With nitrites

Alkyl halides can be converted into nitro compounds by treatment with metal nitrites (for a review see Kornblum146). The older directions almost all prescribe silver nitrite at elevated temperatures (ca. 80-110°). However, because of the numerous side reactions it is only for the simplest primary iodides (up to about C5) that this reaction gives satisfactory yields (about 50%). Only in a few cases can bromides be used.643 Recently, however, the process has been made economic by using considerably milder conditions. It is advisable 

1- nitrooctane can be generalized for preparation of any of the lower primary nitro compounds from the iodide or bromide. 

Until recently there were few cases in which an alkali nitrite could replace silver nitrite in the synthesis of nitro compounds. Such a case was Kolbe s nitroalkane synthesis, in which an alkali salt of a 2-haloalkanoic acid was treated with a boiling aqueous solution of an alkali nitrite the 2-nitroalkanoic acid formed lost carbon dioxide under the reaction conditions and the nitroalkane distilled over in the steam. The Kolbe synthesis is, however, of practical use only for the preparation of nitromethane (38% yield from chloro-acetic acid648) and nitroethane (about 50% yield from 2-bromopropionic acid649) it is substantially valueless for higher fatty acids.649,650 

however, 2-bromoalkanoic esters are kept for several days in an aqueous-alcoholic solution of sodium nitrite at room temperature, good yields of the 

Recently, however, Kornblum et al.651 showed that alkali nitrites, in particular sodium nitrite, can replace silver nitrite in the preparation of nitro compounds if dimethylformamide is used as solvent. The method has the additional advantage that not merely primary but also secondary alkyl iodides and bromides react readily in this solvent. Yields are around 60% in both cases. It usually suffices to stir the halide with an excess of sodium nitrite in dimethylformamide for some hours at room temperature primary iodides need about 2.5 hours, primary bromides about 6 hours for complete reaction. With secondary halides it is advisable to add urea as this raises the solubility 

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The carcinogenicity of nitrosamines has created widespread concern over the safety of food products that are significant sources of nitrates and nitrites. Nitrosamines are readily formed by reaction of secondary amines with nitrites at acid pH, conditions which may occur in the gastrointestinal tract. 

Analytical and Laboratory Operations. Sulfamic acid has been recommended as a reference standard in acidimetry (55). It can be purified by recrystaUization to give a stable product that is 99.95 wt % pure. The reaction with nitrite as used in the sulfamic acid analytical method has also been adapted for determination of nitrites with the acid as the reagent. This reaction is used commercially in other systems for removal of nitrous acid impurities, eg, in sulfuric and hydrochloric acid purification operations. 

Biochemical Functions. Ascorbic acid has various biochemical functions, involving, for example, coUagen synthesis, immune function, dmg metabohsm, folate metaboHsm, cholesterol cataboHsm, iron metaboHsm, and carnitine biosynthesis. Clear-cut evidence for its biochemical role is available only with respect to coUagen biosynthesis (hydroxylation of prolin and lysine). In addition, ascorbic acid can act as a reducing agent and as an effective antioxidant. Ascorbic acid also interferes with nitrosamine formation by reacting direcdy with nitrites, and consequently may potentially reduce cancer risk. 

To obtain optimum results with nitrite in HW heating systems, it is necessary to take precautions, including ... 

Molybdate is always used in conjunction with other anion inhibitors, not only to reduce the cost of the inhibitor program, but also because, through synergism, much-improved barrier films are produced when coupled with nitrite or silicate. 

For larger, more complex LPHW systems and for LP steam heating systems, silicates are seldom used alone but are formulated with nitrite or molybdate inhibitors to provide synergistic corrosion protection. 

Determination of the content of diazotizable amine by titration with nitrite. 

The reaction with nitrite proceeds smoothly and with relatively high yields of the corresponding nitroarene (see Sec. 10.6). Obviously a major part of the driving force of this reaction is the formation of a stable, i. e., an energetically favorable, radical, nitrogen dioxide. With the hydroxide ion — a much stronger nucleophile than the nitrite ion — the reaction is expected to produce very unstable radicals, the hydroxy radical OH and the oxygen radical anion O, from the diazohydroxide (Ar - N2 — OH) and the diazoate (Ar-N20 ) respectively. Consequently, dediazoniation in alkaline aqueous solution does not follow the simple Scheme 8-41 with Yn = OH, but instead involves diazoanhydrides (Ar — N2 —O —N2 —Ar) as intermediates (see Sec. 8.8). 

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... 

It is probable that the test of Wolski88 for sulphoxides depends on the first reaction. He used acetyl chloride or bromide the product from the former gave a red colour with nitrite ion, absorption maximum at 545 nm, and the latter gave a yellowish-orange colour directly. The method was used also by Besyadetskaya and colleagues89 to determine dimethyl sulphoxide in ointments. 

Intoxication delirium may occur with solvents, nitrous oxide (Sterman and Coyle 1983), ether, or other general anesthetics (Delteil et al. 1974). However, to our knowledge, there are no reports describing delirium associated with nitrite intoxication. The description of delirium presented here derives mainly from what has been observed during solvent intoxication. 

