Nitrite occurrence

Jones RD, Schwab AP. 1993. Nitrate leaching and nitrite occurrence in a fine-textured soil. Soil Sci 155(4) 272-282. 

Nitrite occurrence in foods is minimal. Interestingly, a naturally occurring source of nitrites appears to be the saliva. 

Methyl-5-aminothia2ole-4-carboxylic acid is diazotized with isoamyl nitrite in the presence of furan in 1.2-dichloroethane to give a mixture of products 163 (53%), 164 (33%). 165 (11%), and 166 (3%) (Scheme 104) (334). This reactivity experiment was carried out to examine the possibility of the occurrence of 4,5-dehydrothiazole (hetaryne). Hetaryne intermediates seem not to be involved as an intermediate in the reaction. The formation of 163 through 166 can be rationalized in terms of the intermediacy of 166a. 

Disproportionation of Pu(IV). There are several needs associated witn the occurrence, detection, and mitigation of the disproportionation of Pu(IV) in applied plutonium recovery/ purification procedures. First, there is a great need for much more detailed information concerning the effect of typical process conditions [e.g., temperature, concentration of plutonium, hydrogen ion, nitrate ion, nitrite ion, fluoride ion, other metal ions (e.g., A13+, Fe3+, etc.), etc.] on the occurrence and extent of the reaction ... 

In order to check whether the occurrence of the Rieske-type sequence motif is unique for the assimilatory nitrite reductase from Bacillus subtilis, the sequences of other assimilatory nitrite reductases were searched for the presence of the four putative ligands of Rieske-type clusters. A well-conserved sequence pattern... 

Oxidized species of nitrogen, chiefly nitrite and nitrate, occur in all soils and in the soil solution. Nitrite in the environment is of concern because of its toxicity. Its occurrence is usually limited because the oxidation of nitrite to nitrate is more rapid than the oxidation of ammonia to nitrite. Both nitrite and nitrate move readily in soil and nitrate is available to plants as a source of nitrogen and can move to plant roots with water. 

Various NOC can be found in food processing operations. The most commonly known contributors to dietary volatile and non-volatile N-nitrosamines are nitrite cured meats, particularly fried bacon and beer. Several reviews cover the occurrence and formation of... 

Fan, A.M. Steinberg, VE. (1996) Health implications of nitrate and nitrite in drinking water an update on methemoglobinemia occurrence and reproductive and developmental toxicity. Regul. Toxicol. Pharmacol, 23, 35 3... 

Although the potentially carcinogenic nitrosamines may he present in foods, particularly cured meats, occurrence is infrequent and at low levels. USDA regulations stipulate that ascorbic acid be added to cured meats at live limes the level of nitrates and nitrites to prevent the formation of carcinogenic Af-nitroso compounds. See also Food Additives. 

The occurrence of nitrous acid and nitrites in atm. air has already been discussed. 

The reactions of the nitrites described have also been observed under FA conditions at much higher pressures. The increased pressure might explain the occurrence of an additional pathway observed in the reaction between enolate anions and nitrites and exemplified in (25b) (King et al., 1981). Path (b) has also been reported to occur in the reaction between the enolate anion of diisopropyl ketone and methyl nitrite in an ICR instrument operating at the relatively high pressure of 10 3 Pa (Klass and Bowie, 1980). 

Nitrate and nitrite have been classified in the EPA s Group D (not classifiable). Owing to its potential toxicity and occurrence in drinking water, it is regulated. 

The upper wavelength range in which reaction 9 has been studied is relatively near the lower end of solar UVB radiation, but at present very little information is available on the real environmental role of such a process, if it has any. However, since the occurrence of reaction 9 under UVB irradiation cannot be excluded, Mack and Bolton discussed the need to revisit the reaction pathways proposed for the transformation of organic molecules in the presence of irradiated nitrate and nitrite in the light of the findings concerning the possible formation of HOONO/ONOCT [24], Since new data concerning the transformation reactions of phenol in the presence of N03 + hv, N02 + hv and HOONO are now available, the possible role of peroxynitrous acid in that particular case will be discussed later (Sect. 3.2.3). 

Finally, 4-nitrosophenol has also been detected as a transformation intermediate of phenol upon nitrate photolysis [54,58,79,99,100]. The occurrence of 4-nitrosophenol might be accounted for by the irradiation of photoformed nitrite and by the thermal reactions induced by nitrous acid. Indeed, the formation of 4-nitrosophenol upon nitrate irradiation is favoured at acidic pH [58] and 4-nitrosophenol forms in relevant amount in the presence of both nitrite under irradiation [44,59,110] and nitrous acid in the dark [55, 65-67]. 

Nitrate and nitrite photochemistry might also play a role in atmospheric hydrometeors. Nitrite photolysis has been shown to account for the majority of hydroxyl photoformation in irradiated fog water from a polluted site [ 14]. In addition, the generation of mutagenic and carcinogenic compounds from amino acids and amines dissolved in fog water [147] is a process that can be linked with nitrite photochemistry [20,141]. Furthermore, the formation of atmospheric nitrophenols partially takes place in aqueous solution. Reactions in the aqueous phase can account for about 30% of the atmospheric sources of mononitrophenols and for the vast majority of the dinitrophenol ones [ 148], and irradiation of nitrate and nitrite can possibly play a role in the process (see Sect. 3.2). Mono- and dinitrophenols are toxic compounds, and their occurrence in rainwater is thought to be a contributory factor in forest decline [149-151]. 

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