1,2‐Pentadiene decomposition

Abstract

Abstract1,2‐Pentadiene has been decomposed in single pulse shock tube experiments. There appear to be a large number of parallel decomposition and isomerization channels. The following rate expressions for isomerization in the temperature range 1100–1250 K and pressures between 200 and 300kPa have been obtainedk(1,2‐pentadiene → 1‐pentyne) = 1.0 × 1013exp(−32300 ± 900 K/T) s−1k(1,2‐pentadiene → cis/trans‐1,3‐pentadiene = 2.2 × 1014exp(−33900 ± 900 K/T) s−1k(1,2‐pentadiene → cyclopentene) = 1.8 × 1011exp(−26080 ± 900 K/T) s−1Overall, we estimate the 2σ uncertainty in the absolute rate constants to be about 30%. From detailed balance the rate expression for 1,3 to 1,2‐pentadiene isomerization has been found to bek(1,3‐pentadiene → 1,2‐pentadiene) = 1.2 × 1015exp(−42070 ± 900 K/T) s−1The significance of the 1,3 to 1,2 isomerization process as a bridge between the two‐carbon and three‐carbon species in high temperature hydrocarbon decomposition systems is discussed.The decomposition processes involve bond breaking and retroene reactions. The rate expression for the latter has been found to bek(1,2‐pentadiene → propyne + ethylene) = 6.6 × 1012exp(−29240 ± 900 K/T) s−1The rate constants for fission of the C3C4and C4C5bonds appear to be close to each other. Our results indicate that the resonance energy of the 1,3‐butadiene‐2‐yl radical is smaller than that of allyl radical by an amount equal to the π bond conjugation energy of butadiene. © 2001 John Wiley & Sons, Inc.*This article is a US Government work and, as such, is in the public domain in the United States of America.Int J Chem Kinet 33: 755–767, 2001