Triazole Explosives [Published]
AndersHoveland
Acolyte
Triazole molecules contain a pentagonal ring, consisting of 2 carbon atoms and 3 nitrogen atoms. This post focuses on 1,3,5-triazoles, in which one of the nitrogen atoms in not bonded to either of the other nitrogen atoms in the ring. Triazole explosives are typically both very powerful and safe, requiring a decent detonating charge to set off.
3-nitro-1,2,4-triazol-5-oxide (NOTO)
formula: C2H2N4O3
the molecular structure is here: http://www.molport.com/buy-chemicals/moleculelink/3-nitro-4-5-dihydro-1H-1-2-4-triazol-5-one/1002005
detonation velocity: 8510-8590 m/sec density: 1.93 g / cubic cm
has a minimum diameter requirement for detonation (somewhat analogous to ammonium nitrate in this way), must be kept away form moisture, hydrolyzes with water (similar to nitrourea). unlike HMX, this compound has hydrogen bonds that allow the small molecules to pack closely together
This compound is thermally stable. When heated to 120degC for 24 hours, this compound gives off 0.3 cubic cm of decomposition gasses per gram, which is only a third as much as HMX gives off under similar conditions. Rapid decomposition begins at 240 degC. This compound can form salts with ammonia. It is already being used by the USA Airforce as an insensitive explosive.
synthesis:
Condensation of semicarbazide hydrochloride with a concentrated solution of formic acid (if exactly equal molar ratios were not used, then the excess formic acid can later be distilled off):
A mixture of 47 g of semicarbazide and 115 g of 98% formic acid and 200 mL of ethanol is refluxed (heated to 100 degC and stirred) for 1 hour and then the excess of formic acid and the ethanol are distilled off. 58 g of white solid formilsemicarbazide crystallized, with a melting point of 129 degC. This is then dissolved in 150 mL of formic acid and refluxed for 1 hour. The excess of formic acid is distilled off. 25 g of a white solid are obtained which is mostly 1,2,4 triazol-3-oxide. The white solid can then be directly nitrated. 70% nitric acid is gradually added, the mixture is then heated to near boiling, 55-60 degC. The reaction generates even more heat, so the heat source is removed. Brown nitrogen dioxide gas is evolved from the solution. Alternatively, if a regular nitration with concentrated acids is done, it will give the final product in 70% yield. After nitration, the mixture is cooled to 0-10 degC and filtered with water. The product, 3-nitro-1,2,4-triazol-5-oxide, is cystallized, then dried at 70 degC.
Preparation of Semicarbazide
A mixture of 30 g of 100% Hydrazine Hydrate with 30,1 g of urea is heated at 110 degC for 4 hours. After cooling,100 mL of pure ethanol are added with stirring. After standing for 8 hours, a white solid is filtered off and washed with pure ethanol. This product initially melts at 94 degC; after recrystallization with methanol or ethanol the melting point reaches 96.5C.
3-amino,5-nitro-1,2,4-triazole (ANTA)
detonation velocity: 8450-8460 m/sec
detonation pressure: 314 kbar
low sensitivity
density: 1.82 g/cm3.
melting point: between 238.2 - 244 degC
ANTA is lemon-yellow in color. ANTA can from salts if very strong bases are used (sodium ethoxide). A solution of these salts in pure EtOH (the salt would hydrolyze with water) can react with dinitro-paradichlorobenzene in 60% yield to give a compound with an 8.5 km/sec deonation velocity. Aminotriazole (3-AT) is used as a herbacide, and can be nitrated into ANTA. Alternatively dinitrotriazole can be reduced in the procedure below, but this seems like somewhat of a waste of precious hydrazine.
Synthesis:
The salt of 3,5-dinitro-1,2,4-triazole can be reduced with hydrazine hydrate into ANTA. (hydroxylamine is also a reactive reducing agent, like hydrazine, and it is likely that the hydrazine and hydroxylamine salts of 3,5-dinitro-1,2,4-triazole do not exist)
29 grams of ammonium dinitrotriazolate (ADNT) is added to 38.5 g hydrazine hydrate. The reaction mixture was stirred for 10 minutes while being warmed to 78-80 °C and left at this temperature about 1.5 hours to fully react.
