What happens when: Propanenitrile is treated with phenyl magnesium bromide followed by hydrolysis?
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Nitriles + Grignard followed by excessive hydrolysis is one of the best ways to prepare aryl alkyl ketones.
Solution and Explanation
• Grignard reagents (\( RMgX \)) act as nucleophiles and attack the electrophilic carbon of the nitrile group (\( -C\equiv N \)).
• The initial addition product is an imine salt.
• Acidic hydrolysis of this imine salt yields a ketone.
Step 1: Nucleophilic attack
Phenyl magnesium bromide (\( C_{6}H_{5}MgBr \)) attacks the carbon of propanenitrile (\( CH_{3}CH_{2}CN \)). The phenyl group attaches to the carbon, and the \( MgBr \) attaches to the nitrogen. \[ CH_{3}CH_{2}C\equiv N + C_{6}H_{5}MgBr \rightarrow CH_{3}CH_{2}C(C_{6}H_{5})=NMgBr \]
Step 2: Hydrolysis
The addition of water/acid breaks the carbon-nitrogen double bond. The Nitrogen is lost as an ammonium salt, and the Carbon becomes a carbonyl group. \[ CH_{3}CH_{2}C(C_{6}H_{5})=NMgBr + H_{2}O/H^{+} \rightarrow CH_{3}CH_{2}C(=O)C_{6}H_{5} \]
Step 3: Identify the product
The resulting product is 1-phenylpropan-1-one, also commonly known as propiophenone. The final answer is Propiophenone (1-phenylpropan-1-one).
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