Decomposition of nitrite

SCN ) also exist. Nitrite glasses such as those in the Ca(N02)2 ICS[02 system have been prepared, but decomposition of nitrite melts is a problem. 

The fact that nitrite reacts with the iron of the heme compound was described earlier. Because such a large number of metal ions are present in meat, and because some occur in relatively high concentration, there has been considerable interest in them. For the most part, studies have dealt with how metal ions influence reactions of nitrite. The role of sodium chloride (which is used extensively in meat processing) must also be recognized both in terms of its functional role in making reactants in the meat more or less available, and in terms of reports that it directly influences nitrosation reactions (50). Ando (51) studied the effect of several metal ions on decomposition of nitrite, and in the absence of ascorbate, only Fe++ caused a loss of nitrite but in its presence, the effect of Fe " was more pronounced and Fe+++, Mg++, Ca++ and Zn++ showed similar effects. Lee e al. 

There are also significant natural sources of oxides of nitrogen, in particular nitric oxide, which is produced by biomass burning as well as by soils where nitrification, denitrification, and the decomposition of nitrite (N02) contribute to NO production. Figure 2.4b, for example, shows the relative emission rates for biogenically produced NO in the United States in 1990 (EPA, 1995). 

Similarly, the decomposition of nitrite esters has been the subject of much study " and the complexity of the reaction is due to secondary processes following the initial O-N bond cleavage... 

Oxidative decomposition of nitrite esters. Aldehydes and ketones are formed on... 

It is worth noticing that the steps discussed above for the Fast SCR chemistry, reaction (9.6) does not involve changes in the formal oxidation state of the catalytic sites. In fact, formation of nitrates and nitrites occurs via disproportionation of NO2 (steps R1 -F R2 in Table 9.1), reduction of nitrates to nitrites is compensated by the simultaneous oxidation of NO to NO2 (step R3), and decomposition of nitrites to N2 by NH3 (step R5) is also red-ox neutral. Accordingly, we can expect that in the presence of NO2, a strong oxidizer, the SCR catalyst sites remain at their highest oxidations states. This is a substantial difference from the case of the Standard SCR reaction (9.5), wherein reduction of NO by NH3 to N2 does involve catalyst reduction, and therefore closure of the catalytic cycle... 

The chemical responsible for the red color of cured meat. It is formed by the decomposition of nitrites to nitric oxide (NO)... 

Sodium nitrite, NaNOg, Mol. Wt. 69 00. This is the only inorganic nitrite used pharmaceutically. The assay of alkali nitrites by means of permanganate is not possible by direct titration in acid solution owing to the decomposition of nitrite by the acid and loss of oxides of nitrogen by volatilisation. Corfield and Self pointed out that this method is only accurate when the nitrite solution is added slowly to the warm dilute acidified solution of permanganate so that the liberated nitrous acid is oxidised before any loss occurs. This form of assay is now used by the B.P.C. 

Thompson and colleagues initiated spectroscopic as well as photochemical investigations of organic nitrites in the vapor phase during the 1930s at Oxford. The interpretation of the primary mode of the photochemical decomposition of nitrite esters by Thompson, however, differed from what has now become established as the primary process for nitrite photolysis. Subsequent to Thompson s study, Coe... 

The solution of the aniline hydrochloride should be cooled to 5°C., and this temperature maintained throughout the addition of the sodium nitrite solution. External cooling has to be maintained, otherwise the heat of the reaction would cause the temperature to rise, with the consequent decomposition of the diazonium chloride and the production of phenol. If, on the other hand, the temperature is reduced to about o , diazotisation becomes extremely slow and unchanged nitrous acid may remain in the solution for an impracticably long time. 

