Question

What are the reagents A, B, and C respectively in the following reaction sequence? Reaction Sequence: 

• A. \(\text{KMnO}_4/\text{OH}^- ; \text{NH}_3 ; \text{P}_2\text{O}_5\)
• B. \(\text{KMnO}_4/\text{OH}^- ; \text{NH}_3 ; \text{Br}_2/\text{OH}^- \)
• C. \(\text{CrO}_2\text{Cl}_2, \text{H}^+ ; \text{NH}_2\text{OH} ; (\text{CH}_3\text{CO})_2\text{O} \)
• D. \(\text{CrO}_2\text{Cl}_2, \text{H}^+ ; \text{NH}_2\text{OH} ; \text{P}_2\text{O}_5 \)

Hint:

- KMnO₄ / OH⁻ oxidizes methyl (-CH₃) to carboxyl (-COOH).
- Ammonia (NH₃) converts -COOH to -CONH₂ (amide).
- Br₂ / OH⁻ (Hofmann Bromamide Reaction) converts amide (-CONH₂) to amine (-NH₂).

Answer 1

The Correct Option is B

Step 1: Understanding the Reaction Sequence 
- A: KMnO₄ / OH⁻ 
- Oxidizes the methyl (-CH₃) group to carboxylic acid (-COOH). 
- Carboxylic acids are soluble in NaHCO₃, confirming that X is a carboxylic acid. 
- B: NH₃ (Ammonia) 
- Converts the carboxyl (-COOH) group into an amide (-CONH₂), forming Y (which is neutral). 
- C: Br₂ / OH⁻ (Hofmann Bromamide Reaction) 
- Hofmann degradation converts amide (-CONH₂) into amine (-NH₂), forming Z. 
- Amines are soluble in HCl, confirming Z is an amine.

 Step 2: Analyzing the Given Options 
- Option (2): Correct sequence of reagents 
- Option (1): Incorrect because P₂O₅ is a dehydrating agent, not used here 
- Option (3) and (4): Incorrect because they involve chromyl chloride, which is unnecessary for this reaction 

Step 3: Conclusion 
- Since Option (2) follows the correct reaction pathway, it is the correct answer.