Vibrational relaxation, dissociation, and dissociation incubation times in norbornene

Article abstract of DOI:10.1063/1.466151

Shock waves in norbornene (bicyclo <2,2,1> hept-2-ene, C7H10)-krypton mixtures have been examined with the laser-schlieren technique over the very wide range of conditions, 542-1480 K, and 34-416 Torr in 0.5percent, 2percent, and 4percent C7H10.The experiments exhibit both vibrational relaxation (542-1480 K) and the retro-Diels-Alder dissociation, norbornene -> 1,3-cyclopentadiene + ethylene (869-1480 K).Over 869-1304 K, and for pressures below 140 Torr, both relaxation and dissociation are resolved.These experiments provide the first measurements of unimolecular incubation (induction) times for the dissociation of a large polyatomic molecule.The ratio t_i/τ decreases from ca. 5 to 2 in 900-1300 K.Vibrational relaxation is rapid, log₁₀ Pτ (μs atm) = 0.066-6.70/T^1/3, with a weak inverse temperature dependence, but is completely consistent with series excitation through the lowest-frequency mode.Dissociation shows very strong unimolecular falloff.A Rice-Ramsperger-Kassel-Marcus (RRKM) model, parametrized to fit the observations (E₀ = 44.2 kcal/mol, <ΔE>_down = 280 cm^-1), finds the reaction closer to the low pressure limit k₀ than to k for 1400 K and 100 Torr.Earlier work at low temperatures ( < 750 K) has E_a too low to extrapolate to the present results.Thus a significant increase in E_a is indicated over 700-1000 K, suggesting a change in mechanism.

Full text of DOI:10.1063/1.466151

Vibrational relaxation, dissociation, and dissociation incubation times in
norbornene
J. H. Kiefer, S. S. Kumaran, and S. Sundaram
Citation: The Journal of Chemical Physics 99, 3531 (1993); doi: 10.1063/1.466151
View online: http://dx.doi.org/10.1063/1.466151
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/99/5?ver=pdfcov
Published by the AIP Publishing
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This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
155.247.166.234 On: Fri, 21 Nov 2014 20:06:43