Absolute rate constants for reactions of free radicals in the high‐temperature photolysis of formamide vapor. II. Amino radicals

The rotating‐sector method has been applied to the photoinitiated radical‐chain decomposition of formamide at 300°C to measure the rate constant for the bimolecular disappearance of NH 2 radicals. The decomposition is propagated by the reactions (1)\documentclass{article}\pagestyle{empty}\begin{document}$$ NH_2 + NH_2 CHO \to NH_3 + NH_2 CO $$\end{document}(2)\documentclass{article}\pagestyle{empty}\begin{document}$$ NH_2 CHO \to N_2 + CO $$\end{document}Conditions were chosen so that reaction (1) was rate controlling and NH 2 the terminating radical. A flow system was employed with C 2 F 6 as a carrier gas at a pressure of 300 Tort, and the chain reaction was initiated by the photolysis of either formamide or NH 3 . A value of 4.7(±2.0) × 10 10 (M ·sec) −1 was estimated for the termination reaction (3)\documentclass{article}\pagestyle{empty}\begin{document}$$ 2NH_2 \to N_2 H_4 $$\end{document}and a value of 8.4 × 10 6 (M ·sec) −1 for reaction (1) in the same system, both at 300°C.