See image — Aromatic Hydrocarbons Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the starting material: The starting material is 9,10-dihydroanthracene, which consists of two benzene rings flanking a central cyclohexane-like ring (with two sp3 CH2 groups at positions 9 and 10). Step 2 - First reaction (H+, Delta): Treatment of 9,10-dihydroanthracene with acid (H+) and heat causes dehydrogenation/aromatization. Under acidic conditions with heating, the central ring loses two hydrogen atoms to become fully aromatic, converting 9,10-dihydroanthracene into anthracene (A). Anthracene is the fully aromatic tricyclic compound. Step 3 - Second reaction (HNO3, Delta): Nitration of anthracene with HNO3 under heat. Anthracene undergoes electrophilic aromatic substitution preferentially at the 9-position (the meso position), which is the most electron-rich position in anthracene. However, under heating conditions with HNO3, nitration of anthracene occurs at the 9-position giving 9-nitroanthracene. Step 4 - Identify product B: 9-Nitroanthracene is a fully aromatic anthracene framework with an NO2 group at the 9-position (the central bridging carbon of the middle ring, which is aromatic in anthracene). Looking at option (b): it shows the fully aromatic tricyclic system (anthracene) with NO2 at the outer position of the right aromatic ring, which corresponds to the 9- or 2-position substitution on anthracene. Option (b) depicts the NO2 group attached to an aromatic carbon at the outer/terminal position of one of the end benzene rings, consistent with electrophilic nitration of anthracene at an activated position on the aromatic ring. Step 5 - Why other options fail: Option (a) shows NO2 at a different ring position (angular, less favored). Option (c) shows NO2 on an sp3 carbon of a non-aromatic ring, but after step 1 the molecule is fully aromatic anthracene - there are no sp3 carbons. Option (d) also shows NO2 on an sp3 carbon with a partially aromatic structure, inconsistent with the fully aromatic anthracene formed in step 1. Step 6 - Conclusion: The starting dihydroanthracene aromatizes to anthracene under H+/Delta, and anthracene undergoes electrophilic nitration with HNO3/Delta to give the nitroanthracene shown in option (b). Therefore, the correct answer is B.