Aminophenols from nitrophenols

Many commercial dyes contain one or more sulfonic acid groups to confer water solubility to the dye and assist in binding the dye to the polar fibres in the textile (cotton, nylon, silk, wool, etc.). An example is Congo Red (12) (Figure 3). This is red in alkaline solution thus, the sodium salt will dye cotton red, but it is very sensitive to acids and on acidification the colour changes from red to blue, and so this compound is also used as a type of indicator. Vat dyes, known as sulfur dyes, can be prepared by heating various organic compounds, e.g. amines, aminophenols, and nitrophenols, with sodium polysulfide. 

Uses. (9-Nitrochlorobenzene is used in the synthesis of azo dye intermediates such as o-chloroaniline (Fast YeUow G Base), i9-nitroani1ine (Fast Orange GR Base), o-anisidine (Fast Red BB Base), o-phenetidine, and (9-aminophenol (see Azo dyes). It also is used in corrosion inhibitors, pigments, and agriculture chemicals. -Nitrochlorobenzene is used principally in the production of intermediates for azo and sulfur dyes. Other uses include pharmaceuticals (qv), photochemicals, mbber chemicals (qv), and insecticides (see Insectcontroltechnology). Typical intermediates manufactured from the para isomer are -lutioaruline (Fast Red GC Base), anisidine, -aminophenol, -nitrophenol, -phenylenediamine, 2-chloro-/)-anisidine (Fast Red R Base), 2,4-dinitrochlorobenzene, and l,2-dichloro-4-nitrobenzene. 

Iron Reduction. The reduction of nitrophenols with iron filings or turnings takes place in weakly acidic solution or suspension (30). The aminophenol formed is converted to the water soluble sodium aminopheno1 ate by adding sodium hydroxide before the iron-iron oxide sludge is separated from the reaction mixture (31). Adjustment of the solution pH leads to the precipitation of aminophenols, a procedure performed in the absence of air because the salts are very susceptible to oxidation in aqueous solution. 

Production is by the acetylation of 4-aminophenol. This can be achieved with acetic acid and acetic anhydride at 80°C (191), with acetic acid anhydride in pyridine at 100°C (192), with acetyl chloride and pyridine in toluene at 60°C (193), or by the action of ketene in alcohoHc suspension. 4-Hydroxyacetanihde also may be synthesized directiy from 4-nitrophenol The available reduction—acetylation systems include tin with acetic acid, hydrogenation over Pd—C in acetic anhydride, and hydrogenation over platinum in acetic acid (194,195). Other routes include rearrangement of 4-hydroxyacetophenone hydrazone with sodium nitrite in sulfuric acid and the electrolytic hydroxylation of acetanilide [103-84-4] (196). 

DNB included m-nitrophenol, m-aminophenol, resorcinol, fumaricacid, and some volatile fatty acids (Dey and Godbole 1986). A pure culture of Rhodococcus sp. isolated from soils contaminated with nitroaromatics was capable of using 1,3-DNB as a sole source of nitrogen. This culture metabolized 1,3-DNB to nitrite via a 4-nitrocatechol pathway even in the presence of high amounts of ammonia (Dickel and Knackmuss 1991). 

Ingestion of alcohol aggravates the toxic effects of nitrobenzene. In general, higher ambient temperatures increase susceptibility to cyanosis from exposure to methemoglobin-forming agents." p-Nitrophenol and p-aminophenol are metabolites of nitrobenzene, and their presence in the urine is an indication of exposure."... 

Sulfur Bake. The yellow, orange, and brown sulfur dyes belong to this group. The dyes are usually made from aromatic amines, diamines, and their acyl and nuclear alkyl derivatives. These may be used in admixture with nitroanilines and nitrophenols or aminophenols to give the desired shade. The color formed is said to be the result of the formation of the thiazole chromophore, evident in dye structure (1). 

The mixture of 1.4 kg o-nitrophenol, 2.1 kg o-aminophenol, 6 kg glycerine (d = 1.26) and 5 kg sulfuric acid (d = 1.848) was heated at reflux to temperature 130°-140°C. This temperature was kept for 1.5 hours. The obtained oxyquinoline precipitated, the liquid was removed with water-steam distillation. The residue was diluted with water and alkalized with sodium hydroxide and sodium carbonate to the strong alkaline reaction. The repeated distillation with water steam gave the oil, which hardened as the long needles by cooling. MP 75°-76°C recrystallized from diluted ethanol. 

Replacement of the diazo group by hydrogen has been reported for a number of diazo oxides. For example, the diazo oxide from 2-nitro-4-aminophenol yields o-nitrophenol in 53% yield,42 - 43 and that from 1-amino-2-hydroxy-6-bromonaphthalene-4-sulfonic acid gives XV in approximately 50% yield.44... 

Scow et al. 1986, 1989 Zaidi et al. 1988, 1989). The products of biodegradation have also been studied with pure cultures of microorganisms. Catechol, beta-keto adipic acid, and nitrite have been identified as products of aerobic biodegradation of 2-nitrophenol (Zeyer and Kearney 1984) and 4-nitrocatechol, hydroquinone, gamma-hydroxymuconic semialehyde, and nitrite from 4-nitrophenol (Raymond and Alexander 1971 Spain et al. 1979). On the other hand, 2-aminophenol and 4-aminophenol have been isolated from anaerobic biodegradation of 2-nitrophenol and 4-nitrophenol, respectively (Adhya et al. 1981 Villanueva 1961). 

Reduction of 2-nitrochIorobenzene-4-sulfonic acid gives o-chlorometanilic acid which is used in making azo dyes. The real technical value of nitrochlorobenzene-sulfonic acid, however, lies in the ability of its chlorine atom to be replaced by various groups. For example, o-nitrophenol-p-sulfonic acid is obtained by treatment wiui sodium hydroxide, and this product, on reduction, yields o-aminophenol-p-sulfonic acid. An ogously, nitrochlorobenzenesulfonic acid gives o-nitroanisole-p-sulfonic acid by treatment with alcoholic methanol, and from this is obtained o-anisidine-p-sulfonic acid. The action of ammonia on nitrochlorobenzenesulfonic acid produces o-nitroaniline-p>sulfonic acid aniline and its derivatives produce o-nitrodiphenylamine-p Sulfonic acids (cf. Table II). 

Urinary excretion rates of p-nitrophenol were found in 7 volunteers who had inhaled 6 ppm nitrobenzene for 6 hours (Salmowa et al. 1963). The rate of urinary elimination varied considerably from individual to individual, but showed a general dose dependence at 1 to 6 ppm nitrobenzene. In general, excretion was most rapid during the first two hours and then leveled off. In some cases, p-nitrophenol could be detected for as long as 100 hours after exposure to 6 ppm for 6 hours. In a 47-year-old woman who had been occupationally exposed to nitrobenzene for 17 months, p-nitrophenol and p-aminophenol were found in the urine (Ikeda and Kita 1964). 

It may be prepared by the reduction of/j-nitrophenol and the resulting -aminophenol is acetylated by a mixture of acetic anhydride and glacial acetic acid. The crude product can be purified by recrystallization from a water ethanol mixture (1 1) or from other appropriate solvents. 

---