Miles N. Braten,Claire Castro,*Rainer Herges,*Felix Köhler, and
William L. Karney*
Departments of Chemistry and Environmental Science, University of San Francisco, 2130 Fulton Street,
San Francisco, California 94117, and Otto-Diels Institut für Organische Chemie, Universität Kiel,
D-24118 Kiel, Germany
A new global minimum for [12]annulene has been computationally located. This mono-trans minimum
5 (CCCCCT) is computed to be 1.5 kcal/mol more stable (CCSD(T)/cc-pVDZ//BHHLYP/6-311+G**)
than the known tri-trans isomer 1 (CTCTCT) and 2.4 kcal/mol lower than the di-trans isomer 4 (CCTCCT),
for which there is indirect evidence. The barriers for several rearrangements of 5 were all computed to
be above 15 kcal/mol, indicating that direct experimental characterization of 5 should be possible. The
computed barriers for the dynamic processes (including conformational automerization) coupled with
computed 1H NMR shift values should aid in the future characterization of this [12]annulene isomer.
