CF3CO dissociation kinetics

Abstract

Flash photolysis of CldCF3CHOhI gas mixtures (M = N2, SF6) combined with transient diode laser detection of CO is used to investigate the kinetics of the CF3CO + M -CF3 + CO + M dissociation reaction and the competition with the CF3CO self-reaction. The studies are carried out over a temperature range 223-353 K and a pressure range 25-650 Torr. The temperature dependent low-and high-pressure-limiting rate constants in NZ are given by k2.0 = (3.9 x 10-")e-(255M650fl cm3 s-I and &2,.. = (1.5 x 10")e-(424M660Y7 s-I, respectively, with F, = 0.6. Essentially the same high-pressure rate constant is obtained for a bath gas of SF6. These results clarify a previous discrepancy of about 10 k c d m o l in the activation energy. As part of this study, we report a rate constant of k3 = (2.5 f 1.5) x lo-'' cm3 s-' for the reaction CF3CO + CF3CO -(CF3CO)2 and a rate constant of k4 = (6.1 f 2.5) x cm3 s-I for CF3CO + C12 -CF3C(O)C1+ C1. Both are essentially independent of temperature over the range 223-353 K.

Fragmentation Pathways in a Series of CH3COX Molecules in the Strong Field Regime

“…As seen in Figure 4, the CF 3 -C and CH 3 -C bond dissociation energies in neutral trifluoroacetone are nearly equal (3.72 and 3.88 eV, respectively) and are very similar to the C-CH 3 bond energy in acetone (3.61 eV). The computed energetics for the subsequent dissociation of the acyl radicals, 0.25 eV for CF 3 CO and 0.42 eV for CH 3 CO, are in good agreement with published experimental and calculated dissociation energies [11][12][13][14] (but it should be noted that these processes have barriers that are 0.2-0.3 eV above the dissociation energy). Of the possible dissociation paths for CF 3 COCH 3 , formation of CH 3 + and CF 3 + are disfavored because these have higher IP's than CX 3 CO. Production of CH 3 CO + is preferred thermodynamically because of the stability of acetyl cation.…”

Tropospheric photooxidation of CF<sub>3</sub>CH<sub>2</sub>CHO and CF<sub>3</sub>(CH<sub>2</sub>)<sub>2</sub>CHO initiated by Cl atoms and OH radicals

“…This observation is consistent with a rate ratio Maricq et al, 1995;Wallington et al, 1994). On the other hand, the addition of O 2 decreased the detection sensitivity of Cl atoms, as O 2 is an efficient quencher and absorber of the fluorescence of Cl atoms.…”

Temperature dependence of the gas-phase reactions F+CHFO, CFO+F, and CFO+CFO

“…Maricq et al [15] claimed this process to be nearly temperature independent: [15]). We wish to point out that for these measurements at higher temperatures an Arrhenius equation can be calculated yielding Ϫ1 E ϭ 6100 J mol A which is only a little lower than our value.…”

“…Reaction (3) was studied at several temperatures before by following the CFO concentration in a flashphotolysis experiment [15]. Maricq et al [15] claimed this process to be nearly temperature independent: [15]).…”