Nonclassical aryl radicals: Intermediates or transition states for the hydrogen shift reactions?
- Florida State Univ., Tallahassee, FL (United States)
Electronic properties of aryl radicals obtained by removing single hydrogen atoms from the sterically congested regions of benzo[c]phenanthrene, biphenyl, triphenylene, phenanthrene, and perylene are studied at the UBLYP/6-311G** level of theory. Two structures are considered by each radical, the classical one involving a C-H{hor_ellipsis}C arrangement of atoms and the nonclassical one possessing a three-center C-H-C linkage. The five nonclassical radicals under study are found to be transition states for degenerate 1,4- and 1,5-hydrogen shift reactions that interconvert the classical species. However, the results of the present calculations indicate that the nonclassical structures with the C-H distances in the C-H-C linkages shorter than 1.34 {angstrom} should be energy minima representing potentially observable chemical systems. The predicted energy barrier to the 1,5-hydrogen shift in the 1-benzo[c]phenanthrenyl radical is only 9.3 kcal/mol with the zero-point energies included, making the hydrogen migration in this system facile at relatively low temperatures. Rigorous analysis of the computed electronic wave functions provides a clear-cut picture of bonding in both the classical and nonclassical aryl radicals. 2 figs., 4 tabs.
- DOE Contract Number:
- FG05-95ER14523
- OSTI ID:
- 401726
- Journal Information:
- Journal of Organic Chemistry, Vol. 61, Issue 12; Other Information: PBD: 14 Jun 1996
- Country of Publication:
- United States
- Language:
- English
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