Aniline nitrobenzene reduction

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 ... 

The decrease of aniline yields (mole 8 ) during nitrobenzene reduction with various alcohols, temperature - 450°C, donor acceptor ratio-3, HLSV-l... 

Nitroaromatic compounds (NACs) are one of the widespread contaminants in the environments. Sources of NACs are numerous they originate from insecticides, herbicides, explosives, pharmaceuticals, feedstock, and chemicals for dyes (Agrawal and Tratnyek, 1996). Under anaerobic conditions, the dominant action is nitro reduction by zero-valent iron to the amine. Other pathways do exist, such as the formation of azo and azoxy compounds, which is followed by the reduction of azo compounds to form amines. Also, in addition to the possibility of azo and azoxy compounds, phenylhydrox-ylamine may be an additional intermediate (Agrawal and Tratnyek, 1996). Nitrobenzene reduction forms the amine aniline. Known for its corrosion inhibition properties, aniline cannot be further reduced by iron. Additionally, it interferes with the mass transport of the contaminant to the surface of the iron. The overall reaction is as follows ... 

Aniline was first produced in 1826 by the dry distillation of indigo, the oldest known vat dye. Fritsche also obtained aniline from indigo by heating it with potash (K20). Hofmann obtained aniline by reduction of nitrobenzene in 1843. Aniline is a colorless, oily, flammable liquid that is slightly soluble in cold water and infinitely soluble in alcohol and ether. Its physical properties are summarized in Table 22.33. 

The aniline processes that are currently in use include (1) hydrogenation of nitrobenzene, (2) nitrobenzene reduction with iron filings, and (3)... 

Nitrobenzene Reduction with Iron Filings. The older Bechamp method for iron oxide pigment production gives aniline as a coproduct and is operated by Bayer in West Virginia. Nitrobenzene is reduced by reaction with iron filings in the presence of a hydrochloric acid catalyst. The iron is oxidized to the ferrous or ferric state and the coproduct aniline is separated. The yield is 90 to 95 percent of theoretical. The reactions are represented as follows.138... 

About 70% of all iron oxide pigments are produced synthetically. Copperas or ferrous sulfate heptahydrate (FeS04-7H20) is the primary source of iron. It is a byproduct of the sulfate process for the manufacture of titanium dioxide as well as a by-product of pickling operations in the steel industry. Other sources of iron include ferric sulfate, ferrous chloride, ferric chloride, and the iron oxide slurry from the production of aniline by nitrobenzene reduction. 

Mechanism Mechanism of nitrobenzene reduction to aniline is shown in Scheme 6.36. 

II. MANUFACTURE OF ANILINE A. Reduction of Nitrobenzene by Batch Processes... 

The general principles of modeling a vapor-phase reaction on a solid catalyst in a fixed-bed reactor are illustrated by applying them to the specific case of nitrobenzene reduction to aniline. Several models of varying complexity are discussed. 

The TPPFe Cl-NaBHa system also achieves the reduction of nitrobenzene to aniline. Although catalysts such as TPPCo or TPPMn Clcan also effect nitrobenzene reduction, the reactivities were lower. 

The forward scheme is shown here. Benzene is first treated with a mixture of sulfuric acid and nitric acid, giving nitrobenzene. Reduction, followed by basic work-up, gives aniline, which will undergo... 

It is manufactured by reacting benzene with a mixture of nitric and sulphuric acids. Most of the nitrobenzene produced is used to manufacture aniline, which is obtained by reduction. A considerable proportion is used as a raw material in the dyestufTs industry, either as nitrobenzene as such, or as aniline. 

Further nitration gives w-dinilrobenzene sulphonation gives w-nitrobenzene sulphonic acid. Reduction gives first azoxybenzene, then azobenzene and aniline depending upon the conditions. Used in the dyestufTs industry as such or as aniline. 

