|Chapter 10: Conjugation in Alkadienes and Allylic Systems|
Molecular Orbital Analysis of Ethene Dimerisation
|Again compare the phases of the orbitals in the HOMO
of one ethene molecule with the phases of the LUMO of the ethene
At one end there is a favourable bonding interaction (colours match) but there is an unfavourable anti-bonding interaction (colour mis-match) the other end.
Therefore the reaction is said to be a "symmetry forbidden" - interestingly, this reaction is rare and very slow !
A more complete analysis using molecular orbital methods (beyond our scope) can also explain:
|© Dr. Ian Hunt, Department of Chemistry, University of Calgary|