Nitrosamines, hydrogenation

N-Nitrosamines. Hydrogenation of IV-nitrosamines over palladium, platinum, and nickel catalysts usually proceeds to give amines, and in rather few cases have unsym-hydrazines been obtained in good yields. Amines may also be formed directly from nitrosamines by a rather complex parallel reaction. 

This property has been exploited in syntheses of /V-nitrosamine derivatives by the reaction of electrophiles (E) with a-Hthiated intermediates. These intermediates are prepared by hydrogen—Hthium exchange using Hthium dusopropylamide [4111-54-0] (LDA) (76,77). 

Wet chemical methods determining titratable amine ate reported for products entering urethane (amine number as meq/g) or epoxy (AHEW = amine hydrogen equivalent weight) trade appHcations. For secondary amines /V-nitrosamine contaminants are reportable down to ppb using Thermoelectron Corporation thermal energy analy2er techniques. 

The acidic reagents vary widely In their ability to lower NDPA levels In trifluralin The concentration of the acid Is critical to produce the desired effect In some Instances, the acid promoted additional nitrosamine formation, e g 10% hydrochloric acid, 40% phosphoric acid, ascorbic acid, etc Hydrochloric acid and hydrogen chloride gas were the most efficient at destroying NDPA Impurity ... 

The acid initially, protonates the nitrosamine to give a charged intermediate having significant water solubility. When the agent is gaseous hydrogen chloride or concentrated hydrochloric acid, the protonated intermediate is rapidly... 

Primary amines react readily with nitrosating agents (Scheme 3.1) to provide deamination products. The intermediates, primary nitrosamines (RNHNO), are not stable therefore after a series of rapid reactions, they give rise to the diazonium ion (RN2+), and then decompose to the final products. The reactions of secondary amines can stop at the nitrosamine stage, since no a-hydrogen atoms are available for the necessary proton transfer reactions, which lead to diazonium ion formation. 

The choice of reagent determines whether a nitrosamine undergoes conversion to a nitramine by either nitrolysis or oxidation. An example is given for the conversion of 1,3,5-trinitroso-1,3,5-triazacyclohexane (109) to l,3,5-trinitro-l,3,5-triazacyclohexane (3) (RDX) - the use of 30 % hydrogen peroxide in 99 % nitric acid at subambient temperature goes via oxidation of the nitrosamine functionality, whereas dinitrogen pentoxide in pure nitric acid makes use of a nitrolysis pathway via C-N bond cleavage. 

One of the oldest-known reactions of N-nitrosamines is their reduction to 1,1-disubstituted hydrazines discovered by Fischer (19) The most common method to perform this transformation has been zinc dust in acid, generally acetic acid tetrazenes are sometimes formed as by-products (20) and denitrosation can also occur. Several other reducing methods have been investigated reduction with lithium aluminum hydride and catalytic hydrogenation are sometimes useful. Sodium dithionite reduction of benzyl substituted N-nitrosamines in base can result in fragmentation to... 

Hie generality of the induced circular dichroism with the three nitrosamines and four alcohols (Table 1) indicates that this technique will provide a method for studying interactions of nitrosamines with biological systons such as enzymes. Hi is method furnishes a highly sensitive procedure for detecting an interaction of nitrosamines with any chiral hydrogen bonding donor. 

If 3-chloro-N-nitrosopiperidine is used instead of the tosylate, 3,4-dehydro-N-nitrosopiperidine is formed in high yield. Another, perhaps more general, route to the vinylnitrosamines makes use of the acidity of the hydrogens on the a-carbon of nitrosamines (18). The resulting carbanion reacts smoothly with phenyl-selenyl chloride. The adduct is then oxidized with m-chloroper-benzoic acid (19). 

Oxidation of (I) leads to cyclonite. According to the work of Brockmann, Downing and Wright [12] oxidation with a solution of hydrogen peroxide (30%) in nitric acid (99%) in the ratio of 1 mole (I) to 82 moles of nitric acid, 3 moles of H202 and 3.7 moles of H20, at — 40°C, gives dinitro-nitrosamine (IV) as an intermediate ... 

Nitrosamines show a strong tendency to associate molecular weight determinations in non-polar media suggest the existence of dimeric forms, possibly due to the presence of hydrogen bonds in structures such as 255 or 256.170... 

Formationand Properties ofTriazens (Diazoamino-1,2,4-thiadiazoles) In aqueous or alcoholic solutions, two molecules of 5-nitrosamine (257) undergo self-condensation to triazens (diazoamino-1,2,4-thia-diazoles) (261).86,170,191 The reaction is catalyzed by hydrogen ions and... 

---