Amines from azo compounds

Cuprous salts Sym. azo compounds from amines Cu 2 RNH2 -V RN NR ... 

Peroxyacetic acid/cupric chloride Azo compounds from amines s. 2d, 211... 

With concentrated mineral acids azobenzene gives red salts, as may be shown by pouring hydrochloric acid on it. Addition of hydrogen leads to the re-formation of the hydrazo-compound. Oxygen is added on and the azoxy-compound formed by the action of hydrogen peroxide or nitric acid. The synthesis of asymmetrical aromatic azo-compounds from nitroso-compounds and primary amines was discussed above. 

In its simplest form this reaction, by means of which the extremely numerous technical azo-dyes are manufactured, consists in condensation of aromatic diazo-compounds with phenols or aromatic amines to form azo-compounds. From the labile diazo-system the very stable azo-complex is produced. The azo-dyes, therefore, are, without exception, derivatives of azobenzene or else of azonaphthalene, etc. 

Characteristic of an azo compound is the ease with which the molecule is cleaved at the double bond by reducing agents to give two amines. Since amines are colorless, the reaction is easily followed by the color change. The reaction is of use in preparation of hydroxyamino and similar compounds, in analysis of azo dyes by titration with a reducing agent, and in identification of azo compounds from an examination of the cleavage products. 

Reduction of azo compounds to amines, with fission of the N=N double bond, assumes practical importance because so many azo compounds are readily accessible, even on an industrial scale, by coupling of diazonium salts with reactive molecules. In this way a large number of primary amines can be obtained free from isomers, which is not always easy to achieve by other... 

Mow has developed the use of rotary mills using freely moving ponderous agitators, such as iron balls, for the reduction of nitro, nitroso, and azo compounds to amines with iron in aqueous emulsion in order to effect grinding action during the reduction. Such mills are also useful in the distillation of aromatic amines from the iron oxide sludges in vacuum. 

With GiO as carbocatalyst, oxidative cross condensations of various anihnes and ahphatic amines with benzyl amine to the corresponding Af-benzylidene derivatives have also been achieved by suppressing homocondensation of benzyl amine by using an excess of the cross-coupling partner [77]. Reduced GeO served as a reusable aerobic dehydrogenation catalyst for the preparation of azo compounds from their hydrazo precursors [79]. 

It can be seen that yields of azo compounds produced from p-toluidine and p-anisidine are almost quantitative, whereas yields of azo compounds from o-toluidine and c -anisidine are poor. Kinoshita rationalized this difference on the basis of steric hindrance to copper amine complex formation exerted by the ortho substituents. It is of interest to note that the yield of azo compounds obtained in the free radical initiated autoxidation of aromatic amines are not significantly affected by the position of substituent groups on the aromatic ring [175,176]. 

Lithium tetrahydridoaluminate Sym. azo compounds and amines from nitro compounds... 

Grirrane, A., Corma, A. and Garcia, H. (2010). Preparation of Symmetric and Asymmetric Aromatic Azo Compounds from Aromatic Amines or Nitro Compounds Using Supported Gold Catalysts, Nature Protocols, 5, pp. 429-438. 

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... 

Reaction with arenediazonium salts Adding a phe nol to a solution of a diazonium salt formed from a primary aromatic amine leads to formation of an azo compound The reaction is carried out at a pH such that a significant portion of the phenol is pres ent as its phenoxide ion The diazonium ion acts as an electrophile toward the strongly activated ring of the phenoxide ion... 

Hydroperoxides have been obtained from the autoxidation of alkanes, aralkanes, alkenes, ketones, enols, hydrazones, aromatic amines, amides, ethers, acetals, alcohols, and organomineral compounds, eg, Grignard reagents (10,45). In autoxidations involving hydrazones, double-bond migration occurs with the formation of hydroperoxy—azo compounds via free-radical chain processes (10,59) (eq. 20). 

The first-order decomposition rates of alkyl peroxycarbamates are strongly influenced by stmcture, eg, electron-donating substituents on nitrogen increase the rate of decomposition, and some substituents increase sensitivity to induced decomposition (20). Alkyl peroxycarbamates have been used to initiate vinyl monomer polymerizations and to cure mbbers (244). They Hberate iodine quantitatively from hydriodic acid solutions. Decomposition products include carbon dioxide, hydrazo and azo compounds, amines, imines, and O-alkyUiydroxylarnines. Many peroxycarbamates are stable at ca 20°C but decompose rapidly and sometimes violently above 80°C (20,44). 

Although this reduction is more expensive than the Bnchamp reduction, it is used to manufacture aromatic amines which are too sensitive to be made by other methods. Such processes are used extensively where selectivity is required such as in the preparation of nitro amines from dinitro compounds, the reduction of nitrophenol and nitroanthraquinones, and the preparation of aminoazo compounds from the corresponding nitro derivatives. Amines are also formed under the conditions of the Zinin reduction from aromatic nitroso and azo compounds. 

Atorvastatin, structure of, 105. 516 ATP (see Adenosine triphosphate) ATZ, see Anilinothiazolinone, 1031-1032 Aufbau principle. 6 Axial bonds (cyclohexane), 119 drawing, 120 Azide, amines from, 929 reduction of, 929 Azide synthesis, 929 Azo compound, 944 synthesis of, 944-945 uses of. 945... 

Iodosobenzene diacetate is used as a reagent for the preparation of glycol diacetates from olefins,9 for the oxidation of aromatic amines to corresponding azo compounds,10 for the ring acetylation of N-arylacetamides,11 for oxidation of some phenols to phenyl ethers,12 and as a coupling agent in the preparation of iodonium salts.13 Its hydrolysis to iodosobenzene constitutes the best synthesis of that compound.14... 

The reductive cleavage of azo compounds to aromatic amines requires anaerobic conditions and then bacterial biodegradation of the aromatic amines is an almost exclusively aerobic process therefore, a combined anaerobic-aerobic bacterial process is most effective for removing azo dyes from wastewater. 

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