Synthesis and performance study of methylene-bridged bis(nitramino-1,2,4-oxadiazole) and its energetic salts

Article abstract of DOI:10.1039/C9NJ00421A

In this work, a series of new compounds, 2-9, was synthesized through a simple, safe and efficient route. Dihydroxyimino-malonic acid diamide was chosen as the starting material to react with trichloroacetic anhydride to form 1,2,4-oxadiazole rings. Then, the products from the ring-forming reaction were reacted with an excess amount of ammonia in methanol to give 3,3′-methylenebis(1,2,4-oxadiazol-5-amine) (2). Further nitration of compound 2 gave N,N′-(methylenebis(1,2,4-oxadiazole-3,5-diyl))dinitramide (3, DNAMBO). A series of DNAMBO-based energetic salts, 4-9, paired with nitrogen-rich cations was readily obtained by treating compound 3 with two equivalents of free base. The physicochemical and energetic properties of compounds 3-9, including density, thermal stability, and sensitivity, were investigated, and the detonation performances were calculated by using the Kamlet-Jacobs equations. Among them, the hydrazinium salt (5) shows the best detonation performance (5: d = 1.69 g cm^?3; T_d = 147.5 °C; P = 27.1 GPa; v_D = 7962 m s^?1).

Full text of DOI:10.1039/C9NJ00421A

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ISSN 1144-0546
PAPER
Jason B. Benedict et al.
The role of atropisomers on the photo-reactivity and fatigue of
diarylethene-based metal–organic frameworks
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Synthesis and Performance Study of Methylene bridged
Bis(Nitramino-1,2,4-oxadiazole) and its energetic salts
Yupeng Caoa,b, Xiangyang Lin*a, Jun Yang*b, Xuedong Gonga, Guijuan Fanc and Haifeng Huang*b
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
In this work, a series of new compounds 2-9 was synthesized through a simple, safe and efficient route. Dihydroxyimino-
malonic acid diamide was chosen as the starting material to react with trichloroacetic anhydride to form 1,2,4-oxadiazole
rings. Then the products from the ring-forming reaction reacted with an excess amount of ammonia in methanol to give
www.rsc.org/
3,3'-methylenebis(1,2,4-oxadiazol-5-amine) (2). Further nitration of compound
2 gave N,N'-(methylenebis(1,2,4-
oxadiazole-3,5-diyl))dinitramide (3, DNAMBO). A serial of DNAMBO-based energetic salts 4-9 pairing with nitrogen-rich
cations were readily obtained by treating compound 3 with two equivalents of free bases. The physicochemical and
energetic properties of compounds 3-9, including density, thermal stability, and sensitivity, were investigated, as well as
the detonation performances were calculated by the Kamlet-Jacobs equations. Among them, the hydrazinium salt (5)
shows the best detonation performances (5: d=1.69 g cm-3; Td=147.5 oC; P=27.1 GPa; vD=7962 m s-1).
oxadiazole-2-oxide (c)[6] (scheme 1). These reported energetic
salts show good comprehensive performances (scheme 1).
Introduction
N
N
N
N
In the development of new energetic materials, high energy,
high stability, and green synthesis have always been among
our most sought after goals[1]. Taking the nitrogen-oxygen
heterocycle as the skeleton and introducing explosophores
such as nitro and nitramino group are one of the main ideas
for constructing energetic compounds in recent years. It is
undeniable that, guided by this idea, a large number of new
energetic compounds with excellent properties have been
synthesized[2]. However, we should also note at the same time
that there are some problems in the synthesis of these
energetic molecules, for example, the synthetic route is two
long, the raw materials are not readily available or safe enough
to use, which will make it very difficult for scale-up and further
application.
O
N
NNO2
N
NNO2
N
O
N
N
O
N
O
NNO2
O
N
O
O2NN
N
O2NN
N
N
N
O
N
2NH3OH
2NH3OH
2NH3OH
b
c
a
Td=193 o
C
Td=198 o
C
d=1.84 g cm-3
D=8889 m-1
Td=179.2 o
d=1.84 g cm-3
D=8977 m-1
C
d=1.85 g cm-3
D=9046 m-1
Scheme 1 Selected energetic materials based on 1,2,4-oxadiazole ring.
