Aromatic compound nitration

The existence of the nitronium ion in sulfuric-nitric acid mixtures was demonstrated both by cryoscopic measurements and by spectroscopy. An increase in the strong acid concentration increases the rate of reaction by shifting the equilibrium of step 1 to the right. Addition of a nitrate salt has the opposite effect by suppressing the preequilibrium dissociation of nitric acid. It is possible to prepare crystalline salts of nitronium ions, such as nitronium tetrafluoroborate. Solutions of these salts in organic solvents rapidly nitrate aromatic compounds. ... 

The fact that nitronium salts in which nitronium ion is known to be present (by X-ray studies) nitrate aromatic compounds shows that this ion does attack the ring. 

Dinitrogen pentoxide (prepared by the oxidation of N204 with 03) in nitric acid is a potent nitration system. It can be used for nitrating aromatic compounds at lower temperatures than conventional system. It is also convenient for preparing explosives that are unstable in nitrating media containing sulfuric acid (Eq. 2.7).20... 

Tokiwa H, Nakagawa R, Horikawa K, et al. 1987. The nature of the mutagenicity and carcinogenicity of nitrated, aromatic compounds in the environment. Environ Health Perspect 73 191-199. 

Tokiwa, H., R. Nakagawa, K. Horikawa, and A. Ohkubo, The Nature of the Mutagenicity and Carcinogenicity of Nitrated, Aromatic Compounds in the Environment, Environ. Health Per-spect., 73, 191-199 (1987). 

TNT is the abbreviation of the aromatic nitrated aromatic compound 2,4,6-trinitrotoluene. It is a pale-yellow crystalline solid that was first synthesized in 1863 by the German chemist Joseph Wilbrand (1811—1894), but it was not immediately used as an explosive. TNT is made by nitrating toluene using nitric acid, sulfuric acid, and oleum (a mixture of sulfuric acid and S03). Nitration of toluene occurs in stages, with the nitro units added sequentially in a stepwise process as the reaction proceeds. The last nitro unit is accomplished by using oleum (SO, dissolved in sulfuric acid). After nitration, unused acids are recycled, and the product is washed with sodium sulfite and water to remove impurities. 

The molecular composition of picric acid was established in the early ninteenth century when it was the only highly-nitrated aromatic compound then known. It was evident that its oxygen content was insufficient for complete combustion (to C02 and H20). This was considered to be an adequate foundation for the erroneous theory that, because of its insufficient oxygen content, the substance has no explosive properties. It was believed that explosive properties are achieved only by mixing picric acid with oxidizing agents such as chlorates, or sodium or potassium nitrates. 

Diphenylamine is not used for stabilizing powders containing nitroglycerine since it hydrolyses this ester. Diphenylamine also causes the decomposition of higher nitrated aromatic compounds and therefore should not be used in powders containing such compounds. 

Nitrosomum ions, NO+, are, however, the ions employed to start the nitration sequence foi easily nitratable aromatic compounds such as phenol. 

These systems nitrate aromatic compounds by a process of electrophilic substitution, the character of which is now understood in some detail ( 6.1). It should be noted, however, that some of them can cause nitration and various other reactions by less well understood processes. Among such nitrations that of nitration via nitrosation is especially important when the aromatic substrate is a reactive one ( 4.3). In reaction with lithium nitrate in acetic anhydride, or with fuming nitric acid, quinoline gives a small yield of 3-nitroquinoline this untypical orientation (cf. 10.4.246) may be a consequence of nitration following nucleophilic addition.5... 

Ingold, Hughes and Reed [39] have studied the kinetics of nitration with nitric acid in the presence of nitromethane and found the reaction to be of zero order in the case of readily nitrated aromatic compound, and of first order with compounds... 

The rule was checked by Tronov and Ber [15] when nitrating aromatic compounds with nitric acid in nitrobenzene. They found there was no simple correlation between the influence of a substituent on the reaction rate and its orienting activity. The rule is true only for the groups with strong orienting activity (e.g. N02, CN, CH2CN, C6H5CO). 

It inspired Wieland [55] in 1921 to investigate the possibility of nitrating aromatic compounds with nitrogen dioxide. 

Nitric esters in mixtures with sulphuric acid. Raudnitz [171] was the first to draw attention to the nitrating properties of solutions of ethyl nitrate in sulphuric acid. Later in 1941, Titov [34] expressed the view that such a solution contains the nitronium ion, and L. P. Kuhn (p. 15) proved this by cryometric measurements. A solution of ethyl nitrate in sulphuric acid has been used for nitrating aromatic compounds. 

