1 Introduction
Pursuing new insensitive high explosive is the main research hot‑point in explosive field．To maximize the detonation performance while minimize the sensitivity, researchers have focused on azoles as the core of energetic compounds, such as triazoles, tetrazoles and furazan
s[1,2,3,4,5,6] . In addition, one approach to synthesize new energetic compounds is the preparation of energetic salts, which mostly have a high density and high stability as a result of their high lattice energy[7,8] . For example, ditriaminoguanidinium 3,5‑bis(dinitromethyl)‑1,2,4‑triazolate was identified as a kind of potential explosive with high‑performance and insensitivity. It has some desirable traits, including a low impact sensitivity(22 J), a low friction sensitivity(>360 N), and a high detonation velocity (8557 m·s-1 )[9] . In view of the above observations, based on 3,5‑bis(dinitromethyl)‑1,2,4‑triazolate, a novel compound, diguanylurea 3,5‑bis(dinitromethyl)‑1,2,4‑triazolate (DMDNMT) was firstly designed and synthesized. The detailed studies of the synthesis and characterization of DMDNMT were carried out in this work. In addition, the thermal stability and detonation parameters were investigated. The properties of DMDNMT were estimated by B3LYP[10] method on 6‑31G(d, p) basis set of Gaussian 09 procedure[11] and EXPLO5 6.04[12] . The main thermal property of DMDNMT was analyzed by DSC and TG‑DTG.2 Experimental
2. 1 Materials and Instruments
Ethyl 2‑(3‑(dinitromethyl)‑1H‑1,2,4‑triazol‑5‑yl) acetate was prepared and purified according to the reference [13], and other reagents were purchased from the commercial sources.
1 H NMR and13 C NMR were obtained in DMSO‑d6 on a Bruker AV500 NMR spectrometer. Infrared spectra were obtained from KBr pellets on a Nicolet NEXUS870 Infrared spectrometer in the range of 4000-400 cm-1 . Elemental analyses (C, H and N) were performed on a VARI‑El‑3 elemental analyzer. Differential scanning calorimetry (DSC) studies were carried out on a Q200 apparatus (TA, USA) at a heating rate of 10 K⋅min-1 under dry oxygen‑free nitrogen atmosphere with a flowing rate of 50 mL⋅min‑1 . The TG‑DTG experiment was performed with a SDT‑Q600 apparatus (TA, USA) operating at a heating rate of 10 K⋅min-1 in a flow of dry oxygen‑free nitrogen at 100 mL⋅min-1 .2. 2 Synthesis and Characterization
Using ethyl 2‑(3‑(dinitromethyl)‑1H‑1,2,4‑triazol‑5‑yl)acetate as a starting material, the title compound DMDNMT was firstly synthesized via the reactions of nitration, hydrolysis and metathesis (Scheme 1).
2.2.1 Ethyl 2‑(5‑(Dinitromethyl)‑4H‑1,2,4‑triazol‑ 3‑yl)‑2,2‑dinitroacetate
5 mL 98% sulfuric acid was added dropwise to 6 mL 98% nitric acid and sulfuric acid at -5 ℃. To the reaction mixture, ethyl 2‑(3‑(dinitromethyl)‑1H‑ 1,2,4‑triazol‑5‑yl)acetate (1.0 g, 3.86 mmol) was added slowly. After complete addition, the reaction mixture was stirred at room temperature for other 6 h. Then the reaction mixture was poured into ice water. The white precipitate was filtered to obtain 1.11 g solid with a yield of 82.4% and a purity of 98.5% (HPLC). IR(KBr, ν/c
m-1 ): 3345, 2997, 1759, 1619, 1596, 1524, 1379, 1353, 1306, 1282, 1260,1190,1117,1070,1029,993,973,845,801.1 HNMR (DMSO‑d6 ,500 MHz)δ: 10.217-10.237(1H, NH), 4.508-4.551(2H,CH2 ), 1.280-1.308(3H,CH3 );13 C NMR(DMSO‑d6 ,125 MHz)δ: 157.570, 153.268, 149.285, 66.234, 13.890; Anal.calcd forC7 H7 N7 O10 : C 24.08, H 2.02, N 28.08; found: C 24.25, H 1.96, N 27.81.2.2.2 Diguanylurea 3,5‑Bis(dinitromethyl)‑1,2,4‑ triazolate (DMDNMT)
Ethyl 2‑(5‑(dinitromethyl)‑4H‑1,2,4‑triazol‑3‑ yl)‑2,2‑ dinitroacetate (0.5 g, 1.43 mmol) was dissolved in 10 mL deionized water. To the reaction mixture, potassium carbonate (0.2 g, 1.43 mmol) was added. The solution was stirred for 30 min. Silver nitrate (2.9 g, 5.72 mmol) was added and the solution was stirred at ambient temperature for other 1 h, which started instantly to precipitate and was filtered. The wet powder was mixed with 10 mL water, and the mixture was transferred into a three‑necked round‑bottomed flask with a mechanical stirrer. Then guanylurea hydrochloride (0.3 g, 2.14 mmol) was added. The reaction mixture was stirred for 6 h at ambient temperature, and the mixture was filtered. The solution was evaporated to dryness to give 0.42 g with a yield of 61.1%. IR(KBr, ν/c
