See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: When an alkylbenzene is treated with hot alkaline KMnO4 (a strong oxidizing agent), the entire alkyl side chain attached to the benzene ring is oxidized down to a carboxyl group (-COOH), regardless of the chain length, as long as there is at least one benzylic hydrogen. The benzene ring itself remains intact. Reasoning: n-Butylbenzene has a benzene ring with an n-butyl group (-CH2CH2CH2CH3) attached. The benzylic carbon (the carbon directly attached to the ring) has hydrogens, so hot alkaline KMnO4 oxidizes the entire four-carbon side chain completely. The product is benzoic acid (C6H5COOH), where the -C4H9 chain is converted to -COOH. Why other options fail: (b) Butanoic acid - This would require the benzene ring to be oxidized and the side chain to remain, which does not occur under these conditions. (c) Benzyl alcohol - This is a mild oxidation product and would not result from hot alkaline KMnO4, which is a vigorous oxidant. (d) Benzaldehyde - This would require only partial oxidation of the side chain; hot alkaline KMnO4 fully oxidizes the chain to the carboxylic acid level. Therefore, the correct answer is A.