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Energetics of proton transfer between carbon atoms (H3CH [BOND] CH3)

Authors

  • Zdzisław Latajka,

    1. Department of Chemistry & Biochemistry, Southern Illinois University, Carbondale, Illinois 62901
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    • On leave from Institute of Chemistry, University of Wrocław, Poland.

  • Steve Scheiner

    1. Department of Chemistry & Biochemistry, Southern Illinois University, Carbondale, Illinois 62901
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    • Recipient of NIH Research Career Development Award (1982‒1987).


Abstract

Ab initio calculations were carried out to study the potential energy surface of (H3C[BOND]H[BOND]CH3). The 6–31G* basis set is supplemented by a set of diffuse p functions on both C and H (with a range of exponents for the latter). The binding energy of CH4 and CH3 to form the (H3CH[BOND]CH3) complex is about 2 kcal/mol, much smaller than for comparable ionic H-bonded systems involving O or N atoms. Nearly half of this interaction energy is due to correlation effects, computed at second and third orders of Møller-Plesset perturbation theory. Correlation is also responsible for substantial reductions in the energy barrier to proton transfer within the complex. This barrier is computed to be 13‒15 kcal/mol at the MP3 level, depending upon the exponent used for the H p functions.

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