In the reports of these documents, the construction of
amino-1,2,4-oxadiazole, the precursor of nitramino-1,2,4-
oxadiazole, exclusively proceed by the reaction between
amino-oxime and cyanogen bromide (Route 1 in scheme 2).
Due to the high toxicity and sublimation characteristics of
cyanogen bromide, there are huge potential safety hazards in
its use. In addition, it was found that the synthesis of some
compounds containing amino-1,2,4-oxadiazole block through
Route 1 was unsuccessful in our previous work. Based on these
considerations, we referred to the literature[7] and selected a
safer and more efficient route (Route 2 in scheme 2) to
construct some new compounds containing amino-1,2,4-
oxadiazole block.
Nitramino-1,2,4-oxadiazole has been intensively used as a
block with high energy and good stability in the construction of
several
new
energetic
compounds[3],
e.g.
the
hydroxylammonium salts of N-(4-(5-(nitroamino)-1,2,4-
oxadiazol-3-yl)-1,2,5-oxadiazol-3-yl)nitramide (a)[4], N,N'-([3,3'-
bi(1,2,4-oxadiazole)]-5,5'-diyl)dinitramide (b)[5] and 4-(5-
(nitroamino)-1,2,4-oxadiazol-3-yl)-3-(1H-tetrazol-5-yl)-1,2,5-
a. School of Chemical Engineering, Nanjing University of Science and Technology,
Xiaolingwei 200, Nanjing, 210094, P. R. China, E-mail: linxiangyang@njust.edu.cn.
b. CAS Key Laboratory of Energy Regulation Materials, Shanghai Institute of Organic
Chemistry, Chinese Academy of Sciences, Ling Ling Road 345, Shanghai, 200032,
P. R. China, E-mail: yangj@sioc.ac.cn; hfhuang@sioc.ac.cn.
c. Institute of Chemical Materials, CAEP, Mianyang, 621050, P. R. China.
Electronic Supplementary Information (ESI) available: [details of any
supplementary information available should be included here]. See
DOI: 10.1039/x0xx00000x
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9
Route 1
Compounds 4-9, a series of energetic salts of compound 3,
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were prepared by treating the solutioDnOoI:f10c.1o0m39p/Co9uNnJd003421inA
ethanol with different free bases and the products
precipitated from the reaction mixture and were collected by
filtration. These energetic salts were fully characterized by
NMR (1H, 13C), IR and elemental analysis, and salt 4 was further
confirmed by single-crystal X-ray diffraction.
NH2
NH2
BrCN: highly toxic
mp 52 o
N
N
BrCN
C
R
R
N
O
bp 61.4 o
C
OH
Route 2
NH2
CCl3
NH2
N
N
NH3
(Cl3CCO)2O
R
R
R
N
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In order to synthesize energetic materials with higher
detonation performances, we tried to introduce nitro group on
the methylene group of compound 2 by treating it with mixed
acid (fuming nitric acid/98% sulfuric acid, and fuming nitric
acid/trifluoroacetic anhydride), but failed to get the target
compound 10.
O
O
N
N
OH
Scheme 2 Common construction route of nitramino-1,2,4-oxadiazole.
In this study, we bridged two nitramino-1,2,4-oxadiazole
blocks with methylene, a non-energetic fragment, and hoped
to build a new energetic compound with low low sensitivity. In
order to construct the nitration precursor (3,3'-
methylenebis(1,2,4-oxadiazol-5-amine) (2)) safely and
efficiently, we chose dihydroxyimino-malonic acid diamide as
the starting material and it reacted with trichloroacetic
anhydride to form 1,2,4-oxadiazole rings. Then the obtained
compound 1 reacted with an excess amount of ammonia in
methanol to give compound 2. After nitration of compound 2,
we successfully synthesized N,N'-(methylenebis(1,2,4-
oxadiazole-3,5-diyl))dinitramide (3). In order to synthesize
energetic materials with higher detonation performances, we
tried to introduce nitro group onto the methylene group of
compound 2, but failed to get the target compound 10. All
new compounds in this work were fully characterized and a
series of physical and chemical properties of these energetic
compounds were investigated in detail.
