Question -
Answer -
When an alkyl groupis attached to a π system, it acts as an electron-donor group by theprocess of hyperconjugation. To understand this concept better, let us take theexample of propene.
In hyperconjugation, thesigma electrons of the C–H bond of an alkyl group are delocalised. This groupis directly attached to an atom of an unsaturated system. The delocalisationoccurs because of a partial overlap of a sp3 –s sigmabond orbital with an empty p orbital of the π bondof an adjacent carbon atom.
The process ofhyperconjugation in propene is shown as follows:
This type of overlapleads to a delocalisation (also known as no-bond resonance) ofthe π electrons, making the molecule more stable.
