THERMAL-DECOMPOSITION REACTIONS OF GASEOUS DIOXYGEN DIFLUORIDE AND DIOXYGEN FLUORIDE AT AMBIENT-TEMPERATURE

The decomposition of gaseous dioxygen difluoride (FOOF) and dioxygen f luoride (FOG) to F-2 and O-2 at ambient temperature has been studied b y electron paramagnetic resonance (EPR) spectroscopy, Fourier-transfor m infrared (FT-IR) spectroscopy and transient gas pressure measurement s. The formation of oxygen in FOOF/FOO gas mixtures, as demonstrated b y stopped-flow EPR, was first-order under low-pressure conditions (1-1 0 Torr) with rate constants in the range of 0.1-0.2 s(-1), depending u pon wall materials. EPR spectroscopy detected neither F atoms nor FOO radicals as intermediates despite the presence of FOO radicals shown b y complementary FT-IR experiments. The FT-IR spectra of gaseous FOOF u ndergoing decomposition at ambient temperature showed prominent, isola ted bands near 1210 cm(-1) (FOOF) and near 1490 cm(-1) (FOG). Overlapp ing bands attributable to both species were seen near 650 cm(-1), and weak features appeared elsewhere. At nominal initial FOOF/FOO pressure s of 4-20 Torr, results from stopped-flow FT-IR kinetics analysis usin g these bands generally agreed with the EPR results and yielded first- order rate constants of 0.12 +/- 0.01 s(-1) and 0.22 +/- 0.03 s(-1), r espectively, for FOO and FOOF disappearance. Oxygen-carrier FT-IR expe riments strongly suggested that a reversible reaction between FOOF and O-2 forms FOO (K-eq approximate to 0.018), and that this reaction was rapid relative to FOOF/FOO decomposition. Analysis of the stopped-flo w FT-IR results yielded infrared peak absorptivities for FOOF absorpti on at 1205 cm(-1) of 1.8 +/- 0.4 X 10(-3) (Torr cm)(-1) and for FOO ab sorption at 1486 cm(-1) of 3.5 +/- 1 X 10(-3) (Torr cm)(-1). The obser ved kinetics are discussed in terms of the possible decomposition reac tion mechanisms.