Nitrosyl nitrate

Dinitrogen tetroxide, N2O4, as a liquid, has some power as a solvent, and appears to dissociate slightly to give nitrosyl nitrate, thus ... 

Uranium Purification. Subsequent uranium cycles provide additional separation from residual plutonium and fission products, particularly zirconium— niobium and mthenium (30). This is accompHshed by repeating the extraction/stripping cycle. Decontamination factors greater than 10 at losses of less than 0.1 wt % are routinely attainable. However, mthenium can exist in several valence states simultaneously and can form several nitrosyl—nitrate complexes, some for which are extracted readily by TBP. Under certain conditions, the nitrates of zirconium and niobium form soluble compounds or hydrous coUoids that compHcate the Hquid—Hquid extraction. SiUca-gel adsorption or one of the similar Hquid—soHd techniques may also be used to further purify the product streams. 

It is evident that the molecule N204, formed from N02 at low temperatures, may have the structure NO+NOf (nitrosyl nitrate), too. Both NO NOf and NO NO in the liquid and solid states seem more probable than the formula 02N.N02 given earlier, because in the ionic forms there is not the repulsion between the two positively-charged N atoms. 

Benzene activated with sulphuric acid would add on to N204 which, according to Battegay, has the structure of nitrosyl nitrate N02.0N0. An addition product was thought to be formed which, in the presence of an excess of sulphuric acid, would decompose to yield a nitro compound and nitrosylsulphuric acid. 

The features of initiation of free radical reactions in polymers by dimers of nitrogen dioxide are considered. The conversion of planar dimers into nitrosyl nitrate in the presence of amide groups of macromolecules has been revealed. Nitrosyl nitrate initiates radical reactions in oxidative primary process of electron transfer with formation of intermediate radical cations and nitric oxide. As a result of subsequent reactions, nitrogen-containing radicals are produced. The dimer conversion has been exhibited by estimation of the oxyaminoxyl radical yield in characteristic reaction of p-benzoquinone with nitrogen dioxide on addition of aromatic polyamide and polyvinylpyrrolidone to reacting system. The isomerisation of planar dimers is efficient in their complexes with amide groups, as confirmed by ab initio calculations. 

Keywords nitrogen dioxide, nitrosyl nitrate, polyamides, stable radicals, EPR spectra. 

The support, zirconia (ISA), was supplied by the Norton Company. The oxide was grounded and sieved to a particle size ranged from 0.16 to 0.25 mm, and calcined at 773 K. Its surface properties, 63.3 m g of specific surface and average pore diameter of 8.60 nm, were determined from the nitrogen adsorption isotherms. The catalysts were prepared by adsorption from solution and/or impregnation of precursor(s), ruthenium nitrosyl nitrate (Alfa) and hexachloroplatinic acid (Aldrich), onto the support. Being zirconia isoelectric point 6.5 (determined by electrophoresis [17] using a Malvern Instrument Zetasizer 4) the precursors solution pH value was kept sufficiently low to enable the desired adsorption of complex metal anions. 

The following scheme presents nitrosation mechanism of monometh-ox q)henol groups of lignin with the formation of iminoxyl radicals. Initiators are dimers of NO2 in the form of nitrosyl nitrate. 

In parallel with conversions of phenols, nitrosyl nitrate is capable of oxidising multitude of hydroxyl groups of nonphenolic structures linking aryl rings in lignin. As a result, aldehydes are formed. 

Thus, the heterolytic reaction path connected with nitrosyl nitrate ONONO apparently eliminated by the use of non-polar solvents. 

Direct Experimental Detection of Primary Radical Cations and Products of Their Decomposition in the Reactions of Nitrosyl Nitrate... 

The ion-radical mechanism postulated for interaction of aromatic compounds with nitrosyl nitrate [13-19, 21, 22] is mainly based on an analysis of indirect... 

The key role of nitrosyl nitrate in the formation of II via the ion-radical mechanism is confirmed by kinetic measurements done at different NO concentrations in the gas phase. The initial rates of accumulation of this compound plotted against the square of the initial concentrations of NO are shown in Figure 7.3. 

