2-Fluoro-1,3-diamino-4,6-dinitrobenzene (ZXC-7) and 2-Fluoro-1,3,5-triamino-4,6-dinitrobenzene (ZXC-8): Thermally Stable Explosives with Outstanding Properties

Article abstract of DOI:10.1002/cplu.201800598

Two novel, thermally stable explosives, 2-fluoro-1,3-diamino-4,6-dinitrobenzene (ZXC-7) and 2-fluoro-1,3,5-triamino-4,6-dinitrobenzene (ZXC-8), are reported. These two compounds can be prepared by means of simple synthetic methods and they show outstandin

Full text of DOI:10.1002/cplu.201800598

Accepted Article
Title: 2-fluoro-4,6-dinitrobenzene-1,3,5-triamine (ZXC-7) and 2-
fluoro-4,6-dinitrobenzene-1,3,5-triamine (ZXC-8): Thermally
Stable Explosives with Outstanding Properties
Authors: xingcheng zhang, Zheng Zhang, jinchao ma, qiuju zhou, and
wenxiang hu
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2-fluoro-1,3-diamino-4,6-dinitrobenzene (ZXC-7) and 2-fluoro-
1,3,5-triamino-4,6-dinitrobenzene (ZXC-8): Thermally Stable
Explosives with Outstanding Properties
Zheng Zhang,[a] § Jinchao Ma, [b] § Qiuju Zhou,[a] Wenxiang Hu,[c] Xingcheng Zhang*[a]
Abstract: Two novel, thermally stable explosives 2-fluoro-1,3-
diamino-4,6-dinitrobenzene (ZXC-7) and 2-fluoro-1,3,5-triamino-4,6-
dinitrobenzene (ZXC-8) are reported. These two compounds can be
prepared by means of simple synthetic methods and shows
outstanding properties (detonation velocity, detonation pressure,
sensitivity toward mechanical stimuli, and temperature of
decomposition). Their structures are very similar to the structure of
1,3,5-triamino-2,4,6-trinitrobenzene (TATB). They were isolated
and characterized by means of mass spectrometry, and multinuclear
(1H, 13C) NMR spectroscopy. The structure in the crystalline state of
ZXC-7 was determined by low-temperature single-crystal X-ray
diffraction. From the calculated standard molar enthalpy of formation
(CBS-4M) and the densities (were determined by a gas pycnometer),
the Chapman–Jouguet detonation properties were predicted by
using the EXPLO5 V6.01 thermochemical computer code. The
sensitivity of ZXC-7 and ZXC-8 towards impact, and friction were
determined.
excellent melt casting explosive. TNT is a very mature carrier
explosive with the density of 1.64 g cm-3, the melting point of
80.8 ℃, The thermal decomposition temperature (Tdec) is 295 ℃,
the detonation velocity (vC-J) of 6881 m s-1 and the detonation
pressure (PC-J) of 19.50 GPa. It has high explosion point and low
mechanical sensitivity. As melt-cast explosives, TNT have been
recognized worldwide and been widely used in industrial and
military explosives although they have some high toxicity to the
environment [3]. Because TNT is a melt-casting explosive with
excellent properties, the performance of its heat-resistant
explosive has been neglected slowly. However, it is difficult to
remove the isomers of mononitrobenzene and dinitrobenzene,
which leads to the decrease of the solidification point of TNT and
makes the performances of TNT unstable.[4]
Introduction
Heat-resistant explosives are particularly stable at the high
temperatures encountered in drilling deep oil wells or in space
exploration. They have been widely used in nuclear weapons or
on civilian perforating shells used in oil and gas fields today.[1] In
this area, the following explosives have received special
attention: 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 2,6-
bis(picrylamino)-3,5-dinitropyridine (PYX), 2,2’,4,4’,6,6’ –hexane
-trostilbene (HNS) and 2,4,6-trinitrotoluene (TNT) shown in
Figure 1.
