Dinitrogen trioxide

It is prepared by cooling a mixture of NO and N02 at -20 to -30 °C or by the reaction of NO with N2O4. Two forms of N203 are possible having the structures 

The dominant form appears to be II, in which the N-N bond length is 186 pm. It reacts with water to produce a solution containing nitrous acid, HNO2  

It also reacts with strong acids such as HCIO4 and H2S04 to produce species containing the NO+ ion  

The major importance of the compound is that it reacts with water as one step in the preparation of nitric acid  

The nitronium ion, N02+, derived from N02, is of considerable interest because it is the attacking species in nitration reactions (see Chapter 5). It is generated by the interaction of concentrated sulfuric and nitric acids, 

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Dinitrogen trioxide, N2O3. Only stable in solid state (m.p. — 102 C). Pale blue solid giving deep blue liquid the gas contains some ONNO2 molecules. Prepared from NO and O2 or NO and N2O4 with freezing decomposes to NO and NO,. 

Dinitrogen trioxide, the anhydride of nitrous acid, is very unstable. At low temperature it dissociates thus ... 

In aqueous solutions of sulphuric (< 50%) and perchloric acid (< 45 %) nitrous acid is present predominantly in the molecular form, although some dehydration to dinitrogen trioxide does occur.In solutions contairdng more than 60 % and 65 % of perchloric and sulphuric acid respectively, the stoichiometric concentration of nitrous acid is present entirely as the nitrosonium ion (see the discussion of dinitrogen trioxide 4.1). Evidence for the formation of this ion comes from the occurrence of an absorption band in the Raman spectrum almost identical with the relevant absorption observed in crystalline nitrosonium perchlorate. Under conditions in which molecular nitrous... 

The condition of dinitrogen trioxide in acid solution is discussed in 4-i-... 

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. 

Salpetrigsaure, /. nitrous acid, -anhydrid, n. nitrous anhydride, dinitrogen trioxide, -atlier, m. nitrous ether (ethyl nitrite), salpetrisch, a. nitrous. 

N205 dinitrogen pentaoxide N203 dinitrogen trioxide... 

At — 20°C, dinitrogen trioxide separates from the mixture as a blue liquid. 

NMe is now commercially available and is prepd by the vapor phase nitration of methane at a ratio of 9 moles of methane to I mole of nitric acid at 475° and a residence time of 0.18sec (Ref 12) or by the similar nitration of aliphatic hydrocarbons (Ref 8). Other prepns are from Me sulfate and Na nitrite (Ref 26) by the oxidn of Me amine with dinitrogen trioxide in the gas phase or in methylene chloride, yield 27%... 

Schmid s observation of the dependence of the reaction rate on the square of the concentration of nitrous acid was interpreted by Hammett (1940, p. 294) as due to the rate-limiting formation of dinitrogen trioxide, N203. The consequent attack of the amine by N203 was postulated to be faster therefore the concentration of the amine has no influence on the overall rate (zero order with respect to amine). Similarly, Hammett regards the second factor of Schmid s equation for diazotization in the presence of hydrochloric or hydrobromic acid as the result of the formation of nitrosyl halide. 

At first sight this seems surprising, as nitrous acid is a fairly weak acid (pKa = 3.15, Tummavuori and Lumme, 1968) and therefore the low equilibrium concentration of nitrite ions in Scheme 3-9 does not appear to favor the formation of dinitrogen trioxide. 

Table 3-1. Equilibrium constants Kxno (Scheme 3-28) and rate constants for diazotization of aniline (Ar2, Scheme 3-29) and of 1-naphthylamine (k2 and k-2/k Scheme 3-34) in water by nitrosyl chloride, nitrosyl bromide, nitrosyl thiocyanate, S-nitrosothiuronium ion [(NH2)2CSNO], and dinitrogen trioxide at 25 °C.

It is appropriate to add here some comments on diazotization in anhydrous carboxylic acids. They may be relevant for the diazotization of heteroaromatic amines carried out in acetic acid/propionic acid mixtures (Sec. 2.2). Extensive studies by Casado et al. (1983, 1984) showed that in nitrosation of secondary amines the nitrosyl ion, nitrosyl acetate, and dinitrogen trioxide are formed, and all three may act as nitrosating agents. The results do not, however, account for the considerable improvement that is claimed in the patent literature (Weaver and Shuttleworth, 1982) to result from the addition of carboxylic acids in the diazotization of heteroaromatic amines. 

Sfi.F-Test D.4A Write the formulas for (a) vanadium(V) oxide (b) calcium carbide (c) germanium tetrafluoride (d) dinitrogen trioxide. 

The blue gas dinitrogen trioxide, N203 (Fig. 15.6, 1), in which the oxidation number of nitrogen is +3, is the anhydride of nitrous acid, HN02, and forms that acid when it dissolves in water ... 

FIGURE 15.6 Dinitrogen trioxide, N2Oj, condenses to a deep-blue liquid that freezes at 100°C to a pale-blue solid, as shown here. On standing, it turns green as a result of partial decomposition into nitrogen dioxide, a yellow-brown gas. 

The earliest reported Fxs were the result of the reaction of nitrous acid with naturally occurring alkenes being the identified intermediate a a-nitrooxime that suffers dehydration with cyclization. Apart from these conditions, the most recent Fxs synthesis descriptions have involved reactions between alkenes and dinitrogen trioxide (Fig. 3), nitroalkanes and aluminum trichlo-... 

An N-nitrose compound that is unstable is obtained by the effect of dinitrogen trioxide on caproiactam at a low temperature. The compound detonates when the medium is not cooled enough. 

During preparation of the IV-nitroso derivative from the lactam in acetic acid solution, the treatment with dinitrogen trioxide must be very effectively cooled to prevent explosive decomposition. 

Among other solid P-N compounds examined, the title compound ignited immediately on contact with nitric acid, hydrogen peroxide or dinitrogen trioxide. 

Hydrogen iodide ignites in contact with fluorine, dinitrogen trioxide, dinitrogen tetraoxide and fuming nitric acid. 

MRH Dinitrogen monoxide 6.99/84, dinitrogen trioxide 9.25/75, nitrogen oxide 9.71/78, nitrous acid 7.11/79... 

Pure phosphine is rendered pyrophoric by traces of dinitrogen trioxide, nitrous acid, or similar oxidant. 

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