H+CH 2CO→CH 3+CO at high temperature: A high pressure chemical activation reaction with positive barrier

Abstract

The Laser Photolysis-Shock Tube (LP-ST) technique coupled with H-atom atomic resonance absorption spectrometry (ARAS) has been used to study the reaction, H+CH2CO→CH3+CO, over the temperature range, 863–1400 K. The results can be represented by the Arrhenius expression, k=(4.85±0.70)×10−11 exp(−2328±155 K/T) cm3 molecule−1 s−1. The present data have been combined with the earlier low temperature flash photolysis-resonance fluorescence measurements to yield a joint three-parameter expression, k=5.44×10−14 T0.851 exp(−1429 K/T) cm3 molecule−1 s−1. This is a chemical activation process that proceeds through vibrationally excited acetyl radicals. However, due to the presence of a low-lying forward dissociation channel to CH3+CO, the present results refer to the high pressure limiting rate constants. Hence, transition state theory with Eckart tunneling is used to explain the data.