Nitro-compound, removal from

Cautiously add 250 g. (136 ml.) of concentrated sulphuric acid in a thin stream and with stirring to 400 ml. of water contained in a 1 litre bolt-head or three-necked flask, and then dissolve 150 g. of sodium nitrate in the diluted acid. Cool in a bath of ice or iced water. Melt 94 g. of phenol with 20 ml. of water, and add this from a separatory funnel to the stirred mixture in the flask at such a rate that the temperature does not rise above 20°. Continue the stirring for a further 2 hours after all the phenol has been added. Pour oflF the mother liquid from the resinous mixture of nitro compounds. Melt the residue with 500 ml. of water, shake and allow the contents of the flask to settle. Pour oflF the wash liquor and repeat the washing at least two or three times to ensure the complete removal of any residual acid. Steam distil the mixture (Fig. II, 40, 1 or Fig. II, 41, 1) until no more o-nitrophenol passes over if the latter tends to solidify in the condenser, turn oflF the cooling water temporarily. Collect the distillate in cold water, filter at the pump, and drain thoroughly. Dry upon filter paper in the air. The yield of o-nitrophenol, m.p. 46° (1), is 50 g. 

Reduction of a nitro compound to a primary amine. In a 50 ml. round-bottomed or conical flask fitted with a reflux condenser, place 1 g. of the nitro compound and 2 g. of granulated tin. Measure out 10 ml. of concentrated hydrochloric acid and add it in three equal portions to the mixtiue shake thoroughly after each addition. When the vigorous reaction subsides, heat under reflux on a water bath until the nitro compound has completely reacted (20-30 minutes). Shake the reaction mixture from time to time if the nitro compound appears to be very insoluble, add 5 ml. of alcohol. Cool the reaction mixture, and add 20-40 per cent, sodium hydroxide solution imtil the precipitate of tin hydroxide dissolves. Extract the resulting amine from the cooled solution with ether, and remove the ether by distillation. Examine the residue with regard to its solubility in 5 per cent, hydrochloric acid and its reaction with acetyl chloride or benzene-sulphonyl chloride. 

Condensation ofDianhydrides with Diamines. The preparation of polyetherknides by the reaction of a diamine with a dianhydride has advantages over nitro-displacement polymerization sodium nitrite is not a by-product and thus does not have to be removed from the polymer, and a dipolar aprotic solvent is not required, which makes solvent-free melt polymerization a possibiUty. Aromatic dianhydride monomers (8) can be prepared from A/-substituted rutrophthalimides by a three-step sequence that utilizes the nitro-displacement reaction in the first step, followed by hydrolysis and then ring closure. For the 4-nitro compounds, the procedure is as follows. 

The ring-chlorinated derivatives of toluene form a group of stable, industrially important compounds. Many chlorotoluene isomers can be prepared by direct chlorination. Other chlorotoluenes are prepared by indirect routes involving the replacement of amino, hydroxyl, chlorosulfonyl, and nitro groups by chlorine and the use of substituents, such as nitro, amino, and sulfonic acid, to orient substitution followed by their removal from the ring. 

The nitration route shows insufficient alpha-selectivity in addition to producing considerable dinitro product. Although a large amount of work has been done to maximize the yield of 1-nitro compound, the best result is less than 80%. Several methods have been developed to remove 2-nitroanthraquinone and dinitroanthraquinones from cmde 1-nitroanthraquinone. Purification is carried out, for example, by recrystaUization from nitric acid, or from organic solvents (15). 

The common impurities found in amines are nitro compounds (if prepared by reduction), the corresponding halides (if prepared from them) and the corresponding carbamate salts. Amines are dissolved in aqueous acid, the pH of the solution being at least three units below the pKg value of the base to ensure almost complete formation of the cation. They are extracted with diethyl ether to remove neutral impurities and to decompose the carbamate salts. The solution is then made strongly alkaline and the amines that separate are extracted into a suitable solvent (ether or toluene) or steam distilled. The latter process removes coloured impurities. Note that chloroform cannot be used as a solvent for primary amines because, in the presence of alkali, poisonous carbylamines (isocyanides) are formed. However, chloroform is a useful solvent for the extraction of heterocyclic bases. In this case it has the added advantage that while the extract is being freed from the chloroform most of the moisture is removed with the solvent. 

