The chemical reactions which ocur in a single step via a cyclic transition state, bond making and bond breaking occurs simultaneously are known

The features are

1. Proceeds in single cyclic transition state.
2.Reactions not influenced by any solvent, reagent, structural changes, catalysts, etc.
3.These are highly stereospecific in nature.
4. These reactions are initiated either by heat or light. Such class of reactions are
called as pericyclic reactions.
Reactions are either carried out thermally or photochemically.