See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Concept: Corannulene (C20H10) is a fully aromatic polycyclic hydrocarbon consisting of a central cyclopentadienyl ring surrounded by five fused benzene rings, giving it a bowl-shaped structure. The synthesis involves dehydrogenation (aromatization) of a partially saturated precursor using Pd/C under heat. Step 1 - Identify the starting material: The starting material shown is a partially saturated corannulene precursor. It contains the lower aromatic portion (acenaphthylene-like fused rings forming part of the corannulene skeleton) but has two saturated six-membered rings (cyclohexane rings) at the top, connected by a saturated bridge. This is a dihydro or tetrahydro precursor of corannulene. Step 2 - Reaction with Pd/C and heat: Pd/C at elevated temperature is a classic condition for catalytic dehydrogenation/aromatization. The saturated rings lose hydrogen to become aromatic benzene rings. The CH2-CH2 bridges become part of the aromatic framework. Step 3 - Count atoms: The starting material appears to be C20H14 or similar (corannulene precursor with extra H2 units). Dehydrogenation removes H2 molecules to give C20H10 (corannulene). Step 4 - Identify the product structure: Corannulene (C20H10) consists of one central five-membered ring fused to five six-membered aromatic rings around its periphery. This matches option (a), which shows a fully aromatic structure with circles in all rings - the central pentagon surrounded by 5 hexagons, all aromatic. Step 5 - Eliminate other options: - Option (b) shows fewer rings or incomplete aromatization - not fully consistent with C20H10 corannulene's complete structure. - Option (c) shows saturated rings remaining - this would be an intermediate, not the final fully aromatic corannulene. - Option (d) shows a similar but structurally different arrangement that does not correctly represent corannulene's topology. Option (a) correctly depicts corannulene with the central five-membered ring surrounded by five fully aromatic six-membered rings, consistent with C20H10 and the known structure of corannulene. Therefore, the correct answer is A.