NO3 radical

In marked contrast there exists a volumnous literature on pulse radiolysis studies of nitric acid solutions (9). The NO3 radical has been identified as a major product although the mechanism of formation is still a matter of debate. While a number of reactions of this radical have been reported (10) there has evidently not been any pulse radiolysis studies of reactions with Pu ions. 

The kinetics of the various reactions have been explored in detail using large-volume chambers that can be used to simulate reactions in the troposphere. They have frequently used hydroxyl radicals formed by photolysis of methyl (or ethyl) nitrite, with the addition of NO to inhibit photolysis of NO2. This would result in the formation of 0( P) atoms, and subsequent reaction with Oj would produce ozone, and hence NO3 radicals from NOj. Nitrate radicals are produced by the thermal decomposition of NjOj, and in experiments with O3, a scavenger for hydroxyl radicals is added. Details of the different experimental procedures for the measurement of absolute and relative rates have been summarized, and attention drawn to the often considerable spread of values for experiments carried out at room temperature (-298 K) (Atkinson 1986). It should be emphasized that in the real troposphere, both the rates—and possibly the products—of transformation will be determined by seasonal differences both in temperature and the intensity of solar radiation. These are determined both by latitude and altitude. 

Rapid reactions of linalool with OH radicals, NO3 radicals, and ozone in which the major products were acetone and 5-ethenyldihydro-5-methyl-2(3//)-furanone (Shu et al. 1997). 

Products formed by reaction of NO3 radicals with a-pinene have been identified and include pinane epoxide, 2-hydroxypinane-3-nitrate, and 3-ketopinan-2-nitrate formed by reactions at the double bond, and pinonaldehyde that is produced by ring fission between C-2 and C-3 (Wangberg et al. 1997). These reactions should be viewed in the general context of odd nitrogen to which alkyl nitrates belong (Schneider et al. 1998). 

Wangberg 1,1 Barnes, KH Becker (1997) Product and mechanistic study of the reaction of NO3 radicals with a-pinene. Environ Sci Technol 31 2130-2135. 

NO is added to inhibit photolysis of NOj that would produce O3 and NO3 radicals ... 

Nitroarenes were formed under laboratory conditions when PAH reacted with gas-phase OH radical (in presence of NO ) and N2O540 45. The atmospheric nitroarene formation rate depends upon the concentration of the individual species N2O5-NO3-NO2 An analogous reaction sequence occurs when PAH reacts in N2O5-NO3-NO2 systems46. Naphthalene reacts with NO3 radical forms NO3-naphthalene adduct, which dissociates or reacts with NO2 to form nitronaphthalene and other products as shown in Figure 6. 

Table 3 shows the atmospheric lifetime for eleven PAH with respect to gas-phase reaction with OH and NO3 radicals, O3 and N2O5. This was calculated from the estimated and calculated rate constants. It is evident that most of the nitroarenes formed under ambient atmospheric conditions were produced by reaction of PAH with OH. The PAH reaction with NO3 radical was also considered as an important step because it resulted in the formation of nitroarenes from the N2O5 reaction with gas-phase PAH. 

TABLE 3. Calculated atmospheric lifetimes of PAH due to gas-phase reactions with OH and NO3 radicals, O3 and N2O547... 

By indirect oxidation with electrogenerated NO3 radicals in f-butanol/ water/HN03/02, saturated hydrocarbons were oxidized to ketones with a statistical H-abstraction at the methylene... 

Rate constants of 1.90-2.53 x lO cmVmolecule-sec (Atkinson, 1985), 1.99 x 10 " cmVmolecule-sec (Atkinson, 1990), and 2.29 x 10 " cmVmolecule-sec (Sabljic and Glisten, 1990) were reported for the gas-phase reaction of acrolein and OH radicals. Acrolein reacts with ozone and NO3 radicals in gas-phase at rates of 6.4 x 10cmVmolecule-sec (Atkinson and Carter, 1984) and 1.15 x 10cmVmolecule-sec, respectively (Sabljic and Glisten, 1990). 

Photolytic. The following rate constants were reported for the reaction of 1,3-butadiene and OH radicals in the atmosphere 6.9 x 10 " cmVmolecule-sec (Atkinson et al., 1979) and 6.7 x lO " cmVmolecule-sec (Sabljic and Glisten, 1990). Atkinson and Carter (1984) reported a rate constant of 6.7-8.4 X 10 " cmVmolecule-sec for the reaction of 1,3-butadiene and ozone in the atmosphere. Photooxidation reaction rate constants of 2.13 x 10 and 7.50 x 10cm /molecule-sec were reported for the reaction of 1,3-butadiene and NO3 (Renter and Schindler, 1988 Sabljic and Glisten, 1990). The half-life in air for the reaction of 1,3-butadiene and NO3 radicals is 15 h (Atkinson et al., 1984a). 

Photolytic. A second-order rate constant of 1.21 x 10 cm /molecule-sec was reported for the reaction of ethyl mercaptan and NO3 radicals in the atmosphere at 297 K (Atkinson, 1991). 

Photolytic. Fluorene reacts with photochemically produced OH radicals in the atmosphere. The atmospheric half-life was estimated to range from 6.81 to 68.1 h (Atkinson, 1987). Behymer and Hites (1985) determined the effect of different substrates on the rate of photooxidation of fluorene (25 tig/g substrate) using a rotary photoreactor. The photolytic half-lives of fluorene using silica gel, alumina, and fly ash were 110, 62, and 37 h, respectively. Gas-phase reaction rate constants for OH radicals, NO3 radicals, and ozone at 24 °C were 1.6 x lO , 3.5 x 10 and <2 x 10in cmVmolecule-sec, respectively (Kwok et al., 1997). 

