Woodward−Hoffmann Rule in the Light of the Principles of Maximum Hardness and Minimum Polarizability: DFT and Ab Initio SCF Studies

Abstract

Electrocyclic transformation between cis-butadiene and cyclobutene has been studied at the HF and DFT levels with 6-311G** basis sets. The disrotatory stationary point with two imaginary vibrational frequencies is associated with higher energy and polarizability values and a smaller hardness value in comparison to those of the symmetry-allowed conrotatory transition state for the thermolysis of cyclobutene. For cis-butadiene, the actual minimum energy structure is of C2 symmetry. cis-Butadiene and cyclobutene have energy and polarizability values lower than those of both stationary points, and the respective hardness values are higher than the stationary point hardness values.