Nitrogen dioxide dissociation

The brown nitrogen dioxide gas condenses to a yellow liquid which freezes to colourless crystals of dinifrogen tetroxide. Below 150°C the gas consists of molecules of dinifrogen tetroxide and nitrogen dioxide in equilibrium and the proportion of dinifrogen tetroxide increases as the temperature falls. Above 150°C nitrogen dioxide dissociates into nitric oxide and oxygen. 

When heated above 150°C, nitrogen dioxide dissociates to nitric oxide and oxygen ... 

Because nitrogen dioxide dissociates into nitric oxide and atomic oxygen under the action of sunlight as shown in Equation (16.39), it plays a central role in the formation of photochemical smog, as we will discuss in the selected topic in depth. It also serves as a useful nonaqueous solvent. 

Peroxonitrous acid can decompose by two pathways isomerization to nitric acid, and dissociation into the hydroxyl radical and nitrogen dioxide. 

These fragments either combine intramolecularly to form the ortho and para nitro compounds or dissociate completely and then undergo an intermolecular reaction to form the same products. The theory was not developed to include a detailed transition state and no mention was made of how the para isomer was formed. Reduction of the cation-radical could give the amine (which was observed experimentally76), but one would expect the concurrent formation of nitrogen dioxide and hence nitrite and nitrate ions however, the latter has never been... 

C15-0087. Nitrogen dioxide in smog can combine in an elementary reaction to form N2 O4 molecules. The combination reaction is exothermic by 57 kJ/mol. For the reverse reaction, the dissociation of N2 O4, = 70 kJ/mol. (a) Draw a molecular picture of NO2 combining to form N2 O4. ... 

The existence of the nitryl ion in the presence of acidic substances suggested that nitrate ion in fused alkali nitrates might dissociate into N02+ and 0 2 ions (5). To determine the extent of the dissociation, it was necessary to develop an electrode potentiometrically responsive to either N02+ or 0 2. The only possibility for a reversible N02+ electrode that came to mind was nitrogen dioxide gas bubbling over platinum. This electrode did respond to N02+ in acidic solutions, but as ex-... 

Nitrogen dioxide is one of a few simple molecules in which the primary quantum yield near the dissociation limit (3980 A) has been measured nearly continuously as a function of incident wavelength. The energetics of photodissociation is given in Table VI- 5. The thcrmochcmical threshold at O K for the reaction, N02 - NO + O( P), corresponds to the incident wavelength 3978 A, which nearly coincides with the wavelength 3979 1 A below which... 

Nitric oxide first reacts with atmospheric 02 to give nitrogen dioxide, a poisonous brown gas. Subsequently, N02 absorbs sunlight and dissociates to give an oxygen atom, which then reacts with 02 to form ozone. As usual, the catalyst (NO) and the intermediates (N02 and O) do not appear in the chemical equation for the overall reaction. 

The equilibrium mixture of nitrogen dioxide and dinitrogen tetraoxide is completely associated at —9°C to the latter form which is marginally endothermic (Allj (g) +9.7 kJ/mol, 0.10 kJ/g). Above 140°C it is completely dissociated to nitrogen dioxide, which is moderately endothermic (AHf (g) +33.8 kJ/mol, 0.74 kJ/g). 

The methane oxidation to methanal is thus realized in the catalytic cycle in which atmospheric 02 is the oxidant and the OH radicals are the catalyst, and which is coupled to photoassisted dissociation of nitrogen dioxide (Figure 9.7). The latter process yields two ozone molecules per photocatalytic cycle. 

An alternative mechanism has been proposed,18 according to which the activated nitrogen dioxide molecule collides with a molecule of nitrogen pentoxide and causes dissociation of the latter. It is easier to decompose a molecule of nitrogen pentoxide than a molecule of nitrogen dioxide. The over-all reaction is exactly the same and one cannot distinguish between the two mechanisms by stoichiometry, but the facts just cited favor the mechanism proposed by Norrish and none of the experimental data are in opposition to it. 

Ingold and his co-workers [144] present the dissociation of nitrogen dioxide and nitrous anhydride in the following way ... 

At physiological pH the protonated form of ONOO-, the peroxynitrous acid (ONOOH), is unstable and decomposes to nitrate (N03). ONOOH can also react directly with reductants or can decompose by homolytic dissociation to form nitrogen dioxide (N02) and hydroxyl radical (OH"), or can dissociate by a heterolytic mechanism to yield nitryl cation (NOj), which reacts with thiol, methionyl, tyro-syl, and tryptophanyl residues in proteins. 

The discussion of these data is made easier via their graphical representation as shown in Fig. 3-10. As can be deduced from the examples presented in Fig. 3-10 the threshold wavelength A-thw calculated from the bond dissociation energy D%g lies shghdy below the absorption onset Xonset only for the compounds nitrogen dioxide and ozone (see Tab. 3-5). The photodissociation of NO2 leads to the forma-... 

Tab. 6-2, the propyl-peroxyl radical and the butyl-peroxyl radical (Getoff, 1991). Finlayson-Pitts and Pitts (1986) comprehensively discussed gas phase absorption data of many atmospheric components, such as nitrogen dioxide (NO2), sulfur dioxide (SO2), nitrosyl chloride (ClNO), etc. Carbon dioxide (CO2) dissociates at wavelength X<227Anm vdth formation of CO( Sg) and 0( D) (Sonnemann, 1992). 

In the gas phase, N2O5 dissociates (AH = 95.6(1.5)kJ moU ) to nitrogen dioxide and nitrogen trioxide, which can decompose further according to (202) and (203). This... 

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