Acetaldehyde nitrate radical reaction

Morris, E. D., and H. Niki (1974). Reaction of the nitrate radical with acetaldehyde and propylene. J. Phys. Chem. 78, 1337-1338. 

The OH radical-initiated photooxidation of 2-butanone in a smog chamber produced peroxyacetyl nitrate and acetaldehyde (Cox et al., 1981). Reported rate constants for the reaction of 2-butanone with OH radicals in the atmosphere and in water are 1.15 x lO and 1.50 x 10 cmVmolecule-sec, respectively (Wallington and Kurylo, 1987 Wallington et al, 1988a). The rate constant for the reaction of 2-butanone and OH radicals in the atmosphere at 300 K is 2.0 x 10 cmVmolecule-sec (Hendry and Kenley, 1979). Cox et al. (1981) reported a photooxidation half-life of 2.3 d for the reaction of 2-butanone and OH radicals in the atmosphere. 

Chemical/Physical. Atkinson et al. (2000) studied the kinetic and products of the gas-phase reaction of 2-heptanone with OH radicals in purified air at 25 °C and 740 mmHg. A relative rate constant of 1.17 x 10 " cmVmolecule Sec was calculated for this reaction. Reaction products identified by GO, FTIR, and atmospheric pressure ionization tandem mass spectroscopy were (with respective molar yields) formaldehyde, 0.38 acetaldehyde, L0.05 propanal, X0.05 butanal, 0.07 pentanal, 0.09 and molecular weight 175 organic nitrates. 

Major products reported from the photooxidation of o-xylene with nitrogen oxides include formaldehyde, acetaldehyde, peroxyacetyl nitrate, glyoxal, and methylglyoxal (Altshuller, 1983). The rate constant for the reaction of o-xylene and OH radicals at room temperature was 1.53 x 10 " cmVmolecule-sec (Hansen et al, 1975). A rate constant of 8.4 x 10 L/molecule-sec was reported for the reaction of o-xylene with OH radicals in the gas phase (Darnall et al., 1976). Similarly, a room temperature rate constant of 1.34 x 10 " cmVmolecule-sec was reported for the vapor-phase reaction of o-xylene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 1.25 X 10 " cmVmolecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). 

As shown, NO3 radical leads to different chemistry than does HO radical the peroxy radical can decompose to yield several products, including acetaldehyde, formaldehyde, 1,2-propanediol dinitrate (PDDN), nitroxyperoxypropyl nitrate (NPPN), and a-nitrooxyacetone. The reactions of the peroxy radicals with NO , species can lead to highly functionalized (and oxidized) organic compounds. 

As seen earlier in this chapter, the oxidation of organics produces a variety of free radicals, some of which can form peroxyacyl nitrates. For example, acetaldehyde is a classic precursor to the PAN through the following reaction sequence ... 

In the second series of experiments, the products from the photo-oxidation of diethyl ether, carried out in a Teflon bag reactor at ppm and ppb levels, have been determined by withdrawing vapour samples and monitoring by gas chromatography, HPLC and by chemiluminescence analysis. The major reaction products which have been measured are ethyl formate, ethyl acetate, acetaldehyde, formaldehyde, PAN, methyl nitrate and ethyl nitrate. The products observed arise from the decomposition reactions of the 1-ethoxyethoxy radical and from its reaction with oxygen. The data enable the establishment of a quantitative mechanism for the photo-oxidative reaction. In addition the rate of conversion of NO to NO2, determined by chemiluminescence analysis, shows that for each molecule of ether reacted only one molecule of NO is converted to NO2. In further end-product analyses experiments, the OH radical initiated photo-oxidation of n-hexane or the photolyses of 2- or 3-hexyl nitrites were studied to examine the... 

The major products were ethyl formate and formaldehyde and the minor products were ethyl acetate, acetaldehyde, peroxyacetyl nitrate, and methyl and ethyl nitrates. The products arise from the decomposition reactions of the 1-ethoxyethoxy radical and from its reaction with molecular oxygen ... 

The oxidation reactions of aldehydes with OH in the presence of NOx are very important from the point of forming peculiar compoimds with strong biological toxicity called peroxy acyl nitrates (PANs, RC(0)00N02). The initial reaction of OH and aldehydes are H-atom abstraction forming the aldehyde group to form acyl radicals as seen in Chap. 5, Sect. 5.2.11. For example, in the case of acetaldehyde, the reaction mechanism is. 

These reaction pathways are in parallel with those for alkanes mentioned in Sect, 7.2.2, and the reactions (7.7, 7.8 and 7.9) after CH3 radicals are formed in reaction (7.43) are the same as those in the oxidation processes of methane described in Sect. 7.1. The specific feature of oxidation reactions of aldehydes is the formation of a metastable peroxy acyl nitrates from the reaction of peroxy acyl radicals with NO2 by reaction (7.41). In the case of acetaldehyde, peroxy acetyl nitrate, CH3C(0)00N02, is formed. This compound is called PAN (Peroxy Acetyl Nitrate), and is known to have much stronger toxicity to plants than ozone. A group of peroxy acyl nitrates are collectively called PANs. 

An important reaction of the acylperoxy radical is with NO2 to form an acylperoxy nitrate. In the example shown, the oxidation of acetaldehyde gives acetyl peroxy radicals which can react with NO2 to form peroxyacetyl nitrate, CH3C(0)02N02, generally known as PAN ... 

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