Gas Phase α,α Elimination of Hydrogen Halides from Halomenthanes. I. Thermal Decomposition of Chlorodifluoromethane, Trifluoromethane, and Trichloromethane Behind Shock Waves

Abstract

AbstractThe thermal decomposition of CHClF2, CHF3, and CHCl3 has been studied behind incident and reflected shock waves. The unimolecular decomposition was observed to proceed via the α,α elimination reactionsmagnified imagemagnified imagemagnified imagein agreement with previous work. The progress of reaction was monitored via time resolved absorption spectrometry of CF2 at 253 nm (for (1) and (2)) and of the secondary reaction product C2Cl4 at 230 nm (for (3)). The pressure dependence of k1, k2, and k3 was investigated over a pressure range of a factor of ∼ 100. From the experiments in the fall off region, low and high pressure limiting rate constants (k0 and k∞) were obtained by application of a modified Kassel theory. For k∞, the Arrhenius expressionsmagnified imagewere deduced. Excellent agreement with previous work is achieved for k1∞ and k2∞, provided that fall off is properly taken into account.