Electronic Transition Expected in Ethene

Electronic Transition Expected in Ethene

Electronic Transition Expected in Ethene


Electronic Transition Expected in C2H4

The energy order of molecular orbitals of ethene is shown below-
Electronic Transition Expected in Ethene
When ethene is exposed to uv-vis light (200-750nm), the electron goes from lower filled to higher vacant molecular orbitals by absorbing energy equal to the energy gap between these two molecular orbitals leading to σ → σ*, π → σ* & π → π* transitions.


We know that σ-bonds are very strong, so the excitation of σ-electron is very difficult because σ → σ* transition involves a high energy process. Therefore, it can be observed in far uv region (> 200 nm).
π → σ* & σ → ℼ* transitions are symmetry forbidden transitions. So, the only allowed transition in ethene is π → π* transition which occurs at ~ λmax value 170 nm. π → π* transition occurs with high probability as both π → π* orbitals lie in xz plane.


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