Thermal stability of peroxynitrates

Peroxynitrates are thermally unstable intermediates (at ambient temperature s) in the atmospheric degradation of hydrocarbons. In this work, thermal li fetimes of nine peroxynitrates have been measured as a function of temperat ure and. for two of them, also. as a function of total pressure. In the pre sence of excess NO, relative concentrations of the peroxynitrates were foll owed in a 420 l reaction chamber as a function of time by means of Longpath IR absorption using a Fourier transform spectrometer. Original data on the unimolecular decomposition rate constants are presented for the peroxynitr ates RO2NO2 with R = C6H11, CH3C(O)CH2, C6H5CH2,CH2I, CH3C(O)OC(H)CH3, C6H5 OCH2, (CH3), NC(O), C6H2OC(O), and C2H5C(O). Thermal lifetimes at room temp erature and atmospheric pressure are very short (in the order of seconds) f or substituted methyl peroxynitrates (i.e., R'CH2O2NO2) but rather long for substituted formyl peroxynitrates (i.e., R " C(O)O2NO2). Kinetic data from this and previous work from our laboratory are used to derive structure-st ability relationships which allow an estimate of the thermal lifetimes of p eroxynitrates from readily available C-13 n.m.r. shift data. (C) 1999 John Wiley & Sons, Inc.