What is Hyperconjugation and inductive effect?

What is Hyperconjugation and inductive effect?

Aug 26, 2022, 16:45 IST

Hyperconjugation (Baker and Nathan Effect):

Shifting of σ electrons induces resonance in rest of the molecule. The delocalization of σ and π bond orbitals is called hyperconjugation.

In the resonating structures, there is no definite bond between carbon atom and one of the hydrogen atoms, hence hyperconjugation is also known as no−bond resonance.

Applications of hyperconjugation effect:

1. Stability of alkenes: More number of methyl groups attached to double bonded carbon atom more would be the stability of alkene.

CH ₂ = CH ₂ < CH ₃ – CH = CH ₂ < (CH ₃ ) ₂ C = CH ₂

No hyperconjugation 3 hyperconjugation 6 hyperconjugation

structures structures structures

2. Stability of carbonium ions: More number of hyperconjugation structures of the carbocation more will be its stability.

tert–butyl > isopropyl > ethyl

9 hyperconjugation 6 hyperconjugative 3 hyperconjugation

structures structures structures

3. Bond lengths: The bond length in a molecule changes if there is hyperconjugation. In , the C ₁ −C ₂ bond length is found to be more than 1.34 (normal C = C bond length) while the C ₂ −C ₃ bond distance is less than 1.54 (normal C – C bond length).

4. Directive influence of the group: +M effect of methyl group in toluene is due tohyperconjugation.

Due to hyperconjugation, there are nine different structures having negative charge at ortho and para positions. Hence, + M effect of alkyl group attached to benzene ring follows the order: .

In the same way, the meta directing influence and deactivating effect of –CCl ₃ group in benzotrichloride can be explained on the basis of hyperconjugation as follows,

Due to low electron density at ortho and para positions, the meta position becomes point of high electron density, hence electrophilic substitution takes place in meta position.

Physics Wallah Chemistry Doubts page consist of more questions for reference.

Hyperconjugation and inductive effect pdf