White crystalline plates, melts ~210C (explosive decomposition). Crystal density is 2.07 g/cm3 and is greatest among CHNO explosives made so far. Heat of explosion is 5.81 MJ/kg, detonation pressure is 46.1 GPa, throwing ability is 118% of HMX (HNIW – 108%). Sensitive to impact and friction, impact sensitivity is 21 cm with 2.5 kg weight (HMX – 26 cm). Detonation velocity is 9019 m/sec at 1.862 g/cm3, 9546 m/sec at 1.995 g/cm3 and 9800 m/sec at 2.07 g/cm3 (TMD). Soluble in acetone and benzene, insoluble in water.

1. l,4-Diformyl-2,3,5,6-tetrahydroxypiperazine. Formamide (135 g, 119 ml, 3.0 mol) was added to stirred aqueous glyoxal (40% w/w, 435 g, 3.0 mol), and the pH was adjusted to 8.5 by using aqueous sodium hydroxide solution (10 M). The temperature rose slowly to 30°C over the first 30 min, and the solution developed a yellow tinge. The exotherm subsided, and after 4 h of stirring, the mixture was left to stand for 3 days. A first crop of the product (93 g) was collected by filtration, and a second crop was obtained by adjusting the pH of the filtrate to 9, the temperature of the mixture being controlled at 25°C with ice/water and the additional product being collected after 5 h. Both crops were washed well with water, dried, and purified by digesting the solid twice in a hot mixture of dimethylformamide/water (80:20). This involved using 70 ml of this mixture for each 30 g of solid, maintaining the stirred slurry at 75°C for 30 min, then cooling it to 30°C, collecting the solid, and washing it well with water. The product was dried over a desiccant to give a white solid (204 g, 66%), which darkened substantially above 190 °C and decomposed above 210°C (lit. mp ca. 225°C dec).

2. cis-syn-cis-2,6-Dioxodecahydro-lH,5H-diimidazo[4,5-b:4',5'-e]pyrazine. Finely ground l,4-diformyl-2,3,5,6-tetrahydroxypiperazine (24 g, 0.115 mol) was added to a stirred solution of urea (21 g, 0.35 mol) in concentrated hydrochloric acid (37% w/w, 100 ml) over 15 min. The mixture was stirred for 90 h, after which time the HNMR spectrum of a sample showed that all starting material had been consumed (#1). The solid was collected by filtration, washed with methanol (300 ml), and dried at aspirator vacuum and then at 75°C (1 mm) to give the crude product (28.2 g, 80.2%) as a hydrate of the dihydrochloride salt. This was dissolved in chilled water (22.5 ml/g) and precipitated by the addition of cold methanol (100 ml/g) to give the mono-hydrochloride salt (10.3 g, 38%), which darkens above 170°C: mp 183-185°C dec. (corrected). Alternatively, the crude salt may be converted to the mono-hydrochloride by precipitation from an aqueous solution (1 g/10 ml) by the addition of acetone (3 ml/ml of solution); the yield was 32% based on piperazine starting material.

3. cis-syn-cis-2,6-Dioxo-1,3,4,5,7,8-hexanitrodecahydro-lH,5H-diimidazo[4,5-b:4',5'-e]pyrazine. Phosphorus pentoxide (15.6 g, 10.0 mmol) was slowly added to absolute (100%) nitric acid (30 ml, 750 mmol) which was stirred under nitrogen and cooled in ice/water to keep the temperature of the acid below 30°C. The mixture was then maintained at 30°С for 40 min to give a clear yellow solution. The stirred solution was cooled to -15°C and kept below -10°C as the monohydrochloride salt (1.2 g, 0.5 mmol) was added in portions over 30 min (#2). The mixture was allowed to warm to 25°C over 1.5 h and was maintained at this temperature for 30 min, then at 35°C for 1 h, and at 45°C for 2h. The cooled mixture was stirred into ice/water (300 ml). The precipitated solid was quickly collected by filtration (#3), washed with cold water and dichloromethane, and then dried to give the crude product (1.78 g, 74%): mp 210°C explosive dec.

1. It is essential that stirring must be continued during all aging period, because without stirring condensation reaction slows down greatly, and after aging period only traces of reaction product are formed. During aging process mixture becomes more and more viscous, so strong mechanical stirring is advised. Insolubility of source product l,4-Diformyl-2,3,5,6-tetrahydroxypiperazine allows to control reaction state, by measuring amount of water-insoluble material in sample taken from reaction flask. At the end of aging period mixture must have visible pink coloration, and sample of reaction product should easily dissolve in water, leaving no insoluble residue.

2. Addition of phosphorus pentoxide to 99% nitric acid is very exothermic, and effort must be taken to keep mixture temperature below 30C during all addition period, to minimize thermal decomposition of forming nitrogen pentoxide. This can be achieved by cooling acid in ice bath and adding phosphorus pentoxide in small portions, allowing exotherm to subside before adding new several portions. Addition of monohydrochloride salt is also exothermic, but in this case temperature must be maintained below -10C during course of addition, because higher temperature can lead to uncontrollable oxidation processes. It is convenient to use ice/table salt bath for cooling during this period, bath has cryoscopic point at -21.3°C, and can be prepared by mixing 33g of sodium chloride per 100g of finely crushed ice, placing it by thin layers at the top of each other.

3. Reaction product is readily hydrolyzed by water, hydrolysis goes with visible speed even at 30C, so contact time with warm water should be minimized to prevent loses of reaction product. Pouring acid mixture to ice/water should be accompanied by intense stirring, to prevent local overheat, and precipitated product must be filtered and dried with organic solvent as fast as possible. Dichloromethane washing can be substituted by washing with small amount of isopropyl alcohol and placing product to desiccator.

Condensation of glyoxal with formamide in basic environment proceeds smoothly, soon after beginning of aging product begins to precipitate as layer of snow white solid. Then reaction is complete it is filtered, dried, weighted and purified. Right photo shows pure l,4-Diformyl-2,3,5,6-tetrahydroxypiperazine.

Condensation of 1,4-Diformyl-2,3,5,6-tetrahydroxypiperazine with urea in hydrochloric acid, proceeds harder and require constant stirring. Then mixture is left unstirred during aging, only traces of condensation product are formed. During aging mixture becomes more and more viscous, so mechanical stirring is advised. Then reaction is close to completion mixture became pinkish, and sample of solid taken from reaction mixture easily dissolves in water, leaving no insoluble residue. Photo on the right show crude piperazine/urea condensation product.

Mother liquor obtained after filtering has intense red coloration, substance causing it is unknown. Crude product is purified by dissolving in water (middle photo) and reprecipitated by addition of acetone, forming snow-white flakes of pure monohydrochloride salt, shown on right photo.

Nitration of monohydrochloride to HHTDD takes place only by action of N2O5 solution in anhydrous nitric acid, such solution has characteristic yellow color, show on left photo. Solution of nitrogen pentoxide is cooled to ~ -20C, and monohydrochloride is added in small portions with rate, not allowing temperature to rise above -10C. Then all monohydrochloride is added solution is allowed to warm to room temperature in 1.5 hours, and deep nitration is forced by further heating as described in synthesis procedure. For relatively low temperature baths, it is convenient to use running hot water stream from water supply system, eventually checking out water temperature on thermometer.

Then reaction mixture is heated to 45C substantial amount of nitrogen dioxide and nitric acid fumes are evolved, these are allowed to escape from reaction flask through the small hole in flask cap. Left photo shows reaction mixture after 2 hours at 45C, photo on the right shows HHTDD, obtained by pouring acid mixture on ice/water and quick filtering.