Thermal lifetimes of peroxynitrates occurring in the atmospheric degradation of oxygenated fuel additives

Peroxynitrates are thermally unstable intermediates in the atmospheric degradation of hydrocarbons. New classes of peroxynitrates, alkoxyalkyl and alkoxyformyl peroxynitrates, can be formed during the atmospheric degradation of dialkyl ethers being extensively used as fuel additives. In this paper, the thermal lifetimes of methoxymethyl peroxynitrate, methoxyformyl peroxynitrate, and tert-butoxyformyl peroxynitrate [i.e., RO2NO2 with R = CH3OCH2, CH3OC(O), and t-C4H9OC(O), respectively] are reported at atmospheric pressure as a function of temperature. Relative concentrations of the peroxynitrates are followed in a 420-L reaction chamber in the presence of an excess of NO as a function of time via long-path IR absorption using a Fourier transform spectrometer. Thermal lifetimes at room temperature and atmospheric pressure are very short (in the order of 1 s) for CH3OCH2O2NO2; however, for the alkoxyformyl peroxynitrates [R'OC(O)O2NO2], the lifetimes are much longer with values similar to that of PAN. Alkoxyformyl peroxynitrates, in particular tert-butoxyformyl peroxynitrate, could accumulate to detectable levels in polluted air and thus make a contribution to the long-range transport of NOx.