The thermal decomposition of CC1302N02, CC12F02N02, and CClFZO2NO2 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 ko/[Nz] and k , and the fall-off curvature parameter F, (in units of cm3 molecule-' s-', s-'): CC1302N02, ko/[Nz] = 6.3 x exp(-85.1 k J . mol-'/RT), k , = 4.8 x 10l6 exp(-98.3 k J . mol-'/RT), F, = 0.22; CClzF02N02, ko/[Nz] = 1.01 x lo-' exp(-90.3 k J . mol-'/RT), k , = 6.6 x 10l6 exp(-101.8 k J . mol-'/RT), F, = 0.28; and CClF202N02, ko/[Nz] = 1.80 x exp(-87.3 k J . mol-'/RT), k , = 1.60 x 10l6 exp(-99.7 k J . mol-'/RT), F, = 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 (= AH:o) of 100, 103, and 104 kJ/mol were derived for the R02-N02 bonds in CC1302N02, CC12FOZN02, and CClFzOZN02, 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.