Pericyklické

Pericyklické is a term used in organic chemistry to describe a class of concerted reactions that proceed through a cyclic transition state. These reactions involve the reorganization of electrons in a cyclic array of atoms, leading to the formation of new bonds and the breaking of old ones. The key characteristic of pericyclic reactions is their stereospecificity and regioselectivity, meaning they often produce a single stereoisomer or regioisomer as the primary product. This predictable outcome is a consequence of the symmetry of the molecular orbitals involved in the transition state.

Common examples of pericyclic reactions include the Diels-Alder reaction, the ene reaction, the sigmatropic rearrangement, and electrocyclic reactions. These reactions are often catalyzed by heat or light, which provide the necessary activation energy to overcome the energy barrier of the cyclic transition state. The Woodward-Hoffmann rules are a set of theoretical guidelines used to predict the feasibility and stereochemical outcome of pericyclic reactions based on the number of pi electrons involved and whether the reaction is thermally or photochemically induced. Understanding pericyclic reactions is crucial for synthetic organic chemists, as they offer powerful and efficient methods for constructing complex molecular architectures with precise control over stereochemistry.