Picric acid addition compounds

Complexes in Which the Acceptor Is an Organic Molecule. Picric acid, 1,3,5-trinitrobenzene, and similar polynitro compounds are the most important of these. Picric acid forms addition compounds with many aromatic hydro... 

Dry mixtures of picric acid and aluminium powder are inert, but addition of water causes ignition after a delay dependent upon the quantity added. Other nitro compounds and nitrates are discussed in this context. 

Data from the Griesheim factory [1] show that this may be avoided by adding other aromatic nitro compounds, e.g. TNT, to the picric acid. The addition of even a small amount (5-10%) of such a substance facilitates melting without seriously decreasing the explosive power of the picric acid. 

These mixtures found no practical application since picric acid gradually reacts with salts to form picrates with the evolution of free acid. The picrates so formed are highly sensitive to friction and impact, and the free acid acts corrosively. Mixtures with chlorates showed a particular sensitiveness to friction and impact, hence doubt was expressed as to their practical value. Nevertheless, the idea of completing the defective oxygen balance in aromatic nitro compounds by the addition of such oxidizing agents as nitrates was carried out in such a way as to produce mixtures useful for various practical purposes. 

In addition to aluminium, calcium silicide or ferro-silicon, the use of silicon was also recommended. The comparative figures illustrating the effect of the addition of these compounds on the strength of the explosive have been given by Sar-torius [70] (Table 59). The power is expressed in terms of expansion in the lead block (taking picric acid as 100). 

Hphe formation of molecular or addition compounds by organic sub-stances is well known, and many handbooks cite as an example the mixture of benzophenone and diphenylamine to produce a stable equi-molecular addition compound. Another example is the molecular compound formed by benzene and picric acid. This is stable only in the presence of an excess of picric acid. 

The ability to form addition compounds, especially with aromatic hydrocarbons composed of condensed rings, is one of the specific properties of aromatic poly-nitro compounds. For example, compounds of trinitrobenzene or picric acid with naphthalene, as well as with other hydrocarbons with condensed rings, are very characteristic. Generally they are intensely coloured. 

Molecular addition compounds are readily formed and decomposed, e.g. by acting with a suitable solvent, which would dissolve one of the components and extract it. For example addition compound formed between picric acid and a hydrocarbon can be split into its components by extracting the picric acid with alcohol while the hydrocarbon remains undissolved. Another fact also indicative of the instability of the addition products is that those of picric acid may be decomposed by treating their solutions with saturated solution of potassium chloride. Potassium picrate is then precipitated, while the other component remains in solution (Taben and Kosak [117]). Generally speaking, the organic addition compounds... 

The heat of formation in solution of the addition compound of picric acid and naphthalene determined by Bronsted [131], using e.m.f. measurements, was found to be 2.15 kcal/mole. Similar figures were obtained by cryometric measure... 

A detailed list of addition compounds formed by sym- trinitrobenzene, 2,4,6-trinitrotoluene, picric acid and other polynitro compounds is given in the appropriate paragraphs devoted to these nitro compounds. 

Jefremov and Khaibashev [60] have also investigated melts of TNT with other nitro compounds. They observed deep minima on the isotherms of plastic flow of mixtures of TNT and picric acid, trinitroxylene or 1,8-dinitronaphthalene. corresponding to eutectic mixtures. Unlike those the corresponding curves for mixtures of TNT and 2,4-dinitrotoluene, m- dinitrobenzene, and tetiyl, showed an additive character. 

The presence of nitro groups enhances the acidic properties of the phenol group. This is why the trinitro derivatives are also called acids, e.g. trinitrophenol is known as picric acid and trinitroresorcinol as styphnic acid. These compounds readily form salts with metals or bases. Polynitro derivatives of phenols also form addition compounds with hydrocarbons, e.g. naphthalene. 

Here are some of the addition compounds formed by picric acid combined with other substances in molecular proportion of 1 1 ... 

During World War I materials of this type were used fairly extensively, However, it has been proved that some of them can undergo hydrolysis, yielding free picric acid, thus rendering any further use of such explosives unjustifiable. In addition, most of the products have strongly toxic properties. Hence during World War II compounds of this type were used only on a small scale. 

Thiadiazoles are weak bases. They form readily hydrolyzable salts with mineral acids and addition compounds with heavy-metal salts. Amino-1,2,4-thiadiazoles also form salts with picric acid and picrolonic acid (65AHC(5)il9). 

Properties Addition of nitronaphthalene lowers the melting point of the picric acid and makes it safer for loading into shells by casting. The mixture becomes fluid at about 100°, Like picric acid, it forms sensitive compounds with some metals (zinc, lead). 

Such is the reaction described by Hakanson and Nielsen (25) of the oxidation of o-nitrotoluene with dilute (35%) nitric acid at 190 C to yield (30%) picric acid. On the contrary m- and p-nitrotoluenes yield m-and p nitrobenzoic acids. In addition to picric acid also nitro- and dinitrobenzoic and 3,3-dinitro-salicylic acids were formed. A large quantity of nitrogen was evolved and this led the authors to rationalize the reaction as passing through the formation of a diazo compound. 

Explosives, examination of finisheblack powder, 29 dinitrobenzene, 47 dinit rocdil or hydrin, 41 dinitroglycol, 40 industnal blasting explosives, 54 lead azide, 60 mercury fiilminate, 59 nitrated polysaccharides, 42 nitrocellulose, 32 nitro-compounds (additional), 48 nitroglycerine, 39 nitromannite, 43 nitronaphthaienes, 47 picric acid and picrates, 44 smokeless powders, 49 starch nitrate, 41... 

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