Azoxy-benzene

Fig. 41.5. Multicomponent analysis (aniline (jC ), azobenzene (xi), nitrobenzene (xi) and azoxy-benzene (X4)) by recursive estimation (a) forward run of the monochromator (b) backward run (k indicates the sequence number of the estimates solid lines are the concentration estimates dotted lines are the measurements z).

Wallach transformation orgchem By the use of concentrated sulfuric acid, an azoxy-benzene is converted into a pura-hydroxyazobenzene. wal ak. tranz-far.ma-shan wall-coated capillary column analychem Acaplllary column characterized bya layer of stationary liquid coated directly on the Inner wall of a colled capillary tube. wol kod-3d kap-3 ler-e. kal am )... 

Under similar conditions, cw-azobenzene could be oxidized to cw-azoxy-benzene. Evidently the only major precaution to be taken in this preparation is the exclusion of ultraviolet light (by carrying the reaction out in a dark room) [24]. Whether this precaution is truly required is open to some doubt since cis-azoxybenzenes were prepared more recently by oxidation while warming with a heating lamp [28]. The isomerization by ultraviolet light is probably an equilibrium process in which equilibrium constants have a pronounced dependence on the chemical constitution of the materials involved. Therefore variations in the observations of the stability of the products are not entirely surprising. 

The details of the mechanism for the conversion of nitrobenzene into azoxy-benzene need further amplification. It also should be pointed out that, in the preparation of azo compounds by bimolecular reduction, hydrazo compounds seem to form invariably since the directions invariably call for the reoxidation of the hydrazo product with air (see Chapter 14, Azo Compounds and Meisenheimer and Witte [39]). 

NOTE Higher nitrated derivs of Dichloro-azoxy benzene were not found in Beil or in CA thru 1961... 

Azoxydibenzoic Acid or Azoxy benzene-dicarboxyl ic Acid (called Azoxybenzoesaure or Azoxybenzol-dicarbonsaure in Ger), HCX>C-QH4-(N20)-QH,-C00H mw 286.24,... 

Bis(2,4,6 trinitrobenzeneazo) azoxy benzene. See under Bis(benzeneazo)-azoxy-benzene... 

Axoxybenxene, C HS -(N20)-C6H5 mw 198,22, N 14. i3%. Exists in two modifications ordinary, mp 36° and isoazoxybenzene mp 84°. Sneilmg Wyler (Ref 2) found that -AN is sensitized by the addn of 1-6% azoxy-benzene. Some of its azido derivs and high nitro compds may be of interest as expl ingredients... 

C6Hj mw 227.22, N 18.49% sulfur yel crysts, mp ca 106° with a blue-green color becoming orn-red. It was prepd by heating on a steam bath 2-hydroxyl-am ino-azoxy benzene with freshly pptd mercury oxide in ether... 

Upon screening various transition metal catalysts in the reaction of a-methyl-styrene lh with N-phenylhydroxylamine 29a, Jorgensen and coworkers obtained the best result for 2-phenyl-3-(phenylamino)propene 30a with iron(III) phthalocyanine [Fe(Pc)]. In this case, the decomposition of 29a to aniline, azobenzene and azoxy-benzene was minimized (Scheme 3.34). 

Heating a mixture of nitrobenzene, flake sodium hydroxide and a little water in an autoclave led to an explosion [1], During the technical-scale preparation of a warm solution of nitrobenzene in methanolic potassium hydroxide (flake 90% material), accidental omission of most of the methanol led to an accelerating exothermic reaction which eventually ruptured the 6 m3 vessel. Laboratory investigation showed that no exothermic reaction occurred between potassium hydroxide and nitrobenzene, either alone, or with the full amount (3.4 vol.) of methanol, but that it did if only a little methanol were present. The residue was largely a mixture of azo- and azoxy-benzene [2]. The violent conversion of nitrobenzene to (mainly) 2-nitrophenol by heating with finely powdered and anhydrous potassium hydroxide had been described earlier [3]. Accidental substitution of... 