Dissolve 15 ml. (15-4 g.) of aniline in a mixture of 40 ml. of concentrated hydrochloric acid and 40 ml. of water contained in a 250 ml. conical flask. Place a thermometer in the solution, immerse the flask in a mixture of ice and water, and cool until the temperature of the stirred solution reaches 5°. Dissolve I2 5 g. of powdered sodium nitrite in 30 ml. of water, and add this solution in small quantities (about 2-3 ml. at a time) to the cold aniline hydrochloride solution, meanwhile keeping the latter well stirred by means of a thermometer. Heat is evolved by the reaction, and therefore a short interval should be allowed between consecutive additions of the sodium nitrite, partly to allow the temperature to fall again to 5°, and partly to ensure that the nitrous acid formed reacts as completely as possible with the aniline. The temperature must not be allowed to rise above 10°, otherwise appreciable decomposition of the diazonium compound to phenol will occur on the other hand, the temperature... 

Difluorodiphenyl. Bis-diazotise a solution of 46 g. of benzidine (Section IV,88) in 150 ml. of concentrated hydrochloric acid and 150 ml. of water by means of a solution of 35 g. of sodium nitrite in 60 ml. of water add about 200 g. of crushed ice during the process (compare p-Fbtorotoluene above). Filter the solution and add it to a filtered solution of 85 g. of sodium borofluoride in 150 ml. of water. Stir for several minutes, collect the precipitated bis-diazonium borofluoride by suction filtration, wash with 5 ml. of ice-cold water, and dry at 90-100°. Place the dry salt in a flask fitted with an air condenser, immerse the flask in an oil bath, and slowly raise the temperature to 150° (Fume Cupboard ). When decomposition of the salt is complete, steam distil the mixture collect the 4 4 difluoro-diphenyl which passes over and recrystallise it from ethanol. The yield is 21 g., m.p. 92-93°. 

In agreement with the theory of polarized radicals, the presence of substituents on heteroaromatic free radicals can slightly affect their polarity. Both 4- and 5-substituted thiazol-2-yl radicals have been generated in aromatic solvents by thermal decomposition of the diazoamino derivative resulting from the reaction of isoamyl nitrite on the corresponding 2-aminothiazole (250,416-418). Introduction in 5-position of electron-withdrawing substituents slightly enhances the electrophilic character of thiazol-2-yl radicals (Table 1-57). 

Some 2-halogeno-5-nitrothiazoles and 2-nitro-5-halogenothiazoles are known. 2-Halogeno-5-nitrothiazoles can be prepared by a Sandmeyer reaction from 2-amino-5-nitrothiazole (1, 85), while 2-nitro-5-halo-genothiazoles can be analogously prepared by decomposition of dia-zonium salts arising from 2-amino-5-halogenothiazoles in presence of nitrite anion (82, 84). 

Unpiotonated hydioxylamine is oxidized rapidly by ozone, / = 2.1 X 10 (39). The reaction of ozone with the lower oxides of nitrogen (NO and NO2) is also rapid and quantitative the end product is nitrogen pentoxide, which is also a catalyst for the decomposition of ozone (45). Nitrous oxide, however, reacts slowly (k < 10 ) (39). Nitrogen-containing anions, eg, nitrite and cyanide, also ate oxidized by ozone (39). Nitrite is oxidized to nitrate (fc = 3.7 X 10 and cyanide is oxidized rapidly to cyanate (fc = 2.6 X 10 (46) and 10 -10 (39)). Cyanate, however, is oxidized slowly. 

Thermal or photo-induced decompositions of dialkyl peroxides in the presence of suitable substrates yield various products. For example, with nitric oxides, alkyl nitrites or nitrates are formed and, with carbon monoxide, Z fZ-alkyl esters are obtained (44) ... 

Sodium nitrite is stable in alkaline solutions. Acidification liberates nitrous acid which is unstable. The decomposition of nitrous acid yields nitric acid [7697-37-2] HNO, according to the following reaction ... 

