Aniline from chlorobenzene

To manufacture aniline from chlorobenzene and ammonia, cuprous oxide or diamino cuprous chloride has been used as the catalyst and the reaction is usually carried out in the liquid phase under pressure (7). There are few reports on the reaction in gas phase. Jones (8) found that CuX was active for aniline formation while ZnX led to the formation of dichlorobenzenes. The reaction of benzaldehyde with ammonia over zeolite has never been reported. 

The replacement of a nuclear substituent such as hydroxyl (-OH), chloro, (-C1), or sulfonic acid (-S03H) with amino (-NH2) by the use of ammonia (ammonolysis) has been practiced for some time with feedstocks that have reaction-inducing groups present thereby making replacement easier. For example, l,4-dichloro-2-nitrobenzene can be changed readily to 4-chloro-2-nitroaniline by treatment with aqueous ammonia. Other molecules offer more processing difficulty, and pressure vessels are required for the production of aniline from chlorobenzene or from phenol (Fig. 3). 

Such a process parallels that for making aniline from chlorobenzene and ammonia and involves a copper catalyst which promotes the reaction of the aryl halogen atom. 

A certain amount of phenol, as well as the cresols, is obtained from coal tar (Sec. 12.4). Most of it (probably over 90%) is synthesized. One of the synthetic processes used is the fusion of sodium benzenesulfonate with alkali (Sec. 30.12) another is the Dow process, in which chlorobenzene is allowed to react with aqueous sodium hydroxide at a temperature of about 360°. Like the synthesis of aniline from chlorobenzene (Sec. 22.7), this second reaction involves nucleophilic substitution under conditions that are not generally employed in the laboratory (Sec. 25.4). 

It is economically advantageous to conduct the manufacture of aniline from chlorobenzene in conjunction with the large-scale production of chlorine and chlorinated products, to permit the introduction of cheap chlorobenzene into the aniline plant. With such a setup, this process competes favorably with the older method involving the iron-acid reduction of nitrobenzene. 

Evidence for symmetrical intermediates such as benzyne cannot be established by quantitative analysis of the reaction mixture unless a labelled starting substance is used. By applying labeling techniques, Roberts and his collaborators obtained results which indicated that benzyne (13) occurs as an intermediate in the amination of chlorobenzene with potassium amide in liquid ammonia. From chlorobenzene-1-C (12) about equal amounts of anUine-l-C (14) and aniline-2-C (15) were formed. More or less probable alternative... 

An alternative way to produce aniline is through ammonolysis of either chlorobenzene or phenol. The reaction of chlorobenzene with aqueous ammonia occurs over a copper salt catalyst at approximately 210°C and 65 atmospheres. The yield of aniline from this route is also about 96% ... 

We know that nuclear halogens can be replaced by amine groups but with difficulty. Yet aniline has been manufactured from chlorobenzene by heating it with excess aqueous ammonia in presence of Cu20 at about 250° under pressure. 

From chlorobenzene Treatment of chlorobenzene with ammonia (NH3) at high temperature and high pressure in the presence of a catalyst yields aniline. 

N,N -Diphenyl-p-phenylenediamine [39529-22-1 ] M 260.3, m 148-149°. Crystd from chlorobenzene/pet ether or benzene. Has also been crystd from aniline, then extracted three times with absolute EtOH. 

Table I. Yield of Aniline and Benzene from Chlorobenzene and Ammonia at 395°C...

The main products were aniline and benzene, and a trace of dichlorobenzenes was formed. The yields of aniline and benzene increased proportionally with increasing amounts of catalyst. This indicates that both aniline and benzene are formed independently from chlorobenzene and ammonia—i.e., one is not the product of the further reaction of the other. 

The catalytic activity for the aniline formation from chlorobenzene and ammonia of the Y zeolites with various cations was studied at 395° C (Table I). It is clear that the transition metal-exchanged zeolites have the catalytic activity for the reaction, while alkali metal and alkaline earth metal zeolites do not. The fact that alkaline earth metal-exchanged zeolites usually have high activity for carbonium ion-type reactions denies the possibility that Bronsted acid sites are responsible for the reaction. Thus, catalytic activity of zeolites for this reaction may be caused by the... 

Amination is also achieved by the use of ammonia (NH3), in a process referred to as ammonolysis. An example is the production of aniline (C6H5NH2) from chlorobenzene (C6H5C1) with ammonia (NH3). The reaction proceeds only under high pressure. 

The nucleophilic substitution (SN) of aromatic compounds is one of the fundamental organic reactions in the condensed phase. For example, it is known that aniline can be produced from chlorobenzene under a severe basic condition such as in liquid ammonia (Pine et al. 1980). This bimolecular reaction depends strongly on the solvent. In this respect, the SN reaction in the gas phase may be inefficient due to the absence of solvent molecules assisting the attack, by the nucleophilic agent, on the aromatic ring. However, the situation is completely different for molecular complexes where the nucleophile can be directly bound to the aromatic ring and then can attack the positively charged carbon atom (Mayeama and Mikami 1988). 

When Cl, Br, or I is the substituent, there is a size mismatch, and therefore a poor overlap, between the 2p orbitals from the carbon atoms and the p orbitals from the halogen (3p for chlorine, 4p for bromine, and 5p for iodine). This size mismatch is clearly illustrated by comparing the reactivities of aniline and chlorobenzene chlorine and nitrogen have approximately the same electronegativity, but aniline is much more reactive than chlorobenzene because of the better overlap between the carbon and nitrogen 2p orbitals. 

Deep red needle from chlorobenzene, rhombs from nitrobenzene. Also described as coppery red needles with metallic sheen. Practically insol in low boiling organic solvents. Sparingly sol in aniline, nitrobenzene, chlorobenzene, quino -line. So] in coned sulfuric acid first giving a scarlet-red color which turns olive-green on standing. 

Aniline, C6H5NH2, derives its name from the fact that it was first formed as the result of the distillation of indigo, for which the Spanish name is anil. It occurs in small quantities in coal-tar and in bone-oil. Aniline can not be made conveniently from chlorobenzene by the action of ammonia it is foVmed when the halogen compound is heated with a concentrated solution of ammonia under pressure at 180 in the presence of copper sul-... 

The ammonolysis of chlorobenzene previously operated by Dow in the USA, analogous to the synthesis of phenol from chlorobenzene, has had no commercial importance for some years. Table 5.8 summarizes the production capacities of the major aniline producer countries it is striking that aniline production is limited to a small number of countries. 

Chlorobenzene was one of the first basic organic chemicals produced on a large scale it was already manufactured in 1909 by United Alkali Co, Wipnes/USA. The importance of chlorobenzene rose dramatically during World War I, since it was needed as an intermediate in the production of phenol for the manufacture of picric acid. Other uses, now principally of historic importance, are the production of DDT (l,l,l-trichloro-2,2-di(4-chlorophenyl)ethane) from chlorobenzene and chloral in the presence of sulfuric add, first synthesized in 1874 by Othmar Zeid-ler, and the ammonolysis to produce aniline. 

Aniline, which is essentially phenylamine, is the simplest aromatic amine. Commercial aniline can be chemically synthesized from nitrobenzene which is prepared from benzene with nitric acid by electrophilic substitution reaction, as shown in Fig. 7.3, or from chlorobenzene by heating with ammonia in the presence of a copper catalyst. Some aromatic amines are natural, such as 2- and 4-aminobenzoic... 

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