The experimental heat of hydrogenation of cyclohexene is kcal/mol. If benzene were a hypothetical 'cyclohexatriene' with localized double bonds, its expected heat of hydrogenation would be kcal/mol. G

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 $3 	imes (-28.6) = -85.8$ kcal/mol. Given that the actual heat of hydrogenation of benzene is $-49.8$ kcal/mol, what is the resonance energy of benzene?

Prashant Kotian · Accepted Answer

Correct answer: A. 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 = kcal/mol. Actual = kcal/mol. Difference = kcal/mol. This missing energy represents the stabilization due to resonance.

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