Primary explosives reactions

Pentaerythritol may be nitrated by a batch process at 15.25°C using concentrated nitric acid in a stainless steel vessel equipped with an agitator and cooling coils to keep the reaction temperature at 15—25°C. The PETN is precipitated in a jacketed diluter by adding sufficient water to the solution to reduce the acid concentration to about 30%. The crystals are vacuum filtered and washed with water followed by washes with water containing a small amount of sodium carbonate and then cold water. The water-wet PETN is dissolved in acetone containing a small amount of sodium carbonate at 50°C and reprecipitated with water the yield is about 95%. Impurities include pentaerythritol trinitrate, dipentaerythritol hexanitrate, and tripentaerythritol acetonitrate. Pentaerythritol tetranitrate is shipped wet in water—alcohol in packing similar to that used for primary explosives. 

The Ter Meer reaction has not been widely exploited for the synthesis of m-dinitroaliphatic compounds. This is partly because the Kaplan-Shechter oxidative nitration (Section 1.7) is more convenient, but also because of some more serious limitations. The first is the inability to synthesize internal em-dinitroaliphatic compounds functionality which shows high chemical stability and is found in many cyclic and caged energetic materials. Secondly, the em-nitronitronate salts formed in the Ter Meer reactions often need to be isolated to improve the yield and purity of the product. Dry em-nitronitronate salts are hazardous to handle and those from nitroalkanes like 1,1,4,4-tetranitrobutane are primary explosives which can explode even when wet. Even so, it is common to use conditions that lead to the precipitation of gem-nitronitronate salts from solution, a process that both drives the reaction to completion and also provides isolation and purification of the product salt by simple filtration. Purification of em-nitronitronate salts by filtration from the reaction liquors, followed by washing with methanol or ethanol to remove occluded impurities, has been used, although these salts should never be allowed to completely dry. 

Trinitrophenol (4), commonly known as picric acid (VOD 7350 m/s, d = 1.71 g/cm ), was once used as a military explosive although its highly acidic nature enables it to readily corrode metals. This kind of reaction has led to many fatal accidents, a consequence of some metal picrates being very sensitive primary explosives. The lead salt of picric acid is a dangerous explosive and should be avoided at all cost. In contrast, the ammonium (Explosive D, VOD 7050 m/s, d = 1.60 g/cm ) and guanidine salts of picric acid are unusually insensitive to impact and have been used in armour piercing munitions. 

Chemists at the Naval Air Warfare Center (NAWC), China Lake, have conducted much research into the nitration of various substituted anilines as an indirect route to highly nitrated arylene hydrocarbons (Section 4.5). On numerous occasions these chemists found that diazophenols are formed as by-products and sometimes as the main or only product of a reaction. During these studies the diazophenols (65) and (78-81) ° were isolated and characterized. These diazophenols were screened for use as explosive components of both percussion and stab-sensitive primary explosive compositions. ... 

The reaction of aminoguanidine with sodium nitrite under neutral conditions yields tetra-zolylguanyltetrazene hydrate (85), a primary explosive commonly known as tetrazene. Tetrazene (85) is only formed in the absence of free mineral acid and so a common method for its preparation treats the bicarbonate salt of aminoguanidine (84) with one equivalent of acetic acid followed by addition of aqueous sodium nitrite. " Tetrazene (85) is decomposed by aqueous alkali to form triazonitrosoaminoguanidine (86) which is isolated as the cuprate salt (87) on addition of copper acetate to the reaction mixture. Acidification of the copper salt (87) with mineral acid leads to the formation of 5-azidotetrazole (88) (CHN7 = 88 % N).55 56... 

The reaction of aminoguanidine bicarbonate (84) with sodium nitrite in the presence of excess acetic acid produces 1,3-ditetrazolyltriazine (89), another nitrogen-rich heterocycle (C2H3N11 = 85 % N) which readily forms explosive metal salts. The reaction of aminoguanidine bicarbonate (84) with sodium nitrite in the presence of mineral acid yields guanyl azide (90), of which, the perchlorate and picrate salts are primary explosives. Guanyl azide (90) reacts with sodium hydroxide to form sodium azide, whereas reaction with weak base or acid forms 5-aminotetrazole. ... 

High Explosives (HE). A high explosive is a substance that undergoes extremely rapid chemical reaction, when properly initiated, to produce gaseous products at high temperature and pressure. These products are then capable of doing useful work as they expand. It has been customary to divide HE into two categories primary explosives and secondary explosives. 

The net heat difference between the heats of formation of the reactants and products in a chemical reaction is termed the heat of reaction . For oxidation, this heat of reaction may be termed heat of combustion . The energy liberated when explosives deflagrate is called the heat of deflagration whereas the energy liberated on detonation of explosives is called the heat of detonation in kj mol"1 or the heat of explosion in kj kg"1. In primary explosives, which are used as initiators,... 

