Aniline, Azo Derivatives

Oxidative Couplings of Heterocyclic Hydrazones. This method has opened the way to the preparation of azo derivatives of diazo compounds unobtainable by other means, ie, heterocycHc compounds ia which the diazotizable amino group is conjugated with the heterocycHc nitrogen atom as ia 2- and 4-amiQopyridine, compounds which do not normally yield stable diazonium salts (38). The reaction occurs as illustrated by equation 7 for the iateraction of (A/-methylcarbostyryl)hydrazone [28219-37-6] and dimethyl aniline the overall process is oxidation. 

Azido and Azo Derivatives of N-Methylaniline p-A zido-N-Methy aniline, p-MeNHC6 H4N 3, C7H8N4 mw 148.17, N 37.82% crysts, mp 52° prepd by the action of hydroxylamine hydrochloride on N-methyJ p-nitrosoaniline in aq Na carbonate. Upon exposure to light in thin layers, it turns red, then violet Refs 1) Beil 12, 429 2) A. Angeli ... 

It turned out that only the compounds listed on the right side of the scheme, namely those containing one nitrogen atom, are reduced to the aniline base by fermenting yeast no distinct reduction of the azo derivatives was observed. Whether this would be possible by altering the experimental conditions cannot be stated offhand (see p. 100). 

Primary and secondary amines react with diazonium salts to form initially the N-azo derivatives, e.g., diazoaminobenzene, C,HjNHN= NC,Hs, from aniline and benzenediazonium chloride. In the presence of acids, these compounds isomerize to the corresponding p-aniinoazo derivatives for example, the above compound goes to p-aminoazobenzene, p-NH2CjH4N = NC6Hs. If the para position is not free, isomerization to the ortho position occurs. The isomerization may proceed by a fission of the diazoamino compound to the progenitors, which then undergo... 

MisceUaneons oxidations, Some aromatic amines (e.g., aniline, p-toluidine, p-chloroaniline) are oxidized by silvei(ll) oxide to the corresponding azo derivative in moderate yield. Hydroquinone is oxidized by AgO rapidly to p-benzoquinone in quantitative yield. Oxidation of benzil dihydrazone with AgO gives dipfaenylacctylene in 95% yield. 

In basic solution head-to-head coupling of the deprotonated radicals result in the formation of azo compounds (21) from Ai -unsubstituted anilines. This occurs via the formation of hydrazo derivatives. p-Substituted anilines also preferentially undergo head-to-head coupling to yield azo derivatives. 

Soluble indulines are also obtained —(1) By heating spirit-soluble indulines, azophenine, quinone, chloranil, azobenzene, azotoluene, or oxyazobenzene with paradiamines (Poirrier). (2) By heating diamidoazoxybenzene Avith aniline and aniline hydrochloride. (3) By heating nitro-derivatives of the amines with aniline c. in-presence of ferrous chloride. (4) By heating the azo-derivatives of naphthylenediamine [1, 5] with paraphenylenediamine and benzoic acid. 

Scheme 10.42. The Fischer-Hepp rearrangement. A representation of diazotization of ami-nobenzene (aniline) with nitrons acid and subsequent reaction of the diazonium ion with N-methylaminobenzene (A-methylanihne) to yield a nitrogen-substituted derivative, which then undergoes intramolecular rearrangement to the corresponding 4-substituted azo derivative.

Experimental conditions azo derivative = 200 mg, T = 200 °C, in dichlorobenzene (10 ml). ) Amine/azo molar ratio. ) Selectivity calculated with resirect to the converted azo compound. ) THF as solvent. ) Toluene as solvent. Tlie only product observed was aniline. 

The most noteworthy reaction of azo-compounds is their behaviour on reduction. Prolonged reduction first saturates the azo group, giving the hydrazo derivative (C NH-NH C), and then breaks the NH NH linkage, with the formation of two primary amine molecules. If method (1) has been employed to prepare the azo-compound, these two primary amines will therefore be respectively (a) the original amine from which the diazonium salt was prepared, and (6) the amino derivative of the amine or phenol with which the diazonium salt was coupled. For example, amino-azobenzene on complete reduction gives one equivalent of aniline, and one of p-phenylene diamine, NHaCeH NH benzene-azo-2-naphthoI similarly gives one equivalent of aniline and one of... 

