Oxoacids of nitrogen

An aqueous solution of the sodium salt of [N202] can be made from organic nitrites by reaction 15.106 or by the reduction of NaN02 with sodium amalgam. Addition of Ag+ leads to the precipitation of Ag2N202. Treatment of this salt with anhydrous HCl in dry diethyl ether leads to the formation of hyponitrous acid, H2N202.  

VIA Fig. 15.16 Part of one of the hydrogen-bonded chains in the solid state structure of the 2,2 -bipyridinium salt of [N202] . The structure was determined by X-ray diffraction at 173 K [N. Arulsamy et al. (1999) Inorg. Chem., vol. 38, p. 2716]. 

The reaction of acid with potassium nitrocarbamate results in the formation of nitramide (equation 15.107) which is an isomer of hyponitrous acid. Nitramide has been structurally characterized one N atom is trigonal planar (O2AN) and the other is trigonal pyramidal (H2AN)- The compound is potentially explosive, and undergoes base-catalysed decomposition to N2O and H2O. 

Nitrous add is known only in solution and in the vapour phase. In the latter, it has structure 15.53. It is a weak acid = 3.37), but is unstable with respect to disproportionation in solution (equation 15.108). It may be prepared in situ by reaction 15.109, the water-soluble reagents being chosen so as to give an insoluble metal salt as a product. AgN02 is insoluble but other metal nitrites are soluble in water. 

Sodium nitrite is an important reagent in the preparation of diazonium compounds, e.g. reaction 15.110 in which HNO2 is prepared in situ. Alkali metal nitrates yield the nitrites when heated alone or, better, with Pb (reaction 15.111). 

Dinitrogen pentaoxide (Table 15.6 and Fig. 15.15) is the acid anhydride of HNO3 and is prepared by reaction 15.107. 

Although the name hyponitrous acid remains in common use, it is no lOTger recommended by the lUPAC. The recommendation is to use dmzenediol (which derives from the substimtion of each H atom in lazene (HN=NH) by an OH group), or bis(hydroxidonitrogen)(N-N). 

NO2 is cooled to 273K, N2O4 condenses as a yellow liquid. 

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Table 26 Oxoacids of nitrogen in different oxidation states...

Nitrogen Oxides 24-16 Some Oxoacids of Nitrogen and Their Salts Phosphorus... 

The main oxoacids of nitrogen are nitrous acid, HNO2, and nitric acid, HNO3. 

Nitrides, phosphides and arsenides Halides, oxohalides and complex halides Oxides of nitrogen Oxoacids of nitrogen... 

Nitrogen Oxoacids and Oxoanions There are two common oxoacids of nitrogen (Figure 14.9) ... 

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