The estimated atmospheric lifetimes for the reaction of 2-methyl-1,3-butadiene with ozone, OH, and NO3 radicals are 28.3, 2.9, and 0.083 h, respectively (Atkinson and Carter, 1984). Chemical/Physical. Slowly oxidizes and polymerizes in air (Huntress and Mulliken, 1941). 

Photolytic. Irradiation of vinyl chloride in the presence of nitrogen dioxide for 160 min produced formic acid, HCl, carbon monoxide, formaldehyde, ozone, and trace amounts of formyl chloride and nitric acid. In the presence of ozone, however, vinyl chloride photooxidized to carbon monoxide, formaldehyde, formic acid, and small amounts of HCl (Gay et al, 1976). Reported photooxidation products in the troposphere include hydrogen chloride and/or formyl chloride (U.S. EPA, 1985). In the presence of moisture, formyl chloride will decompose to carbon monoxide and HCl (Morrison and Boyd, 1971). Vinyl chloride reacts rapidly with OH radicals in the atmosphere. Based on a reaction rate of 6.6 x lO" cmVmolecule-sec, the estimated half-life for this reaction at 299 K is 1.5 d (Perry et al., 1977). Vinyl chloride reacts also with ozone and NO3 in the gas-phase. Sanhueza et al. (1976) reported a rate constant of 6.5 x 10 cmVmolecule-sec for the reaction with OH radicals in air at 295 K. Atkinson et al. (1988) reported a rate constant of 4.45 X 10cmVmolecule-sec for the reaction with NO3 radicals in air at 298 K. 

Chemical/Physical. In the gas phase, cycloate reacts with hydroxyl and NO3 radicals but not with ozone. With hydroxy radicals, cleavage of the cyclohexyl ring was suggested leading to the formation of a compound tentatively identified as C2H5(Cff0)NC(0)SC2H5. The calculated photolysis lifetimes of cycloate in the troposphere with hydroxyl and NO3 radicals are 5.2 h and 1.4 d, respectively. The relative reaction rate constants for the reaction of cycloate with OH and nitrate radials are 3.54 x lO " and 3.29 x 10 cm /molecule-sec, respectively (Kwok et al., 1992). 

Atkinson, R. Kinetics and mechanisms of the gas-phase reactions of the NO3 radical with organic compounds, J. Phys. Chem. Data, 20(3) 459-507, 1991. 

Atkinson, R., Ashmann, S.M., and Arey, J. Reactions of OH and NO3 radicals with phenol, cresols, and 2-nitrophenol at 296 ... 

Benter, T. and Schindler, R.N. Absolute rate coefficients for the reaction of NO3 radicals with simple dienes, Chem. Phys. Lett., 145 67-70, 1988. 

Kwok, E.S.C., Atkinson, R., and Arey, J. Kinetics of the gas-phase reactions of indan, indene, fluorene, and 9,10-dihydro-anthracene with OH radicals, NO3 radicals and O3, Int. J. Chem. Kinet., 29 4299-4310, 1997. 

Sabljic, A. and Glisten, H. Predicting the night-time NO3 radical reactivity in the troposphere. Atmos. Environ., 24A(l) 73-78, 1990. 

Thomas. K.. Volz-Thomas, A., Mihelcic, D., Smit, H.G.J., and Kley, D. On the exchange of NO3 radicals with aqueoirs... 

Zhou, S. Barnes, L Zhu, T. Bejan, 1. Benter, T. Kinetic Study of the Gas-Phase Reactions of OH and NO3 Radicals and O3 with Selected Vinyl Ethers. J. Phys. Chem. A. 2006, no, 7386-7392. 

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. 

In concentrated solutions, direct action of nitrate ion is also taken into consideration. In addition, in concentrated nitric acid, nitric acid molecule (HNO3) coexists. Although it is known that NOs plays an important role in concentrated nitric acid, precise formation process was not known. Recently, it was clarified that the formation of the NO3 radical is formed by two different processes reaction of OH with molecular HNO3 and direct action of radiation to HNO3 and NO3 [121]. Experimentally obtained temporal behavior of N03 and its yield as a function of nitrate ions are shown in Figs. 7 and 8, respectively. 

Therefore the NO3 radical is not formed in diluted nitrate solutions because OH does not react with NO. This finding suggests that the OH reacts with molecular HNO3 through H atom abstraction. The formation of NO3 through direct process is in proportion to the electron fraction of nitrate. In nitric acid, NO3 is formed through two formation processes, but, in concentrated nitrate solutions, only direct process plays a role. The direct action of radiation is commonly observed in concentrated solutions and examples are reviewed in Ref. 122. 

Figure 7 Formation of NO3 radical observed at 640 nm in 3 M HNO3 and 6 M NaN03 solutions in the presence and absence of 0.1 M ethanol. (From Ref. 121.)...

The atmospheric oxidation of dimethyl sulfide (DMS) and DMSO has been reviewed. Kinetics of oxidation of DMS and DMSO with OH and NO3 radicals and with halogen and halogen oxides have been described and the mechanistic aspects have been discussed.244 A review of recent studies of the mechanism and kinetics of the gas-phase oxidation of dimethyl ether has mentioned the pressure dependence of the... 

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