Analysing the symmetry of the reactant molecular orbitals
· We now follow the same procedure for the basic Diels-Alder reaction as we did for the cycloaddition of 2 ethene molecules.
· We consider the MO diagram of the active MOs in the reactants and in the products and draw a correlation diagram -- with conservation of orbital symmetry.
Molecular orbitals of reactants
Lowest 3 MOs of reactants (butadiene +ethene):