Question:
Which reagent is used in the Stephen reaction to reduce nitriles to imines?
Which reagent is used in the Stephen reaction to reduce nitriles to imines?
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Remember: The Stephen reaction converts nitriles into aldehydes through an intermediate imine using \(SnCl_2/HCl\) as the reducing agent.
Updated On: Apr 24, 2026
- \(LiAlH_4\)
- \(SnCl_2/HCl\)
- \(NaBH_4\)
- \(Zn/HCl\)
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The Correct Option is B
Solution and Explanation
Concept:
The Stephen reduction is a chemical transformation in which nitriles \((R{-}C \equiv N)\) are reduced to imines using a mild reducing agent. The imine formed can subsequently be hydrolyzed to produce aldehydes. This reaction is useful because it allows controlled partial reduction of nitriles without reducing them completely to primary amines.
The reagent used in this reaction is stannous chloride in the presence of hydrochloric acid.
Step 1: Understanding the role of the reagent.
In the Stephen reaction, the nitrile group undergoes reduction by \(SnCl_2\) in an acidic medium provided by \(HCl\). The reaction initially produces an iminium salt. \[ R{-}C \equiv N \xrightarrow[HCl]{SnCl_2} R{-}CH=NH \]
Step 2: Formation of aldehyde after hydrolysis.
The iminium salt formed in the first step undergoes hydrolysis when treated with water, leading to the formation of an aldehyde. \[ R{-}CH=NH + H_2O \rightarrow R{-}CHO \]
Step 3: Identifying the correct reagent.
Among the given options, only \(SnCl_2/HCl\) performs this controlled reduction of nitriles to imines in the Stephen reaction.
Step 1: Understanding the role of the reagent.
In the Stephen reaction, the nitrile group undergoes reduction by \(SnCl_2\) in an acidic medium provided by \(HCl\). The reaction initially produces an iminium salt. \[ R{-}C \equiv N \xrightarrow[HCl]{SnCl_2} R{-}CH=NH \]
Step 2: Formation of aldehyde after hydrolysis.
The iminium salt formed in the first step undergoes hydrolysis when treated with water, leading to the formation of an aldehyde. \[ R{-}CH=NH + H_2O \rightarrow R{-}CHO \]
Step 3: Identifying the correct reagent.
Among the given options, only \(SnCl_2/HCl\) performs this controlled reduction of nitriles to imines in the Stephen reaction.
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