Thermal Decomposition of CxF2x+1C(O)OONO2 (x = 2, 3, 4).

ABSTRACT

The atmospheric degradation of molecules containing the CxF2x+1C(O) moiety, such as perfluoroaldehydes CxF2x+1C(O)H (x = 2-4) formed in the degradation of telomeric alcohols, could lead to the formation of perfluoroacyl peroxynitrates CxF2x+1C(O)OONO2. The thermal decomposition of the CxF2x+1C(O)OONO2 family (x = 2, 3, 4) was investigated by infrared spectroscopy and computational models. Each peroxynitrate synthesis was performed through the photolysis of gas mixtures of the corresponding perfluoroaldehyde, chlorine, nitrogen dioxide, and oxygen. Kinetic analysis for the thermal decomposition of peroxynitrates were performed in the range from 297.0 to 313.7 K at a total pressure of 1000 mbar and the activation energy was experimentally determined. Experimental data were complemented with theoretical data using the Gaussian09 Program Suite. The structures of peroxynitrates were optimized using DFT methods. The activation energies were calculated and investigated taking into account the stereoelectronic effects and using theoretical calculations as well as NBO analysis. The influence of anomeric interaction over the O-N bond was evaluated for all the molecules. Analysis of the results shows that CxF2x+1C(O)OONO2 stability is independent of CxF2x+1 chain length, in contrast to the behavior for perfluoroalkyl peroxynitrates (CxF2x+1OONO2).