Nitrosonium Nitrate

Significantly, the minor isomer in equation (88) undergoes a ready disproportionation to form nitrosonium nitrate, which is stabilized by strong complexa-tion with organic donors240 (equation 89)... 

Nitration of fluoroolefins can be achieved by several methods. Widely studied thermal reaction of N204 with fluoroolefins has a radical mechanism, although the low temperature reaction of nitrogen dioxide with polyfluorinated vinyl ethers proceeds as electrophilic addition of nitrosonium nitrate NO+ N02 across the C=C bond [6] ... 

Solid 2-mercaptobenzothiazole (as benzothiazoline in the crystal) 1 (335 mg, 2.00 mmol) and the nitrosonium nitrate 2 (436 mg, 1.00 mmol) were ball-milled for 30 min to give a solid mixture of 3 and 4. The disulfide 3 is insoluble in water, and 4 can be oxidized to the corresponding nitroxyl (TEMPO), from where 2 can be recycled by gas-solid oxidation with NO2. 

The Raman spectrum of quenched products (Fig. 7) consists of the symmetric stretching of excess P-O2 at 1585 cm, two Fermi-resonance bands of CO2 at 1270 and 1400 cm", and three new additional sharp bands at 734, 1079, and 2242 cm". The systematic of the latter three bands are very similar to those of nitrosonium nitrate N0" N03", an ionic dimer of nitrogen dioxide. This similarity suggests that the products also include a species with carbonates and carbosonium, CO COa ". The vibrations of carbonate ions appear at 713 and 1082 cm" in CaCOs [84], and the CO vibration appears about 2150 cm" at 5 GPa [85]. Electronic structure calculations for [86, 87] suggest that there are several low lying states of CO " ", whose vibrational frequencies vary between 1000 and 2000 cm". The yield of... 

Transitory formation of nitrosonium nitrate, NO+NOj", occurs in reactions involving dinitrogen tetroxide [9]. There is the evidence for the isomerisation of the planar dimer and its subsequent ionisation... 

The reactions of NO dimers in the form of nitrosonium nitrate with amides provide a general method for the preparation of nitroso amides [12]. The reaction is carried... 

The oxidative conversions of quinone dioximes into dinitroso benzenes can be carried out by interaction with nitrosonium nitrate [18] ... 

The reaction (Equation 7.10), together with subsequent reoxidation of nitric oxide with oxygen, constitutes the reduction-oxidation cycle for the catalytic autoxidation with NO. On the basis of the understanding of the interaction of nitrosonium with aromatic donors [15], hydroquinones are expected to strongly shift the equilibrium (Equation 7.3) to favour the nitrosonium complex in conformity with enhanced donor properties of the aromatic substrates. Accordingly, the oxidation of hydroquinone with NO proceeds via the nitrosonium nitrate ion pair. The overall two-electron oxidation of hydroquinone to quinone by 2 equivalent NO probably proceeds via successive one-electron steps. The labelling studies in the process... 

Nitration has also been effected with the complexes from dinitrogen tetroxide and Lewis acidsin the case of boron trifluoride the complex appears to be a mixture of nitronium and nitrosonium tetrafluoroborates. ... 

The more powerful anticatalysis of nitration which is found with high concentrations of nitrous acid, and with all concentrations when water is present, is attributed to the formation of dinitrogen trioxide. Heterolysis of dinitrogen trioxide could give nitrosonium and nitrite ions 2N2O4 + HjO N2O3 + 2HNO3. 

Ridd - has reinterpreted the results concerning the anticatalysis of the first-order nitration of nitrobenzene in pure and in partly aqueous nitric acid brought about by the addition of dinitrogen tetroxide. In these media this solute is almost fully ionised to nitrosonium ion and nitrate ion. The latter is responsible for the anticatalysis, because it reduces the concentration of nitronium ion formed in the following equilibrium ... 