Then the mixture was cooled by adding water to the mixture, and adding 10% solution of HCl (reducing the pH to about 4.0). ANTA, which is precipitated from the mixture separates from the liquid and is dried under vacuum.
The amount of ANTA obtained is 19.8 grams, giving 94% yield. Normally, the yield reaches to 96%.
Heating the mixture to 80°C is recommended, because it will greatly accelerate the reaction, which otherwise might be a few days. On the other hand, the temperature must not exceed 80 °C, otherwise there will be decomposition and the yield decreases rapidly. The mixture was cooled by adding water to the mixture, the preferred pH after addition of HCl to the mixture is 4.0.
ANTA separation from solution is possible by filtration or centrifugation. Dilute HCl is recommended for safety, but more concentrated HCl may also be used. After the reaction mixture was cooled to room temperature and acidified by adding enough hydrochloric acid to lower the pH to between 2 and 4. The ANTA then precipitates and is filtered off.
If the product is isolated from the mixture before acidification by HCl, the addition of the acid will cause the ANTA to decompose, and only hydrazine hydochloride will be obtained. The hydrochloride of ANTA starts to decompose at 100 °C to give off poisonous hydrazine vapor.
4-amino-1,2,4-triazole
1345g of formic acid, in at least 95% concentration, is added over a half hour into 150g of pure liquid hydrazine hydrate. A distillation is performed on the mixture, which is slowly heated to 165degC, and the distillation continued for three hours. The water is gets distilled out. The reaction mixture is cooled to 80degC and then 1740 g of isopropanol are added.
The heat is kept at 75degC until the solid is completely dissolved, then allowed to slowly cool. The mixture is then cooled to 5degC and the product is filtered out. The crystals are washed with 150 g of cold isopropanol and dried.
4-amino-1,2,4-triazole can then be directly nitrated (by heating with 70% HNO3) into ANTA. Note that the nitration need not be cold because triazoles are not vulnerable to undesirable oxidation.
3-nitro-1,2,4-triazol-5-oxide (NOTO)
formula: C2H2N4O3
the molecular structure is here: http://www.molport.com/buy-chemicals/moleculelink/3-nitro-4-5-dihydro-1H-1-2-4-triazol-5-one/1002005
detonation velocity: 8510-8590 m/sec density: 1.93 g / cubic cm
has a minimum diameter requirement for detonation (somewhat analogous to ammonium nitrate in this way), must be kept away form moisture, hydrolyzes with water (similar to nitrourea). unlike HMX, this compound has hydrogen bonds that allow the small molecules to pack closely together
This compound is thermally stable. When heated to 120degC for 24 hours, this compound gives off 0.3 cubic cm of decomposition gasses per gram, which is only a third as much as HMX gives off under similar conditions. Rapid decomposition begins at 240 degC. This compound can form salts with ammonia. It is already being used by the USA Airforce as an insensitive explosive.
synthesis:
Condensation of semicarbazide hydrochloride with a concentrated solution of formic acid (if exactly equal molar ratios were not used, then the excess formic acid can later be distilled off):
A mixture of 47 g of semicarbazide and 115 g of 98% formic acid and 200 mL of ethanol is refluxed (heated to 100 degC and stirred) for 1 hour and then the excess of formic acid and the ethanol are distilled off. 58 g of white solid formilsemicarbazide crystallized, with a melting point of 129 degC. This is then dissolved in 150 mL of formic acid and refluxed for 1 hour. The excess of formic acid is distilled off. 25 g of a white solid are obtained which is mostly 1,2,4 triazol-3-oxide. The white solid can then be directly nitrated. 70% nitric acid is gradually added, the mixture is then heated to near boiling, 55-60 degC. The reaction generates even more heat, so the heat source is removed. Brown nitrogen dioxide gas is evolved from the solution. Alternatively, if a regular nitration with concentrated acids is done, it will give the final product in 70% yield. After nitration, the mixture is cooled to 0-10 degC and filtered with water. The product, 3-nitro-1,2,4-triazol-5-oxide, is cystallized, then dried at 70 degC.
