Dinitrogen tetroxide, formation

The second equilibrium is the more important, giving rise to the nitronium ion, NOj, already mentioned as a product of the dis sociation of dinitrogen tetroxide. Several nitronium salts have been identified, for example nitronium chlorate(VII), (N02) (C104) . If pure nitric acid is dissolved in concentrated sulphuric acid, the freezing point of the latter is depressed to an extent suggesting the formation of four ions, thus ... 

Solutions of dinitrogen tetroxide (the mixed anhydride of nitric and nitrous acids) in sulphuric acid are nitrating agents ( 4.3.2), and there is no doubt that the effective reagent is the nitronium ion. Its formation has been demonstrated by Raman spectroscopy and by cryoscopy ... 

Nitrogen dioxide rapidly forms an equiUbtium mixture with its dimer, dinitrogen tetroxide (AH g = —28.6 kJ/mol of NO2 consumed). The formation of tetroxide is favored by low temperature and high pressure. 

Figure 6. Formation of S-nitrosoatradne from atrazine and dinitrogen tetroxide...

It is a practice in some countries to add a small amount of sodium hydrogen carbonate to the powder dough, to neutralize dinitrogen tetroxide evolved during the decomposition of the powder. This would lead to formation of sodium nitrate... 

Dinitrogen Tetroxide.—The dimer of nitrogen dioxide is not very stable its enthalpy of formation from the monomer is 13.873 kcal/mole. The molecule is found in both the crystal (x-ray diffraction)29 and the gas (electron diffraction)80 to be planar, with orthorhombic symmetry. The N—N bond length reported for the crystal is 1.64 A. The value for the gas molecule, 1.75 A, is probably somewhat more accurate.81 This value is 0.28 A greater than the single-bond value found for hydrazine the bond number of the bond is accordingly about 0.34 (Equation 7-7). 

Sulfur Dioxide. Presence of dinitrogen tetroxide appears to be essential to catalyze smooth formation of nitrosylsulfuric acid. In its absence, reaction may be delayed and then proceed explosively.46... 

The so-called Tryller s compound, shown to be the furoxan (156), is cyclized to the bis-AT-oxide (53a) with aqueous sodium hydroxide (Scheme 15). Treatment of compound (156) with dinitrogen tetroxide results in the formation of the tris-yV-oxide (53b) <88LA1017>. 

The primary addition product from HFA and diphenylphosphane (32b) has been unambiguously characterized by several groups (97, 755). It is easily oxidized by atmospheric oxygen and dinitrogen tetroxide (97, 755) to form phosphonous acid ester 33b via phosphane oxide 36 (755), which can also be synthesized from HFA and diphenylphosphane oxide. Kinetics of the base-catalyzed rearrangement have been studied (754). Further action of HFA on 32b yields difluorophosphorane 37 (755). A dipolar intermediate with tetra-coordinated phosphorus has been postulated by Stockel (260) in the formation of 33b and 33c (R = c-CgHu). 

The oxidation of oximes by lead(IV) acetate, chlorine and other oxidants results in the formation of a-substituted nitroso compounds R R C(X)NO by attack of the oxidant at carbon. This is also the reaction commonly observ with dinitrogen tetroxide (the Ponzio reaction), the products being gem-... 

The absorption of this complex mixture of gases and the formation of nitric acid follows a complicated mechanism. The main route involves two steps in the hquid phase. First, dinitrogen tetroxide reacts with water to form nitric acid and nitrous acid (AH = -87kJmol ) ... 

Reagents for amination, nitrosation and nitration of tertiary alkylamines are discussed in the appropriate reviews listed in Sections 6.1.3.1.4 and 6.I.3.I.5. Tertiary amines can be nitrosated with dealkylation by dinitrogen tetroxide for example, 1-methylpiperidine gave 1-nitrosopiperidine (80%). lliis reaction probably starts by one-electron oxidation of the amine, the aminium ion then undergoing dealkylation. Other oxidative d ylations and dealkylations include the formation of iV-nitrosodibenzylamine in high yield from the acid chloride (PhCH2)2NCOCl and sodium nitrite and the conversion of the amine (43) into the nitramine (44) with nitric acid. ... 

The type and the stereochemistry of the products depends on the structure of the alkene and the experimental conditions. The use of oxygen as a carrier gas for dinitrogen tetroxide affects the course of the reaction in various ways, depending on the alkene, but it especially prevents reduction of dinitrogen tetroxide to dinitrogen trioxide and thereby permits a cleaner product mixture to be obtained, or it can divert the reaction course toward the formation of /(-nitro nitrates115. 

On the basis of an EPR analysis, the reaction of M(acac) with NO2 (at room temperature it is present as N2O4) has been proposed to occur via a step-by-step oxidation of the metal complex with final formation of metal nitrates and the iminoxy free radical 111 (equation 79). The presence of a donor-acceptor complex between M(acac) and N2O4 has been postulated for the electron transfer to dinitrogen tetroxide. 

More direct evidence for the formation of difluorocarbene as an intermediate comes from the photolysis of difluorodiazirine in the presence of chlorine, iodine, dinitrogen tetroxide, and nitryl chloride when the corresponding difluoromethane derivatives were formed, and in the presence of isobutene, buta-l,3-diene, and cis- and frans-but-2-ene when the corresponding 1,1-difluorocyclopropane derivatives were formed. Even with considerable excesses of olefins, appreciable tetra-... 

The high electron dennty of the oxygert atom iti ox nes is favoFaUe to the formation of addition compounds with Lewis acids. Trimethylene oxide has been obeerved to form an iodine complex a hydrate and two dinitrogen tetroxide adducts, one m mole ratio 1 1 and the other 2 The boron fluoride complex is unstable,... 

At 100°C this equilibrium lies at approximately 90% NOi, 10% N2O4, whereas at 21°C only about 0.1% NO2 is present [41]. This equilibrium may be important for acid production since there is evidence that dinitrogen tetroxide is the molecular species that reacts with water for acid formation. 

A number of Al-cyclopropylurea and Af-cyclopropylcarbamate derivatives have been converted to the corresponding A -nitroso compounds in fair to good yield. The two reagents most commonly used are dinitrogen tetroxide in diethyl ether containing sodium acetate, e.g. formation 182,183,208-218 and sodium nitrite in acetic acid, e.g. formation or hydrochloric acid. " Due to the instability of the products, most reactions are carried out below room temperature. 

Sulfides, including HD, undergo oxidation at sulfur. Initial oxidation produces a sulfoxide, whereas further oxidation produces a sulfone (below). Oxidants include hydrogen peroxide, perox-yacids, nitric acid, permanganate ion, ozone, dinitrogen tetroxide, and dichromate ion. Oxides of mustard are not as volatile as mustard. This may help to explain why British air raid shelters were sometimes painted using the oxidant calcium hypochlorite (Ca(OCl)2). Episulfonium ion formation is less likely in the sulfoxide of HD than in HD itself. 

Reaction with olefins. The addition of dinitrogen tetroxide alone is not generally a useful synthetic system because of the formation of several products. However, Stevens and Emmons found that the reaction of dinitrogen tetroxide with an olefin (ether solution, N2) in the presence of excess iodine led to /3-nitroalkyl iodides, usually in good yield ... 

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