m-1 ): 3436,3372,3009,1731,1687,1604,1567,1509, 1467, 1422, 1340, 1251, 1219, 1188, 1122, 999, 978, 930, 819;13 C NMR(DMSO‑d6 , 125 MHz)δ: 156.108, 155.373, 151.465, 126.450; Anal. calcd forC8 H15 N15 O10 : C 19.96, H 3.14, N 43.65; found: C 19.75, H 3.44, N 43.20.3 Physicochemical and Energetic Properties
All the quantum computations were performed using the Gaussian 09 (Revision A. 02) suite of program
s[11] . The optimized structure was characterized to be true local energy minima on the potential‑energy surface without imaginary frequencies. The density of DMDNMT was computed based on Monte‑Caolo method using the optimized structure at the B3LYP 6‑3G(d,p) level of theory. The gas phase heat of formation was calculated by the atomization method using the Gaussian 09 program package at the CBS‑4M level of theory[14] . Gas phase heat of formation was transformed to solid phase heat of formation by Trouton′s rule[15] . Based on the calculated density and heat of formation, the detonation velocity and detonation pressure for DMDNMT were calculated by EXPLO5 6.04. The thermal behaviors for DMDNMT were indicated by DSC and TG‑DTG measurements. The properties of DMDNMT were obtained by calculation or test as follows: density is 1.81 g·cm-3 , detonation velocity is 8624.8 m·s-1 , heat of formation is -446.1 kJ·kg-1 . DMDNMT exhibits a high density and detonation velocity．In order to evaluate the reliability and safety in the process of application, BAM standard method[16] was used to determine the impact sensitivity (IS) for DMDNMT. It showed prospective low sensitivity (IS24 J). The physicochemical and energetic properties of DMDNMT were listed in Table 1.Table 1 The physicochemical and energetic properties of DMDNMT
properties DMDNMT condition formula C8 H15 N15 O10 molar mass 481 calculated nitrogen content / % 43.65 calculated oxygen balance / % -44.9 calculated appearance orange solid eyeballing(tested) decomposition temperature/℃ 177.3(DSC) DSC(tested) density / g·c m-3 1.81 Gaussian 09 program(calculated) detonation velocity / m· s-1 8624.8 EXPLO5 6.04 (calculated) detonation pressure / GPa 29.2 EXPLO5 6.04 (calculated) heat of formation / kJ·mo l-1 -446.1 Gaussian 09 program(calculated) impact sensitivities / J 24 BMW(tested) 4 Thermal Stability
As show in Fig.1, the DSC curve of DMDNMT exhibits two thermal decomposition peaks at 177.3 ℃ and 221.2 ℃, respectively. The TG‑DTG curves (Fig.2) show that there are two stages in the decomposition process of HDNMT with a mass loss of 82.8% before 192.4 ℃ at first stage, and a total mass loss of 87.4% before 250.9 ℃, finally, 7.2% residue at 381.6 ℃.
5 Conclusions
(1) DMDNMT was firstly synthesized using ethyl 2‑(3‑(dinitromethyl)‑1H‑1,2,4‑triazol‑5‑yl) acetate as a raw material via the reactions of nitration, hydrolysis and metathesis. The structure of DMDNMT was characterized by IR, NMR and element analysis.
(2) The main performance of DMDNMT was calculated by theoretical method. The obtained density is 1.81 g·c
m-3 , heat of formation is -446.1 kJ·kg-1 , detonation velocity is 8624.8 m·s-1 , and detonation pressure is 29.2 GPa.(3) The thermal stability of DMDNMT was analyzed by DSC and TG‑DTG. The results show that the decomposition temperature of DMDNMT is 177.3 ℃. The impact sensitivities of DMDNMT was tested by BAM standard method, and it shows a low sensitivity (IS 24 J).
（责编：王艳秀）
References
- 1
Dippold A A, Klapötke T M . A Study of dinitro‑bis‑1,2,4‑triazole‑1,1′‑diol and derivatives: design of high‑performance insensitive energetic materials by the introduction of N‑Oxides[J]. Journal of the American Chemical Society, 2013, 135(26): 9931-9938.
- 2
Kehler J, Püschl A, Dahl O . Improved synthesis of 1‑hydroxy‑4‑nitro‑6‑trifluoromethylbenzotriazole and 1‑hydroxy‑ 4,6‑dinitrobenzotriazole[J]. Acta Chemica Scandinavica, 1996, 50(12): 1171-1173.
