Nitrites Nitroaniline

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... 

Add 101 g. (55 ml.) of concentrated sulphuric acid cautiously to 75 ml. of water contained in a 1 htre beaker, and introduce 35 g. of finely-powdered wi-nitroaniline (Section IV,44). Add 100-150 g. of finely-crushed ice and stir until the m-nitroaniUne has been converted into the sulphate and a homogeneous paste results. Cool to 0-5° by immersion of the beaker in a freezing mixture, stir mechanically, and add a cold solution of 18 g. of sodium nitrite in 40 ml. of water over a period of 10 minutes until a permanent colour is immediately given to potassium iodide - starch paper do not allow the temperature to rise above 5-7° during the diazotisation. Continue the stirring for 5-10 minutes and allow to stand for 5 minutes some m-nitrophenjddiazonium sulphate may separate. Decant the supernatant Uquid from the solid as far as possible. 

Dissolve 10 g. of p-nitroaniline (Section IV,51) in a mixture of 21 ml. of concentrated hydrochloric acid and an equal volume of water, and cool rapidly to 0° in order to obtain the hydrochloride of the base in a fine state of division. Diazotise in the usual way (see Section IV,68) by the gradual addition of a solution of 6 0 g. of sodium nitrite in 12 ml. of water. Continue the stirring for a few minutes, filter the solution rapidly, and add it from a separatory funnel to an ice-cold solution of 41 g. of sodium sulphite (90 per cent. NajS03,7H20) in 100 ml. of water containing... 

Indazole-2- N has been prepared from 2-methyl-4-nitroaniline and sodium nitrite- N,... 

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... 

It is prepd by the action of methylamine on 4-chloro-l-nitrobenzene (Ref 5) by the action of methyl iodide (Ref 6), or methyl sulfate on 4-nit roaniline (Ref 7) or by the hydrolysis of 4-nitro-N-methylformanilide with hot coned aq HC1 (Ref 8). In a study of the effect of nitric acid concn on the prods of the nitration of N,N-dimethylaniline to form Tetryl, it was isolated in low yield by the action of nitric acid, d 1.046g/cc, plus Na nitrite on N,N-dimethylaniline (Ref 10). A eutectic mixt with N-ethyl-4-nitroaniline has been patented as a stabilizer for NC (Ref 12). Studies at NPF indicate that 4-nitro-N-methyl-aniline is superior to Centralite, 2-nitrodiphenyl-amine, or Acardite in stabilizing. NC Refs 1) Beil 12, 586, (295) 1125 ... 

OB to C02 -54,3%, mp explds at approx 1S4°, hygr crysts. Prepd by dissolving m-nitroaniline in an excess of dil perchloric acid (d 1.12g/cc), the excess being such that, at the end of the reaction, free acid is present. A sufficient quantity nf Na nitrite in solid form or in a sstd soLp. is added to effect diazotization. The mixt is cooled during the Na nitrite addition ,... 

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). 

Sodium nitrite ers in this case the chromatograms are merely sprayed with sulfanilic acid solution (2% fTTlO mol hydrochloric acid) [5], Diazotized 4-nitroaniline can also be used in place of ... 

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. 

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... 

Azide 367 is prepared from 4-r -butyl-2-nitroaniline in 76% yield by its diazotization followed by treatment with sodium azide. In a 1,3-dipolar cycloaddition with cyanoacetamide, azide 367 is converted to triazole 368 that without separation is directly subjected to Dimroth rearrangement to give derivative 369 in 46% yield. Reduction of the nitro group provides ortfc-phenylenediamine 371 in 91% yield <2000EJM715>. Cyclocondensation of diamine 371 with phosgene furnishes benzimidazol-2-one 370 in 39% yield, whereas its reaction with sodium nitrite in 18% HC1 leads to benzotriazole derivative 372, which is isolated in 66% yield (Scheme 59). Products 370 and 372 exhibit potassium channel activating ability <2001FA841>. 

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]. 

A solution of 26 g. of sodium nitrite in 200 cc. of water is then rapidly added (Note 1) to the cold ra-nitroaniline sulfate suspension continual shaking or mechanical stirring should be used until the m-nitroaniline sulfate dissolves completely. This requires about five minutes, during which period the solution gradually darkens. A small flocculent precipitate forms at the same time and should be filtered off. 

In diazotizing w-nitroaniline sulfate, it is necessary to add the sodium nitrite as rapidly as possible in order to prevent any of the diazonium salt from coupling with undia/.otized m-nitroaniline and forming a yellow precipitate of diazoamino compound. The presence of the excess of sulfuric acid, which does not interfere with the formation of the t-nitrophenol, tends to avoid this same difficulty. 

Refs l)Beil 16,431 2 D.Vorlander,Ber 39,2714 (1906) 3)K.A.Hoffmann A.Arnoldi.Ber 39,3147 (1906) 4)E.Herz,BritP 27198(1912) CAS,1672 (1914) 5)A.Stettbacher,SS 11,147(1916) rnsNitrobenzenedsazonium Perchlorate [(l-Diazc-3 -nitrobenzene)-Perchlorate] (called Diazo-m-nitr-anilinperchlorat or Bliizpulver in Get), 02N.CgH4-.N2.0C103-, mw 249.57, N 16.84% crysts, mp-expl ca 154 . This compd was first prepd by Herz (Ref 2) from m-nitroaniline, perchloric acid and Na nitrite. Davis(Ref 4) gives a detailed method of prepn. Also see Stettbacher(Ref 5)... 

Preparation of m-Nitrobenzene.diazonium Perchlorate. Half a gram of m-nitroaniline is suspended in 5 ec. of water in a wide test tube, and 0.5 cc. of concentrated hydrochloric acid and 2.2 cc. of 20% perchloric acid solution are added. After the nitraniline has dissolved, 15 cc. of water is added and the solution is cooled by immersing the test tube in a beaker filled with a slurry of cracked ice. One-quarter of a gram of sodium nitrite dissolved in 1 or 2 cc. of water is added in 3 or 4 portions, the mixture being shaken after each addition or stirred with a stirring rod the end of which is covered with a short piece of rubber tubing. After standing in the cold for 5 minutes, the material is transferred to a filter, and the feltlike mass of pale yellow needles is washed with cold water, with alcohol, and with ether. The product is dried in several small portions on pieces of filter paper. 

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