Formation of formic acid and organic peroxides in the ozonolysis of ethene with added water vapour

Ozonolysis of C 2 H 4 was carried out in a 580 l glass reaction vessel at 1–5 ppm reactant concentrations, with added water vapour. Under dry conditions ([H 2 O] 0 = 0.5 ppm), HCHO, CO, CO 2 , (CHO) 2 O (formic acid anhydride), H 2 O 2 , and CH 3 OOH were identified as the reaction products. Under wet conditions ([H 2 O] 0 = 2 × 10 4 ppm), HCOOH yields approaching ca. 20% of the converted C 2 H 4 , were observed, while no (CHO) 2 O was formed. Hydroxymethyl hydroperoxide, HOCH 2 OOH, was observed as the major peroxide, and found to be formed only in the presence of water vapour. Direct reactions of H 2 O vapour with the excited CH 2 OO * radicals and with stabilized CH 2 OO radicals are postulated to explain the formation of HCOOH and HOCH 2 OOH in the presence of water vapour, respectively.