Hyponitrite ion

Vibrational spectroscopy indicates that the hyponitrite ion has the trans- (C2/1) configuration (1) in the above salts. 

Nitrosamines [115] probably afford the amide ion and nitrogen oxide. The latter accepts the second electron and is converted to hyponitrite ion ... 

In alkaline metal salts, hyponitrite-ion N202 was detected using IR-spectroscopy technique (by the presence of intensive absorption bands at 500 and 1000 cm l) [171] and from qualitative reactions. 

Spectroscopic data indicate that hyponitrous acid, HON=NOH, has the planar trans configuration. Its structural isomer nitramide, H2N-NO2, is a weak acid. The structure of nitramide is shown in Fig. 15.2.2(a) in this molecule, the angle between the NNO2 plane and the H2N plane is 52°. Both trans and cis forms of the hyponitrite ion, (ONNO)2-, are known. The trans isomer, as illustrated in Fig. 15.2.3(a), is the stable form with considerable n bonding over the molecular skeleton in the cis isomer, the N=N and N-O bond lengths are 120 and 140 pm, respectively. 

The silver salt is precipitated from aqueous solutions by AgN03. In the solid state the hyponitrite ion has been found in the cis conformation (9-IX) the trans ion has been reported but its existence has been questioned. The anion is stable in water but is decomposed by dilute acid. Protonation on only one oxygen atom... 

Several brief preliminary reports in the literature indicate the formation of products from nitric oxide containing nitrogen-nitrogen bonds. Lithium aluminum hydride plus nitric oxide is reported to give rise to hyponitrite ion (17), Grignard reagents (27) and aluminum triethyl (3), when reacted with NO, give rise to intermediates which upon hydrolysis produce nitrosated alkyl-substituted hydroxyl-amines. These materials are reported to be unstable and evidence for their existence is indirect. If these products are indeed formed, the reactions can be easily incorporated into the BNO scheme. 

Hyponitrous acid. In contrast to nitrous and nitric acids, hyponitrous acid crystallizes from ether as colourless crystals which easily decompose, explosively if heated. The detailed molecular structure of this acid has not been determined, but it is known that the molecular weights of the free acid and its esters correspond to the double formula, H2N2O2, that it is decomposed by sulphuric acid to N2O, and that it can be reduced to hydrazine, H2N-NH2. Infrared and Raman studies show conclusively that the hyponitrite ion has the trans configuration (a), but the N-N frequency suggests that the central bond has an order of rather less than two. ... 

A compound made by the action of NO on Na in liquid NH3 and long formulated as NaNO is unlikely to contain NO- ions nor does it contain the hyponitrite ion. It has been proposed that it may contain a cw-hyponitrite ion, but there is no positive evidence for this.33... 

In the cis-heme bj mechanism model, it has been proposed that one NO molecule reacts with the heme iron center to form the FeNO complex activating it for attack by a second free NO molecule to generate the cis-N-bound Fe-hyponitrite intermediate complex (Figure 43A) (204). Reduction of the [Fe—N2O2] complex to the hyponitrite ion followed by cleavage of one of the N—O bonds of the hyponitrite then results in the release of N2O and H2O as by-product. In the cis-Fes mechanism however, the two NO molecules interact with the Fe of nonheme complex to generate the dinitrosyl nonheme complex. The dinitrosyl nonheme Fe complex formed then complexes with the heme-Fe to generate the bimetaUic intermediate in which the nonheme Fe coordinates with the hyponitrite... 

The hyponitrite ion, O—N=N—O , exists in solid compounds as the trans isomer. Using valence bond theory, explain why cis-trans isomers might be expected for this ion. Draw structural formulas of the cis-trans isomers. 

Each of the N atoms has a lone pair of electrons and is bonded to two atoms. The N atoms are sp hybridized. The two possible arrangements of the oxygen atoms relative to one another are shown above. Sinc the -ir bond between the nitrogen atoms must he broken to intenconvert these two forms, it is expected that the hyponitrite ion will exhibit cis-trans isomerization. 

Thus it is the conjugate acid of the anion which actually undergoes decomposition. cw-Hyponitrite ion is a suggested intermediate. The activation parameters... 

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