Picric acid preparation

It should, however, be remembered that commercial picric acid prepared by this method contains lower nitrated phenols. To obtain a chemically pure product, commercial picric acid should be subjected to additional nitration (Arundal, Davies and ICI Ltd. [4]). 

CfiHsNjOs. Red needles m.p. 168-169°C. Soluble in dilute acids and alkalis. Prepared by reduction of picric acid with sodium hydrogen sulphide, ft is used for the preparation of azodyes, which can be after-chromed by treatment with metallic salts owing to the presence of a hydroxyl group ortho to the amino-group. 

It is prepared by the direct nitration of toluene with a mixture of nitric and sulphuric acids. TNT is a very stable, violent and powerful high explosive, but less sensitive to shock and friction than picric acid. It is widely used as a filling for shells, bombs, etc. often mixed with ammonium nitrate and other high explosives. The lower grades of TNT may contain isomers which under hot storage conditions may give rise to exudation. 

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... 

Picrates, Many aromatic hydrocarbons (and other classes of organic compounds) form molecular compounds with picric acid, for example, naphthalene picrate CioHg.CgH2(N02)30H. Some picrates, e.g., anthracene picrate, are so unstable as to be decomposed by many, particularly hydroxylic, solvents they therefore cannot be easily recrystaUised. Their preparation may be accomplished in such non-hydroxylic solvents as chloroform, benzene or ether. The picrates of hydrocarbons can be readily separated into their constituents by warming with dilute ammonia solution and filtering (if the hydrocarbon is a solid) through a moist filter paper. The filtrate contains the picric acid as the ammonium salt, and the hydrocarbon is left on the filter paper. 

The foUowing are typical experimental details for the preparation of naphthalene picrate. Dissolve 0 -1 g. of naphthalene and 0-2 g. of picric acid separately in the minimum volume of hot rectified spirit (about 2 ml.), mix the solutions and allow to cool. FUter and wash with 2 ml. of alcohol. RecrystaUise from hot alcohol, ethyl acetate or ether. 

Picric acid, the 2 4 6-trinitro derivative of phenol, cannot be prepared in good yield by the action of nitric acid upon phenol since much of the latter is destroyed by oxidation and resinous products are also formed. It is more convenient to heat the phenol with concentrated sulphuric acid whereby a mixture of o- and p-phenolsulphonic acids is obtained upon treatment of the mixture with concentrated nitric acid, nitration occurs at the two positicsis mela to the —SOjH group in each compound, and finally, since sulphonation is reversible, the acid groups are replaced by a third iiitro group yielding picric acid in both cases ... 

Dissolve 0 01 mol of the phenohc ether in 10 ml. of warm chloroform, and also (separately) 0 01 mol of picric acid plus 5 per cent, excess (0 -241 g.) in 10 ml. of chloroform. Stir the picric acid solution and pour in the solution of the phenohc ether. Set the mixture aside in a 100 mb beaker and ahow it to crystallise. Recrystahise the picrate from the minimum volume of chloroform. In most cases equahy satisfactory results may be obtained by conducting the preparation in rectified spirit (95 per cent. CjHgOH). The m.p. should be determined immediately after recrystallisation. It must be pointed out, however, that the picrates of aromatic ethers suflFer from the disadvantage of being comparatively unstable and may undergo decomposition during recrystaUisation. 

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). 

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. 

Sowinski M. Warman, Lead Salts of Trinitro Phenols. I. Preparation and Properties of Methoxy Picric Acid and Lead Methoxy Picrate , PATR 3344(1966)... 

Some of the authors had drawn attention to the expl character of Picric Acid salts, but it was not until 1830 that Welter (Ref 3) suggested the possibility of using picrates as expls. At that time Picric Acid was prepared solely by the action of nitric acid on indigo. Marchand (Ref 6) expressed the view, which proved to be true, that it was aniline, formed as an intermediate product in the process of decompn of indigo, silk and other organic matter, that yielded Picric Acid under the influence of nitric acid... 

