See image — Haloalkanes and Haloarenes Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is N-methyl-3-tropanol (a nortropane/bicyclo[2.2.1] system with an N-methyl group and an OH group on the ring). Step 2 - First reaction with conc. H2SO4: Concentrated sulfuric acid causes dehydration of the OH group, and also promotes ring-opening/rearrangement of the strained bicyclic system. The bridged bicyclic amine (tropane skeleton) under acidic conditions with dehydration gives a cyclic unsaturated amine - specifically, conc. H2SO4 dehydrates the alcohol and opens the bridged ring to give N-methyl-2,5-dihydropyridine or a cycloheptadienyl amine intermediate. More precisely, the bicyclic system (tropane) on dehydration with conc. H2SO4 gives N-methylcyclohept-2-en-1-amine or a seven-membered ring unsaturated amine (A). Step 3 - Hofmann Exhaustive Methylation sequence 1: (A) is treated with MeI (quaternization), then AgOH (exchange to hydroxide), then heat (Hofmann elimination). This Hofmann elimination removes a beta-hydrogen and expels trimethylamine, introducing another double bond into the ring, giving diene (B) - a cycloheptadiene. Step 4 - Hofmann Exhaustive Methylation sequence 2: (B) still has a nitrogen (if it retained NMe2 after first Hofmann) - actually tracing through: starting bicyclic N-Me compound, after H2SO4 we get a monocyclic N-Me amine (A). First Hofmann (MeI/AgOH/heat) on A gives B with one more degree of unsaturation. Second Hofmann (MeI/AgOH/heat) on B gives C with yet another double bond. The net result of two successive Hofmann eliminations on the seven-membered ring amine is cycloheptatriene (1,3,5-cycloheptatriene), a seven-membered ring with three double bonds. Step 5 - Why cycloheptatriene (option a): The tropane skeleton contains 7 carbons in the ring framework. After ring opening and two Hofmann eliminations, three double bonds are introduced into the seven-membered carbocyclic ring, yielding cycloheptatriene. Step 6 - Why other options fail: (b) cycloheptadiene would be the product after only one Hofmann elimination, not two. (c) N,N-dimethylcyclohexenylamine is not the final product C after complete elimination. (d) benzene is a six-membered ring and cannot result from a seven-carbon framework without loss of carbon. Therefore, the correct answer is A.