Migratory aptitude

Migratory aptitude is the relative ability of a migrating group to migrate in a rearrangement reaction. This can be affected by the leaving group (whichever gives a more stable carbocation)depends upon the electron density of the migrating group i.e. Hydride > Phenyl = Tert-Alkyl > Sec-Alkyl > Primary Alkyl > Methyl

The migratory groups follow the order of increasing stability of carbocation instead of carbanion.