N
CCl3
NH2 NH2
N
NH3
CH3OH
(Cl3CCO)2O
N
HO
OH
N
O
Cl3C
N
N
O
1
BrCN
H
NO2
H2N
N
HNO3 / H2SO4 or
HNO3 / (CF3CO)2O
N
N
O2N
NO2
O
O
N
N
N
N
O2N
N
N
NH2
N
H
O
O
10
2
N2O5/CHCl3
H
N
N
N
NO2
N
2Cation
O2N
NO2
Base/CH3OH
O
N
N
O
N
N
N
O2N
N
N
O
N
H
O
4-9
3
H
N
NH2
H2N
NH2
NH2
NH2
N
NH2
H2N
NH2
Cation
NH4
NH3NH2
=
N
NH2
N
N
N
H
H2N
H2N
H
H
H
4
5
6
7
8
9
Scheme 3 Synthetic route of compounds 1-10.
Results and Discussion
Synthesis
NMR spectroscopy
All NMR (1H, 13C) data were recorded for compounds 1-9 in
DMSO-d6 solution. For compound 2, the position of the
resonance bands for the proton of methylene was observed at
3.67 ppm, and those for amino groups were recorded at 7.74
ppm. Compared to compound 2, the signal of acidic protons of
Dihydroxyimino-malonic acid diamide was chosen as the
starting material to react with trichloroacetic anhydride at 140
oC to give bis(5-(trichloromethyl)-1,2,4-oxadiazol-3-yl)methane
(1) in the yield of 91.5 %. The ammonolysis of 1 took place
when an excess amount of gaseous ammonia was bubbled into
the solution of 1 in methanol, and compound 2 precipitated
from the reaction mixture after stirring overnight. We also
tried to get compound 2 by treating dihydroxyimino-malonic
acid diamide with cyanogen bromide in methanol, but failed to
separate valuable products.
1
compound 3 are downshifted to 9.20 ppm in the H NMR
owing to the powerful electron-withdrawing effect of the nitro
group, the position of the resonance band for the proton of
methylene are shifted to 4.24 ppm at the same time. Since the
deprotonation of 4 with nitrogen-rich bases, the 1H NMR signal
of proton on methylene were observed from 3.82 to 3.88 ppm
for compounds 4-8 and the signal of corresponding cations
were also recorded in the 1H NMR.
In the 13C NMR, the signal of oxadiazole rings in compound 2
were observed at 170.0 and 163.4 ppm, the signal of the
methylene group in compound 2 was at 23.7 ppm. All the 13C
NMR signals of compound 3 are shifted to the higher field
compared with compound 2. This phenomenon is somewhat
abnormal. In general, after the amino group on the oxadiazole
ring is nitrated, the 13C NMR signal of the carbon directly
connected to the nitramino group will move to the lower field
due to the strong electron-withdrawing effect of the nitramino
Initially, we tried to nitrate compound 2 directly by using
100% nitric acid and found that it was difficult to extract the
product with various solvents after quenching the reaction
mixture with water. The reason behind this might be that the
product is quite soluble in water. Therefore we chose the
widely used N2O5 as the nitration agent because the remaining
N2O5 can easily be removed. When the nitration reaction in
N2O5/CHCl3 system was complete, compound 3 was obtained
as high purity solid by simplify removing N2O5 and CHCl3 under
vacuum and washing the crude products with a small amount
of methanol.
2 | J. Name., 2012, 00, 1-3
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1
2
3
4
5
6
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8
9
All energetic salts with the exception of 5 are more thermally
group. For the ionic derivatives (salts 4-9) of 3, deprotonation
of 3 resulted in a downshifting (salt 4: 175.25, 165.94, 24.66
ppm vs 3: 170.26, 159.65, 22.15 ppm).
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stable than compound 3, and their thDeOrmI: 1a0l.1d03e9c/oCm9NpJo0s0i4ti2o1nA
o
temperatures range from 183 (8) to 209 C (4). Unexpectedly,
salt 5 shows a comparatively low decomposition temperature
X-ray crystallography
o
of 148 C, which is even lower than that of compound 3 (152
oC).
X-ray quality crystals of 4 was obtained by evaporation of its
aqueous solution. It crystallized in the monoclinic space group
with C 2/c symmetry, and has four units in the unit cell (Z=4).
