Thermal stability of Peroxynitrates

Abstract

Peroxynitrates are thermally unstable intermediates (at ambient temperatures) in the atmospheric degradation of hydrocarbons. In this work, thermal lifetimes of nine peroxynitrates have been measured as a function of temperature and, for two of them, also, as a function of total pressure. In the presence of excess NO, relative concentrations of the peroxynitrates were followed in a 420 I 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 peroxynitrates RO 2 NO 2 with R ϭ C 6 H 11 , CH 3 C(O)CH 2 , C 6 H 5 CH 2 , CH 2 I, CH 3 C(O)OC(H)CH 3 , C 6 H 5 OCH 2 , (CH 3 ) 2 NC(O), C 6 H 5 OC(O), and C 2 H 5 C(O). Thermal lifetimes at room temperature and atmospheric pressure are very short (in the order of seconds) for substituted methyl peroxynitrates (i.e., RЈCH 2 O 2 NO 2 ) but rather long for substituted formyl peroxynitrates (i.e., RЉC(O)O 2 NO 2 ). Kinetic data from this and previous work from our laboratory are used to derive structure-stability relationships which allow an estimate of the thermal lifetimes of peroxynitrates from readily available 13 C n.m.r. shift data.

A gas chromatograph for quantification of peroxycarboxylic nitric anhydrides calibrated by thermal dissociation cavity ring-down spectroscopy

“…In high concentrations, PANs are lachrymators, and are toxic to plants (Horvath et al, 1986;Kleindienst, 1994). Furthermore, PANs are considered NO x reservoir species, because they are longer lived than NO x (≡ NO + NO 2 ) and generate NO 2 when they decompose (Kirchner et al, 1999). Chemical transport models indicate Published by Copernicus Publications on behalf of the European Geosciences Union.…”

Improved mid-infrared cross-sections for peroxyacetyl nitrate (PAN) vapour

“…In the atmosphere, the highest concentrations of PAN are often found in so-called photochemical smog episodes, such as Los Angeles smog events where it was first noted by Stephens (1956). The chief loss mechanism for PAN in the lower troposphere is thermolysis, which occurs readily at temperatures above 273 K with a PAN lifetime of a matter of hours (Kirchener et al, 1999). However, this thermolysis rate drops quickly with temperature allowing lifetimes in the order of months against thermolysis in the cold upper troposphere (of order 200 K).…”

“…New satellite missions could provide an alternative means to remotely detect trace organic species on a global scale through their characteristic infrared signature. The Michelson Interferometer for Passive Atmospheric Sounding (Nett et al, 2001) onboard the European Space Agency's Envisat platform (Louet, 2001) launched in March 2002, is one such instrument to exploit the potential of using infrared limb emission spectra measured at high spectral resolution to retrieve profile information for trace atmospheric species (Fischer and Oelhaf, 1996). The retrieval of concentration data from satellite-derived spectra requires accurate reference cross-sections measured in the laboratory at sufficiently high spectral resolution.…”

Aircraft based four-channel thermal dissociation laser induced fluorescence instrument for simultaneous measurements of NO<sub>2</sub>, total peroxy nitrate, total alkyl nitrate, and HNO<sub>3</sub>

“…Since all the cells measure NO 2 they are calibrated only for NO 2 since in the heated inlets PNs, ANs and HNO 3 achieve a complete dissociation into NO 2 (Hao et al, 1994;Zabel, 1995;Kirchner et al, 1999;Day et al, 2002). Figure 5 shows a time series of NO 2 , PAN and ethyl nitrates detected by the first three cells of the TD-LIF.…”