Barium nitrite [13465-94-6] Ba(N02)2, crystallines from aqueous solution as barium nitrite monohydrate [7787-38-4], Ba(N02)2 H2O, which has yellowish hexagonal crystals, sp gr 3.173, solubihty 54.8 g Ba(NO2)2/100 g H2O at 0°C, 319 g at 100°C. The monohydrate loses its water of crystallization at 116°C. Anhydrous barium nitrite, sp gr 3.234, melts at 267°C and decomposes at 270 °C into BaO, NO, and N2. Barium nitrite may be prepared by crystallization from a solution of equivalent quantities of barium chloride and sodium nitrite, by thermal decomposition of barium nitrate in an atmosphere of NO, or by treating barium hydroxide or barium carbonate with the gaseous oxidiation products of ammonia. It has been used in diazotization reactions. 

Experiments in which radical scavengers are added indicate that a chain reaction is involved, because the reaction is greatly retarded in the presence of the scavengers. The mechanism shown below indicates that one of the steps in the chain process is an electron transfer and that none of the steps involves atom abstraction. The elimination of nitrite occurs as a unimolecular decomposition of the radical anion intermediate, and the SrnI mechanistic designation would apply. 

Nitrous oxide may also be obtained by the controlled reduction of nitrates or nitrites, decomposition of hyponitrites, or thermal decomposition of hydroxylamine. 

The nitrites aie most conveniently prepared from the corresponding alcohols by treatment with nitrosyl chloride in pyridine. The crude nitrites can be precipitated by addition of water and recrystallized from appropriate solvents. However nitrites prepared from carbinols in which the adjacent carbon is substituted by halogen, free or esterified hydroxyl or a carbonyl function are very readily hydrolyzed and must be recrystallized with great care. In general the photolysis gives higher yields if purified and dried nitrites are used which do not contain acids or pyridine, although occasionally the addition of small amounts of pyridine is recommended in order to prevent hydrolysis of the nitrite. Traces of acids do in fact catalyze the thermal decomposition of secondary nitrites to equimolar amounts of alcohol and ketone. ... 

The Bergmann variation of the Balz Schiemann reaction is a two-step process featuring copper- or copper halide-catalyzed decomposition of aqueous or acetone solutions of arenediazonium fluoroborates containing alkyl or halogen substituents [30] A recent modification is a one-step technique featuring simultaneous diazoti-zation and decomposition by addition of aqueous sodium nitrite at 25 °C to a mixture of fluorobonc acid, copper powder, and 2 isopropyl 6 methylaniline to give 2-isopropyl-6 methylfluorobenzene in 73% yield [37]... 

The corresponding nitrites, MNO2, can be prepared by thermal decomposition of MNO3 as indicated above or by reaction of NO with the hydroxide ... 

The presence of nitrate as acelerator has a pronounced effect on the amount and composition of gas evolved from the work being treated (Table 15.8). It will be observed that hydrogen evolution drops to a very low figure with the zinc/nitrate baths. The formation of nitrite arises from decomposition of nitrate by reaction with primary ferrous phosphate to form ferric phosphate ... 

Diverse and sometimes contrasting types of kinetic behaviour have been described for the decompositions of salts in this class, which includes the metal carbonates, sulphates, nitrates and nitrites, phosphates, oxyhalides, permanganates and chromates (Sects. 3.1—3.7, respectively). It is con-... 

Nitrites generally decompose at lower temperatures than the corresponding nitrates. The formation of nitrites as intermediates during the decomposition of nitrates is doubtful (or difficult to demonstrate). However, with nitrites, the decomposition is supposed to take place according to the scheme... 

Decomposition of the rare earth nitrates proceeded [821] through the intermediate formation of oxysalts of the form MON03 and E values were low Nd(N03)3, 33 kJ mole 1, 663-703 K Dy(N03)3, 23 kJ mole 1, 583—633 K Yb(N03)3, 46 kJ mole 1, 563—598 K. Thermogravimetric curves showed that the formation of anhydrous salts was possible, in contrast to observations by Wendlandt and Bear [826]. In a similar study [827] of the reaction of Pr(N03)3 at 558—758 K, the intermediate formation of a nitrite is postulated during decomposition to a non-stoichiometric residual oxide, Pr0li83 (the actual composition depends on temperature). 

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