Its crystal density is 1.738 g cm-3 at 296 K. It can be seen from
the torsion angles of -179.07o (C2-N2-C1-C3), 175.41o (N2-C1-
C3-C1), 6.27o (C2-N3-N4-O2) and -177.12o (N1-O1-C2-N3) that
all atoms of the entire anion are almost coplanar and two
cations are trapped between the DNAMBO anion planes. The
single-crystal X-ray structure and unit cell view of 4 along b
axis are shown in Figure 1.
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192 o
C
60
40
20
0
9 Peak 206 o
C
183 o
199 o
195 o
C
8 Peak 197 o
7 Peak 223 o
6 Peak 245 o
5 Peak 158 o
C
C
C
C
C
C
146 o
C
209 o
C
4 Peak 223 o
C
152 o
C
3 Peak 163 o
C
100
200
300
Temperature o
C
Figure 2 DSC curves of compounds 3-10 at a heating rate of 5 K min-1
Densities
According to the Kamlet-Jacobs equations, we know that
density is one of the main factors determining the detonation
performance of energetic materials[10-11]
.
(a)
The densities of compounds 3-9 were measured by using a
gas pycnometer at room temperature and the results are listed
in Table 1. The measured densities of compounds 3-9 are
distributed between 1.763 g cm-3 (4) and 1.568 g cm-3 (6).
Among them, compound 4 possesses the highest density of
1.763 cm-3. Except for compounds 6 (1.568 g cm-3) and 7
(1.612 g cm-3), all of these compounds have a higher density
than TNT (1.65 g cm-3).
Sensitivities
For initial safety testing, the sensitivities of the newly
prepared compounds 3-8 towards friction and impact were
measured by using BAM drop hammer (BFH-10) and BAM
friction tester (FSKM-10) and the results are listed in Table 1.
A large number of studies have shown that the impact
sensitivity of energetic materials are closely related to their
electrostatic potential (ESP)[12-14]. In most N-O systems, such as
nitro (−NO2) and nitramine (−NH−NO2), the regions of stronger
positive potential accumulated around the nitrogen atoms will
result in an abnormal imbalance, which in theory will cause the
high impact sensitivity[15]. In order to understand this
relationship more intuitively, we calculated the ESP of
compound 3 using Gaussian 09 at the theoretical level of
B3LYP/6-31+g(d,p) before the actual measurement of the
sensitivity. As can be seen from the calculated EPS image of
compound 3 showed in Figure 3, the positive potential on the
ring is more uniformly dispersed, while the nitrogen atom of
the nitro group accumulates positive potential, so we suspect
that the impact sensitivity of compound 3 may be relatively
high, which was confirmed experimentally.
(b)
Figure 1 a) Displacement ellipsoid plot (30 %) of salt 4. b) Ball-and-stickpacking
diagram of salt 4.
Thermal stabilities
Thermal decomposition temperature is an important
indicator for evaluating the thermal stability of an energetic
material. Energetic material with good thermal stability will
greatly improve their safety during production and use[8].
Generally speaking, the decomposition temperature of a
o
useful energetic material tends to be higher than 150 C[9]. In
this work, the series of newly prepared compounds 3-8 have
acceptable thermal stability with decomposition temperatures
o
o
being between 148 C and 209 C. As shown in Figure 2,
o
compound 3 decompose at 152 C and loses crystal water at
122 C, which corresponded to a weight loss on the TG curve.
o
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According to the Born−Haber energy cycle, the relationship
between the △Hf values of the cations and anion of each salt
can be expressed by the following equation.
△Hfo(ionic salt, 298K) = △Hfo(cation, 298K)＋△Hfo (anion, 298K)
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DOI: 10.1039/C9NJ00421A
－△HL
(1)
The △HL value could be predicted by the formula suggested by
Jenkins et al [Eq. (2)][17], where UPOT is the lattice potential
energy and nM and nX depend on the nature of the ions Mp ＋
and Xq －, respectively, and are equal to three for monoatomic
ions, five for linear polyatomic ions, and six for nonlinear
polyatomic ions.
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△HL = UPOT + [p(nM/2-2) + q(nX/2-2)]RT
(2)
The equation for the lattice potential energy, UPOT, takes the
form of Equation (3), where ρm is the density (g cm-3), Mm is
the chemical formula mass of the ionic material (g), and the
coefficients γ (kJ-1mol-1cm) and δ (kJ-1mol-1) are assigned
literature values.
