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Benzocyclopropenyl Anion: A Stable 8pi-Electron Species
Lenora Moore1, Robin Lubinski, Michael C. Baschky
1Departments of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, and Ruder Boskovic Institute, P.O. Box 1016, 41001 Zagreb, Croatia.
Abstract:
The conjugate base of benzocyclopropene has been generated in the gas phase. Its reactivity and thermodynamic stability were explored. The measured acidity is DeltaH degrees (acid)(benzocyclopropene) = 386 +/- 3 kcal/mol, and the electron affinity of benzocyclopropenyl radical is 0.51 eV < EA < 1.11 eV. Ab initio calculations satisfactorily reproduce the experimental results and provide additional insights. Benzocyclopropene is found to be 34.5 kcal/mol more acidic than the allylic position of cyclopropene and only 4 +/- 3 kcal/mol less acidic than toluene. These findings are explained in terms of the structure and electronic properties of benzocyclopropenyl anion.