See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: The reaction of toluene with chlorine (Cl2) at elevated temperature in sunlight proceeds via a free radical chain mechanism (side-chain chlorination), not electrophilic aromatic substitution. Step 1 - Identify the reaction conditions: Elevated temperature and sunlight (hv) are the hallmark conditions for free radical reactions. Under these conditions, Cl2 undergoes homolytic cleavage to generate chlorine radicals (Cl•). Step 2 - Identify the site of reaction: Under free radical conditions, the reaction occurs at the benzylic position (the CH3 group of toluene), not on the aromatic ring. Cl• abstracts a hydrogen from the methyl group. Step 3 - Identify the intermediate: When Cl• abstracts one H from the CH3 group of toluene, a benzyl radical (C6H5-CH2•) is formed. This is the key intermediate in the free radical chain mechanism. The benzyl radical is stabilized by resonance with the aromatic ring. Step 4 - Evaluate each option: (a) Shows a sigma complex (arenium ion/Wheland intermediate) with both H and Cl on the ring carbon and a positive charge - this is the intermediate for electrophilic aromatic substitution, which requires a Lewis acid catalyst (e.g., FeCl3), not sunlight/heat. Incorrect. (b) Shows a radical addition intermediate on the ring with H, Cl, and a radical dot on the ring carbon - this would be relevant to radical addition to the ring, not side-chain chlorination. Incorrect. (c) Shows a benzyl radical (benzene ring with •CH2) - this is exactly the intermediate formed when Cl• abstracts H from the CH3 group of toluene under free radical conditions. Correct. (d) Shows a benzyl carbocation (benzene ring with +CH2) - carbocations are ionic intermediates, not formed under free radical conditions. Incorrect. Therefore, the correct answer is C.