PHOTO-OXIDATION OF CH2O AT 3130 A IN THE ABSENCE AND PRESENCE OF NO

CH2O was photolyzed at 3130 Å and 296 K in the absence and presence of O2. With O2 present photolyses were also done with excess N2, CO2 or He present. The products of the reaction were CO and H2, both produced with a quantum yield of unity in the absence of O2. In the presence of O2, HCOOH was also produced with a quantum yield which increased to 2.0 as the O2 pressure was raised above 100 Torr. The presence of O2 first increased the CO yield, but then reduced both the CO and H2 yields to zero as the O2 pressure was raised above 100 Torr. The results are interpreted in terms of the primary process {A figure is presented} The intermediate I is probably either triplet CH2O or the {A figure is presented} biradical. The ratio k1a/k1 was found to be 0.61 ± 0.15 in satisfactory agreement with other studies and k4/k1a = 0.43 ± 0.03 Torr-1. In the presence of 50 Torr O2 and a few millitorr NO, a long chain oxidation occurs to produce NO2, HCOOH and CO. Thus the intermediate IO2 must react with NO to produce radical fragments, presumably by the reaction IO2 + NO → HCO + HO + NO2 The oxygenated radicals (HO2 and probably HCO3 and HCO2) also react with NO to give NO2. © 1979.