The migratory aptitude of phenyl group increases with electron donating groups
Generation of Carbonium ion
Benzilic acid rearrangement -Diketones undergo a rearrangement when treated with hydroxide ion, giving -hydroxyacids.
Rearrangement to Electron-deficient Nitrogen
Hofmann rearrangement- A carboxylic acid amide is treated with sodium hypobromite, or bromine in alkali. The N-bromo-amide is formed and reacts with the base to give its conjugate base within which rearrangement occurs.
Migration to Electron-Deficient Oxygen- The Baeyer-Villiger Oxidation