Aminophenols from anilines

Aminophenols from anilines, 35, 2 Anhydrides of aliphatic dibasic acids, Friedel-Crafts reaction with, 5, 5 Anion-assisted sigmatropic rearrangements, 43, 2 Anthracene homologs, synthesis of, 1, 6 Anti-Markownikoff hydration of alkenes, 13, 1... 

The nature of the substituent in a substituted aromatic compound influences the position of hydroxylation. Thus, o-/7-directing substituents, such as amino groups, result in o- and p-hydroxylated metabolites such as the o- and /7-aminophenols from aniline (figure 4.8). Meta-directing substituents such as nitro groups lead to m- and /7-hydroxylated products, for example nitrobenzene is hydroxylated... 

Table 11.2 Crosslink density, glass transition temperature, and Young s modulus (Et from tensile test at 10 3, s 1 strain rate, Eu from ultrasonic propagation at 5 MHz frequency) for triglycidyl aminophenol-diaminodyphenylmethane-aniline (TGAP-DDM-AN) networks. (After Morel et a ., 1989.)... 

Important sulfur dyes are made by treating aryl amines with sodium polysulfides, or by heating the amines with sulfur, followed by treatment with sodium sulfide. Certain sulfur blacks are made from anilines that include p-aminophenol and p-phenylenediamine (22). Derivatives of diphenylamine (8) yield blue shades. Meta-diamines, such as m-phenylenediamine (52a), give brown and yellow colorants. Sulfur dyes are inexpensive, but lack brilliance. There are no red members of this class. They are applied by means of reduction and oxidation processes. 

In 1886, Cohn and Hepp first identified the powerful antipyretic activities residing in both aniline and acetanilid. The basic origin of this particular class of compoimds from aniline has probably suggested these to be known as coal tar analgesics . However, the aminophenols (o, m, p) are reported to be... 

This is based on the reaction of derivatives of pyridine with cyanogen bromide in the presence of an aromatic amine giving specific colors. Amines commonly used are 2-naphthylamine-i-sulfonic acid, />-aminoacetophenone, iV-methyl-aminophenol sulphate, aniline and />-naphthylamine. The reaction gives a yellowish-green color which is measured photometrically. The color is soluble in amyl alcohol which can be used to extract it from water solutions, but is not stable unless a phosphate buffer of pH 6.i is used. This method is not specific for nicotinic acid since other pyridine derivatives and derivatives of nicotinic acid such as trigonelline, nicotinuric acid and nicotine give a similar color. 

The chemical production of aminophenols via the reduction of nitrobenzene occurs in two stages. Nitrobenzene [98-95-3] is first selectively reduced with hydrogen in the presence of Raney copper to phenylhydroxylamine in an organic solvent such as 2-propanol (37). With the addition of dilute sulfuric acid, nucleophilic attack by water on the aromatic ring of /V-phenylhydroxylamine [100-65-2] takes place to form 2- and 4-aminophenol. The by-product, 4,4 -diaminodiphenyl ether [13174-32-8] presumably arises in a similar manner from attack on the ring by a molecule of 4-aminophenol (38,39). Aniline [62-53-3] is produced via further reduction (40,41). 

Thus, acetylation of aniline affords acetanilide (20), an analgesic widely used in proprietary headache remedies. A similar transformation on p-aminophenol gives the analgesic, acetaminophen (21). It is of interest that the latter is also formed in vivo on administration of 21. An interesting preparation of this drug involves Schmidt rearrangement of the hydrazone (24) from p-liydroxyacetophenone. ... 

The polymer resulting from oxidation of 3,5-dimethyl aniline with palladium was also studied by transmission electron microscopy (Mallick et al. 2005). As it turned out, the polymer was formed in nanofibers. During oxidative polymerization, palladium ions were reduced and formed palladium metal. The generated metal was uniformly dispersed between the polymer nanofibers as nanoparticles of 2 mm size. So, Mallick et al. (2005) achieved a polymer- metal intimate composite material. This work should be juxtaposed to an observation by Newman and Blanchard (2006) that reaction between 4-aminophenol and hydrogen tetrachloroaurate leads to polyaniline (bearing hydroxyl groups) and metallic gold as nanoparticles. Such metal nanoparticles can well be of importance in the field of sensors, catalysis, and electronics with improved performance. 

F. Blue 2B 250% (C.I. Direct Blue 6, C.I. No. 22610), Direct Brown BRL 200% (C.I. Direct Brown 95, C.I. No. 30145) Fabricolor Inc. Evans Blue (C.I. Direct Blue 53, C.I. No. 23860), Benzo Azurine G (C.I. Direct Blue 8, C.I. No. 24140) Pfaltz and Bauer Inc. Benzidine was obtained from Sigma Chemical Co., o-tolidine from Fisher Scientific Corp. and 3,3 -dimethoxybenzidine (o-dianisidine) from Eastman Kodak Company. Aniline, -aminophenol, -phenylenediamine and -nitroaniline used in the interference study were obtained from Chem Service Inc. 

