Question

Identify the overlapping orbitals involved in hyperconjugation from following.

• A. \(\sigma -p\)
• B. \(\pi -\pi\)
• C. \(\sigma -\sigma\)
• D. \(p-p\)

Hint:

In hyperconjugation a C-H sigma bond overlaps with an adjacent p orbital or pi system.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Hyperconjugation is the delocalisation of electrons of a C-H (or C-C) sigma bond on a carbon next to an unsaturated or electron-deficient centre.

Step 2: Overlap involved
The sigma orbital overlaps sideways with the adjacent empty or half-filled p orbital (carbocation, free radical) or with the p orbitals of a double bond.

Step 3: Name
It is therefore also called sigma-p (no-bond) resonance.

Final Answer:
The overlap in hyperconjugation is between a sigma orbital and a p orbital. \[ \boxed{\text{(A) }\sigma-p} \]