See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

Concept: Resonance energy (delocalization energy) is the difference between the theoretical heat of hydrogenation (assuming no aromatic stabilization) and the actual experimental heat of hydrogenation. Step 1: Determine the number of double bonds in anthracene. Anthracene is a tricyclic aromatic compound with the molecular formula C14H10. It contains 7 formal double bonds (or equivalently, it can be drawn with 5 C=C double bonds in a Kekule structure, but for the purpose of hydrogenation to perhydroanthracene, the total H2 consumed corresponds to reducing all pi bonds). Anthracene has 5 double bonds in its Kekule structure (it requires 5 equivalents of H2 to fully hydrogenate to perhydroanthracene, giving C14H24 from C14H10, a gain of 14 H atoms = 7 H2). Wait, let me recount: C14H10 + x H2 -> C14H24, so x = (24-10)/2 = 7. Anthracene requires 7 H2 molecules. Step 2: Calculate the theoretical (non-aromatic) heat of hydrogenation. If anthracene had 7 isolated double bonds (like cyclohexene), the expected heat of hydrogenation would be: 7 x (-28.6 kcal/mol) = -200.2 kcal/mol Step 3: The actual heat of hydrogenation is -116.2 kcal/mol. Step 4: Calculate resonance energy. Resonance energy = |Theoretical Delta H| - |Actual Delta H| = 200.2 - 116.2 = 84.0 kcal/mol Step 5: Why other options fail. - (b) 100 kcal/mol would correspond to a different number of double bonds or different reference value. - (c) 110 kcal/mol and (d) 116 kcal/mol do not match the calculation. The resonance energy of anthracene = 200.2 - 116.2 = 84 kcal/mol. Therefore, the correct answer is A.