About the co-product of the OH radical in the reaction of acetyl with O2 below atmospheric pressure

Recent studies have shown that the reaction between acetyl radicals and O2 at low pressures leads to the direct fast formation of OH radical, but the nature of co-products is controversial. Laser photolysis coupled to TDLAS (10-200 Torr, 298 K) has been employed to directly monitor two possible co-products of this reaction, CO and formaldehyde. Only CH2O has been detected in yield of 0.29 ± 0.13, but with time constants much slow than the OH formation under these conditions; the observed CH2O-time profiles are compatible with the known mechanism of peroxyacetyl secondary reactions.