Consecutive Chemical Activation Steps in the OH‐Initiated Atmospheric Degradation of Isoprene: An Analysis with Coupled Master Equations

摘要: The influence of a two-step chemical activation on 1,5-H and 1,6-H shift reactions hydroxyl-peroxy radicals formed in the atmospheric photooxidation isoprene was investigated by means master equation analysis. To account for multiple processes, three equations were coupled. general approach this coupling is described, consequences steady-state regimes are examined. specific calculations show that has no substantial rate coefficients above-mentioned under tropospheric conditions. However, it demonstrated high-pressure limits thermal instead falloff-corrected values have to be used kinetic modeling. This consequence continuous population high-energy part isoprene-OH-O2 adduct distribution forming isomerization at T = 298 K calculated k3a∞ = 1.5 × 10−3 s−1 (1,5-H-shift 1,2-isomer) k4a∞ = 6.5 s−1 (1,6-H-shift (Z)-1,4-isomer). value k4a∞ orders magnitude larger than recently reported experimentally observed coefficient hydrogen intermediates. It shown discrepancy due fact experiment does not distinguish between different structural isomers. A comparison determined isotope effect with shows reasonable agreement.