Halogens are deactivating but ortho-para directing in electrophilic substitution. A nitro group at ortho or para position activates aryl halides for nucleophilic substitution.
Step 1: Track the electrophilic then nucleophilic steps. Chlorobenzene + HNO₃/H₂SO₄ → mainly p-nitrochlorobenzene (Cl is o/p-directing, para avoids steric hindrance). The –NO₂ group activates the ring for nucleophilic aromatic substitution: NaOH at 443K replaces Cl with –OH, giving p-nitrophenoxide. Acidification with H₃O⁺ yields 4-nitrophenol. Step 2: Final Answer: 4-Nitrophenol (option 4).