Primary explosives (also known as primary high explosives) differ from secondary explosives in that they undergo a very rapid transition from burning to detonation and have the ability to transmit the detonation to less sensitive explosives. Primary explosives will detonate when they are subjected to heat or shock. On detonation the molecules in the explosive dissociate and produce a tremendous amount of heat and/or shock. This will in turn initiate a second, more stable explosive. For these reasons, they are used in initiating devices. The reaction scheme for the decomposition of the primary explosive lead azide is given in Reaction 2.2. 

Secondary explosives (also known as high explosives) differ from primary explosives in that they cannot be detonated readily by heat or shock and are generally more powerful than primary explosives. Secondary explosives are less sensitive than primary explosives and can only be initiated to detonation by the shock produced by the explosion of a primary explosive. On initiation, the secondary explosive compositions dissociate almost instantaneously into other more stable components. An example of this is shown in Reaction 2.4. 

The same reaction occurs at lower temperatures 0.665% of a given portion of the material decomposes in 3 years at 20°, 2.43% in 1 year at 35°, 0.65% in 10 days at 50°, and 100% during 14 hours heating at 100°. The decomposition is not self-catalyzed. The product, hexanitrosobenzene, m.p. 159°, is stable, not hygroscopic, not a primary explosive, and is comparable to tetryl in its explosive properties. 

Ammonium nitrate will explode if the reaction is initiated by another primary explosive. Mixtures of NH4NO3 and TNT (2,4,6-trinitrotoluene) are known as AMATOL, a military explosive. Most ammonium salts can be decomposed by heating, but many solid compounds that contain the ammonium cation and an anion that is the conjugate of a weak acid decompose quite readily with only mild heating. Some examples are illustrated in the following equations ... 

Organic peroxides may be explosive. They are usually not manufactured for blasting purposes, but rather as catalysts for polymerization reactions. They are utilized in a safely phlegmatized condition. They will not be discussed in this book, except for two substances displaying properties of primary explosives -< Tricycloacetone Peroxide and -> Hexamethylenetriperoxide Diamine. 

As the samples which explode in this test are highly sensitive substances, one can judge "go" (meaning an explosion occurred) or "no go" (no reaction) with sufficient accuracy by this simple test. In the case of primary explosives, wet primary explosives should be put on the steel roller and should be dried in a desiccator. 

Another promising and thermally stable (Tab. 1.3b) lead-free primary explosive is copper(II) 5-chlorotetrazolate (Cu CIT, PSI LMU). The synthesis is achieved in a one-step reaction (Fig. 1.18a) starting from commercially available aminotetraz-... 

While the environmental impact of cadmium azide in deep oil deposits is relatively low, the long-term use of Pb(N3)2 and lead styphnate in military training grounds has resulted in considerable lead contamination (see Ch. 1.2.3, see Fig. 1.17). On demand lead azide (ODLA) is available from the reaction of lead acetate and sodium azide. The recently introduced iron and copper complexes of the type [Cat]2 [Mn(NT)4(H20)2] ([Cat]+ = NH4, Na+ M = Fe, Cu NT = 5-nitrotetra-zolate) as green primary explosives [3] are relatively easily obtained and show similar initiator properties as those of lead azide (Tab. 2.2). 

SAFETY PROFILE Poison by skin contact and intraperitoneal routes. Moderately toxic by ingestion. A severe human skin and eye irritant. Acts as a primary irritant as well as a sensitizer of skin. An allergen. Mutation data reported. Combustible when exposed to heat or flame. A moderate explosion hazard when exposed to flame, sparks, heated to 150°, or when shocked in a sealed container. Explosive reaction with ammonia at 170°C/40 bar. To fight fire, use CO2, dry chemical. Reacts violently with hydrazine sulfate or hydrazine hydrate. See also NITRO COMPOUNDS of AROMATIC HYDROCARBONS. 

The behaviour of the heavy-metal azides on heating is less predictable, some being extremely unstable and hence of value as primary explosives. Nevertheless it has been stated [18] that "All solid inorganic azides can be thermally decomposed at controllable and measurable rates". Azides which detonate under well-defined conditions have become model systems for the development of theories of "fast" reactions in solids [9,10]. 

Many studies of the thermal stability of this reactant have been completed, due to its technical use as a primary explosive. Four polymorphic forms exist [12] of which the orthorhombic a-form is the most stable. The other forms can be prepared under specific conditions [12], At high temperatures (above 613 K) the reaction accelerates to detonation. This autocatalytic process has been attributed [54] to an increased concentration of defect sites, rather than a mechanism controlled primarily by temperature increases due to self-heating. 

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