Kinetics and mechanism of the reaction of CF3 radicals with NO2

Abstract

The reaction of CF, with NO, was studied at 296 2 2 K using two different absolute techniques Absolute rate constants of ( I 6 ? 0.3) X lo-" and ( 2 1-03+07) X lo-" cm3 molecule-' s-' were derived by IR fluorescence and UV absorption spectroscopy, respectivelyThe reaction proceeds via two reaction channels: CF, + NO, -CF,O + FNO. (70 t 12)% and CF, + NO, + CF,O + NO, (30 ? 12)%. An upper limit of 1 1 % for formation of other reaction products was determined. The overall rate constant was within the uncertainty independent of total pressure between 0.4 to 760 torr. Q

The CF3+NO2 rate constant measured between 1.5 and 110 Torr and between 251 and 295 K by time resolved infrared emission

“…The interpretation of reactant loss data in terms of the overall rate constant for process (1) is straightforward, but that of product formation can be ambiguous if the observed product itself is also subject to removal processes. This is the case in the present experiments (and in previous studies5, 7,8), where time resolved IR emissions from the and FNO CF 2 O products are observed. For a reaction sequence (1a) producing vibrationally excited followed by the quenching CF 2 Ot process…”

“…5) and (1.6 ^0.3) ] 10~11 cm3 molecule~1 s~1 (ref. 8), are sufficiently di †erent to indicate problems with such data analysis, and the agreement of one of them8 with the present result is again probably fortuitous.…”

Kinetic studies of the gas phase INO2 self-reaction

“…Notwithstanding the low [NO 2 ] employed here, the likely fate of the CF 3 radical produced in (10) is reaction with NO 2 . 57,58 The principal products of the CF 3 + NO 2 reaction, COF 2 and FNO, do not undergo further reaction under the chemical conditions employed, and therefore simply represent a non-recoverable loss of NO 2 . Moreover, the COF 2 and FNO products do not absorb in the experimental spectral region, and therefore do not complicate the analysis.…”

Kinetics and Mechanism of the Thermal Gas-Phase Reaction between NO2 and Trifluorochloroethene

“…The room-temperature rate constants reported for CF 3 + NO 2 → COF 2 + FNO by various authors [25][26][27][28][29][30][31][32][33] fall within the range of (0.6 − 1.9) × 10 10 dm 3 mol −1 s −1 . As the reaction (2) is an association reaction, then its activation energy must be very small, E 2 ≈ 0, and its preexponential factor A 2 can be assumed equal to 10 10 dm 3 mol −1 s −1 .…”

“…The kinetics and mechanism of the CF 3 • + NO 2 reaction have been studied by several research groups [25][26][27][28][29][30][31][32][33]. Results of these works indicate that the reaction is pressure independent and the predominant process is the direct formation of COF 2 and FNO.…”