Nitrosamines decomposition

The nitrosation of several secondary and tertiary amines can be blocked in vitro by the addition of vitamin C. The vitamin appears to compete for the nitrite, thus inhibiting nitrosation. It has been demonstrated that vitamin C does not react with amines, nor does it enhance the rate of nitrosamine decomposition. However, it reacts very rapidly with nitrite and nitrous acid. It has been suggested that the vitamin decreases the available nitrite by reducing nitrous acid to nitrogen oxides, leading to inhibition of the nitrosation reaction ... 

Ascorbic acid has been shown to exert a protective effect against carcinogenesis by nitrite reacting with aminopyrine (123), morpholine (174), piperazine (Ref. 174, p. 175), and raw fish (204) as well as to reduce the acute hepatotoxicity resulting from feeding nitrite and dimethylamine (61) or nitrite and aminopyrine (Refs. 145, 168, and 169 Ref. 174, p. 160). Studies with preformed nitrosamines have shown that ascorbic acid exerts little or no protective effect (Ref. 174, p. 175). Ascorbic acid does not react with amines, nor does it increase the rate of nitrosamine decomposition it exerts its protective effect largely by reaction with nitrite... 

These kinetic results are consistent with a fast reversible protonation of the nitrosamine followed by a unimolecular decomposition, viz. 

The trialkyltrlazenes are essentially protected diazo-nlum ions. They decompose cleanly and quantitatively to the dlazonlum ions and the corresponding amines over a wide pH range (M). Good kinetic data were obtained over the range of pH 6.9 - 8.3. In more acid solutions, the reactions are too rapid to measure by conventional kinetics. The decomposition reaction is subject to general acid catalysis. Thus, the trialkyltrlazenes will be a useful tool for the study of the reactive intermediates produced by the metabolism of dialkyl-nitrosamines. 

Decomposition studies confirmed that N-nitrosamides are much less stable than volatile N-nitrosamines such as NPYR and NDMA (79). Thermal studies utilizing heating conditions commonly encountered in the cooking of bacon and pork roasts indicated that N nitrosomethylpropionamide (NOMP) was degraded to the extent of 74-97% compared to 3-14% for NPYR and NDMA (Table V). It was tentatively concluded that the major... 

Possible exposure to pesticide-derived N,-nitroso compounds depends on environmental processes that influence formation, movement, and degradation of the compounds. Although laboratory studies have shown the feasibility of environmental nitrosamine formation, there has been little evidence that it is an important process. Nitrosamines vary greatly in their environmental stabilities, but all seem to be susceptible to one or more modes of decomposition including photolysis, microbiological degradation, and plant metabolism. 

The rate of vulcanisation of a rubber compound is controllable by the choice of accelerator. The range of products offered to the rubber industry has been categorised historically into recognised classes. New developments have resulted in products that improve compound performance and which overcome dermatological problems, and do not generate nitrosamines and other extractable or volatile decomposition products. 

The reaction of NO with a wide variety of enamines, derived from the respective aldehydes and ketones can produce N-hydroxy-N-nitrosamine (Scheme 3.10) [137]. These compounds are relatively stable to thermal decomposition and do not release copious volumes of NO upon adding to concentrated mineral acids. However, on dissolution in aqueous buffer at pH 7.4 and 37 °C, a slow release of NO could be detected by the chemiluminescence method. 

Secondary nitramines have been prepared from the metathesis of dialkylcarbamyl chlorides with silver nitrate in acetonitrile followed by the spontaneous decomposition of the resulting dialkylcarbamyl nitrates.Yields of nitramine are low and accompanied by nitrosamine impurities. 

At temperatures low enough to suppress thermal decomposition, a nltrosamlde XIV In polar or non-polar solvents Is photolytlcally decomposed to amldyl and nitric oxide radicals 4,16,17,18), This Is In sharp contrast to the photostahility of nitrosamines in neutral solvents (Including acetic acid) (ii), although the pattern of photodecomposition Is similar to that of nitrosamines In dilute acidic conditions. However, the overall photolysis pattern of nltrosamldes Is complicated by disproportionation of nitric oxide and existence of a radical pair XV (20,21,22). ... 

S-Nitrosocysteine decomposition has been shown to exhibit first- and second-order dependence on total cysteine concentration. A decomposition pathway has been established via intramolecular nitroso group transfer to give a primary A-nitrosamine that decomposes to give the corresponding diazonium salt (Scheme 71). The nitroso group transfer reaction occurs intermolecularly for the pathway exhibiting a quadratic dependence on cysteine concentration.108... 

We examined the thermal decomposition of a number of nitramines in dilute solution and in the melt phase. The nitramines included acyclic dialkyl mononitramines, where the dialkyls were methyl, ethyl, propyl and isopropyl cyclic mononitramines (N-nitro-pipeiidine and N-nitropyrrolidine) and cycle multifunctional nitramines (N-dinitropiperazhe l,3-dinitro-l,3-diazacyclo-pentane l,3-dinitro-l,3-diazacycbhexane RDX and HMX). For all nitramines, the predominant condensed-phase product was the nitrosamine though the amount formed depending on the nitramine and the phase of the thermolysis. The common trigger in the decompositions was N-N02 ho mo lysis, but the fate of the resultant amine radical depended on the phase. In solution the radical was stabilized sufficiently so that it resisted further decomposition and, instead, reacted with NO to form nitrosamine. In vapor or condensed phase, the amine radical underwent further reaction therefore,... 

D. Naud, R. Brower, Pressure Effects on The Thermal Decomposition of Nitramines, Nitrosamines, and Nitrate Esters, J. Org. Chem., 57 (1992) 3303-3308. J. Wang, K.R. Brower, D.L. Naud, Evidence of an Elimination Mechanism in Thermal Decomposition of Hexahydro-l,3,5-Trinitro-l,3,5-Triazine and Related Compounds Under High Pressure, J. Org. Chem., 62 (1997) 9055-9060. 

Akerblom and Skagius - and Skagius have prepared 3-alkyl-l,3,4-thiadiazolin-2(3)-ones (95) from aminothiadiazoles (4) by ring-alkylation to 95, nitrosation of the imino group to 96, and thermal decomposition of the nitrosamine to 97. The reaction seems to be quite general, since it has been performed with R = amino, alkoxy, and 2-nitro-5-furyl. ... 

SAFETY PROFILE Suspected carcinogen with experimental carcinogenic, neoplastigenic, and tumorigenic data. Poison by ingestion, subcutaneous, intravenous, and intraperitoneal routes. Experimental teratogenic data. Human mutation data reported. When heated to decomposition it emits toxic fumes of NOx. See also NITROSAMINES, N-NITROSO COMPOUNDS, and ESTERS. 

SAFETY PROFILE Poison by subcutaneous and intraperitoneal routes. Moderately toxic by ingestion. Questionable carcinogen with experimental neoplastigenic data. It mimics the action of acetylcholine, a neurotransmitter, and is a parasympathetic nervous system stimulant. Its action on the central nervous system can cause tremors. Human mutation data reported. It is easily nitrosated to several nitrosamines. See also ESTERS and NITROSAMINES. It is the major alkaloid found in betel quid. Combustible, can react with oxidizing materials. When heated to decomposition it emits highly toxic fumes of NOx. 

When heated to decomposition it emits toxic fumes of NOx. See also NITROSAMINES. 

SAFETY PROFILE Poison by ingestion. Questionable carcinogen with experimental carcinogenic data. When heated to decomposition it emits toxic fumes of NOx. See also NITROSAMINES. 

---