Geometric Isomerism: The Simplest Illustrator of Orbital Symmetry Control of Molecular Stereochemistry

  • Nicolaos Demetrios Epiotis
Part of the Lecture Notes in Chemistry book series (LNC, volume 34)


The thermal conversion of 1,3-butadiene to cyclobutene may occur in a conrotatory or a disrotatory fashion. In the former case, an axis of symmetry is maintained along the reaction coordinate while in the latter case a plane of symmetry is preserved during the conversion or reactants to products. This difference with respect to the existing symmetry elements becomes responsible for a difference in the symmetry labels of reactant and product orbitals. In turn, this becomes responsible for the existence of a barrier in the case of disrotation and the absence of a barrier in the case of conrotation at the level of Hückel MO theory. This is clearly revealed by the Longuet-Higgins-Abrahamson-Woodward-Hoffmann MO correlation diagrams1 for con- and dis-rotatory ring closure of 1,3-butadiene. The conrotatory ring closure of 1,3-butadiene is termed a symmetry “allowed” and the disrotatory ring closure of the same molecule is termed a “forbidden” reaction.


Trans Isomer Orbital Symmetry Sigma Bond Symmetry Label Electronegative Ligand 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1983

Authors and Affiliations

  • Nicolaos Demetrios Epiotis
    • 1
  1. 1.Department of ChemistryUniversity of WashingtonSeattleUSA

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