Configuration Interaction and the Woodward-Hoffmann Rules. 2. Sigmatropic Shifts

The Hückel-Hubbard theory is applied to thermal and photochemical [1,3], [1,4], [1,5], and [1,6] sigmatropic shifts. Inclusion of electron correlation is explicit in this treatment and gives considerably more detailed information than the usual molecular orbital theories. Qualitative differences in low-lying excited state surfaces of differing spin symmetry are found. These differences appear to be important in the observed photochemistry of 1,5-dienes.