FORMATION OF HYDROXYMETHYL HYDROPEROXIDE AND FORMIC-ACID IN ALKENE OZONOLYSIS IN THE PRESENCE OF WATER-VAPOR

Ozonolysis experiments of a series of terminal alkenes were performed to study the products formed in the presence of water vapour. Alkenes investigated were ethene, propene, isobutene and isoprene. Concentrati ons of the reactants were 4-6 ppmv alkene and 2 ppm ozone. The concent ration of water vapour was varied from 0.5 ppmv to 17,000 ppmv. Hydrox ymethyl hydroperoxide (HMHP) was found to be the sole product in the r eactions of the stabilized Criegee biradical CH2OO with water vapour. The yield of HMHP relative to ozone consumption was measured to be 42% ethene, 14% propene, 13% isobutene and 30% isoprene in the presence o f 9000-18,000 ppmv H2O. HMHP was not stable under the experimental con ditions and decomposed to HCOOH and water, presumably via a heterogene ous process. The atmospheric fate of HMHP and the relative rate consta nts of the CH2OO Criegee biradical with H2O,HCOOH and NOx are discusse d. (C) 1997 Elsevier Science Ltd.