Nitration of amines

The formation of chloramine as an intermediate, followed by reaction with nitric acid to produce the corresponding nitramine and HOC1, may explain the catalytic action of HC1 in the nitration of amines... 

In the nitration of amines there may be a competition between the formation of nitra-mines or acid salts. This is visualized by Lamberton (Ref 37a) as ... 

Nitroaminocompounds or Nitroamines. Compds containing both —N02 and —NH2 radicals attached to different C atoms, eg, nitroaniline, 02N.C6H4.NH2, etc. Nitroamines can be prepd either by the nitration of amines, or by partial reduction of nitrocompounds contg several —N02 groups. Another method is to treat a chloronitrocompound with ammonia, as in the prepn of dinitroaniiine... 

Neopentyl alcohol, 40, 76 Nickel catalyst for hydrogenation of resorcinol, 41, 56, 57 Nitramines from amines and acetone cyanohydrin nitrate, 43, 84 Nitration, of amines to nitramines by acetone cyanohydrin nitrate, 43, 83... 

A solution of nitric acid in acetic anhydride is a versatile reagent for nitrolysis reactions and for the A-nitration of amines (see Chapters 5 and 6). This reagent has also found considerable use for the C-nitration of aromatic substrates. ... 

DIRECT NITRATION OF AMINES 5.3.1 Nitration under acidic conditions... 

A/-Nitration of amines with nitric acid and its mixtures... 

The founder of the chloride-catalyzed nitration of amines, G. F. Wright, has extensively reviewed chloride-catalyzed nitration. " Even 50 years later, the importance and success of this method as a route to nitramines is illustrated by the number of examples which can be found in the literature. 

Unlike the direct nitration of amines under acidic conditions, nucleophilic nitration is an excellent route to both primary and secondary nitramines. In these reactions the amine or the conjugate base of the amine is used to attack a source of NO2. This source may be a nitrogen oxide, nitronium salt, cyanohydrin nitrate, alkyl nitrate ester or any other similar source of nitronium ion. 

Other reagents have been used for the direct nitration of amines under nonacidic conditions. Mandel reported the synthesis of methylnitramine, dimethylnitramine and diisopropy-Initramine from the reaction of nitryl fluoride with the parent amine. The presence of an excess of amine appears to be of prime importance given that other reports give the nitrosamine as a major by-product. 

Despite the amount of research focused on the iV-nitration of amines with nonacidic reagents, the use of conventional acidic reagents based on nitric acid and acid anhydrides has been far more extensive for the synthesis of energetic materials. 

The role of dialkylchloramines as intermediates in the chloride-catalyzed nitration of secondary amines is discussed in Section 5.3.1. Wright and co-workers" studied this reaction further and prepared a number of dialkylchloramines by treating secondary amines with aqueous hypochlorous acid (Equation 5.12). Treatment of these dialkylchloramines with nitric acid in acetic anhydride forms the corresponding secondary nitramine, a result consistent with the chloride-catalyzed nitration of amines." ... 

Moore and Willer reported the synthesis of some nitramine explosives containing a furazan ring fused to a piperazine ring. The tetranitramine (46) is synthesized from the condensation of 3,4-diaminofurazan (DAF) (24) with glyoxal under acidic conditions followed by A-nitration of the resulting heterocycle (45). The calculated performance for the tetranitramine (46) is very high but the compound proves to be unstable at room temperature. Instability is a common feature of heterocyclic nitramines derived from the nitration of aminal nitrogens. 

The intermediate formation of chloramine explains the catalytic action of hydrochloric acid in the nitration of amines, as mentioned above. The following reaction mechanism was drawn up by Wright [41]... 

The mechanism of the nitration of amines has not yet been explained fully. Wright et al. [34,42] suppose that the nitration of secondary amines and probably of... 

This may be explained by considering the nitration of hexamine with nitric acid as a stepwise degradation by nitrolysis, i.e. the nitration of amine involving the stepwise cleavage of the bond between the nitrogen and carbon atoms. According to Lamberton [39] this idea was first advanced by Linstead. The main work on this subject has been done by British [39] and Canadian [40] authors. 

The nitration of amines results partly in the formation of ring nitrated compounds and partly in formation of nitro derivatives of phenols. For example from aniline small quantities of p- nitroaniline were obtained along with 2,4-di-nitrophenol as the principal product. 

At present there are four good methods for preparing secondary nitramines. They are the oxidation of nitrosamines by peroxytrifluoro-acetic acid (5), the chloride-ion catalyzed direct nitration of amines (3), the nitrolysis of dialkylamides with nitric acid (16), and the alkaline nitration of amines with acetone cyanohydrin nitrate (6). We have found that treating two equivalents of several secondary aliphatic amines... 

Table II. Nitration of Amines and Amine Derivatives with Nitronium Tetrafluoroborate...

The directing influence of primary, secondary and tertiary amino groups is greatly weakened by the presence of large amounts of concentrated sulfuric acid. Hence, considerable quantities of the meta isomers are formed in the nitration of amines in concentrated sulfuric acid solution, and in the sulfonation of amines by concentrated sulfuric acid or oleum. 

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