JEE Chemistry 2025 Question with Solution

Given: The conversion is from ethyl benzene to a product having Br on the benzenoid ring and a vinyl group $CH=CH_2$ on the side chain.

Find: The correct sequence of reagents.

From the solution, the correct option is stated as B.

The extracted working says:

1. Bromination of ethyl benzene is carried out using $Br_2/Fe$.
2. Then chlorination under heat, $Cl_2, \Delta$, is used.
3. Finally, alc. KOH causes elimination to generate the double bond.

Thus the reagent sequence is $Br_2/Fe;\ Cl_2,\Delta;\ alc.\ KOH$

Therefore, the correct option is B.

Given: Ethyl benzene is converted to a brominated styrene derivative.

Find: Which listed reagent set matches the conversion.

The solution explains that bromination of ethylbenzene first occurs using $Br_2$ in the presence of Fe. Then chlorination under heating, $Cl_2, \Delta$, is used. After that, dehydrohalogenation with alc. KOH forms the required double bond.

So the sequence identified in the source solution is: $Br_2/Fe;\ Cl_2,\Delta;\ alc.\ KOH$

This corresponds to option (2).

Hence, the correct option is B.