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Issue 2, 2013
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Tunneling control of chemical reactions: C–H insertion versus H-tunneling in tert-butylhydroxycarbene

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Abstract

Elusive tert-butylhydroxycarbene was generated in the gas phase via high-vacuum flash pyrolysis of tert-butylglyoxylic acid at 960 °C. The pyrolysis products were subsequently matrix isolated in solid Ar at 11 K and characterized by means of IR spectroscopy. While still being exposed to the harsh pyrolysis conditions, the hydroxycarbene undergoes CH-insertion to dimethylcyclopropanol, as well as a CC-insertion to novel methylbutenol, with activation barriers of 23.8 and 31.0 kcal mol−1, respectively. Once embedded in the cold Ar matrix, the carbene transforms to its isomer pivaldehyde not only by photolysis, but it also cuts through the barrier of 27.3 kcal mol−1 by quantum mechanical tunneling. The temperature independent half-life is measured as 1.7 h; the tunneling pathway was entirely blocked upon O-deuteration. The experimental half-life of tert-butylhydroxycarbene was verified by tunneling computations applying the Wentzel–Kramers–Brillouin formalism on the minimum energy path evaluated at the computationally feasible M06-2X/6-311++G(d,p) level of theory. Our experimental findings are supported by relative energy computations at the CCSD(T)/cc-pVDZ level of theory.

Graphical abstract: Tunneling control of chemical reactions: C–H insertion versus H-tunneling in tert-butylhydroxycarbene

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Publication details

The article was received on 19 Sep 2012, accepted on 25 Oct 2012 and first published on 25 Oct 2012


Article type: Edge Article
DOI: 10.1039/C2SC21555A
Chem. Sci., 2013,4, 677-684

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    Tunneling control of chemical reactions: C–H insertion versus H-tunneling in tert-butylhydroxycarbene

    D. Ley, D. Gerbig and P. R. Schreiner, Chem. Sci., 2013, 4, 677
    DOI: 10.1039/C2SC21555A

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