Hyponitrous acid, 132

Hyponitrous acid—H3N4O3—31—Known only in combination. Silver hyponitrite is formed by reduction of sodium nitrate by nascent H and decomposition with silver nitrate. 

Nitrous acid—HNO,—47— has not been isolated, although its salts, the nitrites, are well-defined compounds M NO or M (NOj) . 

The nitrites occur in nature, in small quantity, in natural waters, where they result from the decomposition of nitrogenous 

Nitric Acid. Aquafortis—Hydrogen nitrate-oum—TJ.S. Br.—HNO3—63. 

Preparation.—(1.) By the direct union of its constituent elements under the influence of electric discharges. 

In contact with water it is destroyed, giving rise to nitric acid and deutoxide of nitrogen, thus  

The salts of this acid are obtained by heating a nitrate,—for example, nitrate of potash or soda,—tUl it begins to precipitate nitrate of silver brown. The whole is then precipitated by nitrate of silver, the precipitate dissolved in boiling water, and the hyponitrite of silver crystallises on cooling. From this salt, by the action of soluble chlorides, the other hyponitrites may be obtained. They have been little studied.. 

If a solution of the silver salt is treated with HC1 dissolved in ether, a solution containing 

Evaporation of the ether produces solid H2N202, but the acid is so unstable that it explodes readily. In water, the acid decomposes as shown in the following equation  

Although N20 is formally the anhydride of H2N202, the acid cannot be prepared from N20 and water. In this regard, it is similar to CO, which is the anhydride of formic acid, HCOOH. Hyponitrous acid is oxidized in air to produce nitric and nitrous acids  

Reduction of a nitrate or nitrite by sodium amalgam in the presence of water has been used to prepare hyponitrite salts  

The trans form is more stable, and it is produced by means of the reactions described earlier. 

An aqueous solution of sodium hyponitrite can be made from organic nitrites by reaction 14.103 or by the reduction of NaN02 with sodium amalgam. Addition of Ag leads to the precipitation of Ag2N202. Treatment of this salt with 

Nitrous acid is known only in solution and in the vapour phase, and in the latter, it has structure 14.53. It is a weak acid (p a = 3.37), but is unstable with respect to disproportionation in solution (equation 14.104). It may be prepared in situ by reaction 14.105, 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 14.106 in which HNO2 is prepared in. situ. Alkali metal nitrates yield the nitrites when heated alone or, better, with Pb (reaction 14.107). 

Nitrous acid can be oxidized to [N03] by powerful oxidants such as acidified [Mn04] . The products of the reduction of HNO2 depend on the reducing agent  

The industrial production of nitric acid (scheme 14.109) is carried out on a large scale and its manufacture is closely linked to that of ammonia. About 80% of all HNO3 produced is destined for conversion into fertilizers, with [NH4][N03] being a key product  

dehydrated over Na wire, is saturated with dry HCl, cooled and treated with Ag2N202 until the yellow color of the latter persists. Complete exclusion of atmospheric moisture is required. The solution is rapidly filtered through a dry filter 

Into a crystallization dish placed in a desiccator. To accomplish this, the addition funnel is connected with a tube in the lid of a desiccator provided with a side vent. A small dish with KOH pellets and another with a small amoimt of concentrated HgSO are put in the desiccator. The desiccator is then rapidly evacuated. Hyponitrous acid separates Immediately. 

Colorless, flakelike crystals. Very explosive, detonates even when rubbed with a glass rod. ites with solid KOH. Sometimes decomposes spontaneously, seemingly without cause. Readily soluble in alcohol less soluble in ether, chloroform and benzene very slightly soluble in ligroin. 

Abel and J. Proisl describe an electrolytic method of preparation. 

Yellow powder, stable in the absence of light. Darkens on exposure to light. 

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Nitrous acid, HNO2. See separate entry. Hyponitric acid, H2N2O3, trioxo di-nitrate(Il). Sodium salt from HjNOH in MeOH with CiHiNOi many complexes are known the free acid is unstable. 

