N -nitrosamines

The spectroscopic properties of the /V-nitrosamines, especially the nmr and mass spectra, vary widely depending on the substituents on the amine nitrogen (44—47). The nmr spectra are affected by the E—Z isomerism around the N—N partial double bond and by the axial—equatorial geometry resulting from conformational isomerism in the heterocycles (44,45). Some general spectral characteristics for typical dialkylnitrosamines and simple heterocycHc nitrosamines are given in Table 1. 

Synthesis. The classic laboratory synthesis of /V-nitrosamines is the reaction of a secondary amine with acidic nitrite [14797-65-0] at ca pH 3. The primary nitrosating intermediate is N2O2 arising from nitrous acid [7782-77-6] (48). 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Efficient nitrosations of amines with inorganic nitrosyl compounds also have been reported (60). 

Inhibition of nitrosation is generally accompHshed by substances that compete effectively for the active nitrosating iatermediate. /V-Nitrosamine formation in vitro can be inhibited by ascorbic acid [50-81-7] (vitamin C) and a-tocopherol [59-02-9] (vitamin E) (61,62), as well as by several other classes of compounds including pyrroles, phenols, and a2iridines (63—65). Inhibition of iatragastric nitrosation ia humans by ascorbic acid and by foods such as fmit and vegetable juices or food extracts has been reported ia several instances (26,66,67). 

Most of the over 400 N-nitroso compounds that have been tested for carcinogenic activity have been found to be carcinogenic [13, 39]. It is well known that the predominant initial metabolic activation pathway for N-nitrosamines is a-hydroxyl- 

Critical position/factor Effect on carcinogenic potential Rationale 

Molecular size J, incumbrance area of planar molecule 100 or 135 A2 Affect absorption and metabolic activation 

Shape J, 4condensed linear rings J, high degree symmetry Affect absorption and metabolic activation 

Substitution at L region t if CH3 j if bulky group Prevent detoxification Increase molecular size beyond the optimal range 

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J. -P. Ansehne, ed., N-Nitrosamines, American Chemical Society, Washington, D.C., 1979. 

Sodium nitrite can react with proteins in the stomach or during cooking, especially in high heat (such as frying bacon), to form carcinogenic N-nitrosamines. To prevent this, ascorbic acid or erythor-bic acid is commonly added to cured meats. 

Nitrite, N-nitrosamines and the explosives RDX and HMX yield reddish-violet j chromatogram zones on a pale pink-colored background. 

Nitroindole 418 Nitrophenyl isocyanate reagent 77 1-Nitropyrene 61 N-Nitrosamines 107... 

The sudden consumption of the remaining UDMH, and the increased relative importance of N-nitrosamine formation at -30 minutes into the photolysis can be rationalized by assuming that at that time the [NO I/ENO] ratio, and thus the photostationary state [O3], has become sufficiently high that O3 may be reacting with the hydrazine directly, and that reaction (3) begins to dominate over reaction (10). This results in higher rates of UDMH consumption by the OH radicals formed in the UDMH + O3 reaction (1), and by the OH radicals generated by the reaction of NO... 

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. 

Percentage of N-Nitrosamines in the Fumes Produced During the Frying of Bacon or Ham... 

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