Amines nitrations, nitric acid

Nitration. Direct nitration of aromatic amines with nitric acid is not a satisfactory method, because the amino group is susceptible to oxidation. The amino group can be protected by acetylation, and the acetylamino derivative is then used in the nitration step. Nitration of acetanilide in sulfuric acid yields the 4-nitro compound that is hydroly2ed to -rutroaruline [100-01-6]. 

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

The instability of primary nitramines in acidic solution means that the nitration of the parent amine with nitric acid or its mixtures is not a feasible route to these compounds. The hydrolysis of secondary nitramides is probably the single most important route to primary nitramines. Accordingly, primary nitramines are often prepared by an indirect four step route (1) acylation of a primary amine to an amide, (2) A-nitration to a secondary nitramide, (3) hydrolysis or ammonolysis with aqueous base and (4) subsequent acidification to release the free nitramine (Equation 5.17). Substrates used in these reactions include sulfonamides, carbamates (urethanes), ureas and carboxylic acid amides like acetamides and formamides etc. The nitration of amides and related compounds has been discussed in Section 5.5. 

There is as yet no evidence that in the presence of sulphuric acid secondary amines lose nitric acid which would be capable of nitrating phenol. Attack by concentrated sulphuric acid, presumbaly loosens the linkage between the nitrogen atoms, leading to the expulsion of the nitronium ion NOf, which is a nitrating agent. 

Some nitramines may be prepared without treating amines with nitric acid. The classical example is the so-called E-method of cyclonite preparation in which a nitramine is formed by dehydration of a mixture of paraformaldehyde and ammonium nitrate, i.e. without using either amine or nitric acid (this will be discussed more fully on p. 109). When a nitramine is required with a non-nitrated aromatic ring which readily undergoes nitration with nitric acid, Bamberger s method [45], involving the oxidation of diazo compounds (13), may be applied. 

Gnehm [22] prepared hexanitrodiphenylamine by the nitration of diphenyl-amine with nitric acid, while Mertens [23] used a mixture of anhydrous nitric acid with concentrated sulphuric acid for the purpose. This method was applied in 1910 for the commercial preparation of hexyl. Since the yields obtained were too low (some 60% of the theoretical), during World War I a method patented in 1895 by the Griesheim Works was introduced, the starting materials being chlorodi-nitrobenzene and aniline. The method consists in the preparation of dinitrodi-phenylamine (m. p. 156-167°C) which is then nitrated in two stages, to obtain first tetranitrodiphenylamine (m. p. 199°C) and then hexyl ... 

In many nitrations, for example, of primary amines, the nitric acid must be completely tree from nitrous acid in such cases, before the nitric acid is used, or before it is mixed with the sulfuric acid, it should be freed from nitric oxide by blowing air through it (cf. nitration of p-toluidine, page 165). It is also possible to add saltpeter, instead of nitric acid, to the sulfuric acid solution this procedure is less satisfactory, however, because saltpeter is not readily soluble in uliFuric acid at low temperatures, and a steady reaction is hard to maintain. 

Direct N-nitration of secondary amines by nitric acid is possible only for weakly basic amines. The more basic amines can be nitrated under neutral conditions widi reagents such as dinitrogen pentoxide and nitronium tetrafluoroborate, but nitrosamines are significant by-products. The nitrate ester CF3CMe20N02 has been recommended as a nonacidic nitrating agent for secondary amines which avoids the problem of contamination of the products by A(-nitrosamines piperidine and pyrrolidine were nitrated in yields of 75% and 72%, respectively. Amides and imides are efficiendy N-nitrated using ammonium nitrate in trifluoroacetic anhydride. ... 

Combustible when exposed to heat or flame. Can react with oxidizing materials. Explosive reaction with acetic acid + acetic anhydride + ammonium nitrate + nitric acid, 1-bromopenta borane(9) (above 90°C), iodoform (at 178°C), iodine (at 138°C). Reaction with nitric acid + acetic anhydride forms the military explosives RDX and HMX. Reacts violently with Na202. When heated to decomposition it emits toxic fumes of formaldehyde and NOx. See also AMINES. 

The nitramines are arrived at by various routes, but generally, the reaction is similar to the direct nitration of an organic amine with nitric acid. 

W. E. Bachmann and Sheehan [158] developed a method of preparing RDX containing a small quantity of HMX. The method involved niirolysis of hex-amine with ammonium nitrate-nitric acid solution and acetic anhydride. By varying parameters of temperature and acid concentration, ammonium nitrate and acetic anhydride it wa.s shown that the ratio RDX/IIMX can be altered. These results led Bachmann and co-workeis to prepare mixture rich in HMX. Die optimum yield obtained was 82% conversion of hexamine to HMX/RDX mixture containing up to 73% HMX. 

ACIDO FTALICO (Spanish) (88-99-3) Combustible solid (flash point 334°F/168°C). Dust and powder form explosive mixture with air. Incompatible with strong acids, alkalis, aliphatic amines, alkanolamines, alkylene oxides, ammonia, epichlorohydrin, isocyanates, nitrates, nitric acid, nitromethane, strong oxidizers, sodium nitrite. 

A,A-DIBUTYL N-(2-HYDROXYETHYL)AMINE (102-81-8) Forms explosive mixture with air (flash point 200°F/93°C). Reacts violently with strong oxidizers. Violent reaction with strong acids, isopropyl percarbonate, nitrosyl perchlorate, sodium peroxide, uranium fluoride. Incompatible with aldehydes, boranes, cellulose nitrate (of high surface area), cresols, isocyanates, nitrates, nitric acid, organic anhydrides, phenols, sulfuric acid. 

ISOTHIOCYANATE de METHYLE (French) (556-61-6) Forms explosive mixture with air (flash point 90°F/32°C). Incompatible with strong acids, caustics, chlorates (e.g., potassium chlorate, sodium chlorate), ammonia, amines, amides, alcohols, glycols, caprolactam solution, nitrates, nitric acid, organic peroxides, peroxides, strong oxidizers. 

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