The full molecular orbital correlation diagram is constructed in by matching pairs of symmetric and asymmetric MOs of increasing total energy, as explained above.
22.
Correlation diagrams, which connect the molecular orbitals of the reactant to those of the product having the same symmetry, can then be constructed for the two processes.
23.
This result can either be derived via an FMO analysis based upon the sign of p-orbital lobes of the HOMO of the polyene or with correlation diagrams.
24.
From a molecular orbital correlation diagram one can construct an electronic state correlation diagram that correlates electronic states ( i . e . ground state, and excited states ) of the reactants with electronic states of the products.
25.
From a molecular orbital correlation diagram one can construct an electronic state correlation diagram that correlates electronic states ( i . e . ground state, and excited states ) of the reactants with electronic states of the products.
26.
However, the state ES-1 does not correlate with the state ES-1'as the molecular orbitals do not transform into each other under the symmetry-requirement seen in the molecular orbital correlation diagram.
27.
These correlation diagrams indicate that only a conrotatory ring opening of 3, 4-dimethylcyclobutene is symmetry allowed whereas only a disrotatory ring opening of 5, 6-dimethylcyclohexa-1, 3-diene is symmetry allowed.
28.
Correlation diagrams are of no use in analyzing the conservation of orbital symmetry in sigmatropic rearrangements as there are, in general, only symmetry elements present in the transition state i . e . no conserved symmetry elements.
29.
The ground state ? 1 2 ? 2 2 of 1, 3-butadiene correlates with the ground state ? 2 ? 2 of cyclobutene as demonstrated in the MO correlation diagram above . ? 1 correlates with ? and ? 2 correlates with ?.
30.
If the ring opening of 3, 4-dimethylcyclobutene were carried out under photochemical conditions the resulting electrocyclization would be occur via a disrotatory mode instead of a conrotatory mode as can be seen by the correlation diagram for the allowed excited state ring opening reaction.
