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Waters, nitrosation

We are not concerned here with the mechanism of nitrosation, but with the anticatalytic effect of nitrous acid upon nitration, and with the way in which this is superseded with very reactive compounds by an indirect mechanism for nitration. The term nitrous acid indicates all the species in a solution which, after dilution with water, can be estimated as nitrous acid. [Pg.54]

Snia Viscosa. Catalytic air oxidation of toluene gives benzoic acid (qv) in ca 90% yield. The benzoic acid is hydrogenated over a palladium catalyst to cyclohexanecarboxyhc acid [98-89-5]. This is converted directiy to cmde caprolactam by nitrosation with nitrosylsulfuric acid, which is produced by conventional absorption of NO in oleum. Normally, the reaction mass is neutralized with ammonia to form 4 kg ammonium sulfate per kilogram of caprolactam (16). In a no-sulfate version of the process, the reaction mass is diluted with water and is extracted with an alkylphenol solvent. The aqueous phase is decomposed by thermal means for recovery of sulfur dioxide, which is recycled (17). The basic process chemistry is as follows ... [Pg.430]

As the amines become more weakly basic, the normal method of diazotization becomes progressively more difficult. The equilibrium between amine and ammonium salt increasingly favors the former which, usually because of its poor solubility in water, is prevented from taking part in the reaction. Research into the mechanism of diazotization has demonstrated that the important step is the addition of the nitrosating agent to the base of the amine. Thus, the acidity for each diazotization should be so chosen that the equilibrium concentration of base corresponds to that of its saturated solution. This rule leads to the use of higer concentrations of aqueous mineral acid for weakly basic amines. [Pg.21]

In all the diazotization reactions discussed in Sections 2.1-2.4 an equimolar amount of water is formed as byproduct. There are two general pathways for obtaining diazonium salts without formation of water. One is based on the rearrangement of 7V-nitroso-7V-arylacetamides, the other on the nitrosation of a monoarylated sp2-hybridized nitrogen compound by nitrosating reagents XNO in which X is a weak nucleophile. [Pg.31]

From an analysis of the results, the values of k and k. were determined as 13 x 10-3 and 132 x 10-3 respectively, which implies, not unreasonably, that NO+ is a more reactive electrophile than N204 the nitrosation rate was also relatively independent of the water concentration. [Pg.48]

The effect of various types of inhibitors with respect to structure and solubility on the formation of N-Nitrosodiethanolamine was studied in a prototype oil in water anionic emulsion, Nitrosation resulted from the action of nitrite on diethanolamine at pH 5.2-5.A, Among the water soluble inhibitors incorporated into the aqueous phase, sodium bisulfite and ascorbic acid were effective. Potassium sorbate was much less so. The oil soluble inhibitors were incorporated into the oil phase of the emulsion. [Pg.149]

A research program in progress at Raltech Scientific Services is designed to find inhibitors which will prevent nitrosamine formation in cosmetic products, A review of the literature (4) indicated that the oil phase of emulsions may play an important role in nitrosation chemistry. Thus, results from studies in water alone could be misleading when reduced to practice. [Pg.150]

Evidence exists that the relative solubility of amines and inhibitors in heterogeneous oil-water systems could be decisive in formation of nitrosamines and blocking these reactions, Nitrosopyrrolidine formation in bacon predominates in the adipose tissue despite the fact that its precursor, proline, predominates in the lean tissue (5,6,7). Mottram and Patterson (8) partly attribute this phenomenon to the fact that the adipose tissue furnishes a medium in which nitrosation is favored, Massey, et al, (9) found that the presence of decane in a model heterogeneous system caused a 20-fold increase in rate of nitrosamine formation from lipophilic dihexylamine, but had no effect on nitrosation of hydrophilic pyrrolidine. Ascorbic acid in the presence of decane enhanced the synthesis of nitrosamines from lipophilic amines, but had no effect on nitrosation of pyrrolidine. The oil-soluble inhibitor ascorbyl palmitate had little influence on the formation of nitrosamines in the presence or absence of decane. [Pg.150]

The criteria for choosing inhibitors in this study were the ability to compete with diethanolamine for the nitrite and lack of toxicity. An attempt was made to cover as broad a group as possible within the limits of feasibility. Ascorbic acid in its water soluble form and its oil soluble form, the palmitate, represent the enediols, Sorbate is a diene fatty acid which has been shown to inhibit nitrosation (10), Since the pK of sorbic acid is 4,76, at the pH of these experiments, both water soluble sorbate ion and oil soluble sorbic acid are present in significant amounts. Sodium bisulfite is a strong inorganic reducing agent which has an acceptable lack of toxicity at the concentration... [Pg.153]

