Reaction between NO and

It is significant that in the absence of O2 (solid points in Figure 4) almost no radicals were formed the amount reported is close to the detection limit of the instrument. In one sense, this observation provides an explanation for the positive effect that O, has on the rate of reaction between NO and CH4 [3,4] i.c., O2 enhances CH,- radical formation. However, the results also indicate that NO itself is not very effective in generating active sites which are responsible for CH,- radical production. This means that the reaction of NO with CH4, in the absence of added O, may occur via a nonradical pathway. 

Other postulated routes (Jourd heuil et al., 2003) to RSNO formation include the reaction between NO and 02 to yield N02 via a second-order reaction. NO and thiolate anion, RS, react giving rise to thiyl radical, (RS ) [e]. RS then reacts with NO to yield RSNO [f]. The reaction between RS and RS- can also be the source of non-enzymatic generation of superoxide anion (02 ) [g], [h]. 02 reacts with NO to produce peroxynitrite (ONOO ) [i] (Szabo, 2003). Thiols react with ONOOH to form RSNOs [k] (van der Vliet et al.,1998). 

It is generally thought that NO interferes with lipid peroxidation by providing alternative ways to chain termination (Rubbo et al, 1995 Rubbo et al, 1994). For example, radical-radical reactions between NO and LOO, LO and L radicals, as shown below, likely occur ... 

The experimental results of Hinshelwood and Greenl l tend to support the following mechanism for the reaction between NO and H, ... 

Another observation that supports the proposed scheme comes from the much smaller yield of ABTS - at pH 11 than in acidic solutions in the presence of an excess of NO. The known chemistry of NO, N02, and N203 is responsible for this pH effect. The rapid reaction between NO and N02, Eq. (41) (189), produces N203, which hydrolyzes, Eq. (42), much more rapidly at high pH (190), thus minimizing the reverse reaction and with it the amount of N02 available to other scavengers. 

The same conclusion was also achieved performing a transient experiment at constant temperature (170°C) (Ciardelli et al., 2004b Nova et al., 2006b) the NO conversion levels measured either when the fast SCR reaction was occurring or when the reaction between NO and surface nitrates was occurring were practically unaltered, indicating that the two reactions were actually progressing at the same rate. 

It is noted in conclusion that the reaction between NO and 02 CAg) has been examined by Falick, Mahan, and Myers134 and found to be not detectable. 

The principal reaction between NO and N atoms is the elementary bimolecular exchange reaction... 

Unlike NO autoxidation, the reaction between NO and 02 occurs at near diffusion control [4—7 x 109M-1 s-1 (33, 218)]. 

The spin-forbidden reaction between HNO and 02 is quite slow [ 10 M s (147)] compared to the spin-allowed reaction between NO- and 02 [Eq. 9 ... 

Figure 2. A plot of the log of the rate constant vs. pH for the reaction between NO and HSO /SO .

Figure 3. UV absorption at 280 nm vs. time for the reaction between NO and HS03"/S03 in a typical stopped-flow experiment at pH 4.6.

FIGURE 9.11 Time evolution of ax - aXo vs. time of the reactants and reaction products for the reaction between NO and Fe, where the symbol describes aN2 - aN2, the sign a expresses aN0 - aNOo, and the character denotes aN20 - aN2o0-... 

We now study the reaction between carbon monoxide (CO) and nickel (Ni) [122,123], The reaction was tested in the high-vacuum systems described to study the reaction between NO and Fe (see Figures 9.8 and 9.9). The evaporation of Ni was also carried out at P = 10 6 Torr, with the help of a filament made of a wolfram (W) wire of 0.5 mm diameter and 10 cm length [122], as was previously described [119], The whole vacuum system was attached to a mass spectrometer to analyze the reaction products [122,123] (see Figure 9.9). The methodology to test the reaction was as follows Ni was... 

FIGURE 9.12 Mossbauer spectrum of the solid-phase products of the reaction between NO and Fe. 

FIGURE 9.13 Electron diffraction patterns of the solid-phase reactant and product of the reaction between NO and Fe (a) initial Fe thin film, and (b) thin film reacted with NO at 527 K. 

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