Aromatic amines aminophenols

Antioxidants that break chains by reactions with peroxyl radicals. These are reductive compounds with relatively weak O—H and N—H bonds (phenols, naphthols, hydro-quinones, aromatic amines, aminophenols, diamines), which readily react with peroxyl radicals forming intermediate radicals of low activity. 

Reacting substances aldehydes polyphenols, a-diketones, tartaric acid, reducing sugars, some aromatic amines, aminophenols, hydrazines, etc. Formic acid reacts at elevated temperatures. 

A positive reaction is given, in addition to aliphatic and aromatic aldehydes, by other oxidizable substances, such as, for example, sugars, aromatic amines, aminophenols, polyphenols, and formic acid. With the exception of ketols and diketones, ketones do not react. Organic compounds containing C=S and S—H groups interfere with the reaction, because they precipitate silver sulfide. The sensitivity of the reaction under various conditions was studied by Karaoglanov (1). 

Contaminants and by-products which are usually present in 2- and 4-aminophenol made by catalytic reduction can be reduced or even removed completely by a variety of procedures. These include treatment with 2-propanol (74), with aUphatic, cycloaUphatic, or aromatic ketones (75), with aromatic amines (76), with toluene or low mass alkyl acetates (77), or with phosphoric acid, hydroxyacetic acid, hydroxypropionic acid, or citric acid (78). In addition, purity may be enhanced by extraction with methylene chloride, chloroform (79), or nitrobenzene (80). 

The manufacture of sulfur dyes involves sulfurisation processes, the chemistry of which remains rather mysterious and may arguably be considered still to be in the realms of alchemy The processes involve heating elemental sulfur or sodium polysulfide, or both, with aromatic amines, phenols or aminophenols. These reactions may be carried out either as a dry bake process at temperatures between 180 and 350 °C or in solvents such as water or aliphatic alcohols at reflux or at even higher temperatures under pressure. C. I. Sulphur Black 1, for example, is prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

Residual color due to autoxidation of 4-aminophenol (one of 4-PAP s constituent aromatic amines)... 

Aromatic amines that have been used include o-toluidine, p-aminosali-cylic acid, p-aminobenzoic acid, diphenylamine and p-aminophenol. Their ability to react preferentially with a particular carbohydrate or class of carbohydrate is often useful, e.g. p-aminophenol, which shows some specificity for ketoses compared with aldoses and is useful for measuring fructose. These reagents have proved particularly useful for the visualization and identification of carbohydrates after separation of mixtures by paper or thin-layer chromatography, when colour variations and the presence or absence of a reaction aid the interpretation of the chromatogram. 

One method is to treat 4-aminophenol with just one molar equivalent of acetic anhydride. The main product is paracetamol, which is produced almost selectively since -NH2 is a better nucleophile than -OH. We can predict this from their pATa values as bases, about 5 for the conjugate acid of a typical aromatic amine, and about —7 for a phenol, i.e. the amine is the stronger base. Although the heteroatoms are not the same (see Section 6.1.2), the pATa values are significantly different and allow us to predict that the amine is also going to be the better nucleophile. The higher the pAfa of the conjugate acid, the better the nucleophile. 

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). 

Amine and Aminophenol Derivatives. Amines and aminophenols (Table VIII) react with the F-C reagent about as predicted considering the aromatic amino groups equivalent to phenolic hydroxyls. This would be an important interference with total phenol assay in samples with appreciable aromatic amine content. Fortunately, for this and other reasons as well, the major wine grapes and most other fruit and vegetable products are free of significant concentrations of aromatic amines which would interfere. Correction might be made for methyl anthranilate... 

Like phenols, aromatic amines are oxidized at a graphite electrode over a wide range of oxidation potentials. Some compounds (phenylenediamines, benzidines, and aminophenols) are ideal candidates due to their very low oxidation potentials numerous applications have been developed. 

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. 

Initially, sulfur dyes were water-insoluble, macromolecular, colored compounds formed by treating aromatic amines and aminophenols with sulfur and/or sodium polysulfide. R. Vidal developed these dyes in 1893 but they only became attractive for leather with the introduction of water-solubilizing groups. Today, the sulfur dyes can be divided into three classes conventional water-insoluble, leuco, and solubilized sulfur dyes. Most sulfur dyes are synthesized by condensation of aromatic amines with sulfur or sodium polysulfide in the so-called bake process, or else in water or under pressure as a solvent-reflux reaction. 

The aliphatic n-propyl unit in the siloxane oligomer has been considered to be a source of potential instability and accordingly there has been considerable interest in aromatic aminofunctional polydimethylsiloxane oligomers. Some of the early efforts [39] generated oligomers by reacting the chloropropyl group with aminophenol under nucleophilic displacement conditions to synthesize the aromatic amine functionality. However, this approach has the drawback that the... 