Since a-tocopherol destroys nitrite in the system in absence of the oil phase, we may postulate that the ineffectiveness of these two oil soluble inhibitors resulted from their absence from the aqueous phase. Diethanolamine is miscible with water and presumably its nitrosation occurs in the aqueous phase. There is a significant difference in the solubility characteristics of ascorbyl palmitate. The reducing portion of the molecule is water soluble. Thus the ascorbate moiety may be in the aqueous phase while the fatty acid tails may lie within the oil globules. The a-tocopherol and the BHA may well be effective if they are dispersed in the aqueous phase after preparation of the emulsion. This will be investigated in future experiments. [Pg.155]

Co. and 20 mM nitrite in water, pH 3, 25 C, 60 min reaction], it was nitrosated to yield 3.62 mM 2,6-dimethyl-N-nitrosomorpho-line (DMNM), which was a 10% greater yield than that for a similar nitrosation of morpholine to give NMOR. This indicated a slightly larger rate constant for DMNM than for NMOR formation (3). Crude DMM is a 2 1 mixture of the cis and trans isomers ( 0). GC analysis of the product of the kinetic run showed that the 2 isomers were nitrosated at similar rates. Cis-DMNM [retention time (RT), 320 sec] was well separated from NMOR (RT, 430 sec), but trans-DMNM (RT, 405 sec) was not. Accordingly, we prepared pure cis-DMM, b.p. 133 C, by spinning-band fractional distillation of crude DMM and used it in the analytical procedure. The RT of N-nitrosopyrrolidine (NPYR) was 390 sec. [Pg.183]

The nitrosating agent could be important biologically since lung adenomas were induced in mice exposed to 1-2 ppm NO2 by inhalation and treated with morpholine (1.0 g/L drinking-water) (18). [Pg.190]

Vitamin E can also inhibit nitrosation reactions but the mechanisms may be somewhat different than those for vitamin C (55,56). Of course, vitamin C is water soluble while vitamin E... [Pg.308]

The LCM baths use a mixture of nitrate/nitrite eutectic salts. As it contains up to 40% sodium nitrite the salt system is toxic and can cause water pollution, and also cause nitrosation of volatile secondary amines. [Pg.174]

Nitrosonium (NO+) is a strong oxidant and the reduction potential to NO has been measured in non-aqueous media (1.67 V vs. SCE in CH3CN), and estimated for water (Eq. (3)) (12,15). NO+ is subject to rapid hydrolysis to nitrite (2H+ + N02 ), and therefore if formed in biological media would be short-lived. However, other less water-sensitive chemical species can act as NO+ donors in reactions leading to the nitrosation of various substrates. For example, the reactions of certain metal nitrosyl complexes with nucleophiles such as R SH can lead to the transfer of NO+ as illustrated in Eq. (4). Such reactions will be discussed in greater detail below. [Pg.205]

With respect to the Agency, Section 5 of TSCA has made EPA more familiar with trends in the metalworking fluids industry, the chemical components of the fluids, and the interactions between the various components. Major trends in the industry are (1) a shift from the traditional oil-based to the rapidly growing water-based fluids (2) a shift from the use of the nitrosating agent nitrite as a rust inhibitor (3) the use of multifunctional additives and (4) the careful monitoring of various factors and additives associated with these fluids. [Pg.159]


See other pages where Waters, nitrosation is mentioned: [Pg.243]    [Pg.131]    [Pg.204]    [Pg.4]    [Pg.21]    [Pg.32]    [Pg.45]    [Pg.47]    [Pg.48]    [Pg.49]    [Pg.64]    [Pg.138]    [Pg.457]    [Pg.697]    [Pg.150]    [Pg.168]    [Pg.190]    [Pg.193]    [Pg.275]    [Pg.277]    [Pg.334]    [Pg.350]    [Pg.353]    [Pg.354]    [Pg.355]    [Pg.356]    [Pg.52]    [Pg.455]    [Pg.118]    [Pg.730]    [Pg.58]    [Pg.138]    [Pg.108]    [Pg.158]   
See also in sourсe #XX -- [ Pg.354 ]




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