Benzene nitro-, purification

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 ofp-nitrophenol. Usually, the ri-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 pK values (see Chapter 1). The compounds can thus be purified by preliminary extractions with several sets of aqueous buffers... 

Purification of 2-nitro-2-methyl-l-propanol. Material melting at 86—87° and made by the Commercial Solvents Corp was recrystd from benzene and dried in a vacuum desiccator. The mp was about 88° (not sharp). This materia was used for nitration... 

In either case purification is carried out by washing in cold water and boiling water, the latter hydrolysing tetra-nitro compounds. Finally, the tetryl is recrystallised by solution in acetone and precipitation by water, or recrystallised from benzene. 

Here, one methyl group is oxidized and at the same time the benzene nucleus is nitrated in the 2-, 4- and 6-positions. Recently-developed techniques for the manufacture of tetryl treat methylamine with 2,4- or 2,6-dinitrochlorobenzene to give dinitrophenylmethylamine. This is then nitrated to tetryl. In both processes purification is carried out by washing in cold and boiling water, the latter hydrolysing the tetra-nitro compounds. Finally, the tetryl is recrystallized by dissolving in acetone and precipitated with water, or recrystallized from benzene. 

If trinitro-m-xylene has been prepared from pure m- xylene simple washing with hot water is sufficient to obtain a product of high purity. Otherwise, the removal of oily components by hot centrifugation is necessary. Additional purification by washing the product in the centrifuge with organic solvents (alcohol, benzene) may be applied. In consequence of the higher solubility of nitro derivatives of o mid p- xylene, mainly these compounds are removed. 

Six gms. of nitro compound are dissolved in 50 mL. of 95% ethanol, and 20 gms. of zinc pellets (20 mesh) are added, together with a few drops of ferric chloride. Then while stirring and with the temperature maintained at 40° C., 35 mL. of 12 N. sulfuric acid are added, drop wise, during the course of 1 hour. Stirring is continued at 40° C. for six hours, then for an additional 18 hours at 20-25° C. The solution is then decanted from the zinc, made very alkaline, and extracted with ether. Concentration of the latter yielded crystals of 2-amino-2-methyl-l-phenyl-1-propanol having a melting point prior to purification of 80-89° C. Recrystallization from hot benzene raised the melting point to 99-99.5° C. 

Although fuctisine is obtainable by a great variety of methods, those industrially uscil are Uniited to modifications of two the oxidation of commercial aniline by arsenic acid, or by a mixture of nitro-benzene, hydrochloric acid, ami iron filings and the purification of the pnxluct, after combination with an nchl, by repeated recrystnlUzationa... 

Synthesis of N,N,-bis(4-nitrophenyl)-N, N -bis[4-(2-phenyl-2-isopropyl) phenyl]- ,4-phenylene-diamine (3). In a 250 ml three neck round-bottom lisk was placed bis- [4-(2-pheiiyl- 2-isopropyl)phenyl]-4-aminopheitylamine (2) (7.26 g, 14.63 mmol), 4-Qtoro-nitro- benzene (4.13 g, 29.27 mmol), cesium Qioride (4.41 g, 29.27 mmol), and 80 ml DMSO. The mixture was heated with stirring at 120"C for 24 hr. The reaction mixture was cooled and then poured into 500 ml methanol. The red precipitate was collected by titration and dried under vacuum. The product was puriffed by sihca gel colunrn chromatography ( -hexane dichloromethane = 1 1) to afford dinitio compoimd (3) in a 65% yield mp 224-225 "C (by DSC 10°C /min). 

B, products giving positive Tollen s Reagent tests were obtained. No attempts were made to isolate either 9A or 9B since previous work had indicated that such compounds were subject to decomposition, and bromine oxidation was attempted on the crude reaction mixture. For both systems, as bromine addition was carried out, a transient blue color was noticed and white precipitates appeared in the reaction mixtures. In order to obtain 11A and IIB in purer form, the precipitated crude polymer was subjected to Soxhlet extraction with ethanol. This was followed by azeotropic distillation of benzene over the insoluble products. These two purification steps removed most of the non-polymeric by-products including unreacted or partially reacted nitro compounds as well as water and ethanol. Both llA and IIB showed strong IR absorption at 1200 cm" characteristic of the trans nitroso dimer bond, and a medium sharp absorption... 

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