QJEEAdv08Ch095e: JEE Advanced 2008 Chemistry - Class 11 JEEAdv08Ch095e Solution: Hyperconjugation involves overlapping of the following orbitals:

Hyperconjugation effect is one of the type of permanent effect in which delocalisation of $$\sigma$$ electrons of C-H bond of an alkyl group directly attached to an atom of the unsaturated system or to an atom with an unshared p orbital. The main role of hyperconjugation is to stabilise the carbocation because it helps in the dispersal of positive charge. Higher the number of alkyl groups attached to a positively charged carbon atom, greater is the hyperconjugative effect and stability of carbonation. It generally involves the interaction of electrons in a C-H sigma orbital with nearby non-bonding p or anti-bonding $${\sigma }^{\ast }$$ or $${\pi }^{\ast }$$ orbitals to provide extended conjugation which further increases the stability of the carbocation. Sometimes, low lying anti-bonding $${\sigma }^{\ast }$$ also interact with filled orbitals of lone pair character. This type of conjugation is termed as negative hyperconjugation.