The ability of higher nitrated aromatic compounds to form dark coloured products in alkaline medium can be used for the titration of certain weak acids with bases. For example trinitrobenxene acquires an orange and red colour at pH 12.2 and 13.6 respectively. 

This property of nitro compounds was first observed by Foord [78] with regard to o- nitrophenol, 2,4-dinitrophenol, picric acid, m- dinitrobenzene, 2,4-dinitro-toluene, 1,3,8-trinitronaphthalene, 2,4-dinitroaniline and other higher nitrated aromatic compounds. 

The investigations were continued by Hammett [102] and by Gillespie [103, 103a], This work established that if oleum of high concentration was used as a solvent, higher nitrated aromatic compounds also exhibited basic properties. 

It forms eutectics with other high nitrated aromatic compounds and certain nitric esters (Table 40). (See also Burkhardt [65].)... 

The high, values for the lead block expansion test given by mixtures of tetranitro-methane with higher nitrated aromatic compounds are striking. On the other hand, the rates of detonation of these mixture are lower than those of mixtures containing lower nitrated compounds or benzene. 

Warm the air up (by absorbing solar radiation and thermal-lR radiation) black carbon, iron, and aluminium, polycyclic and nitrated aromatic compounds. 

As known (Vol. I, p. 332) the reaction of sodium sulpliiie with unsymmetri-cal trinitrotoluenes is a major reaction in the puriOcation of crude TNT. known under the name of Scllite Process - sellite being the name of sodium sulphite solution. Sodium sulphite solutions have pll > 8.0. It is known how sensitive higher nitrated aromatic compounds are to bases and sodium sulphite (particularly at a temperature, for example, above 40 45 ( ) can produce a damaging effect on TNT It is therefore advisable to add a certain amount of sodium bisulphite to sodium sulphite to keep the pH value as low as possible. According to Clift and Fedoroff [71] 0.1 -0.3% NaHSOy was added in the U.S.A, as a buffer to keep the pH value down. 

Although the nitronium ion is the nitrating agent, there are known examples when nitration can occur in media in which the concentration of NOj is too small to be detected spectroscopically (Vol. I, pp. 25,48). This was pointed out by Bunton and Halevi [4] who succeeded in nitrating aromatic compounds with 40-60% aqueous nitric acid. Bunton and co-workers (5, 6) showed that the nitronium ion was an intermediate in both oxygen-exchange and aromatic nitration in the sense of reactions ... 

Nitric acid salts in the presence of other acids have been previously described (Vol. I, p, 46). It was recently reported by Crivello [125] that metal nitrates in trifluoroacetic anhydride (TFAA) can nitrate aromatic compounds at room temperature in very good yields. Thus ammonium nitrate with TFAA nitrated benzene to nitrobenzene with a yield of 95%. 

Several papers appeared after the pioneer work of Mine and co-workers (Vol. I, p. 126). Papers by Chernova and co-workers [S3] and Sugimoto and co-workers [54] have shown that even dilute nitric acid (0.1-1.7 N) can nitrate aromatic compounds when subjected to gamma radiation from Co °. Benzene yielded nitrobenzene and p-nitrophenol as the result of free radical reactions. Nitric acid is decomposed by radical mechanism according to equation [55] ... 

Cyclonite is decomposed in concentrated sulphuric acid and the decomposition yielded most likely nitronium ion (Vol. Ill,p. 81). This is evidenced by the fact that a solution of cyclonite in sulphuric acid can nitrate aromatic compounds. 

Nitro dyes are nitrated aromatic compounds which dye protein fibres and are classified as acid dyes. Naphthol Yellow (C.I. acid yellow 1), formula (6), is an example ... 

It is known that ruminal bacteria are capable of biotransforming toxic compounds found in plants at very fast rates, as well as other pollutants with chemical similarities to TNT and other munitions. In fact, among nitrated aromatic compounds that are biotransformed by ruminal bacteria are 3-nitropropionic acid, chloramphenicol, and nitrophenols. The authors used the rumen system to obtain a new isolate, which transforms TNT at rates much faster than previously reported and without any detectable... 

Ordinary eutectics are formed by nitromannitol with higher nitrated aromatic compounds (Table 27). 

Reactions of Pyrazoles. A -Nitropyrazoles nitrate aromatic compounds under L wis acid conditions. Pyrazole as a nucleophile undergoes two successive cine-substitutions with 1,4-dinitropyrazole, yielding the terpyrazolyl (256). Irradiation of the deuterium-labelled cyanopyrazole (257) affords a mixture of the isomeric imidazoles shown in Scheme 5. ... 

Non-nitrated aromatic compounds can be directly aminated by hydroxyl-amine-O-sulfonic acid (aminyl hydrogen sulfate) or hydroxylammonium salts... 

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