Ab initio calculation of the transition-state properties and addition rate constants for H + C/sub 2/H/sub 2/ and selected isotopic analogues

Journal Article · Thu Oct 28 00:00:00 EDT 1982 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100219a009· OSTI ID:6582261

Harding, L B ^[1]; Wagner, A F; Bowman, J M; Schatz, G C; Christoffel, K

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1. Argonne National Lab., IL

GVB-POL-CI ab initio calculations of the geometries, energetics, and normal mode frequencies of C/sub 2/H/sub 2/, C/sub 2/H/sub 3/, and the transition state for the addition reaction of H + C/sub 2/H/sub 2/ are presented. In addition, normal mode frequencies for the isotopic variants D + C/sub 2/D/sub 2/, D + C/sub 2/H/sub 2/, and H + C/sub 2/D/sub 2/ are preented. These results are compared to experimental values for C/sub 2/H/sub 2/ and to ab initio values of Hagase and Kern, and semiempirical values of Keil, Lynch, Cowfer, and Michael. The results are also used to calculate the apparent bimolecular addition rate constant using conventional RRKM theory for chemical activation. The calculated rate constants and their isotopic variants are compared as a function of temperature and pressure to available experimental information. The agreement is little different from that obtained by Keil et al. with a similar calculation using semiempirical values for acetylene, transition-state, and vinyl radical properties. In particular, the calculated high-pressure limit of the rate constant appears to be at least 1 order of magnitude higher than the experimental limit. Several possible reasons for this discrepancy are discussed.

• DOE Contract Number: W-31-109-ENG-38
• OSTI ID: 6582261
• Journal Information: J. Phys. Chem.; (United States), Vol. 86:22
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
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PHYSICAL AND ANALYTICAL CHEMISTRY
ACETYLENE
HYDROGENATION
DEUTERIUM
ISOTOPE EFFECTS
CHEMICAL REACTION KINETICS
WAVE FUNCTIONS
ALKYNES
CHEMICAL REACTIONS
FUNCTIONS
HYDROCARBONS
HYDROGEN ISOTOPES
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KINETICS
LIGHT NUCLEI
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