InterviewSolution
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InterviewSolution
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The enthalpy of hydrogenation of but `-1-` ene is `125.8 kJ mol^(-1)` but that of but `-2-` ene is nearly `120.0 kJ mol^(-1)`. How will justify ? |
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Answer» `gt C = C lt + H - H rarr gt underset(H)underset(|)(C) - underset(H) underset(|)(C) lt, DeltaH = - ve` (hydrogenation) As the enthalpy of hydrogenation of but `-2-` ene is less than of but `-1-`ene, this means that the former has lesser energy and is more stable than the latter. This is explained on the basis of hyper conjugation. In but `-2-`ene, six `alpha-`hydrogen atoms are available for hyper conjugation whereas in but `-1-` ene, there are only two `alpha-`hydrogen atoms present. This means that there is a greater delocalisation of charge in but `-2-` ene than in but `-1-` ene or the former is more stable `underset("But-2-ene")(H - underset(H)underset(|)overset(H)overset(|alpha)(C) - CH = CH - underset(H)underset(|)overset(H) overset(|alpha)(C) - H)" " underset("But-1-ene")(H_(3)C - underset(H)underset(|)overset(H)overset(|alpha)(C) - CH = CH_(2))` |
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