2.3.6- Trinitrophenol

If phenol is heated with more concentrated nitric add (in the presence of sulphuric acid), nitration occurs ultimately at the para and at both the ortho positions, giving picric acid or 2,4,6-trinitrophenol. To prepare picric acid, however, it is more convenient first to heat the phenol with sulphuric acid, whereby a mixture of 0- and p-phenol sulphonic acids is readily obtained. If this mixture is now heated with concentrated nitric acid, nitration occurs at the... 

Picric Acid and Ammonium Picrate. Picric acid (PA) (2,4,6,-trinitrophenol) was the first modem high explosive to be used extensively as a burster ia gun projectiles. It was first obtained by nitration of iadigo, and used primarily as a fast dye for silk and wool. It offered many advantages when compressed, it was used as a booster for other explosives, and when cast (melting poiat 122.5°C) served as a burster ia shell it was stable, iasensitive, nonhygroscopic, relatively nontoxic, and of high density when cast, and could be made economically by simple nitration. 

The compound can be prepared from 2,4,6-trinitrophenol (picric acid [88-89-1]) by reduction with sodium hydrosulfide (163), with ammonia —hydrogen sulfide followed by acetic acid neutralization of the ammonium salt (164), with ethanolic hydrazine and copper (165), or electrolyticaHy with vanadium sulfate in alcoholic sulfuric acid (159). Heating 4,6-dinitro-2-benzamidophenol in concentrated HQ. at 140°C also yields picramic acid (166). 

Reaction with cold nitric acid results primarily ia the formation of 5-nitrosahcyhc acid [96-97-9]. However, reaction with fuming nitric acid results ia decarboxylation as well as the formation of 2,4,6-trinitrophenol [88-89-1] (picric acid). Sulfonation with chlorosulfonic acid at 160°C yields 5-sulfosahcyhc acid [56507-30-3]. At higher temperatures (180°C) and with an excess of chlorosulfonic acid, 3,5-disulfosahcyhc acid forms. Sulfonation with hquid sulfur trioxide ia tetrachloroethylene leads to a nearly quantitative yield of 5-sulfosahcylc acid (1). 

Trimethyl benzene 2.4.6- Trinitrophenol, see Picric acid 2.4.6- Trinitrophenyl-methylnitramine, see Tetryl CT... 

Dipping solution Dissolve 100 mg picric acid (2,4,6-trinitrophenol) in 36 ml acetic acid (96%) and carefully add 6 ml perchloric acid (70%). 

Multiple substitution by strongly electron-withdrawing groups greatly increases the acidity of phenols, as the pK values for 2,4-dinitrophenol (4.0) and 2,4,6-trinitrophenol (0.4) in Table 24.2 attest. 

As we ve seen, aromatic substitution reactions usually occur by an electrophilic mechanism. Aryl halides that have electron-withdrawing substituents, however, can also undergo nucleophilic aromatic substitution. For example. 2,4,6-trinitrochlorobenzene reacts with aqueous NaOH at room temperature to give 2,4,6-trinitrophenol. The nucleophile OH- has substituted for Cl-. 

Historically, the outbreak of the first World War provided a stimulus for the industrial preparation of large amounts of synthetic phenol, which was needed as a raw material to manufacture the explosive picric acid (2,4,6-trinitrophenol). Today, more than 2 million tons of phenol is manufactured each year in the United States for use in such products as Bakelite resin and adhesives for binding plywood. 

Details have been collected for the determination of some 50 elements by this technique21,22 and it is possible to effect many difficult separations, such as Cu and Bi, Cd and Zn, Ni and Co it has been widely used in the nuclear energy industry. A number of organic compounds can also be determined by this procedure, e.g. trichloroacetic acid and 2,4,6-trinitrophenol are reduced at a mercury cathode in accordance with the equations... 

Picric Acid (PA listed as 2,4,6-Trinitrophenol in C A since 1972 Melinite in Fr Melinit in Russ, Lyddit in Engl Granatfullung or Sprengkorper 88 in Ger Pertit in Ital Hcrinit in Span, Ekrasit in Austr TNF in Pol Shimoza in Jap)... 

Trinitrophenol is degraded in a reaction involving ring reduction by hydride transfer from an NADPH-dependent F420 reductase (Hofmann et al. 2004). 

---