Four main types of antioxidants are commonly used in polypropylene stabilizer systems although many other types of chemical compounds have been suggested. These types include hindered phenolics, thiodi-propionate esters, aryl phosphites, and ultraviolet absorbers such as the hydroxybenzophenones and benzotriazoles. Other chemicals which have been reported include aromatic amines such as p-phenylenediamine, hydrocarbon borates, aminophenols, Zn and other metal dithiocarbamates, thiophosphates, and thiophosphites, mercaptals, chromium salt complexes, tin-sulfur compounds, triazoles, silicone polymers, carbon black, nickel phenolates, thiurams, oxamides, metal stearates, Cu, Zn, Cd, and Pb salts of benzimidazoles, succinic acid anhydride, and others. The polymeric phenolic phosphites described here are another type. 

Coupling carbonyl compounds with aromatic amines bearing amino, hydroxy, or thiol groups in o -positions is known to be a general method for the synthesis of 1,3-benzazoles, with the intermediate formation of the respective 2,3-dihydro derivatives. No heterocyclization occurs, however, in the reaction of o-phenylene-diamines or o-aminophenols with /i-quinones. In these cases, the reaction stops at the stage of formation of the deeply colored quinoneimine 105 which is similar to that obtained by the previously studied reaction of a variety of / -substituted anilines with derivatives of p -bcn/oquinonc.6 Compounds 10 do not undergo cyclization under heating or irradiation of its solution (Scheme 4). 

Introduction. The quinones are intermediate products in the oxidation of the aromatic nucleus. They may be prepared in some cases by the direct oxidation of aromatic hydrocarbons. For example, anthracene, naphthalene, and phenanthrene are oxidized to the corresponding quinones by chromic acid mixtures. Quinones are prepared more conveniently by oxidation of primary aromatic amines, particularly the p-substituted amines. p-Benzoquinone is obtained by the oxidation of aniline, p-toluidine, sulfanilic acid, p-aminophenol, and other similar compounds. Similarly the a-naph-thoquinone is obtained by oxidation of 1,4-aminonaphthol, and /9-naphthoquinone by the oxidation of 1,2-aminonaphthol. In the laboratory, although it is possible to prepare p-benzoquinone by the oxidation of aniline with acid-dichromate mixture, the method is tedious and the yield poor. Since hydroquinone is used extensively as a photographic developer and is made industrially, it is more convenient to prepare quinone by its oxidation. 

Permanent hair dyes are often derivatives of an aromatic amine, discovered as a hair dye in 1883, called /Mra-phenylenediamine (H2N-C6H4-NH2), including primary intermediates such as pcirci-aminophenol, dihydroxybenzene, 4-methylaminophenol, tetraaminopyrimidine, 2-aminomethyl-4-aminophenol, and / ara-aminodiphenylamine. The / zrra-phenylenedi-amine compound produces a black color, with its derivative parci- mmo-diphenylaminesulfonic acid used in blond formulations. Couplers are generally aromatic phenols or amines that have an available site that is subject to electrophilic interaction. Typical couplers include chemicals such as resorcinol, wrte-phenylenediamine, 2,4-diaminoanisole, mrm-aminophenol,... 

For the aminophenols pAii pAia for typical protonated aromatic amines, while pAT2 p fa for typical phenols. This can be taken to indicate that K relates to a process which is at least predominantly ... 

Antioxidants inhibit oxidation and are usually employed in combination with UV absorbers. Most antioxidants used for urethane coatings fall into the following classes substituted phenols, aromatic amines, condensation products of aminophenols with aldehydes, thio compounds, and phosphites. Often combinations of antioxidants from the above categories exhibit a synergistic effect. More recently Mathur et al. (125) carried out an extensive study involving the use of one to six stabilizers, selected from the above antioxidants and UV stabilizers, employing several independent test methods, to study the thermooxidation of urethane and urethane-urea films. 

Despite its general validity for the autoxidation of quinonisable phe-nolics and aromatic amines, the scheme outlined above has to be carefully checked when it has to be applied to a particular class of autoxidisable substrates. Therefore, autoxidation of o- and /2-aminophenols proceeds in a different manner with respect to that outlined above, although qui-noneimines are as expected the first non-radical oxidation products, m-Aminophenols behave obviously very differently for they cannot directly... 

Acetylation of amines, phenols, and thiols. This reagent readily transfers two acetyl groups to amines, phenols, and thiols under mild conditions (25°) with conversion to 1,4-diacetylglycouril. Ahphatic primary amines react most readily in fact, primary amino groups can be selectively acetylated in the presence of a secondary amino group. Acetylation of aromatic amines is slower, but can be catalyzed by an acid (e. g., acetic acid). Phenols are also acetylated, but aminophenols can be selectively N-acetylated. Thiophenols and alkyl thiols are acetylated readily, but alcohols react only slowly, even at elevated temperatures. ... 

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