Figure
trobenzene
2,2’,4,4’,6,6’-hexanitrostilbene (HNS); d) 2,4,6-trinitrotoluene (TNT)
1
Most known heat resistant explosives: 1,3,5-triamino-2,4,6-trini-
(TATB); 2,6-bis(picryl-amino)-3,5-dinitropyridine (PYX);
Jackson and Wing firstly synthesized 1,3,5-triamino-2,4,6-
trinitrobenzene (TATB) by the reaction of 1,3,5-tribromo-2,4,6-
trinitrobenzene with ammonia in 1888.[5] TATB is the only
approved insensitive and heat-resistant explosive at present by
the US Department of energy. As a heat-resistant explosive with
good properties, TATB has high thermal decomposition
temperature (Td= 350 °C), high single crystal density (ρ= 1.937 g
cm–3), good detonation property (Detonation velocity: vC-J = 7880
m s-1; PC-J = 27.9 GPa) and very high sensitivity (Impact
sensitivity: IS> 60 J; Friction sensitivity: FS= 360N). TATB is
difficult to initiate because its initiation sensitivity is relatively
high. In addition, because of the strong intramolecular and
intermolecular multiple ammonia bonds in TATB crystal structure,
the solubility of TATB in most common solvents is very low at
room temperature, which is the main difficulty in recrystallization
The synthesis of TNT was first reported by Wilbrand in 1863.[2]
TNT is not only a good heat resistant explosive, but also an
[a]
B.S. Zheng Zhang; Dr. Qiuju Zhou; Associate professor, Dr.,
Xingcheng Zhang
College of Chemistry and Chemical Engineering
Xinyang Normal University, Xinyang (China)
Nanhu 237, Xinyang, Henan (China)，464000
E-mail: zxc791114736@163.com
[b]
[c]
Dr. Jinchao Ma
School of Chemical Engineering
Nanjing University of Science and Technology
Xiaolingwei 200, Nanjing, Jiangsu (China)
Professor Wenxiang Hu
School of chemical engineering & pharmaceutical
Wuhan Institute of Technology
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
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10.1002/cplu.201800598
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[6]
and purification of TATB. Therefore, poor solubility is another
4,6-dinitrobenzene (bright yellow powder, ZXC-7) or 2-
fluoro-1,3,5-triamino-4,6-dinitrobenzene (orange yellow
powder, ZXC-8). In the process of reaction, there were two
fluorine atoms on the compound of 2a or 2b were substituted
by amino groups. The Compounds of ZXC-7 and ZXC-8 are
practically insoluble in water. Unlike TATB, ZXC-7 and ZXC-
8 can be dissolved in most commonly used organic solvents.
No further purification is needed during the whole synthesis
process. The synthesis of ZXC-7 and ZXC-8 are achieved
only through two-step reactions from commercially available
the starting materials 1a and 1b (Scheme 1). The synthetic
route presented herein results in high yields of the target
compounds and selectivity of the desired compounds. The
intermediates and final products are precipitated from the
reaction mixture without involving costly and time-consuming
purification processes.
fatal flaw in the widespread use of TATB.
The search for explosives that are thermally more stable and
better performances than TATB is an ongoing process in many
research groups worldwide. 2,6-diamino-3,5-dinitropyrazine-1-
oxide (LLM-105),[7] 2,2’,4,4’,6,6’-hexanitrostilbene (HNS),[8-10]
and
2,6-bis(picrylamino)-3,5-dinitropyridine
(PYX),[11-12]
tetraazapentalenes[1,3,7,9-tetranit-ro-6H-benzotriazolo[2,1-a]be-
nzotriazol-5-iuminner salt (Z-TACOT),[13] 2,2’,2’’,4,4’,4’’,6,6’,6’’-
nonanitroter phenyl (NONA), 2,6-bis(picrylamino)-3,5-dinitro-
pyridine (PYX),[14] 2,2’,4,4’,6,6’-hexanitrostilbene (HNS)[15-16] and
5,5’-Bis(2,4,6-trinitro-phenyl)-2,2’-bi(1,3,4-oxadiazole)
55).[17]
(TKX-
Since the late 1950s, scientists have studied fluorine-
containing energetic materials extensively. It is found that
the introduction of fluorine atoms into CHON-containing
energetic compounds will result in higher crystal density
and lower sensitivity of energetic compounds due to their
strong oxidation and higher density. In addition, the
introduction of fluorine atoms may form intramolecular
hydrogen bonds, which further improves its stability.[18] For
these reasons, we have designed and synthesized the
a
b
compounds
of
2-fluoro-1,3-diamino-4,6-dinitrobenzene
(ZXC-7) and 2-fluoro-1,3,5-triamino-4,6-dinitrobenzene
(ZXC-8) (Scheme 1). Their structures are very similar to
that of TATB.
