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  • Methyl dynamics flattens barrier to proton transfer in crystalline tetraacetylethane
    Kearley, G. J. ...
    We analyze the interplay between proton transfer in the hydrogen-bond bridge, OŽŽŽHŽŽŽO, and lattice dynamics in the model system tetraacetylethane (TAE) (CH3CO)2CHŽCH(COCH3)2 using density ... functional theory. Lattice dynamics calculations and molecular dynamics simulations are validated against neutron scattering data. Hindrance to the cooperative reorientation of neighboring methyl groups at low temperatures gives a preferred O atom for the bridging proton. The amplitude of methyl torsions becomes larger with increasing temperature, so that the free-energy minimum for the proton becomes flat over 0.2 Å. For the isolated molecule, however, we show an almost temperature-independent symmetric double-well potential persists. This difference arises from the much higher barriers to methyl torsion in the crystal that make the region of torsional phase space that is most crucial forsymmetrization poorly accessible. Consequently, the proton-transfer potential remains asymmetric though flat at the base, even at room temperaturein the solid
    Source: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory. - ISSN 1089-5639 (Vol. 116, no. 9, 2012, str. 2283-2291)
    Type of material - article, component part
    Publish date - 2012
    Language - english
    COBISS.SI-ID - 4957978

    Link(s):

    http://pubs.acs.org/doi/abs/10.1021/jp210212q?prevSearch=%255BContrib%253A%2Bstare%255D&searchHistoryKey=

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