The experimental heat of hydrogenation of cyclohexene is kcal/mol. If benzene were a hypothetical 'c — Aromatic Hydrocarbons Chemistry Question
Question
The experimental heat of hydrogenation of cyclohexene is $-28.6$ kcal/mol. If benzene were a hypothetical 'cyclohexatriene' with localized double bonds, its expected heat of hydrogenation would be $3 \times (-28.6) = -85.8$ kcal/mol. Given that the actual heat of hydrogenation of benzene is $-49.8$ kcal/mol, what is the resonance energy of benzene?
Answer: A
💡 Solution & Explanation
Resonance energy is the difference between the theoretical energy of the most stable localized structure (Kekule structure) and the actual energy of the resonance hybrid. Expected heat of hydrogenation = $85.8$ kcal/mol. Actual = $49.8$ kcal/mol. Difference = $85.8 - 49.8 = 36.0$ kcal/mol. This missing energy represents the stabilization due to resonance.
💬Ask on WhatsApp →
Still have doubts about this question?
Send it to our AI chemistry tutor on WhatsApp — gets answered in minutes