c
Figure 2 ; a) Single-crystal X-ray structure of ZXC-7 (b) Packing diagram of ZXC-7 c)
The hydrogen bonding effect of ZXC-7 on the same layer
Scheme 1. Synthetic routes of compounds ZXC-7 and ZXC-8
Crystal structure. The structure of ZXC-7 in the crystalline state
was determined by means of low-temperature single-crystal X-
ray diffraction. Selected crystallographic data, measurement
parameters, and refinement details are given in the Supporting
Information. Single crystals of ZXC-7 (CCDC: 1877144)
suitable for XRD measurements were obtained by
recrystallization from the hot acetonitrile. The molecule
crystallizes in the monoclinic crystal system and belongs to the
C12/C1 (15) space group with four molecules per unit cell and
an moderately high crystal density of 1.8524 g cm−3 at 170 K
(the crystal density of ZXC-7 at 298 K is 1.835 g cm−3 and the
crystal density of ZXC-8 at 298 K is 1.850 g cm−3), and the
detailed crystallographic data are provided in Supplementary
Tables S3–S6. Figure 2a shows the crystal structure of ZXC-7.
From the crystal structure, it can be found that the molecular
structure is almost planar, while the dihedral angles between
nitro groups and the plane of benzene ring are close to zero
Results
Synthesis of ZXC-7 and ZXC-8. The first step in the synthesis
on compound of ZXC-7 or ZXC-8 was the nitration of the
compound of 2,3-trifluoro-4-nitrobenzene (1a) or (3,4,5-
trifluorophenyl)ethylcarbamate (1b) to form compound 2,3,4-
trifluoro-1,5-dinitrobenzene (2a) or 1,3-bis(3,4,5-trifluoro-2,6-
dinitrophenyl)urea (2b) by using a mixture of KNO3 / H2SO4
(The yield of 2a is 91 % and the yield of 2b is 89 %
respectively, The structure of 2b was confirmed by means of
low-temperature single-crystal X-ray diffraction at the
corresponding temperature (Supporting Information table S2，
CCDC: 1877092). In the second step, that is the last step,
the compound of (2a) or (2b) was added to ammonia and
stirred at room temperature before the reaction mixture had
been filtered to yield the compound of 2-fluoro-1,3-diamino-
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(4.094 º). Like TATB, the crystal of ZXC-7 also has layered
stacking similar to graphite.[19] The interaction between layers is
weak, but the interlayer molecules are tightly bound by strong
intermolecular hydrogen bonds and the length of the hydrogen
bond (HB), −NO2 ∙∙∙H, is 2.36 Å (Figure 2b and 2c). In the
crystallization process, the crystal face still has the growth
advantage and also easy to form flaky crystals.
compounds are much more insensitive than TNT, which makes
them safer to handle.
According to the literature method[20]
,
the detonation
experiments of ZXC-7 and ZXC-8 were carried out. A plastic
bonded ZXC-7 explosive with a density of 1.80 g cm-3 was
detonated by a divergent shock wave with a radius of curvature
of 20 mm and a peak pressure of 20 GPa. A good lateral
detonation wave could be obtained at 20 ºC. At -36 ºC, no
lateral detonation wave could be obtained in the main charge of
finite size. At< –80 ºC, the main charge of ZXC-7 was not
Physicochemical properties. After ZXC-7 and ZXC-8
synthesis, we turned our attention to study its properties and
detonation performance. The thermal stability was one of our
primary concerns since it is a particularly crucial property of
Heat-resistant explosives. Their thermal decomposition
temperatures (Td) were determined by DSC. The DSC curves of
the two compounds (Supplementary Fig. 5 and Fig. 6) shown
that their thermal decomposition temperatures are 294.24 ºC
(endset, ZXC-7) and 304.86 ºC (endset, ZXC-8), respectively.
detonated. Similar results were obtained when ZXC-8 was used
as the main charge (At< –80 º C, ZXC-8 was also not
detonated) . At low temperatures, the plastic bonded ZXC-7 (or
ZXC-8) main charge becomes more insensitive, and the
detonation sequence with higher output pressure must be used
to detonate it and obtain lateral divergent detonation wave.
These results signify that they exhibit
a
rather high
Table 1. Physicochemical properties of ZXC-7 and ZXC-8 in comparison to
decomposition temperature comparable to that of TNT (295 ºC)
(Table 1). Unlike TATB, although these two analogues are
insoluble in water, they have good solubility in most common
organic solvents. This characteristic contributes to the green
synthesis and purification of these two compounds.
TNT and TATB.
ZXC-7
ZXC-8
TNT
TATB
Molecular formula
M.W [g mol-1][a].
