JEE Chemistry 2025 Question with Solution

Given: Four reaction sequences are proposed for obtaining predominantly $3,4,5$-Tribromoaniline.

Find: The correct sequence.

The solution identifies option C as the correct option. The reasoning given is based on directing effects in electrophilic aromatic substitution and the subsequent diazotization–Sandmeyer–reduction sequence.

1. Option A: Bromination of nitrobenzene occurs predominantly at the meta position because $-NO_2$ is strongly deactivating and meta-directing. Reduction afterward converts $-NO_2$ to $-NH_2$, but this does not lead to the required tribromoaniline pattern.

2. Option B: Bromobenzene on further bromination gives brominated products directed by bromine, but the later conversion with $NH_3$ does not selectively furnish the required tribromoaniline.

3. Option C: Starting from $p$-nitroaniline, excess bromination introduces multiple bromine substituents under the directing influence of the substituents already present. Then diazotization with $NaNO_2/HCl$ followed by $CuBr$ replaces the amino-derived diazonium group by bromine. Finally, $Sn/HCl$ reduces the nitro group to an amino group. Hence this is the intended sequence for forming the tribromoaniline product.

4. Option D: Direct bromination of aniline in water gives the usual heavily activated bromination pattern, but not the required sequence as intended in the question.

Conclusion: Therefore, the correct option is C.

Note on the extracted solution: The second approach in the solution itself mentions a regioselectivity inconsistency and discusses $2,3,6$-tribromoaniline versus $3,4,5$-tribromoaniline. Despite that discrepancy, the solution explicitly concludes that the intended correct answer is option C, and that is taken as the answer authority.