title: Stone-Wales Rearrangements in Hydrocarbons: From Planar to Bowl-Shaped Substrates.
abstract: Carbene, cyclobutyl, and potential diradical mechanisms were studied computationally for Stone-Wales rearrangements in several derivatives of as-indacene and pyracyclene, including cyclopent[hi]acephenanthrylene, dicyclopenta[cd,fg]pyrene, corannulene, diindeno[1,2,3,4-defg;1',2',3',4'-mnop]chrysene, and semibuckminsterfullerene. At the UM06-2X/cc-pVDZ and BD(T)/cc-pVDZ//UM06-2X/cc-pVDZ levels of theory, free energies of reaction reveal that transformations involving an increase in curvature are thermodynamically unfavorable. In addition, the carbene transition states or intermediates (corrected to 1000 °C) are generally around 100-120 kcal/mol higher than starting substrates, except for as-indacene (80 kcal/mol), which is the only process considered here that is predicted to have a barrier accessible under typical flash vacuum pyrolysis conditions. For pyracyclene derivatives, the relative free energy of cyclobutyl intermediates rises steadily with increasing curvature of the substrate and increasing annelation. Singlet acetylenic diradicals related to pyracyclene, diindenochrysene, and semibuckminsterfullerene are predicted to be second- or higher-order saddle points that lie more than 40 kcal/mol higher than the corresponding carbenes and cyclobutyl intermediates.
authors: Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117 United States.
authors: Erica E
authors: EE
authors: Irace
authors: Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117 United States.
authors: Evangelina
authors: E
authors: Brayfindley
authors: Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117 United States.
authors: Gail A
authors: GA
authors: Vinnacombe
authors: Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117 United States.
authors: Claire
authors: C
authors: Castro
authors: Department of Chemistry and ‡Department of Environmental Science, University of San Francisco , 2130 Fulton Street, San Francisco, California 94117 United States.
authors: William L
authors: WL
authors: Karney