Nitrobenzene, preparation reduction

The reduction is similar to that of nitrobenzene (Preparation 359), but no condenser need be used in this case. 120 gms. iron powder and 60... 

Nitrosobenzene (3) can be prepared by oxidation of aniline by H2SO5 (see Section 7.2.2) and by oxidation of phenylhydroxylamine (4) with potassium dichromate. Phenylhydroxylamine is available from nitrobenzene by reduction with zinc dust and aqueous ammonium chloride (Scheme 7.10). 

Hofmann found only small amounts of aniline in coal-tar, but when he found benzene in the light oil distilled from the tar he prepared nitrobenzene and reduced this to aniline with nascent hydrogen from zinc and dilute acid, using as a test for benzene its conversion into nitrobenzene, the reduction of this to aniline, and the formation of a blue or purple colour with this and bleaching powder (see p. 184). Bechamp found that nitrobenzene is reduced to aniline by ferrous acetate but not by other ferrous salts, and also by iron filings and acetic acid. This was the foundation of the aniline dye industry, iron and hydrochloric acid being generally used. 

It is prepared by reduction of nitrobenzene with iron and NaOH. It is also prepared by an electrolytic reduction of nitrobenzene. It is widely used for the preparation of benzidine. 

Azoxybenzene is readily prepared by reduction of nitrobenzene in an alkaline medium with dextrose or sodium arsenite ... 

For the preparation of nitrocymene a method developed in the Colour Laboratory and described in the Jour, of Ind. and Eng. Chem. in 1918, p. 453, was used. The nitro group enters in the ortho position with respect to the methyl group. The reduction of this compound to aminocymene or cymidine was accomplished by means of iron powder and hydrochloric acid in exactly the same way as nitrobenzene is reduced to aniline. 

Di-o-nitrophenyl disulfide was first prepared by the action of hydriodic acid on o-nitrobenzene sulfochloride.1 It has also been prepared by the reduction of o-nitrobenzene sulfinic acid with hydrogen bromide 2 by the reduction of ethyl-o-nitro-phenylsulfonacetate with ammonium sulfide 3 and by the deamination of 4,4,-diamino-2,2 -dinitrodiphenyldisulfide.4 The procedure given is the method of Blanksma5 as elaborated by Wohlfahrt.6... 

One of the most important derivatives of benzene is nitrobenzene. The nitro group is —NOi. Nitrobenzene is important chiefly because it is readily converted into an aromatic amine, aniline, by reduction. One preparative procedure uses zinc as the reducing agent ... 

This study involved the preparation and characterization of poly(N-phenyl 3,4-dimethylenepyrrolidine) and the subsequent oxidation and reduction of this polymer. The parent polymer was not very soluble, so it was difficult to characterize. However, after oxidizing in the presence of palladium on carbon in nitrobenzene, the resultant poly(N-phenyl 3,4-dimethylenepyrrole) was soluble in several organic solvents. Attempts to reduce the original polymer to the pyrrolidone were unsuccessful. 

The procedure described for the preparation of l-(m-nitro-phenyl)-3,3-dimethyltriazene is the method of Elks and Hey,2 and the preparation of m-nitrobiphenyl is also a modification of their procedure. The other principal methods for the preparation of m-nitrobiphenyl are the decomposition of N-nitroso-w-nitroacetanilide in benzene 3 and the decomposition of alkaline m-nitrobenzenediazohydroxide in benzene.4 Other methods that have been reported include the decomposition of potassium ire-nitrobenzenediazotate in benzene with acetyl chloride,6 the decomposition of m-nitrobenzoyl peroxide in boiling benzene,6 the decomposition of benzenediazonium borofluoride in nitrobenzene 7 at 70°, and the reduction of 4-(3 -nitrophenyl)-benzenediazonium acid sulfate in boiling ethanol.8... 

The precursors of the carbazoles are the anthrimides, in particular the 1,1 -dianthraquinonylamines (l,T-dianthrimides). These intermediates were originally used as vat dyes themselves, but very few give bright colours and the vatting process also brings about reduction to 1-aminoanthraquinone. Only one dianthrimide is currently active in the Colour Index [11] this grey vat dye is Cl Vat Black 28 (6.83). l,l -Dianthrimides are easily prepared by heating a 1-aminoanthraquinone with a 1-chloroanthraquinone in nitrobenzene or another solvent in the presence of sodium carbonate and a copper catalyst. 

The reduction of aromatic nitro-compounds is of exceptionally great interest, not only scientifically, hut also technically. The conversion of the hydrocarbons of coal tar into useful products began with the discovery of the nitration process the conversion, on the technical scale, of the nitro-group of nitrobenzene into the amino-group gave aniline, the starting material for the preparation of innumerable dyes and pharmaceutical products to aniline were added the homologous toluidines, xylidines, naphthylamines, and so on. 

Bromo-2,5-Dimethoxyamphetamine, This should be prepared by reducing the above nitro-propene with LAH as described below. Other reductions may or may not be compatible with the electronic character of the bromine atom. This particular reduction can also be used to reduce most any nitrostyrene, nitrobenzene, etc. Note These will work too, CPB, 16, 217 or JACS, 72, 2781, also found in this book. 

Direct preparation of azo compounds in good yields is accomplished by treatment of nitro compounds with lithium aluminum hydride [576], with magnesium aluminum hydride [577], with sodium bis(2-methoxy ethoxy)aluminum hydride [575], with silicon in alcoholic alkali [331] or with zinc in strongly alkaline medium [578], Hydrazobenzene was obtained by controlled hydrogenation of nitrobenzene in alkaline medium (yield 80%) [572] and by reduction with sodium bis 2-methoxyethoxy)alumium hydride (yield 37%) [544],... 

On a preparative scale, the product formed during electrochemical reduction of nitrobenzenes in alkaline solution can be readily controlled by adjusting the total numer of Faraday passed under constant current conditions. The formation of az-... 

Reduction of nitrobenzene Aniline can be prepared from nitrobenzene by either chemical reduction using acid and metal or catalytic hydrogenation using molecular hydrogen. 

The preparation of azobenzene by reduction of nitrobenzene with zinc dust and sodium hydroxide has been well described [60] except that no specific mention is made of the desirability of carrying the reaction out in the presence of air. As a matter of fact, in the older literature, mention is made of blowing air through the filtrate after the reduction has been completed and the insoluble salts have been filtered off [59], This procedure has been recommended more recently also. Actually, air has been drawn through the product solution for as long as 6 hr to oxidize any hydrazo compound which may be present [61]. However, as shown by Blackadder and Hinshelwood [50], we believe that the presence of modest amounts of air toward the end of the reduction cycle should be sufficient for obtaining adequate yields. 

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]). 

The counterpart of anodically electrocatalyzed oxidation by redox oxides, namely the cathodic reduction of organic substrates by surface-coup led redox system with sufficiently negative redox potential, is almost unknown. Beck reports that specially prepared TiO coating on Ti-electrodes can be reduced cathodically and that the electrogenerated Ti(III) and Ti(II) species do in fact reduce nitrobenzene to aniline (207). 

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