title: Understanding the Woodward-Hoffmann rules by using changes in electron density.
abstract: The Woodward-Hoffmann rules for pericyclic reactions are explained entirely in terms of directly observable physical properties of molecules (specifically changes in electron density) without any recourse to model-dependent concepts, such as orbitals and aromaticity. This results in a fundamental explanation of how the physics of molecular interactions gives rise to the chemistry of pericyclic reactions. This construction removes one of the key outstanding problems in the qualitative density-functional theory of chemical reactivity (the so-called conceptual DFT). One innovation in this paper is that the link between molecular-orbital theory and conceptual DFT is treated very explicitly, revealing how molecular-orbital theory can be used to provide "back-of-the-envelope" approximations to the reactivity indicators of conceptual DFT.
authors.affiliation: Department of Chemistry, McMaster University, Hamilton, Ontario, L8S 4M1, Canada. ayers@mcmaster.ca
authors.forename: Paul W
authors.initials: PW
authors.lastname: Ayers
authors.forename: Christophe
authors.initials: C
authors.lastname: Morell
authors.forename: Frank
authors.initials: F
authors.lastname: De Proft
authors.forename: Paul
authors.initials: P
authors.lastname: Geerlings