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Pressure Dependence and Branching Ratios in the Decomposition of 1-Pentyl Radicals: Shock Tube Experiments and Master Equation Modeling



Iftikhar A. Awan, Donald R. Burgess Jr., Jeffrey A. Manion


The decomposition and intramolecular H-transfer isomerization reactions of the 1 pentyl radical have been studied at temperatures of 900 K to 1050 K and pressures of 0.8 bar to 6 bar using the single pulse shock tube technique and additionally investigated with quantum chemical methods. The 1-pentyl radical was generated by shock heating dilute mixtures of 1 iodopentane and the stable products of its decomposition have been observed by post-shock gas chromatographic analysis. Ethene and propene are the main olefin products and account for > 97% of the carbon balance from 1-pentyl. Also produced are very small amounts of E pent 2 ene, Z-pent-2-ene and but 1 ene. The ethene/propene product ratio is pressure dependent and varies from about 3 to 5 over the range of temperatures and pressures studied. Formation of ethene and propene can be related to the concentrations of 1-pentyl and 2-pentyl radicals in the system and the relative rates of 5-center intramolecular H-transfer reactions and beta C-C bond scissions. The 3-pentyl radical, formed via a four-center intramolecular H transfer, leads to 1 butene and plays only a very minor role in the system. The observed pent-2-enes can arise from a small amount of C-H bond scission in the 2-pentyl radical. Current experimental and computational results are considered in conjunction with relevant literature data to develop a consistent kinetics model that reproduces the observed branching ratios and pressure effects. A Rice Ramsberger Kassel Marcus/Master Equation (RRKM/ME) analysis has been performed and used to extrapolate the data over a range of pressures and temperatures. High pressure rate expressions for the relevant H-transfer reactions and beta bond scissions are reported.
Journal of Physical Chemistry A


Kinetics, 1-pentyl, shock-tube, decomposition, combustion


Awan, I. , Burgess Jr., D. and Manion, J. (2012), Pressure Dependence and Branching Ratios in the Decomposition of 1-Pentyl Radicals: Shock Tube Experiments and Master Equation Modeling, Journal of Physical Chemistry A (Accessed April 18, 2024)
Created February 21, 2012, Updated October 12, 2021