Alkali metals nitrites

Less stable, more hygroscopic and readily hydrolysed than alkali metal nitrites, it may function as a more powerful oxidant. 

The ter Meer reaction consists of the production of 1,1-dinitro compounds from 1-halo-l-nitroalkanes. The reaction proceeds under the action of alkali metal nitrites in basic medium (Scheme 4.34). 

The synthesis of aliphatic nitro compounds from the reaction of alkyl halides with alkali metal nitrites was discovered by Kornblum and co-workers and is known as the modified Victor Meyer reaction or the Kornblum modification. The choice of solvent in these reactions is crucial when sodium nitrite is used as the nitrite soiuce. Both alkyl halide and nitrite anion must be in solution to react, and the higher the concentration of nitrite anion, the faster the reaction. For this reason, both DMF and DMSO are widely used as solvents, with both able to dissolve appreciable amounts of sodium nitrite. Although sodium nitrite is more soluble in DMSO than DMF the former can react with some halide substrates.Urea is occasionally added to DMF solutions of sodium nitrite to increase the solubility of this salt and hence increase reaction rates. Other alkali metal nitrites can be used in these reactions, like lithium nitrite,which is more soluble in DMF than sodium nitrite but is also less widely available. 

The tautomeric nitronic acids of secondary nitroalkanes or their nitronate salts react with nitrous acid or alkali metal nitrites to yield pseudonitroles.These pseudonitroles are often isolated as their colourless dimers (78b) but are deep blue in monomeric form (78a). Primary nitroalkanes also form pseudonitroles (80b) but these rapidly isomerise to the nitrolic acid (80a).Reactions are commonly conducted by slowly acidifying a mixture containing the nitronate salt and the metal nitrite, during which, the nitronic acid reacts with the nitrite anion. These reactions, first discovered by Meyer, have been used to prepare 2-nitroso-2-nitropropane (78a) and acetonitrolic acid (80a) from 2-nitropropane (76) and nitroethane (22) respectively. ... 

Nitrosation of phenolic substrates usually uses nitrous acid prepared in situ from a dilute mineral acid and an alkali metal nitrite. In general, for every phenolic group present in a substrate an equal number of nitroso groups can be introduced into the aromatic ring phenol, resorcinol and phloroglucinol react with nitrous acid to form 4-nitrosophenol, 2,4-dinitrosoresorcinol and 2,4,6-trinitrosophloroglucinol respectively. 

It is possible that in the use of alkali metal nitrites for nitrosyl synthesis, the first formed nitrito complex undergoes rapid ligand reduction similar to that above, as in equations (15) and (16). 

Decomposition reactions appear to be similar to those of the other alkali metal nitrites, i.e., the course of the decomposition depends on the gas phase. If the gas is continually removed, the reaction proceeds directly to the oxide ... 

This nitroso compound, which is related to Cyclonite, is prepared by treating hexamethylenetetramine with alkali metal nitrites in a dilute acid solution. 

The reaction of l-methoxy-2-phenyl-l,2,3-triazole tetrafluoroborate with alkali-metal nitrites or silver nitrite gives 5-nitro-2-phenyl-l,2,3-triazole [594],... 

Several double salts with alkali-metal nitrites have been described.10 Double compounds with ammonia of the formulae AgN02,NH8 AgNOa,2NH3 and AgN02,3NH3 have also been prepared.11 A double salt with caesium, AgCs(N02)2, is formed by the interaction of caesium nitrite and silver nitrite. It crystallizes in lemon-yellow needles.12... 

With the exception of silver nitrite, which is only slightly soluble, nitrite salts readily dissolve in water. The alkali metal nitrites and ammonium nitrite are hygroscopic. While sodium nitrite melts without decomposition, most other nitrites decompose before reaching the melting point (Ba(N02)2 > 593 K, AgN02 > 413 K, Hg(N02)2 > 348 K). Ammonium nitrite decomposes above 333 K, sometimes explosively, to dinitrogen and water ... 

The reaction of alkali metal nitrites with alkali metal oxides M2O yields salts M3NO3 that do not contain the orthonitrite anion N03 but are mixed crystals of the salts MNO2 and M2O with anti- perovskite structure (N02)0Na3. Some properties of important nitrite salts are given in Table 28. 

The reaction of solid alkali metal nitrites with haloalkanes in acetonitrile in the presence of 18-crown-6 as the PT catalyst gives nitrocompounds as the major products but substantial quantities of alkyl nitrites are also formed (eq. 136). 

The reaction is usually carried out in water with nitrous acid generated firom silver or alkali metal nitrites, although in much recent work acetic acid has been used as the solvent. The rate-determining step in the overall reaction is apparently the formation of a nitroso-amine (equation 145) . Isomerization to the tautomer 50 yields a... 

Sulfur dioxide or bisulfites are rarely used in combination with nitrites, because their reactions in acidic media yield sulfonates of either hydroxylamine or ammonia, which destroys the preservative activity of the individual additives. The reaction of alkali metal nitrites with bisulfite at lower temperatures leads to the formation of hydroxylamine N, JV-disulfonate, H0N(S03)2, which is hydrolysed to hydroxylamine JV-sulfonate, HONHSOj and further to hydroxylamine (H2NOH). At elevated temperatures complete substitution proceeds with the formation of ammonia JV-trisulfonate, N(S03)j , which is hydrolysed to sulfa-mate, H2NSOj . Subsequent reaction of sulfamate with nitrous acid leads to production of bisulfate ion and nitrogen gas ... 

Table 9.6. Preparation of nitroalkanes from alkali metal nitrites under phase transfer conditions...

Figure 7.3.4 Thermogravimetric measurement results of single alkali nitrate salts (filled symbols) and alkali metal nitrite salts (asterisk symbols) and salt mixture (open symbols)...

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