Question

Find the heat of hydrogenation of cyclohexene if the heat of hydrogenation of benzene is 51 kcal `mol^(-1)` and its resonance energy is `36 kcal mol^(-1)`
A. 15 `kcalmol^(-1)`
B. 29 kcal `mol^(-1)`
C. 33 kcal `mol^(-1)`
D. 36 kcal `mol^(-1)`

Answer 1

Correct Answer - 2
Let us assume that `Delta_(h)H^(ɵ)` of cyclohexene is a kcal `mol^(-1)` the heat of hydrogenation of hypothetical cyclohexatriene containing three `C=C` bonds should be `3a` kcal `mol^(-1)` It should be equal to `Delta_(h)H^(ɵ)` of benzene plus its resonance energy. thus,
`3a=51+36=87`
`a=(87)/(3)=29kcalmol^(-1)`