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Energy estimation of the hydrogenation of alkenes with metal catalysts.

By considering the binding and dissociation energies, it is possible to estimate the energy of the reaction.

Energy estimation
Breaking the alkene π bond 276 kJmol-1
Breaking the H2 σ bond 435 kJmol-1
Generation of two new C-H σ bonds -837 kJmol-1
Total energy difference 276+435-837 = -126 kJmol-1

This accounts for the following values:

Calculated heat of hydrogenation
Ethylene 136.9 kJmol-1
Propene 125.6 kJmol-1
Trans-2-butene 115.6 kJmol-1
Cis-2-butene 119.7 kJmol-1