Picric acid structure

Picric acid, synthesis of, 628 Pinacol rearrangement, 646 Pineapple, esters in, 808 Piperidine, molecular model of, 939 structure of. 918 P1TC, see Phenylisothiocyanate, 1031-1032... 

Alkali fusion of the metabolite furnished p-hydroxybenzoic acid in good yield as the only isolable product. Vigorous nitric acid oxidation of M gave a high yield of picric acid. Both degradation products must have arisen from the same site, which can be represented by part structure V. While positions 3 and 5 are probably unsubstituted, the vigorous nature of the degradations allows that those at 2 and 6 could bear carbon atoms. 

Just as a multiplicity of hydroxyl groups is normally related to sweetness, multiple nitro groups and the sulfur atom in the —S—S— or —C=S— linkage have been associated with bitter taste. Thus, it was obseiwed that a compound containing three nitro groups, such as picric acid, is usually bitter, and that those with two nitro group may be bitter. Compounds having structure A are also frequently bitter, and it was deduced that the bitterness of the acyl-thiocarbamide class of compounds is due to structure B. 

We have mentioned above the prevalence of chromoisomeric effects in two-component systems forming solid charge-transfer complexes. This was studied first by Hertel (120) and labeled by him complex isomerism. In a system such as picric acid with an aromatic amine, there are a variety of structural possibilities. There will probably be intermolecular hydrogen bonds, which are associated with short lateral contacts between the near-planar molecules. In addition, there... 

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. 

Picric acid (trinitrophenol) and trinitroresorcinol, when added to fixative solutions, give greater fine structural preservation of cells (11,12). These compounds cause coagulation of proteins by forming salts with positively charged groups of proteins (11). The protein precipitates that form retain their antigenicity (3). Picric acid or trinitroresorcinol are most often added to formalde-... 

The chemical structures of some common mifttary explosives are shown in Figure 1. These include the nitrate esters such as nitrocellulose (NC), NG, EGDN, and (PETN) nitroarenes such as trinitrotoluene (TNT, CH3—C6H2(N02)3), picric acid (HO—C5H2(N02)3), and 2,4,6-trinitrophenylmethylnitramine (tetryl) and nitramines such as RDX (C3H6N6O6), HMX (C4H8N8O8), and hexanitrohexa-azaisowurtzitane (CL— 20). Of these, only CL— 20 is new , that is, less than 50 years old [3]. Mixtures of oxidizers and fuels, such as AN and FO (called ANFO), are also secondary explosives. 

In the dihydrochloride (602), the second molecule of acid is not firmly bound because of protonation of the second basic site by internal hydrogen bond formation. This would suggest that in the dipicrate, one mole of picric acid participates in salt formation, and that the second mole of picric acid is added to the hydrogen-bonded cation (LXI) forming a molecular complex. The existence of a monopicrate might thus serve to point out structures with steric inhibition of hydrogen bonding. 

The two starting components were packed into a glass capillary from opposite ends until they met in the centre. A coloured reaction product was observed visually after 7 to 10 min at the reactant interface. As time progressed, the product interface was observed to advance in the direction of the picric acid reactant. Further study of this reaction supported a vapour diffusion mechanism, bolstered in part by the observation that complexation proceeds even if a small gap of space exists between the two reactants [12]. The nature of the complex was investigated in additional work, whereby it was proposed that a donor/acceptor 71-complex was produced [13]. A crystal structure confirming this deduction was later published [14]. 

It is not customary to attempt the isolation of ketone or aldehyde intermediates (121) the formula serves merely as a reminder that once hydrolysis of the protecting enol ether or acetal occurs, the same type of structure is formed from any given dicarbonyl compound. Cyclization has been carried out in refluxing ethanolic picric acid or acetic anhydride with a few drops of sulfuric acid, but Hansen and Amstutz (63JOC393) offered excellent theoretical reasons for avoiding an excess of acid, and reported that best results (Table 3) can be obtained by refluxing the dry hydrobromide in acetic anhydride containing no sulfuric acid. 

Werner [10] suggested that, on heating, urea tautomerizes to the pseudourea structure which, on reaction with methyl sulfate, allows the isolation of 2-methylpseudourea (Eq. 22). The product was difficult to crystallize and it was isolated as the picric acid derivative. 

An explosive called tetryl was also being developed at the same time as picric acid. Tetryl was first prepared in 1877 by Mertens and its structure established by Romburgh in 1883. Tetryl (1.3) was used as an explosive in 1906, and in the early part of this century it was frequently used as the base charge of blasting caps. 

