Question

Identify the product 'B' in the following sequence of reactions.
Ethanenitrile \( \xrightarrow{\text{SnCl}_2, \text{HCl}} \) A \( \xrightarrow{\text{H}_3\text{O}^+} \) B + NH\(_4\)Cl}

• A. Ethylamine
• B. Ethanamide
• C. Ethanol
• D. Ethanal

Hint:

Stephen Reaction: Nitrile $\rightarrow$ Imine $\rightarrow$ Aldehyde.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question shows a two-step reaction starting from ethanenitrile and asks for the final product 'B'. The reagents suggest a specific named reaction.
Step 2: Key Formula or Approach:
The sequence of reactions is the Stephen's reduction (or Stephen's aldehyde synthesis).
Step 1: Reduction of a nitrile with stannous chloride (SnCl\(_2\)) and hydrochloric acid (HCl) to form an iminium salt (A).
Step 2: Hydrolysis of the iminium salt with water (H\(_3\)O\(^+\)) to form an aldehyde (B).
The general reaction is: R-CN \( \xrightarrow{\text{1. SnCl}_2/\text{HCl}} \) \( \xrightarrow{\text{2. H}_3\text{O}^+} \) R-CHO
Step 3: Detailed Explanation:
The starting material is Ethanenitrile, which has the formula CH\(_3\)-C\( \equiv \)N.
Step 1: Ethanenitrile is treated with SnCl\(_2\) and HCl. The nitrile is reduced to an iminium chloride salt (intermediate A).
\[ \text{CH}_3\text{C} \equiv \text{N} + 2[\text{H}] \xrightarrow{\text{SnCl}_2/\text{HCl}} [\text{CH}_3\text{CH}=\text{NH}_2]^+\text{Cl}^- \quad (\text{Ethaniminium chloride, A}) \] Step 2: The intermediate iminium salt (A) is then hydrolyzed by warming with water (acidic hydrolysis, H\(_3\)O\(^+\)). The C=N bond is broken, and the carbon atom is converted to a carbonyl group (C=O), forming an aldehyde. The nitrogen atom forms ammonium chloride (NH\(_4\)Cl).
\[ [\text{CH}_3\text{CH}=\text{NH}_2]^+\text{Cl}^- \xrightarrow{\text{H}_2\text{O}, \Delta} \text{CH}_3\text{CHO} + \text{NH}_4\text{Cl} \] The product 'B' is CH\(_3\)CHO, which is known as Ethanal (or acetaldehyde).
Step 4: Final Answer:
The final product 'B' of the Stephen's reduction of ethanenitrile is Ethanal.