Preparation of Semicarbazide
A mixture of 30 g of 100% Hydrazine Hydrate with 30,1 g of urea is heated at 110 degC for 4 hours. After cooling,100 mL of pure ethanol are added with stirring. After standing for 8 hours, a white solid is filtered off and washed with pure ethanol. This product initially melts at 94 degC; after recrystallization with methanol or ethanol the melting point reaches 96.5C.
3-amino,5-nitro-1,2,4-triazole (ANTA)
detonation velocity: 8450-8460 m/sec
detonation pressure: 314 kbar
low sensitivity
density: 1.82 g/cm3.
melting point: between 238.2 - 244 degC
ANTA is lemon-yellow in color. ANTA can from salts if very strong bases are used (sodium ethoxide). A solution of these salts in pure EtOH (the salt would hydrolyze with water) can react with dinitro-paradichlorobenzene in 60% yield to give a compound with an 8.5 km/sec deonation velocity. Aminotriazole (3-AT) is used as a herbacide, and can be nitrated into ANTA. Alternatively dinitrotriazole can be reduced in the procedure below, but this seems like somewhat of a waste of precious hydrazine.
Synthesis:
The salt of 3,5-dinitro-1,2,4-triazole can be reduced with hydrazine hydrate into ANTA. (hydroxylamine is also a reactive reducing agent, like hydrazine, and it is likely that the hydrazine and hydroxylamine salts of 3,5-dinitro-1,2,4-triazole do not exist)
29 grams of ammonium dinitrotriazolate (ADNT) is added to 38.5 g hydrazine hydrate. The reaction mixture was stirred for 10 minutes while being warmed to 78-80 °C and left at this temperature about 1.5 hours to fully react.
Then the mixture was cooled by adding water to the mixture, and adding 10% solution of HCl (reducing the pH to about 4.0). ANTA, which is precipitated from the mixture separates from the liquid and is dried under vacuum.
The amount of ANTA obtained is 19.8 grams, giving 94% yield. Normally, the yield reaches to 96%.
Heating the mixture to 80°C is recommended, because it will greatly accelerate the reaction, which otherwise might be a few days. On the other hand, the temperature must not exceed 80 °C, otherwise there will be decomposition and the yield decreases rapidly. The mixture was cooled by adding water to the mixture, the preferred pH after addition of HCl to the mixture is 4.0.
ANTA separation from solution is possible by filtration or centrifugation. Dilute HCl is recommended for safety, but more concentrated HCl may also be used. After the reaction mixture was cooled to room temperature and acidified by adding enough hydrochloric acid to lower the pH to between 2 and 4. The ANTA then precipitates and is filtered off.
If the product is isolated from the mixture before acidification by HCl, the addition of the acid will cause the ANTA to decompose, and only hydrazine hydochloride will be obtained. The hydrochloride of ANTA starts to decompose at 100 °C to give off poisonous hydrazine vapor.
4-amino-1,2,4-triazole
1345g of formic acid, in at least 95% concentration, is added over a half hour into 150g of pure liquid hydrazine hydrate. A distillation is performed on the mixture, which is slowly heated to 165degC, and the distillation continued for three hours. The water is gets distilled out. The reaction mixture is cooled to 80degC and then 1740 g of isopropanol are added.
The heat is kept at 75degC until the solid is completely dissolved, then allowed to slowly cool. The mixture is then cooled to 5degC and the product is filtered out. The crystals are washed with 150 g of cold isopropanol and dried.
4-amino-1,2,4-triazole can then be directly nitrated (by heating with 70% HNO3) into ANTA. Note that the nitration need not be cold because triazoles are not vulnerable to undesirable oxidation.
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