Nitrobenzene formation

When a mixture of aniline, nitrobenzene, glycerol and concentrated sulphuric acid is heated, a vigorous reaction occurs with the formation of quinoline. It is probable that the sulphuric acid first dehydrates the glycerol giving acrolein or acraldehyde (A), which then condenses at its double bond with the amino group of the aniline to give acrolein-aniline (B), The latter in its enol... 

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]. 

The single-step -duoroaruline [31-40-4] process based on duorodeoxygenation of nitrobenzene (via in situ generation of /V-phenylhydroxyl amine) in anhydrous hydrogen duoride (94—96) has not been commercialized primarily due to concurrent formation of aniline, as well as limited catalyst life. The potential attractiveness of this approach is evidenced by numerous patents (97—101). Concurrent interest has been shown in the two-step process based on /V-phenylhydroxylamine (HF-Bamberger reaction) (102—104). 

Mixtures of HNO, H2SO4, and SO also result in high concentrations of NO/, and toluene can be readily nitrated at —40 to — 10°C as a result (6). At these low temperatures, the formation of the meta-isomer of mononitrotoluene (MNT) is greatiy reduced. Such a reduction is highly desired in the production both of dinitrotoluenes (DNTs) employed to produce intermediates for polyurethane production and of trinitrotoluene (TNT), which is a high explosive. > -MNT results in the production of undesired DNT and TNT isomers (see Nitrobenzene and nitrotoluenes). 

Environmental aspects, as well as the requirement of efficient mixing in the mixed acid process, have led to the development of single-phase nitrations. These can be divided into Hquid- and vapor-phase nitrations. One Hquid-phase technique involves the use of > 98% by weight nitric acid, with temperatures of 20—60°C and atmospheric pressure (21). The molar ratios of nitric acid benzene are 2 1 to 4 1. After the reaction is complete, excess nitric acid is vacuum distilled and recycled. An analogous process is used to simultaneously produce a nitrobenzene and dinitrotoluene mixture (22). A conversion of 100% is obtained without the formation of nitrophenols or nitrocresols. The nitrobenzene and dinitrotoluene are separated by distillation. 

Manufacture and Processing. Mononitrotoluenes are produced by the nitration of toluene in a manner similar to that described for nitrobenzene. The presence of the methyl group on the aromatic ring faciUtates the nitration of toluene, as compared to that of benzene, and increases the ease of oxidation which results in undesirable by-products. Thus the nitration of toluene generally is carried out at lower temperatures than the nitration of benzene to minimize oxidative side reactions. Because toluene nitrates at a faster rate than benzene, the milder conditions also reduce the formation of dinitrotoluenes. Toluene is less soluble than benzene in the acid phase, thus vigorous agitation of the reaction mixture is necessary to maximize the interfacial area of the two phases and the mass transfer of the reactants. The rate of a typical industrial nitration can be modeled in terms of a fast reaction taking place in a zone in the aqueous phase adjacent to the interface where the reaction is diffusion controlled. 

Aluminum chloride dissolves readily in chlorinated solvents such as chloroform, methylene chloride, and carbon tetrachloride. In polar aprotic solvents, such as acetonitrile, ethyl ether, anisole, nitromethane, and nitrobenzene, it dissolves forming a complex with the solvent. The catalytic activity of aluminum chloride is moderated by these complexes. Anhydrous aluminum chloride reacts vigorously with most protic solvents, such as water and alcohols. The ability to catalyze alkylation reactions is lost by complexing aluminum chloride with these protic solvents. However, small amounts of these "procatalysts" can promote the formation of catalyticaHy active aluminum chloride complexes. 

Many substituted quinolines are intermediates for antimalarials. The 2,4-di-substituted quinolines are produced from aniline and 1,3-diketones by the Combes quinoline synthesis (28). The reaction of aniline with nitrobenzene in the presence of dry sodium hydroxide at 140°C leads to formation of phenazine [92-82-0] and by-products (Wohl-Aue synthesis) (29). 

Oxidation. Aromatic amines can undergo a variety of oxidation reactions, depending on the oxidizing agent and the reaction conditions. For example, oxidation of aniline can lead to formation of phenyUiydroxylamine, nitrosobenzene, nitrobenzene, azobenzene, azoxybenzene or -benzoquinone. Oxidation was of great importance in the early stages of the development of aniline and the manufacture of synthetic dyes, such as aniline black and Perkin s mauve. 

Quinoline.—The formation of c[uinoline by Skratip s reaction may be explained as follows - The sulphuric acid converts the glycerol into aciolein, which then combines w-ith the aniline to form acrolein-aniline. The latter on o.xidation with nitrobenzene yields quinoline. 

In contrast to the facile condensation of o-nitrotoluene with diethyl oxalate, other a-alky] nitrobenzenes are sluggish to react with diethyl oxalate or fail to react at all. It has been suggested that this is due both to steric and electronic factors effected by the alky] group, which destabilizes the methylene group in regard to formation of the carbanion. ... 

