β Scribed by Xueliang Yang; Robert S. Tranter
No coin nor oath required. For personal study only.
The decomposition of ethyl iodide and subsequent dissociation of ethyl radicals have been investigated behind incident shock waves in a diaphragmless shock tube by laserschlieren (LS) densitometry (1150-1870 K, 55 Β± 2 Torr and 123 Β± 3 Torr). The LS density-gradient profiles were simulated assuming that the initial dissociation of C 2 H 5 I proceeded by 87% C I fission and 13% HI elimination. Excellent agreement was found between the simulations and experimental profiles. Rate coefficients for the C I scission reaction were obtained and show strong falloff. Gorin model RRKM (Rice, Ramsperger, Kassel, and Marcus) calculations are in excellent agreement with the experimental data with E 0 = 55.0 kcal/mol, which is in very good agreement with recent thermochemical measurements and evaluations. However, E 0 is approximately 2.7 kcal/mol higher than previous estimates. First-order rate coefficients for dissociation of C 2 H 5 I were determined to be k 55Torr = 8.65 Γ 10 68 T -16.65 exp(-37,890/T ) s -1 , k 123Torr = 3.01 Γ 10 69 T -16.68 exp(-38,430/T ) s -1 , k β = 2.52 Γ 10 19 T -1.01 exp(-28,775/T ) s -1 . Rates of dissociation for ethyl radicals were also obtained, and these are in very good agreement with theoretical predictions (Miller J. A. and Klippenstein S. J. Phys Chem Chem Phys 2004, 6, 1192-1202). The simulations show that at low temperatures ethyl radicals are consumed through recombination reactions as well as dissociation, whereas at high temperatures, dissociation dominates.
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