Along the disrotatory pathway, the ground state and excited state PES do not come close (Fig. , left). The close presence of the CI in the conrotatory pathway (Fig. , right) can be qualitatively understood within the molecular orbital picture of the Woodward-Hoffmann rules (see Fig. ): Along the conrotatory pathway, the ππ ground state electron configuration of the product correlates with the electron configuration of the π * π * state and vice versa. Thus, they must cross somewhere along this pathway. Conversely, the electron configuration of the product along the disrotatory pathway represents a change in the energetic ordering of two occupied orbitals in the reactant ground state and vice versa.