Nitric oxide , photooxidation

Reactions of this type can be sequentially incorporated into catalytic cycles. An example of such a cycle is shown in Scheme 9.4, where triphenylphosphine is oxidized to triphenylphosphine oxide by reaction with Mn (porph)0, and the nitrite complex Mn (porph)N02 then photoreacts to give Mn (porph)0 and nitric oxideS Photooxidations using Mn(TPP)(OAc) and periodate ion also involve... 

Research has shown that when polychlorpinen, ammonium nitrate, and superphosphate are present together in the soil, phosgene, carbon monoxide, nitric oxide, hydrochloric acid, ammonia, hydrocyanic anions, ozone, hydrogen fluoride and phosphide, etc. could appear in the air over the beet fields. Photooxidants could also appear. Airborne toxic compounds over this crop were noted in areas after precipitation with little wind, and with an air temperature of over 2CP . The combined and complex activity of pesticides and other chemical compounds led people who manually sowed beets to develop symptoms of poisoning. [21]... 

The photooxidation of acrylonitrile by hydroxyl radicals in the presence of nitric oxide has been observed to yield formaldehyde (HCHO) and formyl cyanide (HCOCN) (Hashimoto et al. 1984). 

Glasson, W. A. Effect of carbon monoxide on atmospheric photooxidation of nitric oxide—hydrocarbon mixtures. Environ. Sci. Technol. 9 343-347, 1975. 

Glasson, W. A., and C. S. Tuesday. Hydrocarbon reactivity and the kinetics of the atmospheric photooxidation of nitric oxide. J. Air Pollut. Control Assoc. 20 239-243, 1970. 

Aldehydes may also be thought of as photochemical oxidants. The definition here becomes a bit hazy, because aldehydes in themselves are photooxidative reactants, as well as secondary pollutants that have adverse health effects. Referring to Figure 4-4, we note that aldehyde concentration throughout the day in Rome, Italy, seems to decay at roughly the same rate as the nitric oxide concentration. It would be expected to track the reactive fraction of the hydrocarbons, and this is also borne out approximately by the Rome data. A maximal formaldehyde concen-... 

Photooxidation of chlorobenzene in air containing nitric oxide in a Pyrex glass vessel and a quartz vessel gave 3-chloronitrobenzene, 2-chloro-6-nitrophenol, 2-chloro-4-nitrophenol, 4-chloro-2-nitro-phenol, 4-nitrophenol, 3-chloro-4-nitrophenol, 3-chloro-6-nitrophenol, and 3-chloro-2-nitrophenol (Kanno and Nojima, 1979). A carbon dioxide yield of 18.5% was achieved when chlorobenzene adsorbed on silica gel was irradiated with light (A. >290 nm) for 17 h. The sunlight irradiation of chlorobenzene (20 g) in a 100-mL borosilicate glass-stoppered Erlenmeyer flask for 28 d yielded 1,060 ppm monochlorobiphenyl (Uyeta et al., 1976). 

Photolytic. Methyl vinyl ketone and methacrolein were reported as major photooxidation products for the reaction of 2-methyl-l,3-butadiene with OH radicals. Formaldehyde, nitrogen dioxide, nitric oxide, and HO2 were reported as minor products (Lloyd et al, 1983). Synthetic air containing gaseous nitrous acid and exposed to artificial sunlight (X = 300-450 nm) photo-oxidized 2-methyl-1,3-butadiene into formaldehyde, methyl nitrate, peroxyacetal nitrate, and a compound tentatively identified as methyl vinyl ketone (Cox et al, 1980). 

Tn recent years, a number of reaction models have been proposed to account for the chemical features of photochemical smog observed in atmospheric and laboratory studies (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11). Because of the complexity of smog chemistry and a lack of detailed knowledge of many relevant elementary reactions, numerous assumptions and simplifications are made in these mechanistic interpretations. A model for the chemistry of smog is presented here with a critical evaluation of the factors that control the major course of the reactions. The photooxidation of propylene (CsHq) in the presence of nitric oxide and nitrogen dioxide (NO + NO2 = NO, ) is used as a prototype for this study. 

Examination of Carbon Monoxide Effects. Recent work (44, 50, 51) of smog photochemistry has suggested that carbon monoxide may play a role in accelerating the photooxidation of hydrocarbon/nitric oxide mixtures. The mechanism suggested is... 

Using this type of reaction profile, various methods have been used to define reactivity. In this paper, the discussion is limited to the rate of photooxidation of nitric oxide (expressed as the NO2 f-max, the time to reach maximum N02), the maximum oxidant produced or the dosage of... 

Photolytic. Major products reported from the photooxidation of isopropylbenzene with nitrogen oxides include nitric acid and lienzaldehyde (Altshuller, 1983). A / -hexane solution containing isopropylbenzene and spread as a thin film (4 mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 22% of the applied isopropylbenzene photooxidized into a,a-dimethylbenzyl alcohol, 2-phenylpropionaldehyde, and allylbenzene (Moza and Feicht, 1989). 

Irradiation of ///-xylene isomerizes to p-xylene (Calvert and Pitts, 1966). Glyoxal, methylglyoxal, and biacetyl were produced from the photooxidation of ///-xylene by OH radicals in air at 25 °C (Tuazon et al, 1986a). The photooxidation of ///-xylene in the presence of nitrogen oxides (NO and NO2) yielded small amounts of formaldehyde and a trace of acetaldehyde (Altshuller et al, 1970). ///-Tolualdehyde and nitric acid also were identified as photooxidation products of ///-xylene with nitrogen oxides (Altshuller, 1983). The rate constant for the reaction of ///-xylene and OH radicals at room temperature was 2.36 x 10 " cmVmolecule-sec (Hansen et al., 1975). A rate constant of 1.41 x 10" L/molecule-sec was reported for the reaction of ///-xylene with OH radicals in the gas phase (Darnall et ah, 1976). Similarly, a room temperature rate constant of 2.35 x 10"" cmVmolecule-sec was reported for the vapor-phase reaction of ///-xylene with OH radicals (Atkinson, 1985). At 25 °C, a rate constant of 2.22 x 10"" cm /molecule-sec was reported for the same reaction (Ohta and Ohyama, 1985). Phousongphouang and Arey (2002)... 

The photolysis of nitrate on surfaces is especially important as it could lead to the renoxification of the atmosphere, whereby nitrate (or nitric acid) becomes a source of NO c and thus mineral dust would not be a permanent sink for gaseous nitrogen oxides, uptake of several gases, i.e., NO2 [ 126,172,173], O3 [174], and HCHO [175], while [176] presented similar conclusion for the surface photooxidation of SO2. 

---