Hydrazine azide Hydrazine chlorate Hydrazine dicarbonic acid diazide Hydrazine perchlorate Hydrazine selenate Hydrogen cyanide, unstabilized Hydroxyl amine iodide Hyponitrous acid... 

Thermal decomposition of nitramide, H2NNO2, or hyponitrous acid H2N2O2 (both of which have the empirical formula N2O.H2O) have also been used. The mechanisms of these and other reactions involving simple inorganic compounds of N have been reviewed. 

However, though N2O can be made in this way it is not to be regarded as the anhydride of hyponitrous acid since H2N2O2 is not formed when N2O is dissolved in H2O (a similar relation exists between CO and formic acid). 

Hyponitrous acid crystallizes from ether solutions as colourless crystals which readily decompose... 

H2N2O2 Hyponitrous acid Weak acid HON=NOH, isomeric with nitramide, H2N-N02 salts are known (p. 460)... 

H2N2O3 Hyponitric acid Known in solution and as salts, e.g. Angeli s salt Na2[0N=N02]... 

There is also considerable current environmental interest in hyponitrite oxidation because it is implicated in the oxidation of ammonia to nitrite, an important step in the nitrogen cycle (p. 410). Specifically, it seems likely that the oxidation proceeds from ammonia through hydroxylamine and hyponitrous acid to nitrite (or N2O). 

Nitrosyl-saure, /. nitrosylic acid (hyponitrous acid). -schwefelskure, /. nitrosylsulfuric acid. 

Untersalpetersaure, /. hyponitric acid (old name for nitrogen peroxide). 

The hyponitrites (16), esters of hyponitrous acid (HO N=N OH), are low temperature sources of alkoxy or acyloxy radicals. A detailed study of the effect of substituents on k4 for the hyponitrite esters has been reported by Quinga and Mendenhall,114... 

Dinitrogen monoxide, N,0, reacts with water to form hyponitrous acid, H,N202(aq), in a Lewis acid-base reaction. 

See Hyponitrous acid, also Sodium amide (reference 4)... 

Although they are oxides of nonmetals, CO and N20 do not give acidic solutions when added to water. However, they are formally the anhydrides of formic and hyponitrous acid, respectively. 

Hyponitrous acid, H2N202 is produced in the following reactions ... 

When a solution of Ag2N202 is treated with a solution of HC1 in ether, a solution containing hyponitrous acid H2N202 is obtained. 

Both hyponitrous acid and nitroamide (also known as nitramide) have the formula H2N202. Draw the structures for these molecules and explain any difference in acid-base properties. 

Hydrazine salts have been prepared by the action of hypochlorites on ammonia1 or urea 2 by the hydrolysis of salts of sulfohydrazimethylene disulfonic acid 3 by the hydrolysis of triazoacetic acid 4 by the reduction of diazoacetic ester 5 by the reduction of nitroguanidine followed by hydrolysis 6 by the reduction of the nitroso derivatives of hexamethylene tetramine 7 by the reduction of nitrates or nitrites with zinc in neutral solution 8 by the action of sodium bisulfite on hyponitrous acid... 

The easiest way to 10 goes via the synthesis of KDNM (see Section n.C). Acidification of an aqueous solution of KDNM, which should be buffered with H3PO4 (pH = 6.5), followed by low-temperature extraction with diethyl ether, gives the monomeric emerald-green nitrosolic acid 10 dissolved in the ether phase. Slow removal of the solvent yields the yellowish dimeric form of 10. The acid (10) is only poorly characterized. It is known to slowly decompose into HCN and HNO2 in basic solution (decomposition of the anion DNM), while the free acid (10) rapidly decomposes to give fuhninic acid, HCNO and hyponitrous acid, HON=NOH. It should be noted that both the free acid and its metal DNM salts are highly explosive. 

Formula N2O MW 44.013 a diamagnetic molecule. Synonyms dinitrogen oxide nitrogen monoxide hyponitrous acid anhydride laughing gas. 

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