2-Nitroamino-5-nitro-hexahydro-1,3,5-triazine (NNHT) is a
It is a new type of insensitive explosive, which has attracted people's attention in recent years[1,2].
The molecular structure of NNHT contains both nitro and amino groups, both of which can form
Intermolecular and intramolecular hydrogen bonds have low sensitivity; its density, collision
The impact sensitivity, detonation velocity and specific impulse are respectively 1.88 g·cm－3
, 89 cm, 9094
m•s－1 and 238 s[3～5], it can be seen that it is an insensitive and
Energetic materials with high energy density.
Currently, the United States uses it in gun propellants to make it weapon-resistant
can be improved. The application of NNHT in the M30A1 formulation can make the propellant
The propellant power of propellant is increased by 8%. While NNHT increases the burning rate of propellant, it also
The flame temperature is lowered, and the gunpowder power is increased[6].
In 1990, Huang et al. [3] first designed and synthesized 2-nitroamino-5-
Nitro-hexahydro-1,3,5-triazine (NNHT), its synthesis[7], crystal structure
and molecular geometry[8] have been reported in China. The literature[9, 10] reports are based on
Nitroguanidine, terbutylamine and formaldehyde as raw materials, through Mannich condensation reaction
To obtain 2-nitroamino-5-tert-butyl-hexahydro-1,3,5-triazine (NBHTA),
Then the target compound was obtained through chloride ion catalyzed nitrification reaction (Scheme
1). Wang Bozhou et al. [9] improved the process to increase the Mannich shrinkage
When the combined reaction temperature reaches 82 ℃, the yield can reach up to 89%;
NBHTA was nitrated with industrial nitric acid instead of pure nitric acid, and at 20 °C, the yield
No. 2 Li Yongxiang et al.: A new method for the synthesis of 2-nitroamino-5-nitro-hexahydro-1,3,5-triazine (NNHT) 257
up to 88%; the total yield of the reaction was up to 78%.
Scheme 1
In order to reduce the cost, a new synthetic route (Scheme 2) was adopted in this paper.
NNHT was synthesized from urotropine, nitroguanidine and hydrochloric acid.
In the nitrification reaction, concentrated nitric acid is directly used for nitrification, which is less than the original process.
The raw material ammonium chloride; the raw material terbutylamine in the original process is more expensive, and the market price is
22,000 yuan/ton, while urotropine is much cheaper, and the market price is 99.9%
6800 yuan/ton, the cost of the product is greatly reduced; the revenue of the target product of this route
The yield can reach 64.3%, although the yield is lower than the original process, but the overall average
On balance, the new process is still very economical, saving costs while also
Facilitate the expansion of production scale.
Scheme 2
1 Experimental part
1.1 Instruments and reagents
Beijing Analytical Instrument Factory IR-8400S spectrometer (potassium bromide tablet
method) to test the infrared spectrum of the product; using Element2VARIOEL element
Determination of C, H, N content by element analyzer; Determination by Bruker-AV400
1HNMR and 13CNMR; using Dalian Elite P230 high performance liquid phase
Chromatography to test the purity of intermediates and target products, STA-449C heat fraction
The melting points of intermediates and target products were determined by analyzer.
Hexatropine, methanol, N,N-dimethylformamide, hydrochloric acid (37%)
All were analytically pure; concentrated nitric acid (98.5%) and nitroguanidine were all industrial grade.
1.2 Synthesis of hydrochloride NIHT•HCl (1)
Add 20 mL (0.239 mol) of 37% hydrochloric acid into 100 mL
In the flask, weigh 7 g (0.048 mol) urotropine and add it to hydrochloric acid, stir
Mix; weigh 5 g (0.048 mol) of nitroguanidine, slowly add four-port burner
bottle, stirred at room temperature; after mixing evenly, the temperature was raised to 38 °C, and stirred
Reacted for 3 h; during the reaction, the solution gradually turned milky white;
warmed, filtered, washed with 10 mL of methanol, and dried to obtain an intermediate product
NIHT•HCl is a white powder.