Figure 3 Electrostatic potential of compound 3 [B3LYP/6-311+g- (2d,p), 0.001
electron/b3 isosurface, energy values −0.06 to +0.06 H]. Color coding: yellow,
slightly negative; green, neutral; turquoise, slightly positive; light blue, positive;
dark blue, very positive.
UPOT (kJ-1mol-1) = γ (ρm/Mm)1/3 + δ
(3)
fo
Cation Anion (solid)
aC(s)+bH2(g)+cN2(g)+dO2(g)
Impact sensitivities and friction sensitivities of compounds
3-8 are in the range of 3 J (5) to 14 J (9) and 96 N (5) to >360 N
(6), respectively. Among these compounds, the impact and
friction sensitivity of compound 3 are not particularly
satisfactory, at 5 J and 160 N respectively. Salt 6 has the lowest
friction sensitivity (> 360 N) and good impact sensitivity (12 J).
And the results are listed in Table 1.
o
L
foanion
focation
Scheme 5 Born–Haber cycle for the formation of energetic salts.
(solid)
Cation
Anion (solid)
Heats of formation
As shown in Table 1, the △Hf values of compounds 3-9 were
calculated to be in the range of -39.1 to 429.3 kJ mol-1. Among
them, the △Hf value of compound 3 were calculated to be
115.9 kJ mol-1 and diaminoguanidinium salt (8) possesses the
highest △Hf value of 429.3 kJ mol-1.
Heat of formation is an important parameter in evaluating
the detonation performance of energetic materials. All
calculations were accomplished by using the Gaussian 09
(Revision A.01) suite of programs[16]
.
The geometric
optimization of the structures and frequency analyses were
carried out by using the B3LYP functional with the 6-
31+G**basis set, and single-point energies were calculated at
the MP2(full)/6-311++G**level. All of the optimized structures
were characterized to be true local energy minima on the
potential-energy surface without imaginary frequencies. The
remaining task, the heats of formation of compound 3 and its
corresponding anion, were calculated by employing the
isodesmic reaction approach.
Detonation performances
Detonation velocity (vD) and detonation pressure (P) are two
basic parameters for evaluating the detonation performance
of energetic materials. With calculated heats of formation and
measured densities, we calculated the detonation velocities
and detonation pressures of compounds 3-8 according to the
Kamlet-Jacobs equations[11]. According to the calculation
results, we can see that their detonation velocities are
distributed in the range of 6845 m s-1 to 7962 m s-1, and their
detonation pressures are distributed in the range of 19.1 GPa
to 27.1 GPa. Although the measured density of 5 is relatively
low, it has the best detonation performance (vD=7962 m s-1,
P=27.1 GPa) due to its high heat of formation.
H
N
N
O2N
N
N
2NH3
5CH4
O
2
2CH3CH3
N
2NO2NH2
2CH3NH2
N
O
NO2
N
N
H
O
N
N
O2N
N
N
2NH3
5CH4
O
2
2CH3CH3
N
2NO2NH
2CH3NH2
N
O
NO2
N
N
O
Scheme 4 Isodesmic reactions for calculation of the heats of formation of the
compound 3 and its anion.
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Table 1 Physical properties and thermochemical values of compounds 3-9.
[a]
[d]
[e]
[f]
[h]
Compd
Td
d[b]
△fHL[c]
-
△fHcation
-
635.8
774.1
563.7
660.3
769
△fHanion
-
△fHsalt
P[g]
vD
IS[i]
5
8
3
11
9
7.5
14
15
FS[j]
160
324
96
>360
192
128
168
353
OB[k]
-35.3
-46.9
-47.6
-61.5
-60.9
-60.4
-64.6
-74.0
3
4
5
6
7
8
9
TNT
152
209
148
195
199
183
192
295
1.744
1.763
1.694
1.568
1.612
1.676
1.728
1.65
115.9
-39.1
300.5
-14.8
198.9
429.3
389.1
-59.4
26.4
26.5
27.1
19.1
23.4
24.9
23.0
21.3
7787
7775
7962
6845
7511
7661
7291
7303
1328.8
1265.8
1160.3
1139.8
1126.8
1121.0
-
18.1
18.1
18.1
18.1
18.1
18.1
-
804.5
-
[a] Decomposition temperature (onset) [oC] [b] Density measured by gas pycnometer at 25oC [g cm-3]. [c] Calculated molar lattice energy [kJ mol-1] [d] molar
enthalpy of formation of cation [kJ mol-1] [e] Calculated molar enthalpy of formation of anion [kJ mol-1] [f] Calculated molar enthalpy of formation of salts [kJ mol-1] [g]
Detonation pressure [GPa] [h] Detonation velocity [m s-1] [i] Impact sensitivity [J] [j] Friction sensitivity [N] [k] Oxygen balance (OB) is an index of the deficiency or
excess of oxygen in a compound required to convert all C into CO2 and all H into H2O, for the compound with the molecular formula of CaHbNcOd, OB(%)=1600[(d-2a-
b/2)/Mw] [%].
