Aromatic HydrocarbonshardMCQ SINGLE

See imageAromatic Hydrocarbons Chemistry Question

Question

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Chemistry diagram for: See image
Answer: B

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is naphthalene. Step 2 - Step 1 of the reaction (HNO3, H2SO4, Delta): This is nitration of naphthalene. Nitration of naphthalene preferentially occurs at the alpha (1) position, giving 1-nitronaphthalene. However, under vigorous conditions with heat, further oxidation or the context suggests this may involve oxidative degradation. Actually, with concentrated HNO3/H2SO4 and heat, naphthalene undergoes nitration to give nitronaphthalene, but in some conditions oxidative cleavage can occur. Given the subsequent steps, the key pathway is: nitration gives nitronaphthalene, then the ring is oxidized. More likely interpretation: HNO3/H2SO4/Delta causes oxidative degradation of one ring of naphthalene to give a phthalic acid derivative or nitro-phthalic acid. Actually the standard reaction sequence: naphthalene + HNO3/H2SO4 gives nitronaphthalene; with NH3/Delta (ammonolysis) and KOBr/Delta (Hofmann bromamide degradation). Step 3 - Reconsidering: A classic reaction of naphthalene: (1) HNO3/H2SO4 nitrates to give 1-nitronaphthalene. (2) Treatment with NH3 under heat - this could be nucleophilic substitution or relate to conversion of a carboxylic acid to amide. (3) KOBr (potassium hypobromite) with heat = Hofmann degradation, converting amide (-CONH2) to amine (-NH2). Step 4 - Most consistent pathway: Naphthalene is oxidized with HNO3/H2SO4/Delta to give phthalic acid (one ring gets oxidized away) - wait, that requires stronger oxidant. Alternatively: 1-nitronaphthalene undergoes ring oxidation of the non-nitro ring to give 3-nitrophthalic acid, then reaction with NH3 gives the amide of one COOH (3-nitrophthalamic acid type), but this doesn't match well. Step 5 - Most likely interpretation for the answer being (b): The sequence produces 2-aminobenzoic acid (anthranilic acid) on a benzene ring. Starting from naphthalene: oxidation with HNO3/H2SO4 cleaves one ring and introduces nitro group giving a nitro-benzoic acid; NH3/Delta converts a carboxylic acid to amide (CONH2); KOBr/Delta = Hofmann rearrangement converts CONH2 to NH2. So if naphthalene → nitronaphthalene-dicarboxylic acid intermediate → amide on one COOH → Hofmann gives NH2, with reduction of NO2 somewhere giving NH2, the product is a benzene ring bearing COOH and NH2 groups ortho to each other, i.e., 2-aminobenzoic acid (anthranilic acid), which matches option (b). Step 6 - Why other options fail: (a) is a cyclic imide - not consistent with Hofmann degradation product. (c) has both COOH and CONH2 - this would be the intermediate before Hofmann, not the final product. (d) is a lactam of naphthalene framework - not consistent with the reagents producing ring cleavage/degradation. Therefore, the correct answer is B.

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