JEE Chemistry 2023 Question with Solution

Given: A nitro-substituted toluene derivative is converted into an aromatic compound containing $-COOH$, $-Cl$, and $-Br$.

Find: The correct sequence of reagents.

The sequence must include bromination of the ring, reduction of the nitro group, diazotisation followed by Sandmeyer reaction, and oxidation of the methyl group.

First, bromination is carried out using

$$\mathrm{Br_2/Fe}$$

which introduces $Br$ on the aromatic ring.

Next, the nitro group is reduced to an amino group using

$$\mathrm{Fe/H^+}$$

so that diazotisation becomes possible.

Then the aromatic amine is diazotised using

$$\mathrm{HONO}$$

forming the diazonium salt, which is converted to the chloro derivative by Sandmeyer reaction with

$$\mathrm{CuCl}$$

Finally, the methyl group is oxidised to the carboxylic acid using

$$\mathrm{KMnO_4}$$

Therefore, the correct order is:

$$\mathrm{Br_2/Fe \rightarrow Fe/H^+ \rightarrow HONO \rightarrow CuCl \rightarrow KMnO_4}$$

The correct option is C.

Given: The initial compound contains $-NO_2$ and $-CH_3$, while the final compound contains $-Br$, $-Cl$, and $-COOH$.

Find: Which option matches these conversions in order.

Track the required functional group changes directly:

1. $-NO_2 \rightarrow -NH_2$ requires

$$\mathrm{Fe/H^+}$$

2. $-NH_2 \rightarrow -N_2^+ \rightarrow -Cl$ requires

$$\mathrm{HONO}$$

followed by

$$\mathrm{CuCl}$$

3. $-CH_3 \rightarrow -COOH$ requires

$$\mathrm{KMnO_4}$$

4. Bromine must be introduced by

$$\mathrm{Br_2/Fe}$$

Only option C contains all these essential transformations in the correct sequence. Hence, the correct option is C.