1.3 Purification of intermediate product NIHT•HCl (1)
The intermediate product NIHT•HCl is the hydrochloride, choose concentrated hydrochloric acid for
Purification, using analytically pure concentrated hydrochloric acid to dissolve the water-insoluble intermediate product,
Solubility is small at room temperature, it can be dissolved by heating, and dissolved when the temperature rises
The degree of solubility increased significantly, and then cooled down to room temperature, crystals were precipitated, washed and dried.
Yield 78.3%, purity 98.5%. m.p. 189 ℃.
1.4 Synthesis of NNHT (2)
Add 5 mL (0.118 mmol) of 98.5% concentrated nitric acid into a four-neck flask
medium, ice-salt bath (salt bath formula: 100 g H2O: 20 g NH4Cl: 40 g
NaCl) to -10～-12 ℃; then weigh 1 g (0.01 mmol)
Slowly add NIHT·HCl into concentrated nitric acid, and keep warm for 30 min to increase the reaction
The temperature was 2-3 °C, and the reaction time was 1 h; filtered, washed with water, and vacuum-dried,
The target product was obtained as light yellow powder with a yield of 82.1% and a purity of
98.3%. m.p. 207 ℃ (literature value [10] 207 ℃); 1
H NMR δ: 9.27
(s, 2H, 2×NH), 5.32 (s, 4H, 2×CH2); FT-IR (KBr) ν:
3330, 3216 (N—H), 3123, 3047, 2972 (C—H), 1607 (C—
N), 1572 (NO2) cm－1
. Anal. calcd for C3H6N6O4: C 18.95,
N 44.20, H 3.18; found C 19.58, N 43.91, H 3.21.
2 Results and discussion
2.1 Factors affecting the synthesis of hydrochloride NIHT•HCl (1)
Synthesis of NNHT from Nitroguanidine (NQ) and Hexamethamine (HA)
The first step in the pathway is ring opening by HA, providing nitroguanidine
The CH2NHCH2 group forms a triazine ring, which is then combined with a molecule of HCl to form
Hydrochloride. It is also possible that methenamine reacts with concentrated hydrochloric acid to form formaldehyde and
Ammonium chloride and urotropine have the properties of tertiary amines, thus possessing
Mannich reaction conditions, so the reaction principle is fundamentally the same as Scheme 1
are consistent. The product formed, NIHT·HCl, is para to the N=C double bond
N—H combined with one molecule of hydrochloric acid.
When synthesizing NIHT•HCl, use industrial grade and analytical pure concentrated salt respectively
Acids were used for the synthesis reaction, and the two did not have much influence on the product yield, while
By changing the reaction time to 3, 5, 7, 9, 10 h and the reaction temperature to 30,
38, 50, 55, 70, 80 ℃. The effects of reaction time and temperature on the production
impact on yield.
258 Organic Chemistry Vol. 31, 2011
2.1.1 Effect of reaction time
The order of addition is: concentrated hydrochloric acid → urotropine → nitroguanidine, the reaction temperature
at 38°C
When the temperature is low (<50 °C), with the increase of the reaction temperature, the reaction
The yield rate also increases. This is because the Mannich condensation reaction is a
Endothermic equilibrium reaction, the effect of temperature on the reaction yield depends on the reaction rate
and equilibrium conversion are two factors. When the temperature is lower, the reaction reaches equilibrium
When the conversion rate is low, and it takes a long time. Because the reaction at low temperature
It should be difficult to reach equilibrium, so the conversion rate is low, resulting in low reaction yield.
As the temperature increases, the reaction speed increases and the conversion rate increases accordingly. When
When the temperature rises above 50 °C, with the increase of reaction temperature, the reaction rate
The rate is accelerated, but hydrochloric acid will volatilize to a certain extent with the increase of temperature, resulting in the dissolution
The decrease of the acid concentration in the liquid makes the reverse reaction of the salt formation reaction possible,
On the contrary, it leads to the decrease of the yield of salt. Therefore, the reaction yield increases with the temperature
After the maximum value appears, it gradually decreases. In addition, due to the temperature rise of the reaction system
A certain side reaction occurs after high temperature, which also affects the yield to a certain extent.
Therefore, the yield of the intermediate product reaches the maximum at 50 °C
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