The CF<sub>3</sub>C(O)O<sub>2</sub> Radical. Its UV Spectrum, Self-Reaction Kinetics, and Reaction with NO
作者:M. Matti Maricq、Joseph J. Szente、Gregory A. Khitrov、Joseph S. Francisco
DOI:10.1021/jp9532935
日期:1996.1.1
Flash photolysis combined with time-resolved UV spectroscopy and transient infrared absorption is used to investigate the reactions of CF3C(O)O2 with itself, CF3O2, and nitric oxide. The UVspectrum of CF3C(O)O2 exhibits two bands, the stronger short wavelength component of which has a maximum cross section of 7.1 × 10-18 cm2 at 207 nm. These bands are used to monitor the disappearance of CF3C(O)O2
闪光光解结合时间分辨紫外光谱和瞬态红外吸收用于研究CF 3 C(O)O 2与其自身,CF 3 O 2和一氧化氮的反应。CF 3 C(O)O 2的紫外光谱显示两个波段,其中较强的短波分量在207 nm处的最大横截面为7.1×10 -18 cm 2。这些频带被用于监测CF消失3 C(O)O 2和次级CF的形成3 ö 2,得到的自反应速率常数 ×10 -12 ë(270±200)/ T cm 3 s -1。发现CF 3 C(O)O 2和CF 3 O 2之间的交叉反应缓慢,速率常数≤2×10 -12 cm 3 s -1。瞬态红外监测NO的损失和随之而来的NO 2的形成导致CF 3 C(O)O 2与CF 3 C(O)O 2之间的反应速率常数为 ×10 -12 e (563±115)/ T cm 3 s -1。不。该结果暗示CF 3 C(O)O作为氢氟碳化合物(HFCs)大气降解过程中的中间体形成的2个自由基迅速转化为CF
Rate constants for the reaction of halogenated alkylperoxyl radicals with iodide: influence of substituents, solvent polarity, and proton concentration
polarity of solvent mixtures and electronegativity of the substituents at the α-C atom of the peroxyl radicals. They strongly depend on all these variables, with the actual numbers covering a range from 3 × 105 to 7.0 × 108 M−1 s−1. A good linear relationship is obtained between logk and the dielectric constant of the solvent mixture. Within a particular solvent mixture the rateconstants depend strongly
Decomposition of the CF3CO Radical: Pressure and Temperature Dependencies of the Rate Constant
作者:A. Tomas、F. Caralp、R. Lesclaux
DOI:10.1524/zpch.2000.214.10.1349
日期:2000.1.1
The decomposition rate constant of the CF
CF的分解速率常数
The CF3+NO2 rate constant measured between 1.5 and 110 Torr and between 251 and 295 K by time resolved infrared emission
作者:Ciara Breheny、Gus Hancock、Claire Morrell
DOI:10.1039/b004709k
日期:——
The rate constant k1 for reaction of CF3 with NO2 was investigated over the pressure range 1.5–110 Torr
Ar or N2 and at temperatures between 251 and 295 K. Time resolved emission from vibrationally excited CF2O and FNO products was used as a detection method for CF3 removal. The rate constant at room
temperature shows no marked variation with pressure, with an average value of k1
= (1.75 ± 0.26) × 10−11 cm3 molecule−1
s−1, where the errors are 2σ, but a small reduction at the lowest pressure indicates the possible
contribution from a third body recombination process. We conclude that this process is minor, and if it is treated as a separate reaction channel it results in a limiting high pressure branching ratio of 13 ± 7%, which drops to half that value at 10 Torr. As the limiting high and low pressure rate constants are within the 2σ error bars of k1, we recommend the average value as applying over the full pressure range. Combination with previous results shows that of the possible bimolecular channels, formation of CF2O + FNO dominates (ca. 95%).
No temperature dependence is seen, within experimental error. Pitfalls in the extraction of rate constants from
the analysis of time resolved product emission are discussed, and a method is described to assign rate
constants unambiguously to reactive formation and collisional quenching. CF3 radicals were formed from the 248 nm photolysis of CF3I, and observations of emission from the radical show previously unobserved
excitation in the asymmetric C–F stretching mode ν3.
Kinetics of the reactions of CF3O2 with OH, HO2 and H
作者:Peter Biggs、Carlos E. Canosa-Mas、Dudley E. Shallcross、Alison Vipond、Richard P. Wayne
DOI:10.1039/a700960g
日期:——
The kinetics of the reactions:
CF
3
O
2
+OH→products (1),
CF
3
O
2
+HO
2
→products (2)
and CF
3
O
2
+H→CF
3
O+OH
(3), have been investigated using a discharge fast-flow
tube, at T=296±1 K and
P=ca. 2 Torr. Two detection systems were
used: laser-induced fluorescence of NO
2
produced
from the titration of CF
3
O
2
with NO,
and resonance fluorescence of OH. The rate constants (in
cm
3
molecule
-1
s
-1
) were
found to be,
k
1
=(4.0±0.6)×10
-11
, k
2
⩽3×10
-12
and
k
3
=(1.1±0.3)×10
-
10
. Experimental evidence suggests that the likely
products of the reaction of CF
3
O
2
with
OH are HO
2
and CF
3
O.