Pericyclic Reactions OP Agarwal notes.pdf

### Pericyclic Reactions **Definition:** - A class of organic reactions that proceed via a concerted mechanism involving cyclic transition states. **Types:** 1. **Cycloaddition:** - Two π-systems combine to form a ring. - Example: Diels-Alder reaction, forming a six-membered ring. 2. **Electrocyclic Reactions:** - A conjugated π-system converts to a ring or vice versa. - Example: Ring closure of hexatriene to form cyclohexadiene. 3. **Sigmatropic Rearrangements:** - Migration of a σ-bond along with a shift in π-electrons. - Example: Cope rearrangement. 4. **Group Transfer Reactions:** - Transfer of a group from one part of the molecule to another. - Example: Ene reaction. **Characteristics:** - Stereospecific, governed by orbital symmetries (Woodward-Hoffmann rules). **Applications:** - Synthesis of complex molecules, including natural products and pharmaceuticals. Understanding pericyclic reactions is crucial for advanced organic synthesis and mechanistic organic chemistry.