JEE Main 2025 Apr 3 Shift 2, Chemistry Q8: Preparation of Alkyl Halides (Halo Alkanes) & Aryl Halides (Halo Arenes)

Both reactions are electrophilic aromatic substitutions on a bromobenzene framework, and $-$Br is an ortho/para-director that is sterically modest.

Step 1 (sulfonation): SO${}_3$/H${}_2$SO${}_4$ delivers $-$SO${}_3$H predominantly para to the bulky electrophile and the existing Br, because the para position is sterically least hindered. Hence A is para-bromobenzenesulfonic acid.

Step 2 (bromination): In A, $-$Br directs ortho/para and is weakly deactivating, while $-$SO${}_3$H is strongly deactivating and meta-directing. The positions ortho to Br are also meta to SO${}_3$H, so both directing effects reinforce the same set of positions. The incoming Br${}_2$/Fe places the new Br ortho to the existing Br (and meta to SO${}_3$H).

$\therefore$ A is para-bromobenzenesulfonic acid and B is the trisubstituted ring with two Br ortho to one another and SO${}_3$H para to one of them, matching option (2).