See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Friedel-Crafts acylation requires a Lewis acid catalyst (e.g., AlCl3) and involves electrophilic aromatic substitution. However, the reaction fails or is severely inhibited under certain conditions: 1. When the ring bears a strongly electron-withdrawing group (e.g., -NO2), the ring is deactivated toward electrophilic attack, so Friedel-Crafts acylation does not work. 2. When the ring bears a strongly electron-donating group that also acts as a Lewis base (e.g., -NR2, -NH2), the nitrogen lone pair coordinates with the Lewis acid catalyst (AlCl3), forming a complex that deactivates the catalyst and prevents the reaction. Analysis of each compound (each appears to be a benzyl-type structure where the substituent is attached via a CH2 group to the ring, but the key point is the nature of the ring substituent for Friedel-Crafts compatibility): (I) CH3O- (methoxy group): This is an electron-donating group via resonance. It activates the ring. The methoxy group does NOT coordinate strongly enough with AlCl3 to poison the catalyst. Friedel-Crafts acylation CAN be performed on methoxybenzene derivatives. --> Possible (II) H3C- (methyl group): This is a weakly electron-donating group. It activates the ring. No interference with the catalyst. Friedel-Crafts acylation CAN be performed on toluene derivatives. --> Possible (III) O2N- (nitro group): This is a strongly electron-withdrawing group. It deactivates the ring significantly. Friedel-Crafts acylation does NOT work on nitrobenzene derivatives (the ring is too deactivated). --> Not possible (IV) Me2N- (dimethylamino group): The nitrogen lone pair strongly coordinates with the Lewis acid AlCl3, poisoning the catalyst. Friedel-Crafts acylation does NOT work on dimethylaminobenzene derivatives. --> Not possible Therefore, Friedel-Crafts acylation can be used to obtain compounds I and II only. Why other options fail: - Option (a) II, III, IV: excludes I (which works) and includes III and IV (which don't work) - Option (b) I, III, IV: includes III (deactivated ring) and IV (catalyst poisoning) which are both incompatible - Option (d) II and III: includes III which is incompatible due to ring deactivation Therefore, the correct answer is C.