Question

The reagent ‘R’ in the given sequence of chemical reaction is:
graphics[width=0.5\linewidth]{Screenshot 2026-04-20 175228.png}

• A. CH\(_3\)CH\(_2\)OH
• B. HI
• C. CuCN/KCN
• D. H\(_2\)O
• E.

Hint:

If the reagent had been \(\text{H}_2\text{O}\), the product would have been a phenol. If it had been \(\text{HI}\), the product would have been an aryl iodide.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
The reaction sequence involves the conversion of an amine group (\(-\text{NH}_2\)) into a diazonium group (\(-\text{N}_2^+\text{Cl}^-\)), followed by the removal of the diazonium group to leave only a hydrogen atom. This process is called deamination.

Step 2: Key Formula or Approach
To replace a diazonium group (\(-\text{N}_2^+\text{Cl}^-\)) with a Hydrogen (\(-\text{H}\)), mild reducing agents are used. The two most common reagents for this are Phosphinic acid (\(\text{H}_3\text{PO}_2\)) or Ethanol (\(\text{CH}_3\text{CH}_2\text{OH}\)).

Step 3: Detailed Explanation
1. 2,4,6-tribromoaniline reacts with \(\text{NaNO}_2/\text{HCl}\) to form 2,4,6-tribromobenzenediazonium chloride.
2. When this diazonium salt is treated with Ethanol (\(\text{CH}_3\text{CH}_2\text{OH}\)), the ethanol acts as a reducing agent.
3. The diazonium group is reduced to Hydrogen, and Ethanol is oxidized to Ethanal (Acetaldehyde).
4. The product is 1,3,5-tribromobenzene.

Step 4: Final Answer
The reagent ‘R’ is CH\(_3\)CH\(_2\)OH.