1104 Abstracts CHLORINE AND FLUORINE ATOMS ADDUCTS WITH HALOGENATED COMPOUNDS IN THE GAS PHASE M. Bilde,* J. Sehested,* T. E. Mergelberg,* 0. J. Nielsen* and T. J. Wallington+ * Section for Chemical Reactivity, Environmental Science and Technology Department. Riss National Laboratory, DK-4000 Roskilde, Denmark +Ford Motor Company, Ford Research Laboratory, SRL-3083, Dearborn, P.O. Box 2053, MI 48121-2053. U.S.A. A pulse radiolysis technique was used to investigate the kinetics and products of the reaction of CF,BrH with fluorine atoms at 296 K. This reaction forms an adduct which is in dynamic equilibrium with CF,BrH and fluorine atoms. The UV absorption spectrum of the adduct was measured relative to the UV spectrum of the CH30Z radical over the range 230-380 nm. At 280 nm, an absorption cross section of (1.4 & 0.1) x 10-l’ cm2 molecule-’ was determined. From the absorption at 280 nm the equilibrium constant K5 = [adduct]/([F] [CF,BrH]) was measured to be (1.59 + 0.13)~ lo-“ cm3molecule~‘. In 1 atmosphere of SF,, the forward rate constant ks = (1.5 k 0.5) x lo-” cm3molecule-‘s-’ and the backward rate constant k5 = (8.8 + 3.0) x lo5 s-l were de- termined by monitoring the rate of formation and loss of the adduct. As part of the present work, a relative rate technique was used to measure k(C1 + CFZBrH) = (5.8 i 1.0) x lo-‘” cm” molecule~’ s-l at 296 K and 700 Torr of Nz. The fate of the oxy radical, CFZBrO, in the atmosphere 1s bromine atom elimination and formation of COF,. ALTERNATIVE FUEL AND FUEL ADDITIVES: ATMOSPHERIC CHEMISTRY OF 1,4-DI- AND 1,3,5-TRIOXANE J. Platz,* J. Sehested,* T. Mergelberg,‘” 0. J. Nielsen* and T. J. Wallington+ *Section for Chemical Reactivity, Environmental Science and Technology Department, Riss National Laboratory, DK-4000 Roskilde, Denmark ‘Ford Motor Company. Dearborn. MI 4x121-2053, U.S.A. One way to reduce the CO1 emission from the traffic is to convert petrol vehicles to diesel vehicles, because diesel engines are more efficient than petrol engines. Unfortunately, diesel engines running on conventional fuels have a tendency to produce substantial particulate emissions (soot). Therefore, it is important to find alternative diesel fuels that produce less particulate soot during combustion. Dimethyl ether (DME) has been proposed as an alternative diesel fuel: It gives much less particulate soot, has a high cetane number and gives low combustion noise. However, under ambient conditions DME is a gas and gives therefore some practical problems compared to a liquid as conventional diesel. 1,4-dioxane and 1,3$trioxane are cyclic ethers there may have similar properties like DME. In this work we have used pulse radiolysis (to initiate the reactions) combined with time-resolved UV-VIS spectroscopy and a OMA-II diode array to study the atmospheric chemistry of 1,4-dioxane (liquid) and 1,3,5-trioxane (soft crystals). We studied the UV absorption spectra of the alkyl and the alkyl peroxy radicals for the 1,4-dioxane and 1,3$trioxane. The kinetics of the self-reactions of the alkyl and alkyl peroxy radicals and reactions between the alkyl peroxy radicals and NO/NOL, have been investigated. A FTIR technique has been used to study the atmospheric fate of the alkoxy radicals of 1,4-dioxane and 1,3,5-trioxane. DIMETHYL ETHER OXIDATION: KINETICS AND MECHANISM OF THE CH30CHz + 02 REACTION AT 296 K AND 0.38-940 TORR TOTAL PRESSURE J. Sehested,* T. Msgelberg,* J. Platz,* 0. J. Nielsen,* T. J. Wallington+ and E. W. Kaiser+ *Section for Chemical Reactivity, Environmental Science and Technology Department, Riss National Laboratory, DK-4000 Roskilde, Denmark ‘Ford Motor Company, Research Staff, SRL-3083, P.O. Box 2053, Dearborn, MI 48121-2053, U.S.A. The overall rate constant for reaction of CH,OCHZ radicals with 0, may be written, kl = kROz + kplod, where kRO, is the rate constant for peroxy radical production and k,,,, is the rate constant for the production of other species from reaction (1). k, was measured relative to that for the pressure independent reaction of CH,OCH, radicals with Cl, (k4). Fitting the product yields and relative rate data using a modified Lindemann expression gave the following rate constants; kRo2,,/k, = (1.97 k 0.28) x IO-l9 cm3molecule -I, kRO,, % ik4 = 0.108 i 0.004, and k prod,0/k4 = (6.3 + 0.5) x lo-‘, where kRU,.O and kRO,, i are the overall termolecular and bimolecular rate constants