Hence, reactions considered for PVPR illustrate the mechanism connected with the conversions of primary radical cations generated by nitrosyl nitrate. Nevertheless, the direct detection of radical cations by ESR fails in this system apparently because of fast detachment of protons. For confirmation of the ion-radical initiation concept under the action of NO, triphenylamine (TPA) is a suitable model compound. TPA does not contain chemical bonds capable of reacting with monoradicals of NO. The formation of radical cations in TPA has been revealed in reactions with some Lewis... 

The oxidative ion-radical mechanism of conversions induced by nitrosyl nitrate explains the high reactivity of aliphatic polyamides and polyvinylpyrrolidone (PVP) to NO as well as the nature of stable radicals and the molecular products of nitration. Amide groups can appear as electron donors, and regularities of the conversions for aliphatic polyamides, in particular polycaproamide (PCA), [6, 37] is described by the following scheme ... 

The initial rate for the accumulation of C=0 groups of nitrosoamides in the NO concentration range of 4 x 10 - to 4 x 10 mol/1 is proportional to [NO ]", where n 2. This fact confirms the participation of nitrosyl nitrate in PCA conversions. In reaction (Equation 7.42), an unstable intermediate nitrite is initially generated. The latter gives the detectable acylalkylaminoxyl radicals with an anisotropic triplet spectrum (.<4 =1.94 mT, gj, = 2.003) (Figure 7.7). 

The equilibrium (Equation 7.1) involving planar dimer (PD) and nitrosyl nitrate (NN) could explain an appearance of stable radicals in the polymers not containing specific chemical bonds reacting with NO mono radicals. However, there are certain obstacles connected with the energetic properties of NO dimers for realising the... 

It is expected that the primary act is the oxidative interaction of imide groups with NO dimers (nitrosyl nitrate) ... 

Figure 7.17b demonstrates that the rate of accumulation of radicals XXVIII during thermolysis of PPI pre-exposed to NO linearly depends on concentrations of NO in the gas phase. At first glance, this result contradicts the mechanism with participation of nitrosyl nitrate as an initiator, according to which the square-low dependence should be observed for the rate. However, if we take into account that aromatic nitroso... 

One can assume other parallel process when aromatic nitroso compormds are initially formed and transformed later into XXXIV in the reaction with nitrosyl nitrate ... 

Thus, thermally and chemically stable, PPI is reactive with respect to NO. The significant reactivity of polyimides can be explained by the concept of intermediate radical cations formed as a result of the primary oxidising reaction with participation of nitrosyl nitrate. 

Many covalent nitrosyl compounds are effective nitrosating reagents in organic solvents. It is therefore not surprising to find that even low concentrations of nucleophilic anions promote nitrosation in aqueous solutions by forming nitrosyl compounds other than nitrous anhydride (nitrosyl nitrate). Most of the mechanistic evidence for these reagents comes from diazotisation studies either in halogen acids or catalysed by halide ions. We shall therefore confine our discussion to the reactions of nitrosyl halides. 

The diazotisation of aniline in aqueous nitric acid has also been studied. At low acidities (below 0-2 m), nitrous anhydride is the most important reagent . At higher acidities the kinetics of the reaction are similar to those for equivalent concentrations of perchloric acid and the rate increases rapidly with acidity . This catalysis has been attributed to nitrosation by dinitrogen tetroxide (nitrosyl nitrate) , but other studies of catalysis by neutral nitrate salts indicate the contribution to the overall rate of nitrosation by dinitrogen tetroxide is slight It seems, therefore, that the reagents at high acidity are the nitrous acidium and nitrosonium ions, as for perchloric acid. 

The tri-nitride is easily formed by reaction of cellulose with nitrosyl nitrate or chloride and has been considered as a substitute for xanthate in the manufacturing of - cellulose regenerate. The use of expensive solvents, however, hampered the realization of such ideas. 

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