Experimental Section
CCDC-1877493
(4)
contains
the
supplementary
crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
1
General methods: The H and 13C spectra were recorded on a
400 MHz nuclear magnetic resonance spectrometer operating
at 400 and 100 MHz and chemical shifts are reported relative
to tetramethylsilane. The solvent was [D6]dimethyl sulfoxide Dihydroxyimino-malonic acid diamide
([D6]DMSO) unless otherwise specified. The melting and
Malononitrile (5 g, 75.96 mmol) was dispersed in water (40
decomposition points were recorded on a NETZSCH STA 449F3
equipment at a heating rate of 5oC min-1, respectively. Infrared
spectra were recorded by using KBr pellets. Densities for
compounds 3-9 were measured at room temperature using a
Micromeritics Accupyc Ⅱ 1340 gas pycnometer. Elemental
analyses were obtained on an Elementar Vario MICRO CUBE
(Germany) elemental analyzer.
mL). Hydroxylamine aqueous solution (50%, 10 mL, 151.37
mmol) was added to the above system at room temperature.
After stirring overnight, the precipitate was filtered and
washed with ice water, dried in air to give dihydroxyimino-
malonic acid diamide (9.5 g, yield 95%). H NMR (400 MHz,
DMSO-d6): 4.42 (s, 2H) ppm; 13C NMR (400MHz, DMSO-d6):
175.32, 166.02, 83.15, 24.49 ppm.
1
X-ray crystallography: Crystals of salt 4 were removed from the
flask and covered with a layer of hydrocarbon oil, respectively.
A suitable crystal was selected, attached to a glass fiber, and
placed in the low-temperature nitrogen stream. The single-
crystal X-ray diffraction data were collected at 173 K using a
Bruker CCD area detector diffractometer equipped with a
graphite-monochromatized MoKα radiation (λ=0.71073 Å)
using omega scans. Data collection and reduction were
performed and the unit cell was initially refined by using
Bruker SMART software. The reflection data were also
corrected for Lp factors. The structure was solved by direct
methods and refined by least squares method on F2 using 3,3'-Methylenebis(1,2,4-oxadiazol-5-amine) (2)
Bruker SHELXTL program. Structure was solved in the space
group P-1 by analysis of systematic absences. In this all-light-
atom structure the value of the Flack parameter did not allow
the direction of polar axis to be determined and Friedel
reflections were then merged for the final refinement. Details
of the data collection and refinement are given in Table S1.
Bis(5-(trichloromethyl)-1,2,4-oxadiazol-3-yl)methane (1)
Dihydroxyimino-malonic acid diamide (5 g, 37.84 mmol) was
dispersed in trichloroacetic anhydride (28 mL, 151.37 mmol) at
room temperature. Then, the mixture was heated to 105 °C
and reacted for 3.5 h. After cooled down to RT, the reaction
mixture was poured into ice water (150 mL) and stirred for 0.5
h. The precipitate was filtered and washed with ice water to
give 1 (13.2 g, yield 92%). H NMR (400 MHz, DMSO-d6): 9.01
(s, 2H), 5.33 (s, 4H), 2.68 (s, 2H) ppm; 13C NMR (400MHz,
DMSO-d6): 149.68, 33.40 ppm.
