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

Abstract

Abstract The thermal decomposition of CHClF 2 , CHF 3 , and CHCl 3 has been studied behind incident and reflected shock waves. The unimolecular decomposition was observed to proceed via the α,α elimination reactions magnified image magnified image magnified image in agreement with previous work. The progress of reaction was monitored via time resolved absorption spectrometry of CF 2 at 253 nm (for (1) and (2)) and of the secondary reaction product C 2 Cl 4 at 230 nm (for (3)). The pressure dependence of k 1 , k 2 , and k 3 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 ( k 0 and k ∞ ) were obtained by application of a modified Kassel theory. For k ∞ , the Arrhenius expressions magnified image were deduced. Excellent agreement with previous work is achieved for k 1∞ and k 2∞ , provided that fall off is properly taken into account.