Gas-Phase Reactions of Aliphatic Alcohols with ‘Bare’ FeO+

Authors

  • Detlef Schröder,

    1. Institut für Organische Chemie der Technischen Universität Berlin, Strasse des 17. Juni 135, D–10623 Berlin
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  • Ralf Wesendrup,

    1. Institut für Organische Chemie der Technischen Universität Berlin, Strasse des 17. Juni 135, D–10623 Berlin
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  • Christoph A. Schalley,

    1. Institut für Organische Chemie der Technischen Universität Berlin, Strasse des 17. Juni 135, D–10623 Berlin
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  • Waltraud Zummack,

    1. Institut für Organische Chemie der Technischen Universität Berlin, Strasse des 17. Juni 135, D–10623 Berlin
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  • Helmut Schwarz

    Corresponding author
    1. Institut für Organische Chemie der Technischen Universität Berlin, Strasse des 17. Juni 135, D–10623 Berlin
    • Institut für Organische Chemie der Technischen Universität Berlin, Strasse des 17. Juni 135, D–10623 Berlin
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Abstract

Ion/molecule reactions of ‘bare’ FeO+ with linear and branched aliphatic alcohols have been examined by Fourier-transform ion-cyclotron resonance mass spectrometry. Depending on the chain length of the alcohol, three different types of reactions can be distinguished: (i) Oxidation of the alcohols in the α-positions, to yield the corresponding carbonyl-Fe+ complexes, involves an initial O[BOND]H bond activation of the alcohol resulting in the formation of RO[BOND]Fe+[BOND]OH as the central intermediate. (ii) The formation of Fe(OH)math image, concomitant by loss of the corresponding neutral alkenes, competes with the generation of neutral OFeOH and a carbocation R+. These couples point to the existence of an intracomplex acid-base equilibrium and are connected with each other by a proton transfer from either acid to the other, e.g. i-C3Hmath image + OFeOH⇄C3H6 + Fe(OH)math image. The process is driven by the Lewis acidity of FeO+ and starts with the abstraction of a hydroxide anion from the alcohol. (iii) For longer alcohols, e.g. pentanol, functionalization of non-activated C[BOND]H bonds which are remote from the O functionality is observed. Here, the OH group of the alcohol serves as an anchor, which directs the reactive metal-oxide cation toward a particular site of the hydrocarbon chain.

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