Question

Observe the following reaction sequence:

The final product \( E \) is:

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

In electrophilic aromatic substitution reactions, the substituents (like \( \text{Br} \), \( \text{NO}_2 \), and \( \text{NH}_2 \)) affect the position of new substituents on the benzene ring, with activating groups like amines directing substitutions to the ortho and para positions.

Answer 1

The Correct Option is A

Step 1: Analyze the reaction sequence.
- The starting compound is nitrobenzene (\( \text{NO}_2 \)-C6H5). - Step 1 (Reaction with Br2/FeBr3): This is an electrophilic aromatic substitution reaction where \( \text{Br}_2 \) and \( \text{FeBr}_3 \) generate the electrophilic bromine ion (\( \text{Br}^+ \)), leading to the substitution of a hydrogen atom on the benzene ring with a bromine atom, resulting in the compound \( A \), which is 1-bromo-2-nitrobenzene.
- Step 2 (Reaction with Sn/HCl): Tin and hydrochloric acid are used to reduce the nitro group (\( \text{NO}_2 \)) to an amine group (\( \text{NH}_2 \)). This results in compound \( B \), which is 1-bromo-2-aminobenzene.
- Step 3 (Reaction with Br2/H2O): Bromine and water introduce a second bromine atom at the para position to the amino group, resulting in compound \( C \), which is 1,4-dibromo-2-aminobenzene.
- Step 4 (Reaction with NaNO2/HCl): Sodium nitrite and hydrochloric acid cause the conversion of the amine group into a diazonium ion, which can undergo further substitution.
- Step 5 (Reaction with CuCl/HCl): The diazonium ion undergoes replacement with a chlorine atom, resulting in the final product \( E \), which is 1,4,6-tribromo-2-chlorobenzene.
Step 2: Identify the final product.
The final product is \( \text{C}_6\text{H}_3(\text{Br})_3\text{Cl} \), which corresponds to option (1).