-methylpentan-3-one
Key Concepts:
- Grignard reagents react with both ketones and nitriles.
- Nitriles give ketones after Grignard addition and hydrolysis.
- Multifunctional compounds can undergo multiple Grignard additions.