Ozonolysis of C,H, was carried out at 295 K in 730 torr synthetic air in the concentration ranges of 10310 = I 9-8.2 ppm and [C2H41(, = 4 0-15.0 ppm, in the absence and presence of the added HCOOH [Ipprn), CH,COOH (1-10 pprn), and CH,OH (36-100 ppm]. In the absence of the added compounds, a nearly complete analysis of the reaction products was achieved, with the yields expressed relative to the converted C2H,. HCHO 0.98, CO 0.26, CO, 0 18, HCOOH 0 05, and the sum of formic acid anhydride [FAN) and hydroperoxymethyl formate [HPMF) CHO-0-CH,OOH, 0.19. In the presence of the added HCOOH. the yield of [FAN + HPMFl increased The addition of CH,COOH suppressed the formation of FAN and HPMF completely The addition of large excesses of CH,OH also decreased the yield of IFAN + HPMFl significantly In both cases, new products with the formula R-0-CH,OOH where R = CHJO and CH, For CH,COOH and CH,OH, respectively, were formed The present results, together with the formation of hydroxymethyl hydroperoxide. HO-CH,OOH. with added water vapor (Horie et al., Geophys. Res Lett , 2 1 , 1523, [ 1994)) were explained by the reaction of the Criegee biradical CH,OO with the added hydroxy compounds ROH Formation of the products with the general formula R-0-CH,OOH indicates that the RO-H bond fission has taken place 0 1996 J o h n Wiley & Sons, Inc +