title: Why 6-methylpentacene deconjugates but avoids the thermally allowed unimolecular mechanism.
abstract: [reaction: see text] Tautomeric equilibria involving hydrogen migration in methylacenes were explored computationally using DFT methods. As the aromatic system becomes more extended, the methylene isomer is predicted to become favored. Reasonable-looking pericyclic sigmatropic hydrogen shifts are found to be energetically prohibitive, and bimolecular mechanisms involving radical pair intermediates are energetically feasible.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Norton
authors.forename: Brian H
authors.initials: BH
authors.lastname: Northrop
authors.forename: Colin
authors.initials: C
authors.lastname: Nuckolls
authors.forename: K N
authors.initials: KN
authors.lastname: Houk