Femtosecond Dynamics of Norrish Type-II Reactions: Nonconcerted Hydrogen-Transfer and Diradical Intermediacy.
Norrish type-II and McLafferty rearrangements, which both involve an intramolecular transfer of a gamma H atom, can be differentiated on the femtosecond time scale. The McLafferty rearrangement results in ion fragmentation of the parent ketone, whereas the Norrish type-II reaction leads to a diradical species, which then either cyclizes or fragments (see scheme). For Norrish type-II reactions, the reaction time for the transfer of the hydrogen atom is within 70 - 90 fs, and the lifetime of the diradical intermediate is in the range of 400 - 700 ps at the total energy studied.
De Feyter S
Arthur Amos Noyes Laboratory of Chemical Physics California Institute of Technology Pasadena, CA 91125 (USA).
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