THERMAL-DECOMPOSITION OF CHLOROFLUOROMETHYL PEROXYNITRATES

The thermal decomposition of CCl3O2NO2, CCl2FO2NO2, and CClF2O2NO2 was studied in a temperature-controlled 420 1 reaction chamber using in situ detection of peroxynitrates by long-path IR absorption. The temperature dependence of the unimolecular dissociation rate constants was determined at total pressures of 10 and 800 mbar in nitrogen as buffer gas, and the pressure dependence was measured at 273 K between 10 and 800 mbar. In Troe's notation, the data are represented by the following values for the limiting low and high pressure rate constants k0/[N2] and k-infinity and the fall-off curvature parameter F(c) (in units of cm3 molecule-1 s-1, s-1): CCl3O2NO2, k0/[N2] = 6.3 x 10(-3) exp ( -85.1 kJ . mol-1/RT), k-infinity = 4.8 x 10(16) exp( -98.3 kJ . mol-1/RT), F(c) = 0.22; CCl2FO2NO2, k0/[N2] = 1.01 x 10(-2) exp( -90.3 kJ . mol-1/RT), k-infinity = 6.6 x 10(16) exp( -101.8 kJ . mol-1/RT), F(c) = 0.28; and CClF2O2NO2, k0/[N2] = 1.80 x 10(-3) exp(87.3 kJ . mol-1/RT), k-infinity = 1.60 x 10(16) exp( -99.7 kJ . mol-1/RT), F(c) = 0.30. From these dissociation rate constants and recently measured rate constants for the reverse reaction (see Caralp, Lesclaux, Rayez, Rayez, and Forst [19]), bond energies ( = DELTA-H0r,0) of 100, 103, and 104 kJ/mol were derived for the RO2-NO2 bonds in CCl3O2NO2, CCl2FO2NO2, and CClF2O2NO2, respectively. The kinetic and thermochemical parameters of these decomposition reactions are compared with those of the dissociation of other peroxynitrates. Atmospheric implications of the thermal stability of chlorofluoromethyl peroxynitrates are briefly discussed.