See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Concept: Electrophilic aromatic substitution (EAS) reactivity and regioselectivity are governed by the electronic nature of the substituent already on the ring. Electron-donating groups (EDGs) activate the ring (faster than benzene) and direct ortho/para. Electron-withdrawing groups (EWGs) deactivate the ring (slower than benzene) and direct meta. Step 2 - Classify each substituent: - a. -CH3 (alkyl): EDG by hyperconjugation/induction → activating, o/p director → faster than benzene - b. -N(CH3)2 (dialkylamino): strong EDG by resonance → strongly activating, o/p director → much faster than benzene - c. -SO3H (sulfonic acid): EWG → deactivating, meta director → slower than benzene - d. -NO2 (nitro): strong EWG by resonance → strongly deactivating, meta director → slower than benzene - e. -OCH3 (methoxy): EDG by resonance → activating, o/p director → faster than benzene - f. -NHC(=O)CH3 (acetamido): EDG by resonance (lone pair on N donated to ring, despite carbonyl) → activating, o/p director → faster than benzene - g. -N+(CH3)3 (quaternary ammonium): strong EWG by induction (positive charge) → deactivating, meta director → slower than benzene - h. -C(CH3)3 (tert-butyl): EDG by hyperconjugation/induction (alkyl) → activating, o/p director → faster than benzene - i. -C(=O)CH2CH3 (propanoyl/ketone): EWG by resonance → deactivating, meta director → slower than benzene - j. -Br (bromo): weak EWG by induction but o/p director by resonance → deactivating (slower than benzene) but o/p director Step 3 - Answer A (faster than benzene = activated rings): Compounds with EDGs: a (CH3), b (N(CH3)2), e (OCH3), f (NHAc), h (C(CH3)3) → a, b, e, f, h Step 4 - Answer B (meta substitution under electrophilic bromination = meta directors): Compounds with EWGs that are meta directors: c (SO3H), d (NO2), g (N+(CH3)3), i (C=O) → c, d, g, i Step 5 - Why j is excluded from both answers: Bromobenzene (-Br) is o/p directing (resonance donation overrides inductive withdrawal for regioselectivity) so it does NOT give meta products. It is also deactivated (slower than benzene) so it does not belong in answer A. The note confirms it is less reactive than benzene but o/p directing, excluding it from both A and B. Therefore, the correct answer is {"A": ["a", "b", "e", "f", "h"], "B": ["c", "d", "g", "i"], "note": "yet C6H5Br is less reactive than C6H6 but o/p directing"}.