Around 1902 the Germans and British had experimented with trinitrotoluene [(TNT) (C7H5N306)], first prepared by Wilbrand in 1863. The first detailed study of the preparation of 2,4,6-trinitrotoluene was by Beilstein and Kuhlberh in 1870, when they discovered the isomer 2,4,5-trinitrotoluene. Pure 2,4,6-trinitrotoluene was prepared in 1880 by Hepp and its structure established in 1883 by Claus and Becker. The manufacture of TNT began in Germany in 1891 and in 1899 aluminium was mixed with TNT to produce an explosive composition. In 1902, TNT was adopted for use by the German Army replacing picric acid, and in 1912 the US Army also started to use TNT. By 1914, TNT (1.4) became the standard explosive for all armies during World War I. 

Herbstein, F. H., Marsh, R. E., Crystal-Structures of Trimesic acid, its hydrates and complexes. 2. trimesic acid monohy-drate-2/9 picric acid and trimesic acid 5/6 hydrate. Acta Crystallogr. Sect. B-Struct. Commun. 1977, 33, 2358-2367. 

These dyes are now of only minor commercial importance, but are of interest for their small molecular structures. The early nitro dyes were acid dyes used for dyeing natural animal fibers such as wool and silk. They are nitro derivatives of phenols, e.g., picric acid (4) or naphthols, e.g., C.I. Acid Yellow 1, 10316 [846-70-8] (5). 

Because of its high acidity picric acid exists in dilute sodium hydroxide solution as the picrate ion (Aroax, 3600 A). As the concentration of sodium hydroxide is increased, this absorption is gradually replaced by a more intense band (Araax, 3900 A) which has been attributed by Abe (1960) to 33. Gold and Rochester (1964f) found that the extent of conversion of the picrate ion to complex depends on a high power of base concentration, suggesting that the interaction probably involves more than one hydroxide ion. Evidence that this is the case and that the structure of the complex is in fact 34 has recently been obtained from... 

The safety limit of temperature depends on the chemical structure of the compound being nitrated. For exMnple, in the nitration of dinitrotoluene to trinitrotoluene or of phenol to picric acid, temperatures neM 120°C Mid over are considered dangerous. In the nitration of dimethylaniline to tetiyl, a temperature higher than 80°C must be considered dangerous. Esterification with nitric acid should be carried out at a temperature close to room temperature or lower. 

The structure of the 1,2,6-isomer has been determined by Ostromyslenskii [11] from the following reactions leading to picric acid ... 

Trlnitrophenors more common name, picric acid, reflects the strong acidity of this compound (pKa 0.7 compared to phenol s 10.0). Picric acid used to be used in the dyeing industry but is little used now because it is also a powerful explosive (compare its structure with that of TTUTi). 

A first requirement for a substance to produce a taste is that it be water soluble. The relationship between the chemical structure of a compound and its taste is more easily established than that between structure and smell. In general, all acid substances are sour. Sodium chloride and other salts are salty, but as constituent atoms get bigger, a bitter taste develops. Potassium bromide is both salty and bitter, and potassium iodide is predominantly bitter. Sweetness is a property of sugars and related compounds but also of lead acetate, beryllium salts, and many other substances such as the artificial sweeteners saccharin and cyclamate. Bitterness is exhibited by alkaloids such as quinine, picric acid, and heavy metal salts. 

The structures of haplophytine and cimicidine are still obscure in a recent investigation of the constituents of H. cimicidum, five additional bases were isolated, but no further data concerning haplophytine and cimicidine were reported (5). The additional bases include the two epimers eburnamine (II R = a-OH) and isoeburnamine (II R = jS-OH), which are characteristic alkaloids of Hunteria eburnea Pichon, and O-methyleburnamine (II R = a-OMe). The constitution of this last base was established by its conversion by boiling alcoholic picric acid into the picrate of eburnamenine (HI), and by its oxidation with chromic oxide in pyridine to the lactam eburnamonine (II R = =0). Two new bases were also isolated, namely, haplocine and haplocidine. 

Fig. 1.3 Molecular structures of picric acid (PA), tetryl, trinitrotoluene (TNT), Nitroguanidine (NQ), pentaerythritol tetranitrate (PETN), hexogen (RDX), octogen (HMX), hexanitrostilbene (HNS) and triaminotrinitrobenzene (TATB).

Conductometric and spectrophotometric behavior of several electrolytes in binary mixtures of sulfolane with water, methanol, ethanol, and tert-butanol was studied. In water-sulfolane, ionic Walden products are discussed in terms of solvent structural effects and ion-solvent interactions. In these mixtures alkali chlorides and hydrochloric acid show ionic association despite the high value of dielectric constants. Association of LiCl, very high in sulfolane, decreases when methanol is added although the dielectric constant decreases. Picric acid in ethanol-sulfolane and tert-butanol-sulfolane behaves similarly. These findings were interpreted by assuming that ionic association is mainly affected by solute-solvent interactions rather than by electrostatics. Hydrochloric and picric acids in sulfolane form complex species HCl and Pi(HPi). ... 

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