•Temperature dependences of the reactions of O(3P) with chlorofluoroalkenes”

M.A.TERUEL, P. M. COMETTO,M. B. BLANCO, R.A.TACCONE Y S.I.LANE

Leeds, UK

Simposio; Faraday Discusión 130-Atmospheric Chemistry; 2005

Royal Society of Chemistry

Reactions of ground-state oxygen atoms, O(3P), with alkenes are of both fundamental and practical importance. O(3P) reactions are necessary to accurately model the early stages of smog formation in urban areas and are often important in atmospheric pressure chamber studies of alkene reactions with OH. O(3P) reactions are also of central importance in combustion chemistry and serve as prototype systems for the addition reactions to the C=C bond. Although a substantial body of kinetic data exits for O atom reactions with a variety of alkenes, only limited information is available for haloalkenes, most of which has been reviewed by Cvetanovic. Most of these studies have been indirect measurements of the rate coefficients by the relative rate method. The present work was undertaken in order to augment the existing scant supply of kinetic information about the O(3P)-haloalkene reactions, and to extend our knowledge to include the higher alkenes, propenes and butenes. We have also studied the temperature dependences of these reactions, in the hope that an improved understanding of the reaction mechanism might be forthcoming. Kinetic information for the reactions of O(3P) atoms with CFCl=CH2, (E/Z)-CFH=CClH, (E/Z)-CFCl=CHCl, CCl2=ClCF3, CF2=CFCF3, CF3CCl=CFCF3 and CF3CCl=CClCF3 was obtained from experiments conducted in a fast discharge flow system. The O(3P) concentration was monitored measuring the visible chemiluminescence resulting from the reaction of O atoms with NO to produce electronically excited NO2*. The experiments were carried out under pseudo-first-order conditions with [O(3P)]<< [alkene]. Halogen substituent effects on the reactivity of the alkenes will be analised as a function of extent and positioning about the double bond. Structure-activity relationships will be considered.