Sigmatropic Rearrangements Definition:

A pericyclic reaction in which one s bond is formed at the expense of another.

Sigmatropic Rearrangements Explained:

Molecular rearrangements in which a Q-bonded atom or group, flanked by one or more pi-electron systems, shifts to a new location with a corresponding reorganization of the pi-bonds are called sigmatropic reactions. The total number of σ-bonds and pi-bonds remain unchanged.