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Chemistry LibreTexts

Pericyclic Reaction

[ "article:topic", "pericyclic reaction", "authorname:ggunawardena" ]
  • Page ID
    40862
  • A pericyclic reaction is a concerted reaction in which the number of rings in the transition state is greater than the total number of rings in the reactant molecules.

    eg: Cope Rearrangement

    Mechanism

    • # covalent bonds broken = 3
    • # covalent bonds formed = 3
    • # covalent bonds broken + # covalent bonds formed = 3 + 3 = 6
    • # steps = 1

    Thus, the reaction is a concerted reaction. The transition state of the reaction can be drawn roughly as follows.

    • # rings in the reactant molecule = 0
    • # rings in the transition state = 1
    • # rings in the transition state > # rings in the reactant molecule

    Thus, the reaction is a pericyclic reaction. For more examples of pericyclic reactions, see Cope elimination, Claisen rearrangement, Diels-Alder reaction