Question

Consider the following sequence of reactions. The number of bromine atom(s) in the final product (P) will be :

• A. 3
• B. 5
• C. 6
• D. 1

Hint:

Aniline is so strongly activating that bromination with bromine water results in substitution at all free ortho and para positions without needing a Lewis acid catalyst.

Answer 1

The Correct Option is B

To determine the number of bromine atoms in the final product (P), let's analyze each step in the given reaction sequence.

1. The initial compound has a nitro group (\(\text{NO}_2\)) attached to a benzene ring.
2. Step 1: Bromination
   Bromination using \(\text{Br}_2/\text{FeBr}_3\) introduces a bromine atom ortho or para to the nitro group because nitro is a deactivating group that directs incoming substituents to the meta position.
3. Step 2: Reduction
   The nitro group is reduced to an amino group using \(\text{Sn/HCl}\).
4. Step 3: Diazotization 
   Diazotization occurs using \(\text{NaNO}_2/\text{HBr}\) at low temperatures, converting the amino group to a diazonium salt.
5. Step 4: Sandmeyer Reaction
   CuBr is used to replace the diazonium group with a bromine atom.
6. Step 5: Additional Bromination
   Another bromination step adds additional bromine atoms ortho to the existing bromine atoms.

After these steps, the product generally ends up with multiple bromines substituted at available positions on the benzene ring.

Considering the steps above, the total number of bromine atoms will be introduced as follows:

• Step 1: 1 Bromine
• Step 4: 1 Bromine (Sandmeyer Reaction)
• Step 5: 3 Bromines (Additional ortho/meta orientations)

Resulting in a total of 5 bromine atoms in the final product. Therefore, the correct answer is:

5