Nitroanilines, salts

On acetylation it gives acetanilide. Nitrated with some decomposition to a mixture of 2-and 4-nitroanilines. It is basic and gives water-soluble salts with mineral acids. Heating aniline sulphate at 190 C gives sulphanilic add. When heated with alkyl chlorides or aliphatic alcohols mono- and di-alkyl derivatives are obtained, e.g. dimethylaniline. Treatment with trichloroethylene gives phenylglycine. With glycerol and sulphuric acid (Skraup s reaction) quinoline is obtained, while quinaldine can be prepared by the reaction between aniline, paraldehyde and hydrochloric acid. 

Some amines, such as the nitroanilines and the naphthylamines, give somewhat more stable diazonium compounds and may be diazotised at room temperature, when the reaction proceeds more rapidly. If the amine salt is only sparingly soluble in water, it should be suspended in the acid in a fine state of division (this is generally attained by cooling a hot solution and stirring vigorously), and it passes into solution as the soluble diazonium salt is formed. 

Dissolve 34 g. of o-nitroaniline in a warm mixture of 63 ml. of concentrated hydrochloric acid and 63 ml. of water contained in a 600 ml. beaker. Place the beaker in an ice - salt bath, and cool to 0-5° whilst stirring mechanically the o-nitroaniline hydrochloride will separate in a finely-divided crystalline form. Add a cold solution of 18 g. of sodium nitrite in 40 ml. of water slowly and with stirring to an end point with potassium iodide - starch paper do not allow the temperature to rise above 5-7 . Introduce, whilst stirring vigorously, a solution of 40 g. of sodium borofluoride in 80 ml. of water. Stir for a further 10 minutes, and filter the solid diazonium fluoborate with suction on a sintered glass funnel. Wash it immediately once with 25 ml. of cold 5 per cent, sodium borofluoride solution, then twice with 15 ml. portions of rectified (or methylated) spirit and several times with ether in each washing stir... 

Amino-5-methylthiazole does not react with diazotized p-nitroaniline in solutions acidified with acetic or hydrochloric acid (391). 2-Amino-4,5-dimethylthiazole with the diazonium salts of para-substituted anilines, however, gives product 193, involving reactivity of the exocyclic nitrogen (Scheme 122) (399). 

Nitroaniline (13.8 g., 0.10 mole) (Note 2) is dissolved in a hot solution of 75 ml. of 96% sulfuric acid, 100 ml. of phosphoric acid (density 1.7), and 50 ml. of water in a 1-1. beaker. A stirrer and a thermometer are introduced into the mixture, and the beaker is immersed in an ice bath. A solution of 8.3 g. (0.12 mole) of sodium nitrite in 25 ml. of water is added dropwise to the well-stirred solution at such a rate that the temperature is maintained at 10-15°. Excess nitrite is destroyed by adding sulfamic acid in small portions (Note 3). The mixture is cooled to —10° in an ice-salt bath, and about 50 ml. of liquid sulfur dioxide... 

Nitrophenylnitramine. O2N.CfiH4.NH.NO2, mw 183.12,N 22.95%, OB to C02 -91.2%, pale yel needles or brownish yel plates, mp 65.5°, explds on rapid heating. Can be obtained by nitrating 2-nitroaniline with nitric acid and Ac20. Forms salts, some of which are expl... 

An increased hydrogen ion concentration, that is a considerably greater amount of acid than the theoretical two equivalents of Scheme 2-1, is necessary in the diazotization of weakly basic amines. The classic example of this is the preparation of 4-nitrobenzenediazonium ions 4-nitroaniline is dissolved in hot 5-10 m HC1 to convert it into the anilinium ion and the solution is either cooled quickly or poured onto ice. In this way the anilinium chloride is precipitated before hydrolysis to the base can occur. On immediate addition of nitrite, smooth diazotization can be obtained. The diazonium salt solution formed should be practically clear and should not become cloudy on standing in the dark. Some practice is necessary, and details can be found in the books emphasizing preparative aspects (Fierz-David and Blangey, 1952 Saunders and Allen, 1985 in Houben-Weyl, Vol. E 16a, Part II, the chapter written by Engel, 1990). These books give a series of detailed prescriptions for specific examples and a useful review of the principal variations of the methods of diazotization. Such reviews have also been written by Putter (1965) and Schank (1975). 

Fast blue salt B, fast blue salt BB, fast black salt K, diazotized sulfanilic acid (Pauly s reagent), diazotized sulfanilamide or 4-nitroaniline... 

Phenols (capable of coupling) Fast blue salt B, fast blue salt BB, fast black salt K, diazotized sulfanilic acid (Pauly s reagent) diazotized sulfanilamide or 4-nitroaniline Intensely colored azo dyes are formed. Catecholamines [20, 3S], imidazoles [21] and amines capable of coupling also react. [3, 17]... 

When o-Nitroaniline is treated by sodium nitrite in acid medium and then by an inorganic sulphide, it forms an explosive diazonium sulphide. Note that even though the presence of a nitrated group does not help, it certainly is not a factor that is vital to cause the explosion, since this is a property that is common to all these diazonium salts whatever the nature of the substitution on the ring. The situation is exactly the same with p-nitroaniline. 

LDPE or HDPE extracts has been determined colorimet-rically at 430 nm by oxidation with H202 in the presence of H2S04 [66]. p-Phenylenediamine derivatives such as Flexzone 3C, used as antiozonants in rubber products, have been determined colorimetrically after oxidation to the corresponding Wurster salts [67]. A wide range of amine AOs in polyolefins has been determined by the p-nitroaniline spectrophotometric procedure [68]. Monoethanolamine (MEA) in a slip agent in PE film has been determined as a salicylaldehyde derivative by spectrophotometric quantification at 385 nm [69]. Table 5.6 contains additional examples of the use of 1JV/VIS spectrophotometry for the determination of additives in polymers. 

