The enthalpy of hydrogenation of benzene is -49.8 kcal/mol while its resonance energy is 36.0 kcal/mol. The enthalpy of hydrogenation of cyclohexadiene and cyclohexene is -58 kcal/mol and -29 kcal/mol

Question

The enthalpy of hydrogenation of benzene is -49.8 kcal/mol while its resonance energy is 36.0 kcal/mol. The enthalpy of hydrogenation of cyclohexadiene and cyclohexene is -58 kcal/mol and -29 kcal/mol, respectively, what is the resonance energy of benzene?

Prashant Kotian · Accepted Answer

Correct answer: B. Theoretical hydrogenation (3 isolated double bonds) = 3*(-29) = -87 kcal/mol. Actual = -49.8 kcal/mol. Resonance energy = -49.8 - (-87) = 37.2 kcal/mol. (Book answer key: b = -28.6 kcal — as printed.)

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