Non-basic materials, including nitro compounds were removed from aniline in 40% H2SO4 by passing steam through the soln for Ih. Pellets of KOH were added to liberate the aniline which was steam distd, dried with KOH, distd twice from zinc dust at 20mm, dried with freshly prepared BaO, and finally distd from BaO in an allglass apparatus [Few and Smith J Chem Soc 753 7949]. Aniline is absorbed by skin and is TOXIC... 

Nitro Anions Remov of a proton from an aliphatic nitro compound gives a carbanion (R2C-NO2) that can be alkylated at oxygen or carbon. ... 

Similarly, the reaction of nitro compounds with the M-Boc aromatic imines 86 occurred in the presence of the enantiopure protic catalyst 87, which is a white, crystalline bench-stable salt [52] (Scheme 15). The reactions of ni-tromethane, very slow at - 20 °C, were accelerated in the presence of 10 mol % of 87, and the /3-amino compounds 88 were obtained with moderate yields and moderate to high enantioselectivities. Positive results were also obtained in the corresponding reactions of nitropropane to give the products 90. Hence, the primary diamines 89 and 91 are available by this route, which is advantageous for the significantly lower cost and toxicity of the catalyst and its easy removal from the reaction mixture simply by a basic wash. These results should stimulate further research on the development of new acid-catalyzed systems. 

B. Reduction of Dinitrodurene.—A solution of 90 g. of dini-trodurene in 1 1. of glacial acetic acid is boiled in a 12-I. flask (Note 6) 700 g. of stannous chloride is dissolved in 800 cc. of concentrated hydrochloric acid and heated to boiling. The heat is removed from the acetic acid solution of the nitro compound, and the stannous chloride solution is poured very carefully (during about ten minutes) into the dinitrodurene solution. The reaction is complete in fifteen minutes, and as the solution cools the stannic chloride compound of the diamine begins to crystallize. The reaction mixture is cooled to io° in an ice-water bath, and the solid is filtered off by suction, washed twice with 50 cc. of 95 per cent ethyl alcohol and twice with 50 cc. of ether, and dried. The filtrates from the tin compound contain very little of the reduction product and may be discarded. The composition of this compound is [G (CH i)4(NH2-HCI)2l2-SnCl4, and it crystallizes from the reaction mixture in fine, glistening plates which are almost colorless. The yield is 145 g. (97 per cent of the theoretical amount). 

Removal of a proton from an aliphatic nitro compound gives a carbanion... 

The impurities present in aromatic nitro compounds depend on the aromatic portion of the molecule. Thus, benzene, phenols or anilines are probable impurities in nitrobenzene, nitrophenols and nitroanilines, respectively. Purification should be carried out accordingly. Isomeric compounds are likely to remain as impurities after the preliminary purifications to remove basic and acidic contaminants. For example, o-nitrophenol may be found in samples of p-nitrophenol. Usually, the o-nitro compounds are more steam volatile than the p-nitro isomers, and can be separated in this way. Polynitro impurities in mononitro compounds can be readily removed because of their relatively lower solubilities in solvents. With acidic or basic nitro compounds which cannot be separated in the above manner, advantage may be taken of their differences in pKg values. The compounds can thus be purified by preliminary extractions with several sets of aqueous buffers of known pH (see for example Table 19, p. 43) from a solution of the substance in a suitable solvent such as ethyl ether. This method is more satisfactory and less laborious the larger the difference between the pK value of the impurity and the desired compound. Heterocyclic nitro compounds require similar treatment to the nitroanilines. Neutral nitro compounds can be steam distilled. 

Non-basic materials, including nitro compounds were removed from aniline in 40% H2SO4 by passing steam... 

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