The phenols are as easily sulphonated as are the aromatic amines. When polynitrophenols have to be prepared, sulphonic groups are often first introduced and are then easily eliminated and replaced by N02 by the action of nitric add. This method is used, for example, in preparing picric acid. 

Picric acid was one of the first explosives to have been prepared (in 1758, by nitrating wool). It was also used as a dye because of its bright yellow color. 

To obtain tissue preparations whose constituents were maintained as closely as possible to their state in vivo, the material had to be fixed, i.e. the enzymes inactivated so that cell structures were instantaneously preserved, an almost unattainable ideal. Formalin was the favored fixative, but others (e.g. picric acid), were also employed. Different methods of fixation caused sections to have different appearances. Further artifacts were introduced because of the need to dehydrate the preparations so that they could be stained by dyes, many of which were lipid-soluble organic molecules. Paraffin wax was used to impregnate the fixed, dehydrated material. The block of tissue was then sectioned, originally by hand with a cut-throat razor, and later by a mechanical microtome. The sections were stained and mounted in balsam for examination. Hematoxylin (basophilic) and eosin (acidophilic) (H and E staining) were the commonest stains, giving blue nuclei and pink cytoplasm. Eosinophils in the blood were recognized in this way. 

Methanol is one of the easy solvents to work with using the electric-field-jump technique. The preparation of the solvent is not nearly as arduous as is that of some other solvents such as acetonitrile. In methanol we observed that picric acid anion protonates at the diffusion controlled rate whereas dipicryl-amine sterically hinders the proton from recombining with it. 

Uses Organic synthesis photographic agent manufacture of pesticides, herbicides, explosives, and wood preservatives yellow dyes preparation of picric acid and diaminophenol (photographic developer) indicator analytical reagent for potassium and ammonium ions insecticide. 

Uses Antiseptic and disinfectant pharmaceuticals dyes indicators slimicide phenolic resins epoxy resins (bisphenol-A) nylon-6 (caprolactum) 2,4-D solvent for refining lubricating oils preparation of adipic acid, salicylic acid, phenolphthalein, pentachlorophenol, acetophenetidin, picric acid, anisole, phenoxyacetic acid, phenyl benzoate, 2-phenolsulfonic acid, 4-phenolsulfonic acid, 2-nitrophenol, 4-nitrophenol, 2,4,6-tribromophenol, 4-bromophenol, 4-/ert-butylphenol, salicylaldehyde, and many other organic compounds germicidal paints laboratory reagent. 

Nowadays picric acid is prepared by treating phenol first with concentrated sulphuric acid which converts it to phenol-2,4-disulphonic acid, and then with concentrated nitric acid to get 2,4,6-trinitrophenol. Can you write the equations of the reactions invoived ... 

Trinitrochlorobenzene (picryl chloride) (87) can be prepared from the nitration of 2,4-dinitrochlorobenzene with nitronium tetrafluoroborate or mixed acid composed of fuming nitric acid and oleum. Picryl chloride is also synthesized from the reaction of phosphorous oxychloride with the pyridinium salt of picric acid. ... 

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. 

Tissue Preparation for Electron Microscopy. Tissues were fixed in 2% paraformaldehyde, 2.5% glutaraldehyde in phosphate buffer (0.1 M, pH 7.4) and 0.02% picric acid. They were then dehydrated in glycol methacrylate monomer and embedded in glycol methacrylate (GMA) (24). 

Heraklin (Ger). An expl patented by Dickerhoff, was prepared by soaking sawdust in a coned aqueous soln of equal parts of Picric Acid Amm nitrate. The resulting product waS dried and mixed with various amts of pulverized sulfur and K or Na nitrate Refs 1) Gody (1907), 551 2) PATR 2510, (1958), Ger 88-1... 

In an earlier investigation by the authors (2) (3-cyclodextrin complexes with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) capped with picric acid, (I), were prepared that formed complexes with nucleic acids and were used in gene therapy. 

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