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Isomerization and Decomposition Reactions in the Pyrolysis of Branched Hydrocarbons: 4-Methyl-1-Pentyl Radical



William S. McGivern, Iftikhar A. Awan, Wing Tsang, Jeffrey A. Manion


The kinetics of the decomposition of 4-methyl-1-pentyl radicals have been studied from 927 1068 K at pressures of 1.78 2.44 bar using a single pulse shock tube with product analysis. The reactant radicals were formed from the thermal C I bond fission of 1-iodo-4-methylpentane, and a radical inhibitor was used to prevent interference from bimolecular reactions. 4-Methyl-1-pentyl radicals undergo competing decomposition and isomerization reactions via ?-bond scission and 1,x-hydrogen migrations (x=4,5), respectively, to form short-chain radicals and alkenes. Major alkene products, in decreasing order of concentration, were propene, ethene, isobutene, and 1-pentene. The observed products are fit to a chemical kinetics model with rate constants for the reactions determined from RRKM/master nist-equation analysis at the reaction temperatures and pressures. The presence of the branched methyl moiety has a significant impact on the observed reaction rates relative to analogous reaction rates in straight-chain radical systems. Systems that result in the formation of substituted radical or alkene products are found to be faster than reactions that form primary radical and alkene species. Pressure-dependent reaction rate constants from the RRKM/ME analysis are provided at 500 1900 K and 0.1?1000 bar pressure for all of the decomposition and isomerization reactions in this system.
Journal of Physical Chemistry A


combustion, high-temperature kinetics, pressure-dependence, RRKM/ME, shock tube
Created July 31, 2008, Updated February 19, 2017