Hydrogen Abstraction by Hot CF3 Radicals

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Abstract
The quantum yields of CF3H from the reactions of hot CF3 radicals and thermal CF3 radicals resulting from the photolysis of CF3I at 2537 Å and of CF3Br at 1850 Å in gaseous CH4, C2H6, and C3H8 have been investigated. Reactions of hot CF3 radicals with hydrocarbons appear to be dependent on the translational energy of the radicals when these are produced from CF3I at 2537 Å, and dependent on vibrational energy when the radicals are produced from CF3Br at 1850 Å. Translationally thermalized CF3 radicals from 2537‐Å activation show unusual reactivity with I2 relative to C3H8, which is attributed to a low vibrational excitation. This is quenched by CF3I with a collision number of 30–100. Vibrationally excited CF3 radicals produced from CF3Br at 1850 Å show a selectivity for H abstraction vs D abstraction and secondary vs primary bond attack similar to that of thermal atoms, whereas translationally hot CF3 radicals produced from CF3I at 2537 Å are much less selective. The reaction of hot CF3 radicals from CF3Br at 1850 Å with C3H8 is obscured by the reaction with HBr produced by thermal bromine atoms.