Of nitrite ion

The anticatalytic action is ascribed to the deprotonation of nitric acidium ions by nitrite ions, which, being more basic than nitrate ions, will be more effective anticatalysts. The effect of nitrite ions should depend upon [HNOaJaioich it does. 

Historically, ferrous sulfamate, Fe(NH2S02)2, was added to the HNO scmbbing solution in sufficient excess to ensure the destmction of nitrite ions and the resulting reduction of the Pu to the less extractable Pu . However, the sulfate ion is undesirable because sulfate complexes with the plutonium to compHcate the subsequent plutonium purification step, adds to corrosion problems, and as SO2 is an off-gas pollutant during any subsequent high temperature waste solidification operations. The associated ferric ion contributes significantly to the solidified waste volume. 

Quite recently, it was reported that heating of tetracyano derivative 268 with potassium nitrite and potassium carbonate in DMF provided 53% of phenoxathiin 270 (Scheme 42) (OOlHl 161). The probable mechanism is, that one activated nitro group in 268 is displaced with a nitrosoxy group by nucleophilic substitution of nitrite ion, followed by hydrolysis to 269, which then undergoes denitrocyclization reaction to the final product. 

Schneider and Busch have showed that tetraazafS 1 8 l paracyclophane catalyzes the nitration of alkyl bromides with sodiiun nitrite In dioxane-water d l at 30 C, the reaction of 2-bromomethylnaphthalene with sodiiun nitrite is accelerated by a factor of 20 in the presence of the catalyst Concomitantly, the product ratio of [R-ONO [RNO-, changes from 0 50 1 to 016 1 Thus, an acciuruiladon of nitrite ions at the positively charged cyclophanes or IRA-900-nitrite form provides a new method for selective nitration of alkyl halides... 

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. 

In this context two observations reported by Rondestvedt (1960, p. 214) should be mentioned (i) Meerwein reactions proceed faster in the presence of small amounts of nitrite ion. Meerwein reactions in which N2 evolution ceased before completion of the reaction can be reinitiated by addition of some NaN02. (ii) Optimal acidity for Meerwein reactions is usually between pH 3 and 4, but lower (pH — 1) with very active diazonium compounds such as the 4-nitrobenzenediazonium ion or the diphenyl-4,4 -bisdiazonium ion. At higher acidities more chloro-de-diazoniation products are formed (Sandmeyer reaction) and in less acidic solutions (pH 6) more diazo tars are formed. 

Ellison et propose that the substitution of nitrite ion into chloroam-... 

Indeed, given an improperly designed or understood system, a blocking agent, like ascorbic acid, could be catalytic toward nitrosamine formation. For example, if the source of nitrosatlng agent is nitrite ion and the susceptible amine is in the lipid phase, conceivably ascorbic acid could cause the rapid reduction of nitrite ion to nitric oxide which could migrate to the lipid phase. Subsequent oxidation of NO to NO in the lipid phase could cause nitrosation. 

According to Didenko and Suslick [51], the amount of nitrite ions (N02 ) produced by a bubble per acoustic cycle was about 106 107 molecules. Koda et al. [52] also reported a similar value. 

To overcome the suppression effect of amines in the determination of ammonia, Hampson [56] investigated the effect of nitrite ions added either as nitrite or as nitrous acid. Figure 5.2 indicates that very considerable suppression by nitrite does occur, although it is not as strong as with any of the amines. Again, it is not great so long as the nitrite N concentration is less than the ammonia N concentration, but rapidly increases as the nitrite concentration exceeds the ammonia concentration. In fact, the nitrite modified method was found to be satisfactory in open seawater samples and polluted estuary waters. 

It follows from the above that MPO may catalyze the formation of chlorinated products in media containing chloride ions. Recently, Hazen et al. [172] have shown that the same enzyme catalyzes lipid peroxidation and protein nitration in media containing physiologically relevant levels of nitrite ions. It was found that the interaction of activated monocytes with LDL in the presence of nitrite ions resulted in the nitration of apolipoprotein B-100 tyrosine residues and the generation of lipid peroxidation products 9-hydroxy-10,12-octadecadienoate and 9-hydroxy-10,12-octadecadienoic acid. In this case there might be two mechanisms of MPO catalytic activity. At low rates of nitric oxide flux, the process was inhibited by catalase and MPO inhibitors but not SOD, suggesting the MPO initiation. 

The classical discoveries of the reacting nitrosation reagents mentioned above were mainly the result of kinetic investigations. There were some surprising results, e.g. the dependence of the diazotization rate on the square of the nitrous acid concentration in sulfuric or perchloric acid up to 0.3 M. Nitrous acid is a fairly weak acid (pK = 3.1569). Therefore, the low concentration of nitrite ions in the last step of the nitrous acid equilibria system of Scheme 5 does not appear to favor the formation of dinitrogen trioxide. N2O3 is, however, strongly indicated by the second order of rate on the (analytical) nitrous acid concentration. 