Nitrous acid or nitrite salts may be used to catalyze the nitration of easily nitratable aromatic hydrocarbons, eg, phenol or phenoHc ethers. It has been suggested that a nitrosonium ion (NO + ) attacks the aromatic, resulting initially in the formation of a nitro so aromatic compound (13). Oxidation of the nitro so aromatic then occurs ... 

The NO ligand can be supplied by nitric oxide itself, but there are many other sources such as nitrite, nitrate or nitric acid, nitrosonium salts or N-methyl-7V-nitrosotoluene-p-sulphonamide (MNTS). The introduction of a nitrosyl group into a ruthenium complex is an ever-present possibility. 

The kinetics of aromatic nitrosation at ring carbon have received little attention. The first attempt to determine the nature of the electrophile was made by Ingold et a/.117, who measured the rates of the nitrous acid-catalysed nitration of 4-chloroanisole by nitric acid in acetic acid which proceeds via initial nitrosation of the aromatic ring. Assuming that the electrophiles are the nitrosonium ion and... 

A further point of preparative significance still requires explanation, however. Highly reactive aromatic compounds, such as phenol, are found to undergo ready nitration even in dilute nitric acid, and at a far more rapid rate than can be explained on the basis of the concentration of N02 that is present in the mixture. This has been shown to be due to the presence of nitrous acid in the system which nitrosates the reactive nucleus via the nitrosonium ion, NO (or other species capable of effecting nitrosation, cf. p. 120) ... 

A facile method for the oxidation of alcohols to carbonyl compounds has been reported by Varma et al. using montmorillonite K 10 clay-supported iron(III) nitrate (clayfen) under solvent-free conditions [100], This MW-expedited reaction presumably proceeds via the intermediacy of nitrosonium ions. Interestingly, no carboxylic acids are formed in the oxidation of primary alcohols. The simple solvent-free experimental procedure involves mixing of neat substrates with clayfen and a brief exposure of the reaction mixture to irradiation in a MW oven for 15-60 s. This rapid, ma-nipulatively simple, inexpensive and selective procedure avoids the use of excess solvents and toxic oxidants (Scheme 6.30) [100]. Solid state use of clayfen has afforded higher yields and the amounts used are half of that used by Laszlo et al. [17,19]. 

Aromatic nitrosation with nitrosonium (NO + ) cation - unlike electrophilic nitration with nitronium (NO ) cation - is restricted to very reactive (electron-rich) substrates such as phenols and anilines.241 Electrophilic nitrosation with NO+ is estimated to be about 14 orders of magnitude less effective than nitration with N02+. 242 Such an unusually low reactivity of NO+ toward aromatic donors (as compared to that of NO ) is not a result of the different electron-acceptor strengths of these cationic acceptors since their (reversible) electrochemical reduction potentials are comparable. In order to pinpoint the origin of such a reactivity difference, let us examine the nitrosation reaction in the light of the donor-acceptor association and the electron-transfer paradigm as follows. 

As useful as tetranitromethane is as a charge-transfer nitrating agent, it is generally too unreactive to effect the comparable electrophilic nitration of most aromatic donors, except the most electron-rich ones. Thus in order to make the direct comparison between the photochemical and thermal nitration of the same ArH, we now turn to the A-nitropyridinium acceptor (PyNOj) as the alternative nitrating agent (Olah et al., 1965, 1980). For example, PyNO can be readily prepared as a colourless crystalline salt, free of any adventitious nitrosonium impurity, and used under essentially neutral conditions. Most importantly, the electrophilic reactivity of this... 

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 ... 

A solution of dinitrogen tetroxide in sulfuric acid is also a powerful nitrating agent. In this medium dinitrogen tetroxide is ionized to nitronium and nitrosonium ions. Titov reported using a solution of dinitrogen tetroxide in oleum for the nitration of nitrotoluene to dinitrotoluene and then to trinitrotoluene, the two separate steps proceeding in 98 % and 85 % yields respectively. 

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