Question

The given reaction is known as: \[ \text{PhCH}_2\text{CN} + \text{SnCl}_2 + \text{HCl} \xrightarrow{\text{H}_3\text{O}^+} \text{PhCH}_2\text{CH=NH} \]

• A. Rosenmund reaction
• B. Stephen reaction
• C. Etard reaction
• D. Gatterman-Koch reaction

Hint:

Key points to remember:
- Stephen reaction converts nitriles to aldehydes via imine intermediate
- Uses $SnCl_2/HCl$ as reducing agent
- Different from other nitrile reductions (e.g., $LiAlH_4$ gives amines)
- Important for aromatic aldehyde synthesis

Answer 1

The Correct Option is B

Step 1: Identify the reaction type
The given reaction shows the conversion of a nitrile ($PhCH_2CN$) to an aldimine ($PhCH_2CH=NH$) using $SnCl_2/HCl$ followed by hydrolysis. This is characteristic of the Stephen reaction.
Step 2: Understand the Stephen reaction mechanism
The Stephen reaction involves:
1. Reduction of nitrile to imine using stannous chloride ($SnCl_2$) in acidic medium
2. Hydrolysis of imine to aldehyde (though shown here as stopping at imine stage)
Step 3: Compare with other options
(a) Rosenmund reaction - Reduction of acyl chloride to aldehyde
(c) Etard reaction - Partial oxidation of methyl group to aldehyde
(d) Gatterman-Koch reaction - Formylation of aromatic compounds
Step 4: Final confirmation
The use of $SnCl_2/HCl$ for nitrile reduction is unique to the Stephen reaction, making option (b) correct.