2.4- Dinitrophenol preparation

Dry dinitrophenol prepared by hydrolysis of chlorodinitrobenzene usually melts at 110-111 °C. Its impurities come from the chlorodinitrobenzene, which may contain unhydrolysed admixtures (such as m- chloronitrobenzene, dichlorodinitro-benzene isomers, m- dinitrobenzene). 

Picric acid is produced either by nitrating phenol or by nitrating dinitrophenol prepared by hydrolysis of chlorodinitrobenzene. 

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. 

Dinitrophenol may be readily prepared by taking advantage of the great reactivity of the chlorine atom in 2 4-dinitro-l-chlorobenzene ... 

Peroxyoxalate chemiluminescence is the most efficient nonenzymatic chemiluminescent reaction known. Quantum efficiencies as high as 22—27% have been reported for oxalate esters prepared from 2,4,6-trichlorophenol, 2,4-dinitrophenol, and 3-trif1uoromethy1-4-nitropheno1 (6,76,77) with the duorescers mbrene [517-51-1] (78,79) or 5,12-bis(phenylethynyl)naphthacene [18826-29-4] (79). For most reactions, however, a quantum efficiency of 4% or less is more common with many in the range of lO " to 10 ein/mol (80). The inefficiency in the chemiexcitation process undoubtedly arises from the transfer of energy of the activated peroxyoxalate to the duorescer. The inefficiency in the CIEEL sequence derives from multiple side reactions available to the reactive intermediates in competition with the excited state producing back-electron transfer process. 

Sulfur dyes are used for dyeing ceUulosic fibers. They are insoluble in water and are reduced to the water-soluble leuco form for appHcation to the substrate by using sodium sulfide solution. The sulfur dye proper is then formed within the fiber pores by atmospheric oxidation (5). Sulfur dyes constitute an important class of dye for producing cost-effective tertiary shades, especially black, on ceUulosic fibers. One of the most important dyes is Cl Sulfur Black 1 [1326-82-5] (Cl 53185), prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

C6H2(N02)30H (NH SaQs C02+HN03+HCN When mildly reduced, for example with Na sulfide or hydrosulfite or with ferrous sulfate, PA is converted into picramic acid, a very useful intermediate in the dyestuffs industry and a starting material for the preparation of Diazo-dinitrophenol, a primary expl (see Vol 2, B59-L). Stronger reduction may lead to the formation of triamino phenol... 

VII. Preparation. There are two industrial methods of manufg PA 1) nitration of Phenol 2) nitration of dinitrophenol prepd by hydrolysis of chloro dinitrobenzene... 

The exothermicity and violence of the reaction of hydrazine hydrate with 1-chloro-2,4-dinitrophenol caused destruction of the reactor in which the reaction was carried out. This reaction is of the same kind as the previous one (2,4-dinitrophenylhydrazine preparation). 

The manufacture of sulfur dyes involves sulfurisation processes, the chemistry of which remains rather mysterious and may arguably be considered still to be in the realms of alchemy The processes involve heating elemental sulfur or sodium polysulfide, or both, with aromatic amines, phenols or aminophenols. These reactions may be carried out either as a dry bake process at temperatures between 180 and 350 °C or in solvents such as water or aliphatic alcohols at reflux or at even higher temperatures under pressure. C. I. Sulphur Black 1, for example, is prepared by heating 2,4-dinitrophenol with sodium polysulfide. 

Recently a new ring system, 2-oxa-4,10-diazaadamantane, was prepared as its derivatives from 2,4-dinitrophenol (217).241 2,4-Diacetylaminophenol (218) is reduced to the cyclohexane derivative (219), which is cyclized either... 

The a- and /3-cyclodextrins have been found to accelerate the Smiles rearrangement of 4-nitrophenyl salicylate. The reaction of 2,4-dinitrobenzenesulfonamide with acyl chlorides in the presence of excess triethylamine has been found to produce the corresponding nitrile in good yield. Mechanistic studies have indicated that the reaction proceeds via a Smiles rearrangement of the initially formed iV-(2,4-dinitrobenzenesulfonyl)amide to form the nitrile, 2,4-dinitrophenol, and sulfur dioxide (see Scheme 12). l-Chloro-3-fluorophenothiazines have been prepared by Smiles rearrangement of 3-chloro-5-fluoro-2-formamido-2 -nitrophenyl sulfides in alcoholic... 

The function of an immuno-electrode [28] containing a model antibody (Concanavalin A) fixed in a polymeric film on a platinum electrode is probably based on other effects than those utilized in ISEs. Immuno-electrodes suitable for direct determination of antibodies were prepared by fixing a conjugate of an ionophore and an immunogen (for example the compound of dibenzo-18-crown-6 with dinitrophenol) in a PVC membrane. This system responded to the antibody against dinitrophenol [52, 53]. 

