Definition of migration

1. (1) The (usually intramolecular) transfer of an atom or group during the course of a molecular rearrangement.

   (2) The movement of a bond to a new position, within the same molecular entity, is known as "bond migration".

   Allylic rearrangements, e.g.,

   RCH=CHCH2X RCH(X)CH=CH2

   exemplify both types of migration.