OH formation from the C2H5COÂ +Â O2 reaction: An experimental marker for the propionyl radical

The reaction between C2H5CO and O2(R1a), (R1b) is observed to directly form OH. This reaction proceeds via the formation of energised C2H5CO(O2), which can either dissociate to OH or be collisionally thermalized. This reaction mechanism is analogous to CH3CO + O2(R4a), (R4b), which we have previously studied and extended in this study. The kinetics and OH yield of reactions (R1a), (R1b), (R4a), (R4b) are reported as a function of pressure at 295 and 213 K, and are sufficiently different to allow the identification of the corresponding acyl radical and it is demonstrated for 2-butanone photolysis.