Titanium(III) chloride (particularly in slightly alkaline medium) reduces the p-nitro groups of the thiophosphate insecticides to amino groups, which are then reacted with nitrite in acid mediiun in a second step to yield a diazonium compound as intermediate. This is then coupled to N-(l-naphthyl)-ethylenediamine dihydrochloride to yield an azo dye [3]. In the case of benzodiazepines the first reaction step includes an additional acid hydrolysis to the corresponding benzophenone derivative [2]. 

In the presence of acids, sulfanilic acid — like other primary aromatic amines — reactt with nitrite to yield a diazonium compound that can couple with a suitable aromatic amine to yield an azo dye. 

PEGG R B, FISH K M and SHAHIDI F (2000) The replacement of conventional meat curing with nitrite-free curing system, Fleischwirtschaft, 80 (5) 86-9. 

THiEMiG F, BUHR H, OELKER p (2000) Curing with nitrite - are there alternatives , Fleischwirtschaft, 80 (1) 106-10. 

In order to define the conditions of the growing cultures, buffered medium (VL) inoculated with E, coli ATCC 11775 and supplemented with nitrate, glucose and DMA was incubated at 37 C, and pH, nitrite concentration, nitrate concentration, cell growth and nitrosamine formation were followed (Fig. 1). Within 2 hrs, >90% of the nitrate is converted to nitrite (some of the nitrite is further reduced) and over 8 hrs the pH drops from 7.3 to 6.0. This would indicate that in experiments carried out for 20 hrs or more the control medium should be adjusted to pH 6.0 to 6.5 and nitrite should be added rather than nitrate. Such a control medium (VL) was supplemented with nitrite and DMA and NDMA formation was followed (Fig. 2). It can be seen that even without the addition of cells the rate of nitrosation is 4 fold greater than... 

N-Nitrosamines, formed principally from the reaction of naturally occurring secondary amines with nitrites that may be added to foods or produced by bacterial reduction of nitrates, have been identified in many food systems including cured meat products, nonfat dried milk, dried malt and beer. In addition, the presence of less volatile and non-volatile N-nitroso compounds or their precursors in foods have been suggested from a number of model system studies. 

In the last fifteen years there has been considerable interest in the analysis of volatile N-nitrosamines in foods. The primary focus has been on meat cured with nitrite (3 ) although nitrosamines have been shown to occur occasionally in other foods such as fish and cheese (, 3) Recently, attention has been directed to volatile nitrosamines in beer and other alcoholic beverages. The purpose of this paper is to review current information on the presence of nitrosamines in beer, and to discuss work done in our laboratory and elsewhere on the mode of formation of nitrosamines in beer. 

Cytochrome c is a heme containing protein which occurs in muscle at lower concentrations than does myoglobin. It was demonstrated some time ago (18) that oxidized cytochrome c reacts with gaseous nitrite oxide to produce a nltrosyl compound. Recent work (19, 20, 21) has examined the reactions of cytochrome c with nitrite and the contribution of the product formed to cured meat color in considerably more detail. The general conclusion is that even at the pH normally encountered in meat, the reaction can take place in the presence of ascorbic acid but probably does not affect meat color because of the unstable nature of the reaction product and the low concentration. 

Methylanaline could be transnitrosated with nitrite and S-nitrosocysteine and also by a simulated protein bound nitrite. In the latter case, an important factor was the local concentration of nitrosothiol groups on the matrix. The effects of S-nitrosocysteine as an inhibitor of lipid oxidation, as a color developer, and as an anticlostridial, have been reported recently in a turkey product (31). The Molar concentration of RSNO equating to 25 ppm nitrite gave similar results for color and inhibition of lipid oxidation but had less anti-clostridial activity. Transnitrosation between RSNO and heme protein was demonstrated. 

Some work has been completed on reaction of proteins with nitrite followed by hydrolysis and analysis for amino acids It has been shown that 3-nitrotyrosine and 3,4-dihydroxyphenylalanine are formed from bovine serum albumin when nitrosation occurs under conditions similar to those found in the human stomach (36), Direct demonstration that nitrite reacts with protein has been made by using NaN02 with bovine serum albumin (pH 5.5, 20 C and 200 ppm nitrite). A 60% loss of the originally added nitrite was observed in one week and nearly half of the nitrite (labelled %) could be recovered from the protein. Similar work with myosin revealed that 10-20% of the incorporated label was present as 3-nitrotyro-sine (J7). 

Mirvish (53,54) discovered that vitamin C could inhibit ni-trosation reactions. The purely chemical interaction of ascorbic acid with nitrite has been studied for theoretical reasons and because of its importance in the preservation of foods. This interaction has received increased attention for minimizing the presence of nitrosamines and nitrosamides in the environment, and especially in foods. We have studied the relationship in gastric carcinogenesis between high levels of nitrite, including pickling, and of vitamin C as a protective and inhibiting element. 

Sites and Incidence of Tumors in Rats Given Extracts of Fish Treated with Nitrite or Fish Alone(66)... 

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