Haussermann 2 reduced nitrobenzene and nitrotoluenes both in alkaline and acid solution, the former with iron, the latter with platinum, electrodes. By reduction in alkaline solution, he obtained as principal product hydrazobenzene and hydrazo-toluene respectively in sulphuric-acid solution he got from nitrobenzene, as chief products, benzidine sulphate and azoxy-benzene, besides an easily changeable body which was not further determined. o-Nitrotoluene3 under like conditions gave o-tolui-dine sulphate besides small quantities of o-toluidine p-nitro-toluene yielded principally p-toluidine. 

In the reduction of nitrobenzene in a 2% aqueous sodium-hydroxide solution, according to previous publications, azoxy-benzene is formed at platinum and nickel electrodes, azobenzeno at lead, tin, and zinc cathodes, and aniline at copper cathodes especially in the presence of copper powder. It was found that, in an unchangeable experimental arrangement, a cathodo potential of 1.8 volts, as measured in connection with the deci-normal electrode, could be carried out with all the chosen cathodes and additions. At this constant potential, by using different metals and adding various metallic hydroxides, the whole reduction was carried out and the nature and quantity of the reduction products determined in each case. It turned out that the emphasized differences in the results disappeared and that, with an equal potential of all cathodes, similar yields of azoxybenzene and aniline and traces of azobenzene resulted. The cathodes were of platinum, copper, copper and copper powder, tin, platinum with addition of stannous hydroxide zinc, platinum with addition of zinc hydroxide, lead, platinum with addition of lead hydroxide, and nickel. The yields of azoxybenzene varied from 41-65% of aniline 23-53%. 

An example of angle dependence of shifts is illustrated by the isomeric mixture of p,p -disubstituted azoxy benzenes to which Eu(fod)3 is added. This is illustrated in Fig. 10.16. A scale model was used to estimate the H-Eu-0 angle for the methoxy and methyl protons of one isomer as shown in Fig. 10.17. 

Diozidoozoxybenzene, Nj-QH -fNjO)--C,H N, mw 280.25, N 39.99% ocher col crysts (from petr eth) mp 85-6°, explodes when heated in a tube above its mp. It was prepd by diazotizing 3,3 -diamino-azoxy-benzene, pptg the perbromide of the tetrazo deriv, and treating the latter with NHj Re/s DBeil 16, 629 2)R.Meldola E.R. Andrews, JCS 691, 9(1896)... 

Deoxygenation of sulfoxides and azoxyarenes. This combination is superior to triphenylphosphine-iodine for deoxygenation of sulfoxides to sulfides (70-95% yield) and of azoxy benzenes to azobenzenes ( 90% yield, two examples). The reaction can be promoted by addition of sodium iodide. One advantage is that the by-product, HMPT, is soluble in water and easily removed. 

There are several recent methods for the reduction of azobenzene to hydrazobenzene in near-quantitative yield. Samarium(II) iodide reduces azobenzene to hydrazobenzene rapidly at room temperature. Hydrogen telluride, generated in situ from aluminum telluride and water, reduces both azobenzene and azoxybenzene to hydrazobenzene a mixture of phenyllithium and tellurium powder has been used to reduce azobenzene. A complex of the coenzyme dihydrolipoamide and iron(II) is also effective for the reduction of azo- and azoxy-benzene to hydrazobenzene the reduction probably involves coordination of the azobenzene to iron(II) as shown in structure (1). Electrochemical reduction has been used to prepare a number of hydrazobenzenes from the corresponding azobenzenes. In the presence of an acylating agent a diacylhydrazine (e.g. the pyridazinedione derivative 2) can be isolated from the electrochemical reduction of azobenzene. 

Alcoholic Alkali and Zinc.—A second series of reduction products is formed when the reduction takes place in alkaline solution. When nitro benzene is boiled with zinc in an alcoholic solution of an alkali, the reduction affects two molecules of the nitro benzene, which, by the loss of three atoms of oxygen, become united yielding a product known as azoxy benzene. 

Oxidation Products.—With different oxidizing agents it yields various products. Its water solution oxidizes easily in the air and yields azoxy benzene. 

When boiled with water it is partly volatilized, but is mostly converted into a mixture of nitroso bnezene, CeHs—NO azoxy benzene. 

It is very sensitive to the action of alkalies and by them is converted first into nitro benzene, CeHe—NO2, and then into azoxy benzene. 

Azoxy benzene is the product of the reduction of two molecules of nitro benzene by means of alcoholic sodium hydroxide and zinc. The... 

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