Question

Hyperconjugation involves an overlap of which of the following orbitals?

• A. $\mathrm{\sigma }-\mathrm{\sigma }$
• B. $\mathrm{\sigma }-\mathrm{p}$
• C. $\mathrm{p}-\mathrm{p}$
• D. $\mathrm{\pi }-\mathrm{\pi }$

Answer 1

The correct option is B

$\mathrm{\sigma }-\mathrm{p}$

Explanation for the correct answer

Option (B) $\mathrm{\sigma }-\mathrm{p}$ :-

• The localization of the $\mathrm{\sigma }$ electrons in the $\mathrm{C}-\mathrm{H}$ bond of an alkyl group when it is connected directly to an atom in an unsaturated system or an atom with an unshared $\mathrm{p}$ orbital is known as the hyperconjugation effect.
• Hyperconjugation is the overlapping of the $\mathrm{\sigma }-\mathrm{p}$ orbitals.
• It is also known as no-bond resonance or $\mathrm{\sigma }-\mathrm{\pi }$ conjugation.
• It involves delocalization of $\mathrm{\sigma }$ and $\mathrm{\pi }$-bond orbitals.
• Hyperconjugation is a term used to describe the type of delocalization that involves a sigma bond orbital.
• Hence it is the correct option.

Explanation for incorrect answer

Option (A) $\mathrm{\sigma }-\mathrm{\sigma }$

• $\mathrm{\sigma }-\mathrm{\sigma }$ is the overlapping between both the $\mathrm{\sigma }$ orbitals.
• Hence it is an incorrect option.

Option (C) $\mathrm{p}-\mathrm{p}$

• $\mathrm{p}-\mathrm{p}$ is the overlapping between both $\mathrm{\pi }$ the orbitals.
• Hence it is an incorrect option.

Option (C) $\mathrm{\pi }-\mathrm{\pi }$

• $\mathrm{\pi }-\mathrm{\pi }$ is the overlapping between both $\mathrm{\pi }$ the orbitals.
• Hence it is an incorrect option.

Final answer:- Hyperconjugation is the overlapping of the $\mathrm{\sigma }-\mathrm{p}$ orbitals. Therefore, the correct answer is option B .