No abstract

The bond energy density analysis (Bond-EDA), which can evaluate bond energies in molecules by using the results of theoretical calculations, is applied to investigate chemical bonds in Diels–Alder (DA) reaction. Evaluation of the bond energies confirms the bond alternation in the reactant and product quantitatively, and shows that the TS structure is close to the reactant. In the case of regioselective reaction, local stabilities in newly formed bonds in the TS show significant differences, which correspond to the relationship of the bond distances.