T H E J O U R N A L OF
PHYSICAL CHEMISTRY' Registered in U.S. P a t e n t Office
0 Copyright, 1980, b y t h e A m e r i c a n Chemical Society
VOLUME 84, NUMBER 5
MARCH 6,1980
Single-Pulse Shock-Tube Study of the Thermal Decomposition of Ethyl Fluoride and n-Propyl Chloride K. Okada, E. Tschuikow-Roux," and P. J. Evans Department of Chemistry, University of Calgary, Caigaty, Alberta, Canada T2N IN4 (Received July 5, 1979)
The thermal decomposition kinetics of dilute mixtures of ethyl fluoride and n-propyl chloride in argon have been investigated in a single-pulse shock tube in the temperatuire range -990-1140 K by the absolute and the comparative rate method. Under the experimental conditions used the decompositions proceed almost exclusively via the concerted elimination of hydrogen halide to yield the corresponding olefins. With the absolute rate exp[-(59.5 method the following rate constants are obtained for C2H$ C2H4 + HF (Rl),kl"/s-' = 1013.65*0.20 f 1.0 kcal mol-l)/RT] and for n-C:)H7C1 CH3CHCH2+ HC1 (R2), k2"/s-' = 1013.44*0.2s exp[-(54.8 f 1.3 lkcal mol-l)/RT]. The comparative rate method, using a 0.125% C2H$4).1%5%n-C3H7C1-99.75% Ar mixture, yielded a compatible result: log (kl"/s-') = (1.101 f 0.016) log (k2"/s-') - (0.960 f 0.031). The results are discurised and compared with other data in the literature.
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Introduction The thermal decomposition kinetics of simple fluorohydrocarbons have received considerable attention in the recent past. Specifically, the pyrolysis of ethyl fluoride has been studied by a number of investigators using a variety of meit,hods, including conventional static apparatus,l flow system^,^^^ and a shock tube.4 While there is general. consensus that the principal mode of decomposition a t moderate temperatures is the formation of ethylene, the rate constants for the molecular elimination of hydrogen fluoride are not in such a good agreement. For example, the more recent work of Dastoor and lEmovon3 in a flow system yielded rate constants which
