Stone–Wales Rearrangements
in Polycyclic Aromatic
Hydrocarbons: A Computational Study
Evangelina Brayfindley
Erica E. Irace
Claire Castro
William L. Karney
10.1021/acs.joc.5b00066.s001
https://acs.figshare.com/articles/journal_contribution/Stone_Wales_Rearrangements_in_Polycyclic_Aromatic_Hydrocarbons_A_Computational_Study/2175502
Mechanisms for Stone–Wales
rearrangements (SWRs) in polycyclic
unsaturated hydrocarbons containing a pentafulvalene core have been
studied using density functional, coupled cluster, and multiconfigurational
methods. At the BD(T)/cc-pVDZ//(U)M06-2X/cc-pVDZ level of theory,
free energies of activation (at 1000 °C) range from ca. 70 kcal/mol
for the model system pentafulvalene → naphthalene (<b>1</b> → <b>2</b>) to >110 kcal/mol for the degenerate
SWR
of pyracyclene (<b>3</b>). Systems studied that do not contain
a pyracyclene subunit are predicted to have Δ<i>G</i><sup>⧧</sup> less than about 90 kcal/mol and to proceed by
a carbene-type mechanism. Substrates containing a pyracyclene subunit
should proceed via a cyclobutyl mechanism, and appropriate benzannelation
of <b>3</b> lowers the activation free energy considerably.
Computed Δ<i>G</i><sup>⧧</sup> values are consistent
with experimental observations reported for known systems. SWRs of
two untested substrates, cyclopent[<i>fg</i>]aceanthrylene
(<b>18</b>) and dicyclopenta[<i>fg</i>,<i>op</i>]tetracene (<b>21</b>), are predicted to have Δ<i>G</i><sup>⧧</sup> < 95 kcal/mol and thus to be accessible
via flash vacuum pyrolysis.
2015-04-17 00:00:00
BD
activation
Polycyclic Aromatic Hydrocarbons
kcal
pentafulvalene
pyracyclene subunit
flash vacuum pyrolysis
SWR
mechanism