JEE Main & Advanced Chemistry GOC Rearrangement Reactions

The reactions, which involve the migration of an atom or group from one site to another within the molecule (nothing is added from outside and nothing is eliminated) resulting in a new molecular structure, are known as rearrangement reactions. The new compound is actually the structural isomer of the original one.            

It is convenient to divide rearrangement reactions into following types:            

(1) Rearrangement or migration to electron deficient atoms (Nucleophilic rearrangement) : Those rearrangement reactions in which migrating group is nucleophilic and thus migrates to electron deficient centre which may be carbon, nitrogen and oxygen.

X = Nucleophilic species, Y = Electronegative group, B = Another nucleophile.   

(2) Rearrangement or migration to electron rich atoms (Electrophilic rearrangement) : Those rearrangement reactions in which migrating group is electrophile and thus migrates to electron rich centre.            

(3) Rearrangement or migration to free radical species (Free radical rearrangement) : Those rearrangement reactions in which the migrating group moves to a free radical centre. Free radical rearrangements are comparatively rare.            

(4) Aromatic rearrangement : Those rearrangement reactions in which the migrating group moves to aromatic nucleus. Aromatic compounds of the type (I) undergo rearrangements in the manner mentioned below,

The element X  from which group Y  migrates may be nitrogen or oxygen.