A 1,3-sigmatropic rearrangement is a type of chemical reaction where a sigma bond shifts between two atoms in a molecule. This process involves the migration of a substituent from one atom to another, typically within a cyclic or acyclic compound. The reaction is characterized by the movement of electrons and the formation of new bonds, while maintaining the overall structure of the molecule. In organic chemistry, 1,3-sigmatropic rearrangements are important for synthesizing complex molecules. They often occur under thermal conditions and can be facilitated by catalysts. Understanding these rearrangements helps chemists design reactions for creating specific compounds with desired properties.