2 research outputs found

    Theoretical Investigation of the Gas-Phase Reaction of CrO<sup>+</sup> with Propane

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    Transition metal oxide cations (e.g., MO<sup>+</sup>) have been shown to oxidize small alkanes in the gas phase. The chromium oxide cation is of particular interest because it is more reactive than oxides of earlier transition metals but is more selective than oxides of later transition metals. The reaction of CrO<sup>+</sup> with propane has been shown to produce a number of products: propanol, propene, ethene, and hydrogen. Few theoretical studies exist for reactions of simple transition metal oxide cations with larger alkanes. We have analyzed the potential energy surfaces associated with the reaction of CrO<sup>+</sup> with propane using two DFT methods, B3LYP and M06-L. Energetically viable reaction paths leading to each experimentally observed product have been characterized. Each reaction path begins with formation of a reactive intermediate in which either an α- or β-hydrogen from propane is extracted by the oxygen atom of CrO<sup>+</sup>. While pathways leading to formation of hydrogen and ethene were found to occur on a single spin surface, energetically viable pathways to forming propanol and propene require a transition from the quartet spin surface to the sextet surface. The minimum-energy crossing points between the quartet and sextet surfaces were found to be well below the energy level of the reactants and structurally resemble the initial reactive intermediates

    Simple Mechanism for the Dimerization of Ethylene by Gas-Phase CrOH<sup>+</sup>

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    Dimerization of ethylene by gas-phase chromium hydroxide (CrOH<sup>+</sup>) has been experimentally observed. Recent theoretical work suggests the most likely mechanism associated with this process involves formation of a metallacycle intermediate and involves two spin-inversion processes. We propose a different mechanism that involves the formation of a chromium-aqua complex. While the energetics of this new mechanism are similar to previously proposed mechanisms, all intermediates and transition states remain on the same spin surface as both the reactants and products
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