State-to-state dynamics of atom+polyatom abstraction reactions. II. The H+C sub 2 H sub 6 /C sub 3 H sub 8 r arrow H sub 2 ( v prime , J prime ) +C sub 2 H sub 5 /C sub 3 H sub 7 reactions

Journal Article · Wed Apr 15 00:00:00 EDT 1992 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.462673· OSTI ID:7069938

Germann, G J; Huh, Y ^[1]; Valentini, J J ^[2]

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1. Department of Chemistry, University of California, Irvine, California 92717 (United States)
2. Department of Chemistry, Columbia University, New York, New York 10027 (United States)

The rotational and vibrational quantum state distributions for the H{sub 2} products of the H+HR{r arrow}H{sub 2}+R reactions (HR=C{sub 2}H{sub 6} and C{sub 3}H{sub 8} ) at 1.6 eV collision energy have been measured using coherent anti-Stokes Raman scattering. Total reaction cross sections have also been determined. For the total cross sections we find 1.5{plus minus}0.5 A{sup 2} for the ethane reaction and 2.9{plus minus}0.8 A{sup 2} for the propane reaction. Although several vibrational states are energetically accessible, we observe H{sub 2} products only in {ital v}{prime}=0 and {ital v}{prime}=1, with the majority in the ground vibrational state. The H{sub 2} products are on average rotationally cold as well, and 20% or less of the total energy is partitioned to H{sub 2} internal energy. However, the quantum state distributions show a positive correlation of H{sub 2} product rotational and vibrational energy. That is, the average rotational energy of the H{sub 2} in {ital v}{prime}=1 is substantially greater than the average rotational energy of the H{sub 2} in {ital v}{prime}=0. Comparison with state-to-state dynamics results previously obtained for the kinematically and energetically similar H+CD{sub 4}{r arrow}HD+CD{sub 3} and H+HCl{r arrow}H{sub 2}+Cl reactions seems to indicate that this anomalous energy disposal is an intrinsic characteristic of H + alkane hydrogen atom abstraction reactions at high collision energy. We speculate that this anomalous behavior is the result of inelastic encounters between the nascent H{sub 2} and alkyl radical products in the reaction exit channel.

• OSTI ID: 7069938
• Journal Information: Journal of Chemical Physics; (United States), Vol. 96:8; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ETHANE
CHEMICAL REACTIONS
HYDROGEN
ROTATIONAL STATES
VIBRATIONAL STATES
PROPANE
ATOM-MOLECULE COLLISIONS
POLYATOMIC MOLECULES
QUANTUM MECHANICS
RAMAN EFFECT
TOTAL CROSS SECTIONS
ALKANES
ATOM COLLISIONS
COLLISIONS
CROSS SECTIONS
ELEMENTS
ENERGY LEVELS
EXCITED STATES
HYDROCARBONS
MECHANICS
MOLECULE COLLISIONS
MOLECULES
NONMETALS
ORGANIC COMPOUNDS
400201* - Chemical & Physicochemical Properties