L29. Kinetic study of the reactions of chlorine atoms with 2,3-butadione,

cyclohexanone and cyclopentanone

A. Guschin, T. J. Wallington, and M. D. Hurley

Ford Research Laboratory, SRL-3083

Ford Motor Company

Dearborn, P.O. Box 2053

Michigan 48121-2053, USA

We have conducted relative rate experiments in 10-700 Torr of N₂ or air diluents at 295 K to measure k₁, k₂, and k₃ relative to k(Cl+CH₄), k(Cl+CH₃Cl), k(Cl+C₂H₄), k(Cl+cyclohexane), and k(Cl+cyclopentane) using an FTIR-smog chamber system.

Cl + CH₃C(O)C(O)CH₃ ® products (1)

Cl + cyclohexanone ® products (2)

Cl + cyclopentanone ® products (3)

The results give k₁ = (4.1± 0.5) x 10^-13, k₂ = (1.80± 0.31) x 10^-10, and k₃ = (1.11± 0.10) x 10^-10 cm³ molecule^-1 s^-1, quoted errors reflect statistical uncertainties and an estimated 10% uncertainty in the reference rate constants used. Cyclohexanone and cyclopentanone are factors of 1.9 and 2.8 less reactive than the parent alkanes, this is consistent with the expectation that the deactivating effect of the carbonyl group is confined mainly to the a position. Our findings are in disagreement with the recent results of Olsson et al. [] which suggest that cyclohexanone and cyclopentanone are 4.9 and 6.5 times less reactive than the parent alkanes. Finally, our result for 2,3-butadione is a factor of 1.9 less than that measured by Olsson et al., the origin of these discrepancies will be discussed.