Nitrobenzene direct nitration

A problem of another sort arises in the attempt to prepare an o-disubstituted benzene, even when one of the groups is an ortho, para director. Although appreciable amounts of ortho isomers may form in electrophilic substitutions of benzenes containing such groups, the para isomer is the major product in most such cases (Sections 16-2 and 16-3). Suppose you required an efficient synthesis of l-(l,l-dimethylethyl)-2-nitrobenzene [o-(fert-butyl)nitrobenzene]. Direct nitration of (l,l-dimethylethyl)benzene (tert-butylbenzene) is unsatisfactory. 

Nitrobenzene is an oily liquid, resulting from the direct nitration of benzene, having the following constitution —... 

This procedure illustrates a general method for converting substituted pyrylium salts to nitrobenzene derivatives. The reaction has been the subject of several reviews. - The yields are generally high, and under these conditions only a single product is formed, in contrast to the nitration of 1,3,5-triphenyl-benzene. The preparation of 2,4,6-triphenylnitrobenzene from the corresponding pyrylium salt eliminates isomer separation problems, which are encountered when the direct nitration procedure is used. Also, labeled compounds can readily be prepared by this method. ... 

This is a relatively straightforward synthetic problem. Bromine is an ortho, para-directing substituent nitro is meta-directing. Nitrate first, and then brominate to give 1-bromo-3-nitrobenzene. 

Nitrobenzene (melting point 5.9°C, boiling point 210.9°C, density 1.199, flash point 88°C) is made by the direct nitration of benzene using a nitric acid-sulfuric acid mixture (Fig.l), usually in a cast-iron or steel kettle. 

Nitrobenzene Nitrobenzene is made by the direct nitration of benzene with nitric/sulfuric acid mixtures primarily for aniline production. And aniline is a raw material for the manufacture of methylene diphenyl diisocyanate (MDI) that is used to make rigid foams. 

Nitrobenzene is made by three processes direct nitration, dehydrating nitration and adiabatic nitration. The first process involves the direct nitration of benzene using a mixture of nitric acid and sulfuric acid46,258. 

Nitrobenzene (Aniline). The U.S. nitrobenzene production was about 2 billion lb in 1999. Two types of manufacturing processes were used the direct nitration and the adiabatic nitration process. In the direct nitration system, benzene is mixed with a mixture of nitric/ sulfuric acid. The reaction can be carried out in either a batch or a continuous system. Those reactors require a cooling system to keep it at constant temperature. It also requires a separate system for sulfuric acid reconcentration. In the adiabatic process, water is flashed off under vacuum before the sulfuric acid/nitrobenzene separation. The advantage of the adiabatic process is to eliminate a separated sulfuric acid reconcentration unit. This also will provide a better heat integration. Recently, the disposal of nitrophenols has become a major issue for aniline manufacture. Small amounts of nitrophenols are always made during the benzene... 

Nitrobenzene Nitrobenzene is made by the direct nitration of benzene with nitric/sulfuric acid mixtures. 

Dinitrobenzene is sparingly soluble in water. It is prepared by direct nitration of benzene or nitrobenzene. It is an insensitive explosive. For purposes of official transport regulations, the sensitivity and the reactivity of dinitrobenzene are just on the limit between high-explosive and the non-dangerous zone. 

Dinitrobenzene is prepared by the direct nitration of nitrobenzene. This yields m-dinitrobenzene. 

Nitrobenzene is produced by the nitration of benzene in a mixed nitrating (nitric/sulfuric) acid solution, using either the direct nitration process or adiabatic nitration. The first process involves the direct nitration of benzene in a batch or a continuous reactor. In the adiabatic process, an excess of benzene and a mixture of nitric and sulfuric acid are added to a series of reactors. Product nitrobenzene and dilute sulfuric acid are separated, water is flashed off under vacuum, and the sulfuric acid is recycled. 

The argument for the S 2 process, when the transition from acetic acid as solvent to nitric acid as solvent is considered, is less direct, for because of the experimental need to use less reactive compounds, zeroth-order nitration has not been observed in nitric acid. It can be estimated, however, that a substance such as nitrobenzene would react about 10 faster in first-order nitration in nitric acid than in a solution of nitric acid (7 mol 1 ) in acetic acid. Such a large increase is understandable in terms of the S z mechanism, but not otherwise. 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Aniline is an important derivative of benzene that can be made in two steps by nitration to nitrobenzene and either catalytic hydrogenation or acidic metal reduction to aniline. Both steps occur in excellent yield. Almost all nitrobenzene manufactured (97%) is directly converted into aniline. The nitration of benzene with mixed acids is an example of an electrophilic aromatic substitution involving the nitronium ion as the attacking species. The hydrogenation of nitrobenzene has replaced the iron-... 

The catalytic process for the production of picric acid directly from benzene in one step by the action of nitric acid in the presence of mercuric nitrate has much theoretical interest and has been applied, though not extensively, in plant-scale manufacture. It yields about as much picric acid as is procurable from the same weight of benzene by the roundabout method of sulfonating the benzene, converting the benzene sulfonic acid into phenol, and nitrating the phenol to picric acid—and the benzene which is not converted to picric acid is for the most part recovered as such or as nitrobenzene. The first mention of the process appears to be in the patent of Wolffenstein and Boeters.55... 

Answer Procedures V-6, V-7 and XH-S. Procedures V 6 and V-7 insert a —N02 group directly onto an aromatic ring. However, if one nitrates nitrobenzene the major product is the meta isomer. Thus, the only other available method would be the use of procedure XiI-8. 

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