title: The iconoclastic dynamics of the 1,2,6-heptatriene rearrangement.
abstract: CASSCF(8,8)/6-31G* and AM1-SRP direct dynamics trajectory calculations have been run on the rearrangement of 1,2,6-heptatriene to 3-methylene-1,5-hexadiene. They show that the experimental results of Roth et al. on this reaction can be explained without the need to invoke a concerted, pericyclic mechanism. Instead, bifurcation occurs at the transition state for conversion of the reactant to 2-methylenecyclohexane-1,4-diyl. Some trajectories leaving the transition state do enter the PES local minimum for the intermediate, but others, differing only in the phases of the real-frequency vibrational modes, bypass the intermediate and proceed over a second transition state to the product. A significant fraction of the trajectories that do enter the biradical local minimum proceed on to the product in <500 fs, despite the fact that the minimum is some 12 kcal/mol deep at the CASSCF level. This nonstatistical behavior seems to be due in part to a resonance between key C-H bending and C-C stretching vibrations in the intermediate.
authors.affiliation: Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA.
authors.forename: Stefan L
authors.initials: SL
authors.lastname: Debbert
authors.forename: Barry K
authors.initials: BK
authors.lastname: Carpenter
authors.forename: David A
authors.initials: DA
authors.lastname: Hrovat
authors.forename: Weston Thatcher
authors.initials: WT
authors.lastname: Borden