Nitrogen dioxide, complexes

Peroxynitrite reacts with heme proteins such as prostacycline synthase (PGI2), microperoxidase, and the heme thiolate protein P450 to form a ferryl nitrogen dioxide complex as an intermediate [120]. Peroxynitrite also reacts with acetaldehyde with the rate constant of 680 1 mol 1 s" 1 forming a hypothetical adduct, which is decomposed into acetate, formate, and methyl radicals [121]. The oxidation of NADH and NADPH by peroxynitrite most certainly occurs by free radical mechanism [122,123], Kirsch and de Groot [122] concluded that peroxynitrite oxidized NADH by a one-electron transfer mechanism to form NAD and superoxide ... 

G. B. Bachman and his co-workers [91] investigated the action of the boron trifluoride and nitrogen dioxide complex, formed by combining the two compounds at 0°C ... 

It is also possible to use more powerful reagents to nitrate thiazoles for example, 2-methylthiazole has been nitrated using nitronium tetrafluorobo-rate and the complex nitrogen dioxide-boron tn fluoride (240). The overall yield is about 50 to 60%. 

Nitrogen dioxide in the atmosphere undergoes the same reaction and contributes to the formation of acid rain. It also initiates a complex sequence of smog-forming photochemical reactions. 

The detailed chemistry describing the synthesis of ammonia Is complex, so we Introduce the principles of equilibrium using the chemistry of nitrogen dioxide. Molecules In a sample of nitrogen dioxide are always colliding with one another. As described in Chapter 15, a collision in the correct orientation can result In bond formation, producing an N2 O4 molecule 2 NO2 N2 O4... 

Figure 2.20. Transformation of silica supported dinitrosyl complexes of nickel(II) leading to formation of nitrogen dioxide and its final stabilization on the support. The picture shows the molecular structure and the spin density contours calculated with BP/DNP method of the involved species, and evolution of the X-band EPR spectra of the NiN02 Si02 complex due to spillover of the ligand (adopted from [71]).

It has been suggested (Gabr et al. 1995) that nitric oxide (NO ), which is, of course, a radical, bleaches (3-CAR presumably by forming addition complexes. However, when we completely exclude oxygen from the system we found no evidence of an interaction between NO and 3-CAR (unpublished). Therefore, the observed reaction by Gabr et al. may have been due to nitrogen dioxide (N02 ). 

The miniature fiber optic NO2 sensors based upon dye encapsulation in the silica sol-gel can produce linear and reproducible results87. The nitrogen dioxide sensor based on immobilization of ruthenium complex [Ru(bpy)3]Cl2 demonstrated sensitivity in the hundreds parts per million range with reversibility and rapid response time. 

The disproportionation of nitrogen dioxide has been independently confirmed by the direct observation of nitrosonium cation as the EDA complex of hexamethybenzene by spectroscopic means as well as by the spectral comparison with the authentic [HMB, NO+] complex,240 i.e.,... 

Photochemical air pollution consists of a complex mixture of gaseous pollutants and aerosols, some of which are photochemically produced. Among the gaseous compounds are the oxidizing species ozone, nitrogen dioxide, and peroxyacyl nitrate ... 

The chemical composition of the photochemical-oxidant complex is discussed in Qiapter 2. The major phytotoxic components are ozone, nitrogen dioxide, and the peroxyaiylidtrates. The latter homologous... 

Nitrous acid catalysis also takes place in the nitration of such compounds (naphthalene) that are unable to undergo nitrosation on the given conditions or whose nitrosation proceeds slower than nitration. As accepted, the nitrosonium ion is formed from HNOj in acid media. The nitrosonium ion oxidizes an aromatic substrate into a cation-radical and transforms into nitric oxide. The latter reduces nitronium cation to nitrogen dioxide that gives a a-complex with the aromatic cation-radical ... 

The nitration of moderate to high molecular weight alkane substrates results in very complex product mixtures. Consequently, these reactions are only of industrial importance if the mixture of nitroalkane products is separable by distillation. Polynitroalkanes can be observed from the nitration of moderate to high molecular weight alkane substrates with nitrogen dioxide. The nitration of aliphatic hydrocarbons has been the subject of several reviews. 

As is the case with sulfur dioxide, nitric oxide undergoes a complex variety of reactions by which it is converted to nitrogen dioxide. For example, it too reacts with hydroperoxyl radicals to form nitrogen... 

Here PNO2 partial pressure of nitrogen dioxide in pascals (1 Pa = 0.000145 psi), and the activation energy is 3870 kJ/mol. Other saturated polymers are less susceptible to attack by NO2 than most unsaturated polymers such as synthetic rubbers (polyiso-prene, polybutadiene, and butyl rubber). The presence of oxygen also tends to accelerate degradation by NO2. The reaction of sulfur dioxide with saturated polymers is complex, but appears to be activated by ultraviolet radiation. 

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