The most important color reaction for nitrate esters and nitramines is based on the formation of nitrite ions (NO2 ), upon reaction of these compounds with alkahs [31,32]. The nitrite ions are then detected by the classical Griess reaction [5,6]. 

Several pathways are known to take place in the reaction between nitrate esters and alkalis. The mechanism that leads to the formation of nitrite ions is an (X-ehmination abstraction of an CC-hydrogen atom, with the conversion of the nitrate ester to nitrite ion and the corresponding carbonyl compound [31] (Eq. (4)) ... 

Alkaline hydrolysis of nitramines also leads to the formation of nitrite ions [1, 34]. 

Principally the same, but chemically simpler, sequence was used to prepare arylnitro anion-radicals from arylamines, in high yields. For instance, aqueous sodium nitrite solution was added to a mixture of ascorbic acid and sodium 3,5-dibromo-4-aminobenzenesulfonate in water. After addition of aqueous sodium hydroxide solution, the cation-radical of sodium 3,5-dibromo-4-nitro-benzenesulfonate was formed in the solution. The latter was completely characterized by its ESR spectrum. Double functions of the nitrite and ascorbic acid in the reaction should be underlined. Nitrite takes part in diazotization of the starting amine and trapping of the phenyl a-radical formed after one-electron reduction of the intermediary diazo compound. Ascorbic acid produces acidity to the reaction solution (needed for diazotization) and plays the role of a reductant when the medium becomes alkaline. The method described was proposed for ESR analytical determination of nitrite ions in water solutions (Lagercrantz 1998). 

They suggested conducting the reaction at concentrations of the initial reagents, 1-halo-l-nitro-alkane and sodium nitrite, exceeding 1 mol Then, because of the low solubility of molecular oxygen in water (approximately 10 mol L ), the presence of oxygen does not affect the yield of the target product. An increase in the concentration of nitrite ion promotes ter Meer reaction. 

Figure 13. Possible mechanism of nitrosamine formation in the reaction of nitrite ion with FlyF -disuhstituted carbamoyl chlorides (suggested by J.-P. Anselme)...

Before trying to decide which orientation of nitrite ions is correct, consider the positions of the sodium ions. The outstanding fact bearing on this is that 101 is very strong. With nitrite ions at the corners of the cell, the only way of ensuring this is to put sodium atoms on or... 

Reductive hydrolysis of n-butyl nitrate in an aqueous solution of ethyl alcohol in the presence of sodium hydrosulphide or ammonium hydrosulphide has been carried out by Merrow, Cristol and van Dolah [41], This is a complicated chemical reaction. As the result of hydrolysing the nitrate in the presence of sodium hydro-sulphide (the alkalinity of the solution corresponds to pH 10-11) 93% of nitrite ions and 7% of ammonia are obtained from the ester group nitrogen. When ammonium hydrosulphide is used, the nitrite ions initially produced rise to a maximum concentration and then fall to zero owing to the reducing action of the ammonium hydrosulphide. The reduction process takes place more effectively when the pH is above 10. 

As shown by the eqns. (20-24) owing to the activity of the sulphide or polysul-phide ion, the 0—N linkage is broken to form alkoxide and thionitrate or polythio-nitrate ions. In the other reactions the influence exerted by sulphide on the oxygen atom, which results in the creation of nitrite ions, has been taken into account. Both schemes indicate that the nitrite ion is not produced by the reduction of the nitrate ion. 

The coordination chemistry of nitrite ion has recently been very extensively reviewed.1637 The bonding modes of nitrite ion found in nickel(H) complexes are summarized in Figure 25 and selected nickel(II) complexes containing coordinated nitrite ions are shown in Table 82. 

Sodium nitrite, NaN02, is frequently added to processed meats as a preservative. The amount of nitrite ion in a sample can be determined by acidifying to form nitrous acid (HN02), letting the nitrous acid react with an excess of iodide ion, and then titrating the... 

The kinetics and mechanism of the reactions of/i-nitrocumyl bromide with azide ions in DMSO have been studied.104 In contrast to the reactions of the corresponding chloride in dipolar aprotic solvents, no evidence for an SrnI mechanism was found. A similar situation obtained in a related study of the reactions of nitrite ions with p-nitrocumyl bromide.105... 

Thus, an alkyl iodide can yield either an alkyl nitrite or a nitroalkane depending on whether the oxygen or the nitrogen of nitrite ion attacks carbon. Both do, and the product from 2-iodooctane is a mixture of... 

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