Picramic acid

Picramic acid or 4,6-dinitro-2-aminophenol (m. p. 169-179°C) forms dark red crystals, readily soluble in benzene and acetic acid, but difficult to dissolve in other organic solvents. 

The compound is prepared by reacting sodium sulphide with picric acid (Girard [44]). It is of some importance as an intermediate in the manufacture of azo dyes. It has not found any use as an explosive, being none the less a source for the initiating explosive dinitrodiazophenol (Vol. III). 

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Amino-4,6-dinitrophenol. This derivative (10), also known as picramic acid, forms dark red needles from ethanol and prisms from... 

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). 

The first synthetic dyestuff, mauveine, was discovered by Perkin in 1856 in the UK and led to many investigations of the derivatives of coal tar as potential coloring matters. The first dia2onium salt derived from picramic acid was prepared in 1858 and is still the basic chemistry behind coundess commercial products. Despite these inventions, in 1900 the vast majority of dyestuffs were still of natural origin. Now at the end of the century the situation has changed dramatically synthetic dyes dominate. 

Picramates. Salts of Picramic Acid. See in Vol 1, A242-Lto A243-L... 

Picramic Acid. See under 4,6-Dimtro-2-amino-phenol in Vol 1, A241-R... 

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... 

The fact that practically all aromatic amines are readily converted into diazo compounds contributed greatly to Griess s success. The original method (Griess, 1858) by which he diazotized picramic acid (1.1 see Scheme 1-1) consisted of passing nitrous gases, prepared by the reduction of nitric acid with starch or arsenious acid, into an alcoholic solution of the amine. 

Originally prepared in 1858 by Griess, it is made by diazotising picramic acid with sodium nitrite and hydrochloric acid according to the following reaction ... 

This partially reduced derivative of picric acid, picramic acid , explodes very powerfully when dry. 

Shortly after Perkin had produced the first commercially successful dyestuff, a discovery was made which led to what is now the dominant chemical class of dyestuffs, the azo dyes. This development stemmed from the work of Peter Griess, who in 1858 passed nitrous fumes (which correspond to the formula N203) into a cold alcoholic solution of 2-aminO 4,6 dinitrophenol (picramic acid) and isolated a cationic product, the properties of which showed it to be a member of a new class of compounds [1]. Griess extended his investigations to other primary aromatic amines and showed his reaction to be generally applicable. He named the products diazo compounds and the reaction came to be known as the diazotisation reaction. This reaction can be represented most simply by Scheme 4.1, in which HX stands for a strong monobasic acid and Ar is any aromatic or heteroaromatic nucleus. 

Cl Sulphur Black 1, which is produced from the relatively simple intermediate 2,4-dinitrophenol and aqueous sodium polysulphide. A similar product (Cl Sulphur Black 2) is obtained from a mixture of 2,4-dinitrophenol and either picric acid (6.148 X = N02) or picramic acid (6.148 X = NH2). A black dye possessing superior fastness to chlorine when on the fibre (Cl Sulphur Black 11) can be made from the naphthalene intermediate 6.149 by heating it in a solution of sodium polysulphide in butanol. An equivalent reaction using the carbazole intermediate 6.150 gives rise to the reddish blue Cl Vat Blue 43 (Hydron blue). This important compound, which also possesses superior fastness properties, is classified as a sulphurised vat dye because it is normally applied from an alkaline sodium dithionite bath. Interestingly, inclusion of copper(II) sulphate in the sulphurisation of intermediate 6.150 leads to the formation of the bluish black Cl Sulphur Black 4. 

Korenman, Yak, Nefedova, T.E., andByukova, R.I. Extraction of picramic acid, Int.J. Pharmacol. Ther. Toxicol, 51 734-735, 1977. 

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. 

Hydrcxyaminobenzene. See Aminophenol in Vol, pp A241-L to A244-R. Its expl derivs 1-Hydroxy-2-amino-4,6-dinitrobenzene or Picramic Acid and 1-Hydroxy-4-amino-2,6-dinitrobenzene or Isopicramic Acid are on pp A241-R A243-R... 

Dinitro-2-hydroxybenzenearsonic Acid, yel ndls (from w), mp 244—46° prepd by diazo-tizing picramic acid with Na arsonite in ale soln forms crysts amorph salts (Ref 1)... 

Phosgene Phosphorus Picramic acid Picric acid... 

Glacial acetic acid. Ammonium picramic acid Phenol, Sulfuric acid. Nitric acid. Water Aspirin, Sulfuric acid. Potassium nitrate. Alcohol Phenol, Sodium hydroxide. Sodium nitrite. Nitric acid Chlorobenzene, Potassium nitrate. Sulfuric acid. Acetone, Methanol... 

Picramic acid Picric acid Picric acid Picric acid Picryl chloride... 

Figure A. 138 Picramic acid secondary high explosive.

This substance was the first diazo compound to be discovered. It was prepared by Griess [11] by diazotizing picramic acid. Its explosive properties attracted the attention of Lenze [12] who found it to be as valuable as mercury fulminate in spite of its higher sensitiveness to impact. This compound is also of interest as being the first initiator containing no heavy metals. It has now been utilized in the United States of America and Japan as a component of initiating charges in detonators and caps. 

A solution of 320 g of sodium nitrite in 21. of water is added to a suspension of 1000 g of the sodium salt of picramic acid in 81. of water. Next, 61. of 5.5% hydrochloric acid is added dropwise for 2 hr, stirring continuously. The initial temperature of 20°C rises to 25°C. Completion of the reaction is determined by means of starch-iodide paper. The product is filtered off, washed with cold water and dried at 35-40°C. Its yield amounts to 80% of the theoretical. 

T. Urbanski, Szyc-Lewanska et al. [18] have recently found that dinitrobenzene-diazo-oxide can be prepared by oxidation of picramic acid with chromium trioxide in the presence of sulphuric acid at 55-60°C. One part of picramic acid is fully oxidized by chromic acid to yield gaseous products CO, C02, N02, NH3 and H20. Nitrogen dioxide acts further as a diazotizing agent on undecomposed picramic acid to yield the diazo compound. The yield of this reaction does not exceed 31% of theoretical calculated on the picramic acid used. 

Dinitro< 2>oniinophenol 2-Amino-4,6 dinitrophenol or Picramic Acid(PAA)... 

Chromiumbexammine Picramate or Rexam— minochromic Picramate, lCr(NH,) ](C H4QNj)aJ brn, amor ppt. Was prepd from hexammine-chromic hydroxide and picramic acid... 

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