Stopped-flow studies of the mechanisms of ozone-alkene reactions in the gas phase. Ethylene

by | CIRS

https://pubs.acs.org/doi/pdfplus/10.1021/ja00458a033

Comments; Ozone is very reactive, not as much so as a free radical, but certainly not stable indefinitely under most household temperature & pressure.  Ethylene is an organic compound that outgasses from plastics. Even with the highly substituted ethenes partial cleavage products (indicated by an asterisk) never exceed 10%. Intermediate ozonides must have a lifetime <2 ms as shown by stopped-flow conductometry.  Formaldehyde is toxic, but a lifetime of less than 0.002 seconds means it is very unlikely to harm us.  These radicals are highly reactive, breaking larger VOC’s into their smaller components until they are no longer toxic.

John T. Jerron, Robert E Hule

Institute for Materials Research, National Bureau of Standards, Washington DC January 10, 1977

Abstract;

The reaction of ozone with ethylene has been studied in the gas phase at 298K and 1.1 kPa (8 Torr), using a stopped-flow reactor coupled to a beam-sampling mass spectrometer.  The concentration of C2H4 {ethylene}and the products CO2, H2O, CH2O, HCOOH, CH3OH and an unidentified product at mass 43 were measured as a function of reaction time.  Using a computer model, the role of free radicals in the reaction was quantitatively assessed, and a complex free-radical mechanism proposed.  The initial reactions occurring are postulated to be: C2H4 + O3{ozone}àCH2O {formaldehyde} + CH2O2 {formic acid HCOOH}; CH2O2à[HCOOH]à2H + CO2 (9%); CH2O2à[HCOOH]à(M?, wall?) HCOOH (6%).  If these results hold under atmospheric conditions, they imply that considerably fewer free radicals are produced in the reactions of ozone with terminal alkenes than previously assumed.

Dr. Raymond Oenbrink
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