Dinitrogen tetroxide

As an acceptor solvent dinitrogen tetroxide forms molecular addition compounds with various donor molecules. Amines such as triethylamine, pyridine and quinoline give crystalline compounds which appear to be ionic , but sterically hindered complexes are not formed. Thus 2,6-lutidine and 2-methylquinoline do not give adducts with dinitrogen tetroxide. 

Davenport, D., H. Burkhardt, and H. H. Sisler J. Amer. Chem. Soc. 75,4175 (1953). Recent review C. C. Addison Vol. Ill, Part 1 in Chemistry in Nonaqueous Ionizing Solvents, Ed. G. Jander, H. Spandau, and C. C. Addison, Vieweg Braunschweig, and Pergamon Press, London and New York, 1967. 

Ethers (dioxane, tetrahydrofurane, diethylether), and other 0-containing donor molecules, such as dimethyl sulphoxide, ketones and nitriles give compounds with molecular structures which have been considered as partially ionic in the solid stated . 

Weak molecular adducts are formed with benzene, mesitylene and nitroben-zene59 60. Towards strong acceptors it may also act as weak donor, as is shown by its reaction with boron(III) fluoride to give 

For the pure liquid a self-ionization equilibrium has been assumed to exist according to the equation  

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Other liquid inorganic compounds show the auto-dissociation characteristic of water and liquid ammonia for example, dinitrogen tetroxide (p. 231), as well as undergoing the more familiar homolytic dissociation... 

Unlike nitrogen monoxide, nitrogen dioxide has properties more typical of an odd electron molecule. It is a coloured (brown), reactive gas which dimerises to the diamagnetic colourless gas dinitrogen tetroxide, N2O4. in which the odd electron is paired. The structure of dinitrogen tetroxide can be represented as a resonance hybrid of ... 

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

Hence dinitrogen tetroxide (sometimes mixed with an organic solvent) can be used to prepare anhydrous metal nitrates (many heavy metal nitrates are hydrated when prepared in aqueous solution, and they cannot be dehydrated without decomposition). 

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 ... 

Outline the laboratory preparation of a sample of dinitrogen tetroxide. Describe and explain what happens when it is heated from 290 K to 900 K. Suggest electronic structures for dinitrogen tetroxide and the other nitrogen-containing molecules formed from it on heating to 900 K. Point out any unusual structural features. 

If copper is treated with a solution of dinitrogen tetroxide in ethyl ethanoate (acetate), a blue solution is obtained, which on evapora-... 

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 ... 

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. ... 

In an excess of nitric acid, nitrous acid exists essentially as dinitrogen tetroxide which, in anhydrous nitric acid, is almost completely ionised. This is shown by measurements of electrical conductivity, and Raman and infra-red spectroscopy identify the ionic species... 

In mixtures of nitric acid and organic solvents, nitrous acid exists mainly as un-ionised dinitrogen tetroxide. The heterolysis of dinitrogen tetroxide is thus complete in sulphuric acid ( 4 i), considerable in nitric acid, and very small in organic solvents. 

If we consider the effect of nitrous acid upon zeroth-order nitration in organic solvents we must bear in mind that in these circumstances dinitrogen tetroxide is not much ionised, so the measured concentration of nitrous acid gives to a close approximation the concentration of dinitrogen tetroxide. Further, the negligible self-ionisation of nitric acid ensures that the total concentration of nitrate ions is effectively that formed from dinitrogen tetroxide. Consequently as we can see from the equation for the ionisation of dinitrogen tetroxide ( 4.3.1),... 

The catalysed nitration of phenol gives chiefly 0- and />-nitrophenol, (< 0-1% of w-nitrophenol is formed), with small quantities of dinitrated compound and condensed products. The ortho para ratio is very dependent on the conditions of reaction and the concentration of nitrous acid. Thus, in aqueous solution containing sulphuric acid (i 75 mol 1 ) and nitric acid (0-5 mol 1 ), the proportion of oriha-substitution decreases from 73 % to 9 % as the concentration of nitrous acid is varied from o-i mol l i. However, when acetic acid is the solvent the proportion of ortAo-substitution changes from 44 % to 74 % on the introduction of dinitrogen tetroxide (4-5 mol 1 ). 

It was estimated from an analysis of the results that the nitrosonium ion was at least ten times more effective than dinitrogen tetroxide this is a lower limit, and the ion is likely to be much more reactive than the latter species. 

It has been considered that nitric acid was responsible for the oxidation of the nitroso compoimd, but there is recent evidence from the catalysed nitration of p-dimethoxybenzene in carbon tetrachloride that dinitrogen tetroxide is involved ... 

