Infrared chemiluminescence and energy partitioning from the reactions of fluorine atoms with the primary carbon-hydrogen bonds of alkanes, halogenated methanes, and tetramethyl silane

Abstract

The infrared emission from the HF† product of the elementary abstraction reaction between fluorine atoms and CH4, C2H6, CH3CF3, C(CH3)4, Si(CH3)4, CH3Cl, CH2Cl2, CHCl3, and CH3Br has been observed, and relative vibrational populations (v = 1, 2, 3) were determined. The experiments were conducted at 10−3–10−4 torr in a vessel with cold (77°K) walls, and for most reagents the observed populations are the initial ones of the reaction. The H2reaction also was examined in order to compare the results from our apparatus with studies from other laboratories. The reaction of F atoms with cyclo‐C6H12 was used for calibration of experimental conditions. In general more than 50% of the potential energy was partitioned to vibrational energy of HF†, and a population inversion between the v′ = 1 and 2 levels was observed for every example except CHCl3, but the populations from this reaction may have been affected by relaxation. Although a generally similar pattern for the HF† vibrational distribution was found, the relative populations did vary from one reagent to another. For example, more HF† (v = 3) was found from the CH3Cl and CH3Br reactions than from the reactions with alkanes. Rotational relaxation was partially arrested, and some qualitative differences in the HF† rotational populations from the reagents cited here were found; some much larger differences are reported in the following paper.