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Proton affinity and enthalpy of formation of formaldehyde

Authors

  • Gábor Czakó,

    1. Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322
    2. Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518 Budapest 112, Hungary
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  • Balázs Nagy,

    1. Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
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  • Gyula Tasi,

    1. Department of Applied and Environmental Chemistry, University of Szeged, Rerrich B. tér 1, H-6720 Szeged, Hungary
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  • Árpád Somogyi,

    1. Department of Chemistry, University of Arizona, Tucson, AZ 85721
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  • Ján Šimunek,

    1. Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518 Budapest 112, Hungary
    2. Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH2, SK-84215 Bratislava, Slovakia
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  • Jozef Noga,

    1. Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina CH2, SK-84215 Bratislava, Slovakia
    2. Institute of Inorganic Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84536 Bratislava, Slovakia
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  • Bastiaan J. Braams,

    1. Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322
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  • Joel M. Bowman,

    1. Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322
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  • Attila G. Császár;

    Corresponding author
    1. Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518 Budapest 112, Hungary
    • Laboratory of Molecular Spectroscopy, Institute of Chemistry, Eötvös University, P.O. Box 32, H-1518 Budapest 112, Hungary
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  • This paper is dedicated to Dr. István Mayer, one of the fathers of modern quantum chemical research in Hungary, on the occasion of his 65th birthday.

Abstract

The proton affinity and the enthalpy of formation of the prototypical carbonyl, formaldehyde, have been determined by the first-principles composite focal-point analysis (FPA) approach. The electronic structure computations employed the all-electron coupled-cluster method with up to single, double, triple, quadruple, and even pentuple excitations. In these computations the aug-cc-p(C)VXZ [X = 2(D), 3(T), 4(Q), 5, and 6] correlation-consistent Gaussian basis sets for C and O were used in conjunction with the corresponding aug-cc-pVXZ (X = 2–6) sets for H. The basis set limit values have been confirmed via explicitly correlated computations. Our FPA study supersedes previous computational work for the proton affinity and to some extent the enthalpy of formation of formaldehyde by accounting for (a) electron correlation beyond the “gold standard” CCSD(T) level; (b) the non-additivity of core electron correlation effects; (c) scalar relativity; (d) diagonal Born–Oppenheimer corrections computed at a correlated level; (e) anharmonicity of zero-point vibrational energies, based on global potential energy surfaces and variational vibrational computations; and (f) thermal corrections to enthalpies by direct summation over rovibrational energy levels. Our final proton affinities at 298.15 (0.0) K are ΔpaHo (H2CO) = 711.02 (704.98) ± 0.39 kJ mol−1. Our final enthalpies of formation at 298.15 (0.0) K are ΔfHo (H2CO) = −109.23 (−105.42) ± 0.33 kJ mol−1. The latter values are based on the enthalpy of the H2 + CO → H2CO reaction but supported by two further reaction schemes, H2O + C → H2CO and 2H + C + O → H2CO. These values, especially ΔpaHo (H2CO), have better accuracy and considerably lower uncertainty than the best previous recommendations and thus should be employed in future studies. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009

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