Arrhenius parameters for the hydrogen abstraction from ammonia by CF 3 radicals

The reaction of CF 3 radicals with NH 3 has been studied over a wide temperature range 298–673 K, using the photolysis and the thermal decomposition of CF 3 I as the free radical source. It was found that the reaction could not be explained in terms of a simple mechanismin the whole temperature range because a marked pressure dependence on the rate of products formation and the presence of a dark reaction complicate the system at low temperatures. Thus, Arrhenius parameters for reaction (1) have been calculated relative to the CF 3 recombination from data in the range 523–673 K where pure hydrogen transfer occurs. The rate constant expression is given by\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\,k_H /k_c^{1/2} = (6.17 \pm 0.28) - (57.8 \pm 2.9)/\theta $$\end{document}where k H / k   c 1/2is in units of cm 3/2 /mol 1/2 s 1/2 and θ = 2.303 RT/kJ/mol.