In solutions of acetyl nitrate in acetic anhydride, prepared from purified nitric acid, the 0 -ratio increases slightly with increasing concentrations of acetyl nitrate (table 5.7, expts. 11,13,16). The use of fuming nitric acid in the preparation of the acetyl nitrate considerably accelerates the rates of reaction and also increases the proportion of o-substitution (table 5.7, expts. 12, 15, 18). These effects resemble, but are much stronger than the corresponding effects in nitrations with solutions of nitric acid in acetic acid contaimng dinitrogen tetroxide. 

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 ... 

Considering first pure nitric acid as the solvent, if the concentrations of nitronium ion in the absence and presence of a stoichiometric concentration x of dinitrogen tetroxide are yo and y respectively, these will also represent the concentrations of water in the two solutions, and the concentrations of nitrate ion will be y and x- y respectively. The equilibrium law, assuming that the variation of activity coefficients is negligible, then requires that ... 

Since the first-order rate constant for nitration is proportional to y, the equilibrium concentration of nitronium ion, the above equations show the way in which the rate constant will vary with x, the stoichiometric concentration of dinitrogen tetroxide, in the two media. An adequate fit between theory and experiment was thus obtained. A significant feature of this analysis is that the weak anticatalysis in pure nitric acid, and the substantially stronger anticatalysis in partly aqueous nitric acid, do not require separate interpretations, as have been given for the similar observations concerning nitration in organic solvents. 

From these results it appears that the 5-position of thiazole is two to three more reactive than the 4-position, that methylation in the 2-position enhances the rate of nitration by a factor of 15 in the 5-position and of 8 in the 4-position, that this last factor is 10 and 14 for 2-Et and 2-t-Bu groups, respectively. Asato (374) and Dou (375) arrived at the same figure for the orientation of the nitration of 2-methyl and 2-propylthiazole Asato used nitronium fluoroborate and the dinitrogen tetroxide-boron trifluoride complex at room temperature, and Dou used sulfonitric acid at 70°C (Table T54). About the same proportion of 4-and 5-isomers was obtained in the nitration of 2-methoxythiazole by Friedmann (376). Recently, Katritzky et al. (377) presented the first kinetic studies of electrophilic substitution in thiazoles the nitration of thiazoles and thiazolones (Table 1-55). The reaction was followed spec-trophotometrically and performed at different acidities by varying the... 

Quinoline Dinitrogen tetroxide, linseed oil, maleic anhydride, thionyl chloride... 

Sulfuryl dichloride Alkalis, diethyl ether, dimethylsulfoxide, dinitrogen tetroxide, lead dioxide, phosphorus... 

Copper acetate, ferrous acetate, silver acetate [563-63-3] basic aluminum acetate, nickel acetate [373-02-4] cobalt acetate, and other acetate salts have been reported to furnish anhydride when heated. In principle, these acetates could be obtained from low concentration acetic acid. CompHcations of soHds processing and the scarcity of knowledge about these thermolyses make industrial development of this process expensive. In the eady 1930s, Soviet investigators discovered the reaction of dinitrogen tetroxide [10544-72-6] and sodium acetate [127-09-3] to form anhydride ... 

Yields of the order of 85% were secured in the dry reaction (48). (Propionic anhydride and butyric anhydride can be obtained similarly from their sodium salts.) Inasmuch as dinitrogen tetroxide can be regenerated, the economic prospects of this novel way of making anhydride are feasible. 

Dinitrogen tetroxide is an effective Eriedel-Crafts nitrating agent (152) for aromatics in the presence of aluminum chloride, ferric chloride, or sulfuric acid (153). Dinitrogen pentoxide is a powerhil nitrating agent, even in the absence of catalysts, preferably in sulfuric acid solution (154). SoHd dinitrogen pentoxide is known to be the nitronium nitrate, (N02) (N02). The use of BE as catalyst has been reported (155). 

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. 

Chemical oxidation with strong acid is reportedly selective at the 6-hydroxyl, either with nitric acid—sulfuric acid—vanadium salts (241) which is claimed as specific for the 6-hydroxyl up to 40% conversion, or with dinitrogen tetroxide ia carbon tetrachloride, with similar specificity up to 25% conversion (242). 

Cellulose Solvent. Although DMSO by itself does not dissolve cellulose, the following binary and ternary systems are cellulose solvents DMSO—methylamine, DMSO—sulfur trioxide, DMSO—carbon disulfide—amine, DMSO— ammonia—sodamide, DMSO—dinitrogen tetroxide,... 

Oxidation under moderate conditions (83) yields soUd products referred to as oxyceUuloses. This general term describes various products that must be qualified by indicating the oxidant employed. Among oxidants used are periodate, dinitrogen tetroxide, and sodium hypochlorite. CeUulose is particularly susceptible to oxidation under alkaline conditions. 

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