- 3
ZHOU Qun, WANG Bo‑zhou, JIA Si‑yuan . New synehetic process of 1‑methl‑3‑amino‑5‑nitro‑1,2,4‑triazole[J]. Chinese Journal of Energetic Materials(Hanneng Cailiao),2012,20(1):26-29.
- 4
ZHANG Min, GE Zhong‑xue, BI Fu‑qiang, et al . Synthesis and performance of 2‑dinitromethyl‑5‑nitrotetrazole[J]. Chinese Journal of Energetic Materials(Hanneng Cailiao), 2013, 21(5): 688-690.
- 5
HUO Huan, WANG Bo‑zhou, ZHAI Lian‑jie, et al . An insensitive energetic compound 5,7‑diamino‑4,6‑dinitro‑benzotriazol ‑3‑ium‑1‑oxide: synthesis, characterization and performances[J]. Chinese Journal of Energetic Materials(Hanneng Cailiao), 2016, 24(9): 857-861.
- 6
Wang R, Xu H, Guo Y, et al . Bis[3‑(5‑nitroimino‑1,2,4‑ triazolate)]‑based energetic salts：synthesis and promising properties of a new family of high‑ densityinsensitive materials[J]. Journal of the American Chemical Society, 2010, 132(24): 11904-11905．
- 7
Yin P, Zhang J H, Parrishb D A, et al . Energetic fused triazoles‑a promising C─N fused heterocyclic cation[J]. Journal of Materials Chemistry A, 2015, 3(16): 8606-8612.
- 8
Klapötke T M, Schmid P C, Schnell S, et al . Thermal stabilization of energetic materials by the aromatic nitrogen‑rich 4,40,5,50‑tetraamino‑3,30‑bi‑1,2,4‑triazolium cation[J]. Journal of Materials Chemistry A, 2015, 3(16): 2658-2668.
- 9
Dharavath S, Shreeve J M . A safe synthesis of 3,5‑bis(dinitromethyl)‑1,2,4‑triazole (BDT) and its mono and di salt: high‑perfomance insensitive energetic materials[J]. Propellants, Explosives, Pyrotechnics, 2018, 43(1): 48-53.
- 10
Stephens P J, Devlin F J, Chabalowski C F, et al .Ab initio calculation of vibrational absorption and circular dichroism spectra using densitiy functional force fields. The Journal of Physical Chemical, 1994, 98(45): 11623-11627.
- 11
Frisch M J, Trucks G W, Schlegel H B, et al . Gaussian 09[CP], rev. A.02, Gaussian, Inc., Wallingford, CT, 2009.
- 12
Suceska M, EXPLO 5, Version 6.04[CP], 2017.
- 13
Zhang J h, Dharavath S, Mitchel L A, et al . Energetic salts based on 3,5‑bis(dinitromethyl)‑1,2,4‑triazole monoanion and dianion: controllable preparation, characterization, and high performance[J]. Journal of the American Chemical Society, 2016, 138(29): 7500-7503.
- 14
Montgomery J A, Frisch M . J, Ochterski J W, et al . A complete basis set model chemistry VII. use of the minimum population localization method[J]. The Journal of Chemical Physics, 2000, 112(15): 6532-6542.
- 15
Westwell M S, Searle M S, Wales D J, et al . Empirical correlation between thermodynamic properties and intermolecular forces[J]. Journal of the American Chemical Society, 1995, 117: 5013-5015.
- 16
Tests were conducted according to the UN recommendations on the transport of dangerous goods[M]. Manual of tests and criteria, 5th ed.,United Nations Publication,New York, 2009.
- 1
Abstract
Using ethyl 2‑(3‑(dinitromethyl)‑1H‑1,2,4‑triazol‑5‑yl)acetate as a starting material, diguanylurea 3,5‑bis(dinitromethyl)‑1,2,4‑triazolate (DMDNMT) was firstly designed and synthesized via the reactions of nitration, hydrolysis and metathesis. The structures of all compounds were characterized by
摘要
以3‑偕二硝甲基‑5‑乙酸乙酯基‑5,5‑二硝基‑1H‑1,2,4‑三唑为原料，通过硝化、水解和离子交换反应设计并合成了未见文献报道的新化合物3,5‑双（二硝甲基）‑1,2,4‑三唑的双脒基脲盐（DMDNMT）；采用红外光谱
Graphic Abstract
图文摘要
Using ethyl 2‑(3‑(dinitromethyl)‑1H‑1,2,4‑triazol‑5‑yl) acetate as a starting material, diguanylurea 3,5‑bis(dinitromethyl)‑1,2,4‑triazolate(DMDNMT) was firstly designed and synthesized via the reactions of nitration, hydrolysis and metathesis.
