Increasing order of reactivity of the following compounds for S_{N}1  substitution is :

  • Option 1)


  • Option 2)


  • Option 3)


  • Option 4)


Answers (1)


Mesomeric or Resonance effect -

Migration of lone pair or \pielectron in a conjugated system.

- wherein

It is a permanent effect



Stability due to resonance -

More the no of resonating structure more is the stability.

- wherein






Hyperconjugation or σ-π resonance or Baker and Nathan effect -

The conjugation between \alpha C-H sigma bond and adjacent  multiple bond or carbocation is called Hyperconjugation.

- wherein

It is permanent effect.




Application of Hyperconjugation -

More is the no of Hyperconjugation  structure more is the stability of carbocation

- wherein









order \Rightarrow\:\:\:\:b<a<d<c

1^0 < 3^0

+M>delocalisation >3^{0}>1^{0}

Option 1)


Option 2)


Option 3)


Option 4)