• “Reaction of Cl atoms with haloethers: relative rate constants and atmospheric implications”

P. R. DALMASSO, R. A. TACCONE, J. D. NIETO, M. A. TERUEL AND S. I. LANE

Florianópolis, SC, Brazil

Conferencia; 8th Latin American Conference on Physical Organic Chemistry (CLAFQO); 2005

CLAFQO

Despite the growing kinetic data base for the reaction of Cl atoms with organic compounds there have been relatively few studies of the reaction of Cl atoms with oxygenated organic species. The gas-phase reaction of Cl atoms with oxygenated organic species represents an important loss process for Cl atoms in the atmosphere1. Oxygenated compounds are finding increased use as fuels, solvents, CFC and HCFC substituents, fuel additives and anesthetics and are thus expected to be released in increasing amounts to the atmosphere. As part of an ongoing program in our laboratory to study the atmospheric chemistry of oxygenated species, we have used the relative rate technique to investigate the kinetics of the reaction of Cl atoms with CH3OCF2CHFCl, CHF2OCF2CHFCl (enflurane) and CHF2OCHFCF3 (desflurane) at room temperature and at atmospheric pressure, using N2 or pure air (N2/O2) as the bath gases. All the experiments were carried out in a 80 L collapsible Tedlar chamber at 298 K. A gas chromatograph equipped with a flame ionization detector (GC-FID) was used for the quantitative analysis of the reactants. Chlorine atoms were generated by the UV photolysis of molecular chlorine. Different reference compounds were employed for the reactions. Good agreement was found between the rate coefficients determined using the different reference compounds and bath gases. To the best of our knowledge, this kinetic study constitutes the first experimental determination of the rate coefficients for the reactions of Cl atoms with the haloethers mentioned above. The obtained data will be presented and discussed in terms of the reactivity of the ethers compared to other compounds of similar structure, and used to estimate the day half-life and the Ozone Depletion Potential (ODP) of these ethers in the troposphere.   1. T.J. Wallington, E.P. Dagaut and M.J. Kurylo J. Photochem. Photobiol. A Chem. 42, 173, 1998. 2. NIST Chemistry WebBook, NIST Standard Reference Database Number 68–March, 2003.