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Nitrosamine, formation mechanism

The literature concerning mechanisms of nitrosamine formation in general has been the subject of several excellent reviews, e.g. that of Douglass al. (9). However, the basic principles of nitrosamine formation wTll Fe briefly stated here by way of introduction. [Pg.134]

Brononol (2-Bromo-2-nitropropane-1,3-diol) in combination with methyl and propyl paraben. The paper generated by the Danish group (ref. 5 Knoll BASF publication) shows that the mechanism of action of Bronopol is independent of formaldehyde formation. The inclusion of Tetrasodium EDTA at about 0.02% to remove ions in the water or extracts and carefully excluding any tertiary amines such as triethanolamine to counteract the fears of the marketers with reference to possible nitrosamine formation and release of formaldehyde. The pH used is usually at 6 and below. [Pg.158]

Chemical complexes of various transition metals have been shown to promote N-nitrosation (28). These metal complexes include ferrocyanide, ferricyanide, cupric ion, molybate ion, cobalt species, and mercuric acetate. All of the reactions are thought to proceed by oxidation-reduction mechanisms. However, such promotion may not be characteristic of transition metal complexes in general, since ferricyanide ion has been shown to promote nitrosation in metalworking fluids, whereas ferric EDTA does not (2 0). Since the metalworking operation generates metal chips and fines which build up in the fluids, this reaction could be of significance in the promotion of nitrosamine formation in water-based metalworking fluids. [Pg.162]

Nitrosamine formation is not the only conceivable fragmentation mechanism for compounds of structure I. By analogy to the nitrosative dealkylation reactions discussed above, one might predict that such compounds could also undergo cis elimination of nitroxyl in amide-forming reactions. Such a transformation has possibly been observed (14). During an attempt to synthesize the nitrosamino aldehyde VIII from immonium ion IX, Hecht coworkers were able to isolate only 5-10% of the desired product. The major product proved to be N-methyl-2-pyrrolidone, as shown in Fig. 10. We interpret this as evidence that an intermediate such as li can fragment not only by the Fig. 1... [Pg.99]

Figure 11. Proposed mechanism of nitrosamine formation by cleavage of a four-membered ring in the oxidation of hydrazone X(2A)... Figure 11. Proposed mechanism of nitrosamine formation by cleavage of a four-membered ring in the oxidation of hydrazone X(2A)...
Figure 13. Possible mechanism of nitrosamine formation in the reaction of nitrite ion with FlyF -disuhstituted carbamoyl chlorides (suggested by J.-P. Anselme)... Figure 13. Possible mechanism of nitrosamine formation in the reaction of nitrite ion with FlyF -disuhstituted carbamoyl chlorides (suggested by J.-P. Anselme)...
In vitro and animal studies show that the organosulfur components of garlic suppress tumor incidence in breast, blood, bladder, colon, skin, uterine, esophagus, and lung cancers. Potential mechanisms include decreasing nitrosamine formation, decreased bioactivation of carcinogens, improved DNA... [Pg.133]

The details of this new mechanism have been examined only recently. It is certain that the initial A-nitrosation is again rate determining, because equation (56) is also observed in nitrosamine formation from iV-methylaniline under similar experimental conditions . Equations (55) and (56) differ only in their dependence on the amine moiety the nitrosating reagent is probably the same positively charged species in both cases, but for equation (55) the rate-determining process is attack on the free amine, for equation (56) on the... [Pg.576]

In 1991, it was found that in addition to nitrosamine formation, NO and RNS could also modify DNA and resulting in deamination via nitrosation (Wink et al. 1991 Nguyen et al. 1992). These results suggested that N2O3 and nitrosative stress can lead to deamination of purines and cytosine/methylcytosine. There are a number of chemical mechanisms such as deamination (hydrolysis), depurination,... [Pg.7]

The methodology used in a study of nitrosamine formation in vulcanisation processes accelerated by tetraethylthiuram disulphide is described. This involved the characterisation of nitrosable species and the mechanisms of their formation, and studies of the influence of vulcanisation reactions and curing systems on the formation of nitrosable species. The results of the study are summarised. [Pg.89]

Other possible mechanisms have been considered O), but they either predict formation of products which are not observed, do not explain the observed O3/UDMH stoichiometry, or are inconsistent with the results of the UDMH-NO stoichiometry and the formation of nitrosamine and H2O2 in this system. The other products observed, and the fact that the nitrosamine and H2O2 yields are somewhat less than the predicted 100% and 50% of the UDMH consumed, can be attributed to possible secondary reactions of the nitrosamine with the OH radical. [Pg.121]

Thiocyanate, an anion normally secreted in human saliva, also catalyzes the nitrosation of amines by nitrite (22). The mechanism of the reaction is thought to proceed through the formation of nitrosylthiocyanate and subsequent reaction with amine to form the nitrosamine. This reaction, originally investigated to assess the... [Pg.162]

The first clues that compounds of structure I might be involved in nitrosamine-forming reactions came during the study of tertiary amine nitrosations. Smith and Loeppky had proposed ( ) in their detailed, classical investigation of the mechanism of this reaction that the first steps involve nitrosammonium ion formation followed by elimination of nitroxyl (HNO). The resulting immonium ion was postulated to hydrolyze to the secondary amine, which reacted with nitrosating agent to form the observed product. These mechanistic proposals are summarized in Fig. 2a. [Pg.91]

We have been particularly interested in these potency variations both in terms of environmental exposure and formation and in the context of the mechanism through which nitrosamines initiate cancer. [Pg.153]

Chemists have long been aware that amines can react with various nitrosating agents, under a variety of conditions, to form a wide array of N-nitroso derivatives (1 ). It was generally assumed that only secondary amines can effectively form stable N-nitrosamines. However, it has now become apparent that primary and tertiary amines, as well as tetraalkylammonium salts, can all form N-nitroso derivatives under the appropriate reaction conditions (2-10). It has also become apparent that there are several mechanisms possible for the formation of the most common N-nitroso derivatives. Thus, in addition to the more customary reaction of an amine with nitrous acid, N-nitroso derivatives can also form via the reaction of an amine with NO (NO2, N2O3, N2O4) ( ). Amines can also be transnitrosated with already formed N-N-nitroso or C-nitro compounds via a transnitrosation reaction, they can be converted into their N-nitroso derivatives ). [Pg.175]


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See also in sourсe #XX -- [ Pg.305 ]




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