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Issue 16, 2012
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Hydrogen tunnelling influences the isomerisation of some small radicals of interstellar importance. A theoretical investigation

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Abstract

Hydrogen atom isomerisations within five radical systems (i.e., CH3˙NH/˙CH2NH; CH3O˙/˙CH2OH; ˙CH2SH/CH3S˙; CH3CO2˙/˙CH2CO2H; and HOCH2CH2O˙/HO˙CHCH2OH) have been studied via quantum-mechanical hydrogen tunnelling through reaction barriers. The reaction rates including hydrogen tunnelling effects have been calculated for these gas phase reactions at temperatures from 300 K to 0 K using Wenzel–Kramers–Brillouin (WKB) and Eckart methods. The Eckart method has been found to be unsatisfactory for the last two systems listed above, because it significantly underestimates the width of the reaction barriers for the interconversions. The calculations at all-electron CCSD(T)/CBS level of theory indicate that the barriers for all reactions (forward and reverse) are greater than 100 kJ mol−1, meaning that the chemical reactivity of the reactants is limited in the absence of hydrogen tunnelling. Hydrogen tunnelling, in some cases, enhance rates of reaction by more than 100 orders of magnitude at low temperature, and around 2 orders of magnitude at room temperature, compared to results obtained from canonical variational transition state theory. Tunnelling corrected reaction rates suggest that some of these isomerisation reactions may occur in interstellar media.

Graphical abstract: Hydrogen tunnelling influences the isomerisation of some small radicals of interstellar importance. A theoretical investigation

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Publication details

The article was received on 15 Dec 2011, accepted on 06 Feb 2012 and first published on 06 Feb 2012


Article type: Paper
DOI: 10.1039/C2OB07102A
Citation: Org. Biomol. Chem., 2012,10, 3219-3228
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    Hydrogen tunnelling influences the isomerisation of some small radicals of interstellar importance. A theoretical investigation

    T. Wang and J. H. Bowie, Org. Biomol. Chem., 2012, 10, 3219
    DOI: 10.1039/C2OB07102A

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