The importance of the solvent, in many cases an excess of the quatemizing reagent, in the formation of heterocyclic salts was recognized early. The function of dielectric constants and other more detailed influences on quatemization are dealt with in Section VI, but a consideration of the subject from a preparative standpoint is presented here. Methanol and ethanol are used frequently as solvents, and acetone,chloroform, acetonitrile, nitrobenzene, and dimethyl-formamide have been used successfully. The last two solvents were among those considered by Coleman and Fuoss in their search for a suitable solvent for kinetic experiments both solvents gave rise to side reactions when used for the reaction of pyridine with i-butyl bromide. Their observation with nitrobenzene is unexpected, and no other workers have reported difficulties. However, tetramethylene sulfone, 2,4-dimethylsulfolane, ethylene and propylene carbonates, and salicylaldehyde were satisfactory, giving relatively rapid reactions and clean products. Ethylene dichloride, used quite frequently for Friedel-Crafts reactions, would be expected to be a useful solvent but has only recently been used for quatemization reactions. ... 

It is also interesting to note that quatemization of a chloropyrimi-dine at the nitrogen atom adjacent to the chloro group with methyl iodide results in the easy replacement of the chlorine by iodine, whereas similar salt formation on the remote nitrogen either leaves the chlorine unaffected or replacement occurs only at higher temperatures. A similar reaction occurs between 2-amino-6-chloro-4-methylpyrimidine and dimethyl sulfate in nitrobenzene to give the salt 45 and betaine 46. ... 

Similar to the alkylation and the chlorination of benzene, the nitration reaction is an electrophilic substitution of a benzene hydrogen (a proton) with a nitronium ion (NO ). The liquid-phase reaction occurs in presence of both concentrated nitric and sulfuric acids at approximately 50°C. Concentrated sulfuric acid has two functions it reacts with nitric acid to form the nitronium ion, and it absorbs the water formed during the reaction, which shifts the equilibrium to the formation of nitrobenzene ... 

Diethyl methylphosphonite in refluxing dialkylamine is the favored method for the formation of 37/-azepines from nitroarenes,75,176,207 although tributylphosphane and tri-piperidinophosphane are recommended for the deoxygenation of nitrobenzene in piperidine.79 Deoxygenation of nitrobenzene in diethylamine furnishes Ar,Ar-diethyl-3/f-azepin-2-amine, and a range of 5-substituted 3//-azepines 97 have been prepared in a similar manner from 4-sub-stituted nitroarenes.79,176 Curiously, the corresponding 2-substituted nitroarenes, with the exception of 2-nitrotoluene, yield only tarry products. 

Montravel. In 1889 proposed treating the ingredients used in the prepn of BlkPdr with nitrobenzene. This procedure resulted in the formation of a thin coating on the grains which served as waterproofing Ref Daniel (1902), 443... 

P pentachloride causes ignition on contact with Al powder (Ref 2), while contact with a mixt of chlorine and chlorine dioxide usually results in expln, possibly due to formation of the more sensitive chlorine monoxide (Ref 5). Interaction with diphosphorus trioxide is rather violent at ambient temp (Ref 3) treatment with fluorine causes the entire mass to become incandescent (Ref 1). Ignition occurs when hydroxylamine is mixed with P pentachloride (Ref 6), while mixts with Mg oxide react with brilliant incandescence (Ref 7). The residue from interaction of P pentachloride and anilide in benz and removal of solvent and phosphoryl chloride in vacuo expld violently on admission of air (Ref 12). A soln of P pentachloride in nitrobenzene is stable at 110°, but begins to de-... 

Semiquantitatively, the reaction of an aromatic diazonium ion with the methoxide ion occurs in three phases. The first is the extremely rapid formation of the (Z)-diazo methyl ether. This is followed by a second, partitioning, phase which in the case of the 4-nitrobenzenediazonium ion at 30 °C is completed in 60 s (Boyle et al., 1971). During this phase, some of the (Z)-diazo ether decomposes to form dediazoniation products (mainly nitrobenzene via the hydro-de-diazoniation reaction) and the rest is converted into the (Zi)-diazo ether. 

In DMSO as solvent and in the presence of nitrobenzene, aryl-de-diazoniation of the unsubstituted benzenediazonium ion leads mainly via meta substitution to 3-nitrobiphenyl, whereas in the case of the 4-nitrobenzenediazonium ion the formation of o- and -substituted products (2,4 -and 4,4 -dinitrobiphenyl) prevails (Gloor et al., 1972). 

Up to now this possibility was applied for the preparation of a-ketosulphoxides. The first formation of a-ketosulphoxides in the reaction between a ketone and sulphinyl chloride was reported by Oae and Ikura188 in 1966. They prepared p-nitrobenzene-sulphinyl chloride and identified it by means of its reaction product with acetone which had the analytical composition of a-sulphinylacetone 134 (equation 73). 

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