Increasing order of reactivity of the following compounds for substitution is :
Mesomeric or Resonance effect -
Migration of lone pair or electron in a conjugated system.
It is a permanent effect
Stability due to resonance -
More the no of resonating structure more is the stability.
Hyperconjugation or σ-π resonance or Baker and Nathan effect -
The conjugation between sigma bond and adjacent multiple bond or carbocation is called Hyperconjugation.
It is permanent effect.
Application of Hyperconjugation -
More is the no of Hyperconjugation structure more is the stability of carbocation