1
Compound 1 (13.2 g, 34.4 mmol) was dispersed in methanol
(20 mL) at 5 °C, and excess gaseous ammonia was bubbled into
the methanol solution for 40 min. A large amount of white
solid precipitated from the reaction mixture and was collected
by filtration followed by washing with methanol and drying in
air to give compound 2 (4.57 g, yield 73%). 1H NMR (400 MHz,
This journal is © The Royal Society of Chemistry 20xx
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DMSO-d6): 7.74 (s, 4H), 3.67 (s, 2H) ppm; 13C NMR (400MHz, 1061, 1009, 984, 929, 846, 816, 797, 760, 735, 693, 663, 623,
View Article Online
1
DMSO-d6): 172.02, 166.34, 23.74 ppm.
497; H NMR (400 MHz, DMSO-d6): 7.05D(OsI,: 1104.1H0)3,93/C.892NJ(0s0,422H1A)
ppm; 13C NMR (400MHz, DMSO-d6): 174.83, 165.82, 159.73,
24.50 ppm; Anal. Calcd. For C9H14N18O6: C 22.98, H 3.00, N
53.61; found: C 22.52, H 3.06, N 52.13.
N,N'-(Methylenebis(1,2,4-oxadiazole-3,5-diyl))dinitramide (3·H2O)
Compound 2 (1.4 g, 7.7 mmol) was dispersed in a solution of
N2O5 (9 g, 7.69 mmol) in chloroform (50 mL) under an ice-
water bath. The reaction mixture was allowed to warm to
room temperature and stirred for 12 h. After removing the
Bis(guanidinium)
N,N'-(methylenebis(1,2,4-oxadiazole-3,5-
diyl))dinitramide (6)
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solvent and N2O5 under vacuum, methanol (5 mL) was added One equivalent of guanidine carbonate (132 mg, 0.734 mmol)
and the mixture was stirred for 10 min to give a white was added into the solution of 3 (200 mg, 0.734 mmol) in
precipitate, which was then filtered and washed with ethanol at room temperature. After stirring at room
methanol to give compound 3 (1.5 g, yield 71%). FI-IR (KBr temperature until no further gas evolution, the precipitate was
pellet, cm-1): 3581, 3485, 3238, 2967, 2231, 2085, 2046, 1933, filtered, washed with a small amount of ethanol and dried in
1616, 1506, 1456, 1276, 1174, 1068, 1004, 968, 899, 845, 792, air to give 6 (248 mg, yield 86%). FI-IR (KBr pellet, cm-1): 3178,
779, 758, 728, 666, 625, 615, 504, 468, 429, 418. 1H NMR (400 2804, 2292, 2010, 1651, 1538, 1428, 1300, 1211, 1086, 1030,
MHz, DMSO-d6): 9.20 (s, 2H), 4.24 (s, 2H) ppm; 13C NMR 1011, 997, 972, 949, 937, 915, 871, 828, 842, 773, 741, 633,
1
(400MHz, DMSO-d6): 170.26, 159.65, 22.15 ppm; Anal. Calcd. 543; H NMR (400 MHz, DMSO-d6): 6.93 (s, 12H), 3.82 (s, 2H)
For C5H4N8O6: C 20.70, H 2.08, N 38.62; found: C 20.78, H 2.02, ppm; 13C NMR (400MHz, DMSO-d6): 174.75, 165.78, 24.46
N 38.73.)
ppm; Anal. Calcd. For C7H14N14O6: C 21.54, H 3.62, N 50.25;
found: C 21.39, H 3.63, N 50.17.