C6H5FN4O4
216.03
C6H6N3O6
231.04
C7H5N3O6
227.02
C6H6N6O6
258.03
IS [J] [b]
>60
>60
15
>60
The heat of formation (ΔfH) of ZXC-7 and ZXC-8 were
calculated by the isodesmic reaction approach using Gaussian
09 (Revision D.01) suite program, and were estimated to be
377.7 and 423.84 kJ mol−1 (Supplementary Table 8). In addition
to the isodesmic reaction approach, Bomb calorimetry is also a
well-established experimental technique to measure energies of
combustion and calculated the heat of formation. Therefore, the
Bomb Calorimetry study for ZXC-7 and ZXC-8 was also
determined by an oxygen bomb calorimetry, and the measured
constant volume combustion energies were 4592.99 and
4354.82 kJ mol −1, respectively. Using the calculated density and
FS [N] [c]
360
360
>353
1.64
-63.01
-
360
ρ [g cm –3
]
1.83
1.85
1.83
[d]
ΔfHm° [kJ mol–1
]
377.7
4592.99
294
423.84
4354.82
304
455.78[l]
5181.15[l]
350
[e]
ΔfU° [Kj kg –1
]
[f]
T d [°C] [g]
295
6881
19.5
Vc-J [m s –1 [h]
]
7190
22.62[j]
7220
22.83[k]
7880[l]
27.9[l]
P C-J [Gbar][i]
[a] molecular weight; [b] Impact sensitivity (BAM drophammer, method 1 of 6).
[c] Friction sensitivity (BAM drophammer, method 1 of 6). [d] Density at 298 K.
[e] Heat of detonation; [f] Heat of detonation [g] Temperature of
decomposition; [h] Detonation velocity; [i] Detonation pressure. [j] The
calculated value of detonation pressure when the density is 1.76 gcm –3; [k]
The calculated value of detonation pressure when the density is 1.77 gcm –3 [l]
The calculated value atρ=1.83 [g cm –3 ].
the calculated heat of formation, the detonation velocity (vC-J
)
and the detonation pressure (PC-J) of ZXC-7 and its derivative
were evaluated using EXPLO5 (v6.01) program. As shown in
Table 1, their calculated detonation performance (ZXC-7: vC-J
=
7190 m s-1, PC-J= 22.62GPa at ρ= 1.76 g cm–3 ; ZXC-8: vC-J
=
7220 m s -1, PC-J = 22.83 GPa at ρ= 1.77 g cm–3) is between that
of TNT (vC-J = 6881 m s-1, PC-J = 19.50GPa) and that of TATB
(vC-J = 7880 m s-1, PC-J = 27.90 GPa at ρ=1.83 g cm–3). ZXC-7
and ZXC-8 are attractive candidate explosives for heat-resistant
explosives because of their good thermal stability, good
detonation performance and low water solubility.
Conclusions
We demonstrate the synthesis and characterization of two
energetic compounds of ZXC-7 and ZXC-8. ZXC-7 is
determined via single-crystal XRD and shows a planar molecular
structure, remarkable hydrogen bonding interaction, and
In addition to detonation properties, the impact and friction
sensitivities of ZXC-7 and ZXC-8 were evaluated using a
interlayer π–π stacking interaction which contribute to
a
particularly high density. Their measured densities (ZXC-7 is
1.83 g cm-3 and ZXC-8 is 1.85 g cm-3 at 298 K) are similar to that
of TATB (1.83 g cm-3). Both of them possess decent thermal
stability (ZXC-7 is 294 °C and ZXC-8 is 304 °C as thermal
decomposition temperature). Although they are difficult to
dissolve in water like TATB, ZXC-7 and ZXC-8 are soluble in
most organic solvents. In addition, these two energetic materials
have shown good detonation performances (ZXC-7: vC-J =7190m
standard BAM fall-hammer and
a
BAM friction tester,
respectively. Due to extensive intermolecular HBs and layered
stacking in the crystal, ZXC-7 and ZXC-8 have a low sensitivity
towards mechanical stimuli like TATB. The impact sensitivity (IS)
and friction sensitivity (FS) were estimated to be higher than 60J
and 360N, respectively. This indicates that these two
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s −1; P =22.62 GPa; ZXC-7: vC-J =7220 m s −1; P =22.83 GPa)