Reductive carbonylation of nitro compounds is catalyzed by various Pd catalysts. Phenyl isocyanate (93) is produced by the PdCl2-catalyzed reductive carbonylation (deoxygenation) of nitrobenzene with CO, probably via nitrene formation. Extensive studies have been carried out to develop the phosgene-free commercial process for phenyl isocyanate production from nitroben-zene[76]. Effects of various additives such as phenanthroline have been stu-died[77-79]. The co-catalysts of montmorillonite-bipyridylpalladium acetate and Ru3(CO) 2 are used for the reductive carbonylation oLnitroarenes[80,81]. Extensive studies on the reaction in alcohol to form the A -phenylurethane 94 have also been carried out[82-87]. Reaction of nitrobenzene with CO in the presence of aniline affords diphenylurea (95)[88]. 

AMNES - AMINES, AROMATIC - ANILINE AND ITS DERIVATIVES] (Vol 2) -reduction of nitrobenzene NITROBENZENE AND NITROTOLUENES] (Vol 17)... 

The reduction of the nitro group to yield aniline is the most commercially important reaction of nitrobenzene. Usually the reaction is carried out by the catalytic hydrogenation of nitrobenzene, either in the gas phase or in solution, or by using iron borings and dilute hydrochloric acid (the Bechamp process). Depending on the conditions, the reduction of nitrobenzene can lead to a variety of products. The series of reduction products is shown in Figure 1 (see Amines byreduction). Nitrosobenzene, /V-pbenylbydroxylamine, and aniline are primary reduction products. Azoxybenzene is formed by the condensation of nitrosobenzene and /V-pbenylbydroxylamine in alkaline solutions, and azoxybenzene can be reduced to form azobenzene and hydrazobenzene. The reduction products of nitrobenzene under various conditions ate given in Table 2. 

Fig. 1. Reduction products of nitrobenzene (1) nitrosobenzene [98-95-3] (2) /V-pbenylbydroxyl amine [100-65-2] (3) aniline [62-53-3] (4) azoxybenzene...

The Faux process is a modification of the Bechamp reaction that was discovered in 1854. It has been used for the reduction of nitrobenzene to aniline using metallic iron ... 

Aniline (hen enamine) [62-53-3] is the simplest of the primary aromatic amines. It was first produced ia 1826 by dry distillation of indigo. In 1840 the same oily hquid was obtained by heating indigo with potash, and it was given the name aniline. The stmcture of aniline was estabUshed in 1843 with the demonstration that it could be obtained by reduction of nitrobenzene. 

Aromatic amines can be produced by reduction of the corresponding nitro compound, the ammonolysis of an aromatic haUde or phenol, and by direct amination of the aromatic ring. At present, the catalytic reduction of nitrobenzene is the predominant process for manufacture of aniline. To a smaller extent aniline is also produced by ammonolysis of phenol. 

In the reduction of nitro compounds to amines, several of the iatermediate species are stable and under the right conditions, it is possible to stop the reduction at these iatermediate stages and isolate the products (see Figure 1, where R = CgH ). Nitrosoben2ene [586-96-9] C H NO, can be obtained by electrochemical reduction of nitrobenzene [98-95-3]. Phenylhydroxylamine, C H NHOH, is obtained when nitrobenzene reacts with ziac dust and calcium chloride ia an alcohoHc solution. When a similar reaction is carried out with iron or ziac ia an acidic solution, aniline is the reduction product. Hydrazobenzene [122-66-7] formed when nitrobenzene reacts with ziac dust ia an alkaline solution. Azoxybenzene [495-48-7], C22H2QN2O, is... 

The chemical production of aminophenols via the reduction of nitrobenzene occurs in two stages. Nitrobenzene [98-95-3] is first selectively reduced with hydrogen in the presence of Raney copper to phenylhydroxylamine in an organic solvent such as 2-propanol (37). With the addition of dilute sulfuric acid, nucleophilic attack by water on the aromatic ring of /V-phenylhydroxylamine [100-65-2] takes place to form 2- and 4-aminophenol. The by-product, 4,4 -diaminodiphenyl ether [13174-32-8] presumably arises in a similar manner from attack on the ring by a molecule of 4-aminophenol (38,39). Aniline [62-53-3] is produced via further reduction (40,41). 

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. 

On reduction, with iron and acetic acid, nitrobenzene yields aniline. 

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