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Dimethyl Peroxide Radical Cation: A New Theoretical and Experimental Approach to the C2H6O•+2 Potential Energy Surface

Authors

  • Christoph A. Schalley,

    1. Institut für Organische Chemie der Technischen Universität Berlin Straße des 17. Juni 135, D-10623 Berlin (Germany) Telefax: Int. code +(30)314-21102 e-mail: schw0531@zrzsp5.chem.tu-berlin.de
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  • Andreas Fiedler,

    1. Institute for Molecular Sciences, Myodaiji, 444 Okasaki (Japan)
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  • Georg Hornung,

    1. Institut für Organische Chemie der Technischen Universität Berlin Straße des 17. Juni 135, D-10623 Berlin (Germany) Telefax: Int. code +(30)314-21102 e-mail: schw0531@zrzsp5.chem.tu-berlin.de
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  • Ralf Wesendrup,

    1. Institut für Organische Chemie der Technischen Universität Berlin Straße des 17. Juni 135, D-10623 Berlin (Germany) Telefax: Int. code +(30)314-21102 e-mail: schw0531@zrzsp5.chem.tu-berlin.de
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  • Detlef Schröder,

    1. Institut für Organische Chemie der Technischen Universität Berlin Straße des 17. Juni 135, D-10623 Berlin (Germany) Telefax: Int. code +(30)314-21102 e-mail: schw0531@zrzsp5.chem.tu-berlin.de
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  • Helmut Schwarz

    1. Institut für Organische Chemie der Technischen Universität Berlin Straße des 17. Juni 135, D-10623 Berlin (Germany) Telefax: Int. code +(30)314-21102 e-mail: schw0531@zrzsp5.chem.tu-berlin.de
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Abstract

The structure and the unimolecular fragmentations of the metastable dimethyl peroxide radical cation have been investigated by mass spectrometric and isotopic labeling methods as well as high-level ab initio calculations. In line with the theoretical results, neutralization-reionization and charge reversal experiments suggest that ionized dimethyl peroxide bears a CH3OOCH3 connectivity. In the cation the O-O bond dissociation energy is larger than that of the neutral counterpart; in contrast, the C-O bond strength is slightly and that of the C-H bond significantly reduced upon ionization. These energetic changes upon one-electron oxidation of CH3OOCH3 are also reflected in the NR and CR mass spectra of CH3OOCH•+3. Further, for metastable CH3OOCH3 two major fragmentation pathways are observed: 1) Loss of a hydrogen atom by cleavage of a C-H bond is associated with a skeletal reorganization, which gives rise to a proton-bound formaldehyde dimer. 2) The expulsion of a CH3O radical leads to protonated formaldehyde in a surprisingly specific double hydrogen transfer involving a [CH3OH/CH2O] ion/dipole complex as central intermediate; this complex also accounts for other minor fragmentation channels. The structures of intermediates and transition states are calculated with the BECKE 3LYP density-functional method employing a 6-311++G** basis.

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