Diazo-4,6-dinitrophenol (DDNP or DINOL) (53) can be prepared from the diazotization of 2-amino-4,6-dinitrophenol (52) (picramic acid) with nitrous acid " the latter is obtained from the selective reduction of picric acid with ammonium sulfide." 2-Diazo-4,6-dinitrophenol (53) is widely used as an initiating charge in detonators and caps. 

Amino-4-nitrophenol has been prepared by the partial reduction of 2,4-dinitrophenol chemically -6 and electrolytically,6 and by the action of sulfuric add on 3-nitroazidobenzene.7... 

Preparation of Picric Acid (Catalytic Process). Two hundred grams of benzene in a 2-liter round-bottom flask equipped with a sealed-on condenser is refluxed on the sand bath for 7 hours with 600 cc. of nitric acid (d. 1.42) in which 10 grams of mercuric nitrate has been dissolved. The material is then transferred to another flask and distilled with steam. Benzene comes over, then nitrobenzene, then finally and slowly a mixture of dinitrobenzene and dinitrophenol. The distillation is continued until all volatile matter has been removed. The liquid in the flask is filtered hot and allowed to crystallize. If the picric acid is not sufficiently pure, it is recrystallized from hot water. 

Cognate preparation. Reduction of 2,4-dinitrophenol. It is an interesting student exercise to carry out the reduction of 2,4-dinitrophenol under the conditions described above for m-dinitrobenzene. The spectroscopic features of the isolated and purified product, together with the melting point, in comparison with the literature values for the possible isomers, should enable a deduction to be made on the regioselectivity of the reaction. 

Mode of Action of Dicyclohexylcarbodiimide (DCCD) When DCCD is added to a suspension of tightly coupled, actively respiring mitochondria, the rate of electron transfer (measured by 02 consumption) and the rate of ATP production dramatically decrease. If a solution of 2,4-dinitrophenol is now added to the preparation, 02 consumption returns to normal but ATP production remains inhibited. 

Chemical properties. A chlorine atom ortho or para to a nitro group is especially reactive and is readily substituted. Numerous examples of such reactions, utilized in the preparation of explosives, are given later in the descriptions of preparation methods for dinitrophenol, dinitroanisole, hexanitrodiphenylamine, hexanitro-diphenyl sulphone, dinitroaniline, tetryl, etc. Chlorodinitrobenzene reacts with sodium sulphide and sulphur to yield sulphur dyes. The action of sodium disulphide results in the formation of tetranitrodiphenyl sulphide (p. 554). 

Laurent [8] was the first to obtain dinitrophenol by nitrating phenol. Investigations that followed revealed that Laurent s dinitrophenol was not a chemical individual, but a mixture of the 2,4- and 2,6-isomers. Kiimer [ 17] obtained pure 2,4-dinitrophenol by the nitration of p- nitrophenol and Armstrong [ 18] prepared... 

Hydrolysis of chloronitro compounds. The chlorine atom in chlorobenzene and in its homologues becomes reactive after one or more nitro groups have been introduced into the ring. This is used widely in the preparation of nitrophenols and their ethers. The preparation of dinitrophenol, dinitroanisole and dinitro-phenetole may serve as a classical example (see Chapter XVI). 

Oxidation of nitrosophenols. This method is applied when fewer nitro groups are to be introduced on the ring than those obtained by way of nitration. It is also applied when a pure product, free from its isomers, is to be prepared, e.g. p- nitro-phenol from phenol. Direct nitration of phenol yields a mixture of the o- and p- isomers, dinitrophenol being readily formed as a by-product. Similarly dinitroresorcinol may be obtained by oxidation of dinitrosoresorcinol (p. 537). 

A product of still higher purity may be prepared by washing with sulphuric acid. 100 parts of dinitrophenol and 120 parts of sulphuric acid (sp. gr. 1.84) are agitated for 12 hr at room temperature. Then the sulphuric acid is filtered off and the dinitrophenol is washed with a small quantity of fresh sulphuric acid and finally several times with water. In this way the melting point of the product can be raised to 108.5°C. 

The product thus obtained may be blended with dinitrophenol for the preparation of picric acid. 

This is the most modem industrial method for the preparation of picric acid from chlorobenzene via chlorodinitrobenzene (for preparation of dinitrophcnol from chlorodinitrobenzene, see p. 484). The nitration of dinitrophenol to picric acid is carried out by conventional methods, using nitrating mixtures containing some 0-5% of water. 

Nowadays 2,4-dinitroaniline is prepared on a large scale by treating chloro-dinitrobenzene with ammonia. The method was first reported by Engelhardt and Lachinov [9] in 1870. Heating 2,4-dinitrophenol with an excess of urea at 208°C... 

Addition of DCCD (dicyclohexylcarbodiimide) to mitochondrial preparations decreases the rates of both ATP synthesis and electron transport. Only the latter process can be restored to normal levels upon addition of 2,4-dinitrophenol. How can these observations be explained ... 

---