A. l-(m-Nitrophenyl)-3,3-dimethyltriazene. To a 3-1. threenecked flask containing 276 g. (2 moles) of technical grade tn-nitroaniline (Note 1) are added 250 ml. of concentrated hydrochloric acid and 500 ml. of hot water. The contents of the flask are heated to about 85° to dissolve the m-nitroaniline then 550 ml. of concentrated hydrochloric acid is added, and the solution is cooled rapidly. A stirrer, a thermometer, and a longstemmed dropping funnel are attached to the flask, and its contents are then cooled to —3 to —5° by means of a salt-ice bath. A solution of 144 g. (2.09 moles) of sodium nitrite in 350 ml. of water is added dropwise under the surface of the acid solution... 

The extra base-weakening effect, when the substituent is in the o-position, is due in part to the short distance over which its inductive effect is operating, and also to direct interaction, both steric and by hydrogen bonding, with the NH2 group (cf. the case of o-substituted benzoic acids, p. 63). o-Nitroaniline is such a weak base that its salts... 

The hydroxyphenylbenzotriazole structure was constructed by a coupling of the diazonium salt of o-nitroaniline with 4-ethyl-phenol, followed by reduction of the nitro-azobenzene to the benzotriazole with zinc powder and NaOH. After blocking of the phenol by acetylation, bromination and dehydrobromination were performed as described earlier, and treatment with aqueous NaOH... 

Of a series of substituted anilinium perchlorate salts, that of 4-nitroaniline showed the lowest thermal stability (DTA peak temperature 201°C) and highest shock-sensitivity. 

In a process for preparation of 2-methoxy-5-nitroaniline the anisidine salt was added to stirred sulfuric acid. An accidental deficiency of the latter prevented... 

Nitroaniline reacts almost explosively [1], and 4-nitroaniline, 4-nitroacetanilide, aminonitrobiphenyls, aminonitronaphthalenes and their various derivatives [2], as well as some nitro-N-heterocycles [1,2], also react vigorously. 4-Nitroanilinium sulfate and 4-nitroaniline-2-sulfonic acid and its salts also generate foams when heated without sulfuric acid. The mechanism is not clear, but involves generation of a polymeric matrix foamed by sulfur dioxide and water eliminated during the reaction [1]... 

A gas liquid chromatographic (GLC) method was described for determining residues of Bayer 73 (2-aminoethanol salt of niclosamide) in fish muscle, aquatic invertebrates, mud, and water by analyzing for 2-chloro-4-nitroaniline, a hydrolysis product of Bayer 73 [83]. Residues were extracted with acetone-formic acid (98 + 2), and partitioned from water samples with chloroform. After sample cleanup by solvent and acid base partitioning, the concentrated extract was hydrolyzed with 2N NaOH and H202 for 10 min at 95°C. The 2-chloro-4-nitroaniline was then partitioned hexane ethyl ether (7 + 3) and determined by electron capture GLC. Average recoveries were 88% for fish, 82% for invertebrates, 82% for mud, and 98% for water at 3 or more fortification levels. 

Hassan et al. [39] used a sensitive color reaction method for the determination of primaquine in pharmaceutical preparation. Primaquine was treated with diazo-p-nitroaniline in acidic medium to give an orange-yellow product with an absorbance maximum at 478 nm. When the medium was made alkaline, bathochromic, and hypochromic shifts occurred the new maximum was located at 525 nm. The mean percentage recoveries for authentic samples amounted to 100 and 100.21 by the acid and alkaline procedures, respectively (P = 0.05). Both reactions could be used to determine primaquine salts in pharmaceutical preparations. The results obtained were in good agreement with those of the official methods. Recoveries were quantitative by both methods. 

The oxidative ring-closure method is well known. Halo-substituted benzofurazans are obtained by reaction of aqueous sodium hypochlorite with potassium salts of the corresponding 2-nitroanilines (Equation 79) <2001SC2329, 2002BML233, 2003HCA1175, 2003JFC(121)171, 20030PD436>. 

For the diazotisation reaction to succeed, it is necessary that the amine should be completely converted into the hydrochloride before the addition of sodium nitrite, because any free amine can react with the diazonium salt to form a diazoamino compound (Scheme 4.7). This complication needs to be avoided in the case of amines, such as the dichloro anilines, which do not dissolve easily in dilute hydrochloric acid [17]. With such compounds it is convenient first to dissolve them in a hot acid solution, which is then cooled to 0-5 °C. This procedure ensures the absence of free amine, and even if the hydrochloride precipitates on cooling it readily redissolves as the diazotisation proceeds. Similar precautions are required with the nitroanilines and here an increased amount of mineral acid is advantageous [18]. 

The currently available salt type monoazo yellow pigments are mostly based on 2-nitroaniline-4-sulfonic acid as a diazo component and are mostly sold as calcium lakes (Table 13). 

Sparingly soluble salts of primary aromatic amines are diazotised in suspension, with vigorous stirring. Very weak bases such as halo-genated anilines and nitroanilines require a large excess of acid for salt formation they are first dissolved in just sufficient hot concentrated hydrochloric acid, which is then simultaneously cooled in ice and diluted. In this way the salts, which are mostly sparingly soluble, are precipitated in a finely divided condition. Dissolution in concentrated sulphuric acid and direct diazotisation of the sulphate, precipitated as a fine powder by means of ice, is often to be recommended. The free amines, however, should never be diazotised in acid suspension because they react far too slowly. Salt formation should first be ensured. 

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