F. Zabel et al., THERMAL-DECOMPOSITION OF CF3C(O)O2NO2, CCLF2C(O)O2NO2, CCL2FC(O)O2NO2, AND CCL3C(O)O2NO2, International journal of chemical kinetics, 26(8), 1994, pp. 827-845
Haloacetyl peroxynitrates are intermediates in the atmospheric degrada
tion of a number of haloethanes. In this work, thermal decomposition r
ate constants of CF3C(O)O2NO2, CClF2C(O)O2NO2, CCl2FC(O)O2NO2, and CCl
3C(O)O2NO2 have been determined in a temperature controlled 420 1 reac
tion chamber. Peroxynitrates (RO2NO2) were prepared in situ by photoly
sis of RH/Cl2/O2/NO2/N2 mixtures (R = CF3CO, CClF2CO, CCl2FCO, and CCl
3CO). Thermal decomposition was initiated by addition of NO, and relat
ive RO2NO2 concentrations were measured as a function of time by long-
path IR absorption using an FTIR spectrometer. First-order decompositi
on rate constants were determined at atmospheric pressure (M = N2) as
a function of temperature and, in the case of CF3C(O)O2NO2 and CCl3C(O
)O2NO2, also as a function of total pressure. Extrapolation of the mea
sured rate constants to the temperatures and pressures of the upper tr
oposphere yields thermal lifetimes of several thousands of years for a
ll of these peroxynitrates. Thus, the chloro(fluoro)acetyl peroxynitra
tes may play a role as temporary reservoirs of Cl, their lifetimes in
the upper troposphere being limited by their (unknown) photolysis rate
s. Results on the thermal decomposition of CClF2CH2O2NO2 and CCl2FCH2O
2NO2 are also reported, showing that the atmospheric lifetimes of thes
e peroxynitrates are very short in the lower troposphere and increase
to a maximum of several days close to the tropopause. The ratio of the
rate constants for the reactions of CF3C(O)O2 radicals with NO2 and N
O was determined to be 0.64 +/- 0.13 (2sigma) at 315 K and a total pre
ssure of 1000 mbar (M = N2). (C) 1994 John Wiley & Sons, Inc.