Nitiosobenzene, which shares the general character of nitroso-compoLinds in gnung rise to a gneen vapour or solution, is leadily reduced to phenylhydroxylamine and aniline. It condenses with ammo-compounds, yielding azo- or diazo-derivatives. 

A striking feature of disperse dye development in recent decades has been the steady growth in bathochromic azo blue dyes to replace the tinctorially weaker and more costly anthraquinone blues. One approach is represented by heavily nuclei-substituted derivatives of N,N-disubstituted 4-aminoazobenzenes, in which electron donor groups (e.g. 2-acylamino-5-alkoxy) are introduced into the aniline coupler residue and acceptor groups (acetyl, cyano or nitro) into the 2,4,6-positions of the diazo component. A PPP-MO study of the mobility of substituent configurations in such systems demonstrated that coplanarity of the two aryl rings could only be maintained if at least one of the 2,6-substituents was cyano. Thus much commercial research effort was directed towards these more bathochromic o-cyano-substituted dyes. 

Spengler and Jumar [90] used a spectrophotometric method and thin layer chromatography to determine carbamate and urea herbicide residues in sediments. The sample is extracted with acetone, the extract is evaporated in vacuo at 40°C and the residue is hydrolysed with sulphuric acid. The solution is made alkaline with 15% aqueous sodium hydroxide and the liberated aniline (or substituted aniline) is steam distilled and collected in hydrochloric acid. The amine is diazotized and coupled with thymol, the solution is cleaned up on a column of MN 2100 cellulose power and the azo-dye is determined spectrophotometrically at 440nm (465nm for the dye derived from 3-chloro- or 3.4-dichloroaniline) with correction for the extinction of a reagent blank. 

Other common intermediates for azo pigment production are 2,4-dinitro-aniline, acetoacet-o-chloroanilide, acetoacet-o-toluidide, phenyl- and p-tolyl-methylpyrazolone, 2-hydroxy-3-naphthoic acid, Naphtol AS and its derivatives, and 2-chloro-4-aminotoluene-5-sulfonic acid. 

Pigment synthesis follows the typical route to azo pigment lakes the aniline derivative or the aniline sulfonic acid is diazotized with sodium nitrite in an acidic medium (hydrochloric acid), followed by coupling on the Naphthol AS derivative, which is initially dissolved in an alkaline solution and then precipitated by adding inorganic or acetic acid. If a Naphthol AS sulfonic acid is used as a coupling component, it must be neutralized with alkali for dissolution and coupled directly. 

The pigments are synthesized by diazotizing the aniline derivative or the aniline sulfonic acid with sodium nitrite in hydrochloric acid and subsequently coupling onto the naphthalene sulfonic acid derivative, which is previously dissolved by neutralizing with a sodium hydroxide solution, producing the corresponding azo dye solution. 

Naphthylamine and also its sulphonic acids are likewise employed technically for the manufacture of azo-dyes. In the same way a-naph-thol is made from naphthalene-a-sulphonic acid by fusion with sodium hydroxide although on a smaller scale than /3-naphthol. a-Naphthyla-mine, on the other hand, is obtained by the reduction of a-nitronaph-thalene (analogy to aniline). The fusion of alkali salts of arylsulphonic acids with alkali also serves technically for the production of pure phenol and of many phenol derivatives. 

Arylbenzotriazoles (797) are prepared via 2-nitro- and 2-amino-diphenylamines (Scheme 161). The 2-nitrodiphenylamines (796) are prepared from the appropriate aniline by reaction with 2-fluoronitrobenzene in the presence of KF <808215,85JCS(Pl)2725>. Azo-coupling of 2-amino-1-cyano-azulene (798) with p-tolyldiazonium chloride gives (799) (Scheme 162). Catalytic reduction of (799) quantitatively yields the diamino derivative (800), which on diazotization affords 9-cyano-azuleno[l,2-J]triazole (801) in 77% yield <85TL335>. 

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