calculated by using the EXPLO5 v6.02 program. Compared with
TATB, their detonation performance is weaker, but their
sensitivity is as insensitive as TATB. In addition, ZXC-7 and
ZXC-8 have better solubility, simpler synthetic routes and more
effective purification methods than TATB. The combination of
good physical properties, high thermal decomposition
temperature and detonation performance as well as its
straightforward preparation highlight its great promise of
11 a) M. D. Coburn, J. L. Singleton, Journal of hazardous
materials, 1972, 9, 1039–1044; b) M. D. Coburn,
US3678061A, 1972
12 H. S. Jadhay, M. B. Talawar, R. Sivabalan, D. D. Dhavale, S.
N. Asthana, V. N. Krishnamurthy, Indian Journal of hazardous
materials, 2006, 15, 383–386
13 a) R. A. Carboni, J. C. Kauer, W. R. Hatchard, R. J. Harder,
Journal of the American Chemical Society, 1967, 89, 2626–
2633; b) R. A. Carboni, J. C. Kauer, J. E. Castle, H. E.
Simmons, J. Am. Chem. Soc., 1967, 89, 2618–2625; c) J. C.
Kauer, R. A. Carboni, Journal of the American Chemical
Society, 1967, 89, 2633–2637
potential applications as heat-resistant explosives
.
14 a) T. M. Klapçtke, Chemistry of High-Energy Materials, D.
Gruyter, Berlin, Boston, 2015; b) J. P. Agrawal, Propellants,
Explosives, Pyrotechnics, 2005, 30, 316–328.
Acknowledgements
We acknowledge the funding support from the Natural Science
Foundation of Henan province (182102310277) and the Nanhu
Scholar Program for Young Scholars of XYNU (18078). We
would also like to thank Professor Xuehai Ju in Nanjing
University of Science and Technology for all the relevant
calculations in this manuscript come from his hard work.
15 K. G. Shipp, American Journal of Organic Chemistry, 1964,
29, 2620–2623.
16 B. Singh, R. K. Malhotra, Defence Science Journal, 1983, 33,
165–176.
17 T. M. Klapötke, T. G. Witkowski, ChemPlusChem, 2016, 81(4):
357-360.
18 A. K. Sikder, N. Sikder, Journal of hazardous materials, 2004,
112(1-2): 1-15.
■
Data availability. The data that support the findings of this study
19 W. Zhang, J. Zhang, M. Deng, et al. Nature communications,
2017, 8(1): 181-187.
are available from the corresponding authors on request.
20 Q. Fang, Y. Wei, S. Wen. Combustion, Explosion and Shock
Waves (English Translation), 2000, 20(2): 121-124.
■
AUTHOR INFORMATION
§ These authors contributed equally.
Keywords: explosives • detonation performance • energetic
materials • heat-resistant materials
References
1
2
J. P. Agrawal, Propellants, Explosives, Pyrotechnics, 2005, 30,
316–328.
J. Wilbrand, Justus Liebigs Annalen der Chemie, 1863, 178–
179.
3
4
T. M. Klapötke, A. Preimesser, J. Stierstorfer, European
Journal of Organic Chemistry, 2015(20), 4311-4315.
P. Ravi, D. M. Badgujar, G. M. Gore, S. P. Tewari, A. K.
Sikder, Propellants, Explosives, Pyrotechnics, 36(5), 393-403.
H. H. Cady, A. C. Larson, Acta Crystallogr, 1965, 18, 485–496.
M. B. Talawar, A. P. Agarwal, M. Anniyappan, et al., Journal of
hazardous materials, 2006, 137(3): 1848-1852.
P. F. Pagoria, M. X. Zhang, WO2010123806, 2010.
K. G. Shipp, American Journal of Organic Chemistry, 1964,
29, 2620–2623.
5
6
7
8
9
a) F. Gerard, A. Hardy, Acta Crystallographica, Section A:
Crystal Physics, Diffraction, Theoretical and General
Crystallography, 1987, 43, C167; b) F. Gerard, A. Hardy, Acta
Crystallographica, Section A: Crystal Physics, Diffraction,
Theoretical and General Crystallography, 1988, 44, 1283–
1287.
10 J. S. Lee, C. K. Hsu, C. L. Chang, Thermochimica Acta, 2002,
392–393, 173–176.
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COMMUNICATION
The synthetic route of 2-fluoro-
4, 6-dinitrobenzene-1,3,5-
triamine
Zheng Zhang, [a] § Jinchao Ma [b] §
Qiuju Zhou,[a] Wenxiang Hu,[c]
Xingcheng Zhang*[a]
,
These two compounds can be
prepared by means of simple
synthetic methods and shows
outstanding properties (detonation
Page No. – Page No.
Title
velocity,
sensitivity
stimuli,
detonation
toward
pressure,
mechanical
and
temperature
of
decomposition).
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