This system resolved the aniline peak (retention time (rt) = 2.67 min) from the benzidine peak (rt = 2.27 min) as can be seen in Figure 2. Other potential interferences were selected for study by looking at the expected fragments from the reduction of various dyes. Reduced dye samples were spiked with aniline (rt = 2.67 min), -aminophenol (rt = 1.97 min), -phenylenediamine (rt = 1.93 min) and -nitroaniline (rt = 3 16 min). None of these materials interfered with the detection of the benzidine peak. To determine if other types of dyes might interfere with the analysis, two sets of filters were spiked at low and high levels separately with C.I. Direct Red 28 (13 7 yg and 137 yg), C.I. Direct Blue 53 formulation (o-tolidine-based) (21.2 yg and 212 yg) and C.I. Direct Blue 8 formulation (o-dianisidine-based)(23.3 yg and 233 yg). 

HO.C H,.N2) Cr207 N 12.2%, crysts, mp- expl ca 154° when dry and pure was prepd by diazo-tization of p-aminophenol followed by addn of a dichromate. It is fairly stable, but less so than the chromate obtd from p-phenylenediamine(Ref 2,pp 4-5). The same author prepd chromates of diazonium and nitrodiazonium derivatives of aniline, bromoaniline, chloroaniline, benzidine, p-phenylenediamine, etc and found them more or less expl when dry... 

The procedure has also been applied for the hydroxylation of aromatic amines. Aniline and its /V-alkyl-substimted derivatives show similar behavior under similar conditions to afford the meta-substi tuted aminophenols as the major hydroxylated product.627 Product formation was interpreted by the attack of protonated hydrogen peroxide on the anilinium ion protected by /V-protonation from oxidation or degradation. Indoles, indolines, and tetrahydroquinoline have also been successfully hydroxylated with H202 in HF-SbF5 with the hydroxyl group meta to the nitrogen function.559,628 Hydroxylation of tryptophane and tryptamine derivatives affords pretonine and serotonine derivatives in 42% and 38% yields, respectively.629... 

Another major group of epoxy monomers derived from epichlorohydrin is that comprising monomers synthesized with an aromatic amine, such as aniline (DGA), para-aminophenol (TGpAP) and methylene dianiline (TGMDA) - (Table 2.1 e, f, and g). The reaction of epichlorohydrin with an alcohol is more difficult. Liquid monomers based on butanediol, neo-pentylglycol, and polypropylene oxide (molar mass in the range of 500 g mol-1), are the most common. 

The use of a fixed-bed cell with Cu particles as the cathode 576 has been suggested for the synthesis. p-Aminophenol, produced by electrochemical reduction of nitrobenzene, was used for the synthesis of hydroquinone 577). According to recent work, the addition of emulsifiers, for example, trialkylamine oxides 578), is supposed to suppress the formation of aniline as a byproduct. The electrosynthesis of p-amino-phenol from nitrobenzene is carried out industrially in India 276). 

The aniline formed simultaneously can be removed by adding lime, and steam-distilling the mixture. After filtering calcium sulphate from the residue, crystals of aminophenol can be obtained by evaporation. The average yield is reported to be 50 per cent, of the nitrobenzene used. 

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). 

Disposition in the Body. Readily absorbed from the skin and mucous membranes. Metabolised to 4-aminophenol and 4-acetamidophenol which are excreted in the urine as glucuronide and sulphate conjugates. 7V-Phenylsulphamic acid (aniline N-sulphate) is also a metabolite. The main toxic effect of aniline, the formation of methaemoglobin, is thought to be due to an oxidation product of aniline, phenylhydroxylamine. 

Compounds such as aniline, aminophenol, and other compounds generated from the diaminodiphenyl ether moiety are common in the pyrolysate of all polymers. The presence of specific fragments allows the polymer identification and the structure of the cycles determines the decomposition mechanism of each polymer [15]. 

It is worth noting that in the 1 1 complex of hydroxy aniline (or aminophenol) with a water molecule, the most stable cluster formed arises from an O—H—O interaction, in which water plays the role of hydrogen bond acceptor275. It is also remarkable that association of ANI with the CF3H molecule yields a weak C—H-N complex, but it induces a blue-shift of the CH stretch frequency276. The latter is blue-shifted by 30 cm-1, and the... 

Finally, it should be remembered from earlier works that in acidic media the oxidation of p-aminophenol (84) and its derivatives results136 in the formation of p-quinone (17) formed by hydrolysis of intermediate quinoneimine (85, equation 10). This oxidation resembles the analogous process of 83, as expected from the similar electron-releasing character of the NH2 and OH substituents. A similar reaction is also important in the mechanism of the electro-oxidation of ortho- and meto-substituted anilines, as discussed below. 

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