Unimolecular Decomposition of Peroxynitrates

Thermal decomposition rate constants of peroxynitric acid (H02N02) and chloromethyl peroxynitrate (CH2C102N02) were measured as a function of temperature and total pressure in a photochemical reaction chamber of 420 1 volume. Peroxynitrate concentrations were monitored by long-path IR absorption using a Fourier transform spectrometer. Analysis of these results in terms of unimolecular reaction rate theories yields kinetic parameters which allow to calculate decomposition rate constants of H02N02 and CH2C102N02 for all pressures and temperatures which are of interest for atmospheric applications. These results, together with kinetic data on the thermal decomposition of other peroxynitrates previously obtained in our laboratory, allow to rationalize the change of the bond energies in peroxynitrates (R02-N02) with the nature of the group R. Combination of the decomposition data with experimental results on the reverse reactions from the literature