Multichannel Decomposition and Isomerization of Octyl Radicals

Published

October 9, 2008

Author(s)

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

Abstract

The thermal cracking patterns from the decomposition and isomerization of octyl-1 radicals have been determined from the pyrolysis of n-octyl iodide in single pulse shock tube experiments at temperatures in the 850-1000 K range and pressures near 2 bar.  Rate constants for the six beta bond scission and five of the six isomerization processes have been derived over all combustion conditions [0.1-100 bar, 700-1900 K].  Comparisons are made with previous studies on the decomposition of other primary radicals.  Results are consistent with similar types of reactions having equal rate constants.  The larger size of the octyl radicals makes contributions from secondary to secondary radical isomerization increasingly important.  The results confirm that the 1-3 H-transfer process (involving a seven member cyclic transition state) have rate constants that are within a factor of 2 of those for the 1-4 process (six member cyclic transition state).  It appears that rate constants for 1-2 H-transfer isomerization, involving an eight member cyclic transition state is unimportant in comparison to contributions from other isomerization processes.  The strain energy does not appear to play an important role for these larger transition states.  The implications of these results to larger fuel radicals will be discussed.

Volume

32

Issue

1

Conference Dates

August 3-8, 2008

Conference Location

Montreal, CA

Conference Title

32nd International Symp. on Combustion

Pub Type

Conferences

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Keywords

Octyl, unimolecular, decomposition, isomerization, pyrolysis

Citation

Tsang, W. , McGivern, W. and Manion, J. (2008), Multichannel Decomposition and Isomerization of Octyl Radicals, 32nd International Symp. on Combustion, Montreal, CA, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=832207 (Accessed October 14, 2025)