Dinitrochlorobenzene Dinitrophenol

DNCB Dinitrochlorobenzene DNP Dinitrophenol Dpt4 Dermatophagoides ptetrmyssinus alleigen 4... 

Phenol ethers, like the parent phenols, are reactive substrates. Phenol ethers like anisole and phenetole are readily nitrated to their picryl ethers, 2,4,6-trinitroanisole and 2,4,6-trinitrophenetole respectively, on treatment with mixed acid composed of concentrated nitric and sulfuric acids at 0 °C. Such reactions are vigorous, prone to oxidative side-reactions, and pose a considerable safety risk. The direct nitration of 2,4-dinitrophenol ethers, obtained from the reaction of 2,4-dinitrochlorobenzene with alkoxides, provides a more practical route to picryl ethers on an industrial scale. ... 

The best process for the production of dinitrophenol is probably the autoclaving of dinitrochlorobenzene with aqueous caustic soda. The product is obtained on acidification and is used as such, or is nitrated to picricacid for the commercial production of that material by the so-called synthetic process. 

Much of the development in this field is traceable to two quite different original interests. The first goes back to Ullmann and Nddai s observation27 that the p-toluenesulfonate of 2,4-dinitrophenol, like 2,4-dinitrochlorobenzene, reacts with amines these cause desulfonyloxyla-tion. For example, with aniline, the following reaction occurred ... 

The explosive power of picric acid is somewhat superior to that of -> TNT, both as regards the strength and the detonation velocity. Picric acid is prepared by dissolving phenol in sulfuric acid and subsequent nitration of the resulting phenoldisulfonic acid with nitric acid or by further nitration of dinitrophenol (prepared from dinitrochlorobenzene). The crude product is purified by washing in water. 

Technical Observations. Dinitrochlorobenzene is manufactured on a very large scale, and is used in the preparation of sulfur black T (q.v.) and other important dyes. It is, moreover, the starting material for a whole series of condensation products made by replacing the very labile chlorine atom by basic and other residues. Thus, it is easy to prepare dinitroaniline and dinitrophenol, as well as picric acid and dinitroanisole, from dinitrochlorobenzene. The accompanying formulas show only a small part of the reactions actually used (also see Table V). 

Replacement of a labile halogen by the hydroxyl group, e.g., dinitrophenol from dinitrochlorobenzene, and many other similar preparations (see sulfur black T, page 337). 

Picric acid (Figure 3.9) is made by dissolving phenol in sulfuric acid, then nitrating with nitric acid. Another route is from nitration of dinitrophenol, which is made from dinitrochlorobenzene. Picric acid was used extensively in World War I as a bomb and grenade filler both by itself and in mixtures with other explosives. Its major drawback (besides its toxicity) is that it reacts with metals... 

Manufacture (1) Chlorobenzene is nitrated with a mixture of sulphuric acid and nitric acid to produce dinitrochlorobenzene, which is synthesized to dinitro-sodium phenolate under reaction with sodium hydroxide. This is further changed to dinitrophenol with hydrochloric acid and then the dinitrophenol is nitrated by a mixture of sulphuric acid and nitric acid to trinitrophenol5 picric acid. (2) Phenol is mixed with cone, sulphuric acid and heated to obtain phenol-sulphonic acid. This is nitrated with a mixture of sulphuric acid and nitric acid to trinitrophenol. 

The commercial dinitrophenol mixture is produced by heating phenol with dilute sulfuric acid, cooling the product, and then nitrating while keeping the temperature below 50 °C, or by nitrating with a mixed acid under careful temperature control (Sax and Lewis 1987). 2,3-, 2,5-, and 3,4-DNP are prepared by nitration of m-nitrophenol. 3,5-DNP is prepared by the replacement of one nitro group by methoxyl in 1,3,5-trinitrobenzene and demethylation of the dinitroanisole by anhydrous aluminum chloride. 2,6-DNP is prepared by sulfonation and nitration of o-nitrophenol (Harvey 1959). 2,6-DNP is also produced as a byproduct in the synthesis of 2,4-DNP by way of 2,4-dinitrochlorobenzene. 

Dinitrochlorobenzene is commercially available (e.g. Aldrich). Alternatively it can be obtained by nitration of chlorobenzene and recrystallization of the raw productt l or, conveniently for lab scale preparations, by brief heating of the commercially available 2,4-dinitrophenol with POCI3 and diethylanilinef l. 

C-allylation of PhO" Na with H2C=CHCH2C1 in a variety of solvents in the presence of different crown ethers is most effective in each case when using poly(vinylbenzo-15-crown-5)polyether. Only in the presence of the crown ethers 15-crown-5 and 18-crown-6 are the anions in potassium phthalimide and sodium saccharinate, respectively, sufficiently activated to bring about nucleophilic aromatic substitution of the 4-fluorine in pentafluoropyridine. The formation of 2,4-dinitrophenol, in addition to the expected ether, from 2,4-dinitrochlorobenzene and potassium 2-propoxide in 2-propanol-benzene (1 1), in the presence of dicyclohexyl-18-crown-6 polyether, has been accounted for on the basis of a nucleophile-radical reaction (5rn1)/ ... 

VNS hydroxylation of nitroarenes with alkylhydroperoxides proceeds according to mechanism similar to that of the reaction with a-halocarbanions— reversible nucleophiUc addition, followed by the base-induced p-ehmination of alcohols from the intermediate a"-adducts. These mechanistic features were established by detramination of effects of base on the rate of the reaction, namely, on the competition between VNS hydroxylation and S Ar of chlorine in 4-chloronitrobenzene and 2,4-dinitrochlorobenzene. For instance, the reaction of these hydropaoxides with 2,4-dinitrochlorobenzene carried out in the presence of an excess of f-BuOK proceeds exclusively as VNS to give 2,4-dinitro-5-chlorophenol, whereas in the presence of equimolar amount of f-BuOK substantial quantity of 2,4-dinitrophenol, product of S,.jAr is formed (Scheme 11.43) [66]. 

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