Diammonium
dinitramide (4)
N,N'-(methylenebis(1,2,4-oxadiazole-3,5-diyl))
Bis(aminoguanidinium) N,N'-(methylenebis(1,2,4-oxadiazole-3,5-
diyl))dinitramide (7)
Compound 3 (200 mg, 0.734 mmol) was dispersed in ethanol
(1.5 mL), and gaseous ammonia was bubbled into the system Tow equivalents of aminoguanidine bicarbonate (200 mg, 1.47
until its pH value was higher than 7. After stirring at room mmol) were added into the solution of 3 (200mg, 0.734mmol)
temperature for 3 h, the precipitate was filtered, washed with in ethanol at room temperature. After stirring at room
a small amount of ethanol and dried in air to give 4 (174 mg, temperature until no further gas evolution, the precipitate was
yield 77%). FI-IR (KBr pellet, cm-1): 3193, 2251, 1982, 1543, filtered, washed with a small amount of ethanol to give 7
1444, 1393, 1262, 1211, 1094, 988, 926, 777, 763, 753, 741, (298mg, yield 96%) after drying in air. FI-IR (KBr pellet, cm-1):
724, 621, 478, 411; 1H NMR (400 MHz, DMSO-d6): 6.98 (s, 8H), 3449, 3347, 3296, 2990, 2949, 1671, 1655, 1559, 1543, 1511,
3.87 (s, 2H) ppm; 13C NMR (400MHz, DMSO-d6): 175.25, 1432, 1404, 1313, 1262, 1181, 1089, 987, 966, 841, 827, 781,
1
165.94, 24.66 ppm; Anal. Calcd. For C5H10N10O6: C 19.61, H 750, 740, 726, 664, 654, 610, 477; H NMR (400 MHz, DMSO-
3.29, N 45.74; found: C 19.59, H 3.33, N 45.99.
d6): 8.62 (s, 2H), 7.25 6.80 (d, 8H), 4.68 (s, 4H), 3.83 (s, 2H)
ppm; 13C NMR (400MHz, DMSO-d6): 174.79, 165.84, 158.83,
24.50 ppm; Anal. Calcd. For C7H16N16O6: C 20.00, H 3.84, N
53.32; found: C 19.85, H 4.08, N 52.71.
General procedures for the preparation of salts 5 and 9.
Compound 3 (200 mg, 0.734 mmol) was dispersed in ethanol
(1.5 mL) at room temperature followed by adding two
equivalents of free base (hydrazine hydrate (80%) or 3,5-
diamino-1,2,4-triazole) in one portion. After stirring at room
Bis(diaminoguanidinium)
3,5-diyl))dinitramide (8)
N,N'-(methylenebis(1,2,4-oxadiazole-
temperature for 3 h, the precipitate was filtered, washed with N,N'-Diaminoguanidine hydrochloride (185 mg, 1.47 mmol)
a small amount of ethanol and dried in air to give the desired was neutralized with equal molar solution of NaOH (40 mg, 1.0
product.
mmol) in ethanol (2 mL). After stirring at room temperature
for 30 min, the filtrate A was obtained by filtration. 3 (200 mg,
0.734 mmol) was dispersed in the filtrate A and stirred for 3 h.
The precipitate was collected by filtration and washed with
ethanol to give the product 8 (208 mg, yield 63%) after air
drying. FI-IR (KBr pellet, cm-1): 3419, 3268, 3087, 2992, 2892,
2292, 2005, 1682, 1542, 1436, 1378, 1358, 1272, 1180, 1085,
1032, 996, 970, 932, 910, 870, 779, 765, 753, 744, 725, 655,
642, 547, 477, 426; 1H NMR (400 MHz, DMSO-d6): 8.57 (s, 4H),
7.14 (s, 4H), 4.59 (s, 8H), 3.82 (s, 2H) ppm; 13C NMR (400MHz,
DMSO-d6): 174.83, 165.82, 159.73, 24.50 ppm; Anal. Calcd. For
Dihydrazinium
dinitramide (5)
N,N'-(methylenebis(1,2,4-oxadiazole-3,5-diyl))
White powder; Yield: 198 mg, 80%; FI-IR (KBr pellet, cm-1):
3342, 3242, 2989, 2007, 1594, 1559, 1513, 1404, 1362, 1313,
1262, 1182, 1088, 1000, 950, 869, 841, 776, 752, 739, 620,
479, 444; 1H NMR (400 MHz, DMSO-d6): 8.44 (s, 10H), 3.88 (s,
2H) ppm; 13C NMR (400MHz, DMSO-d6): 174.93, 165.66, 24.35
ppm; Anal. Calcd. For C5H12N12O6: C 17.86, H 3.60, N 49.99;
found: C 17.82, H 3.61, N 50.02.
Bis(3,5-diamino-1,2,4-triazolium)
oxadiazole-3,5-diyl))dinitramide (9)
N,N'-(methylenebis(1,2,4- C7H18N18O6: C 18.67, H 4.03, N 55.99; found: C 19.16, H 4.03, N
54.32.
White powder; Yield: 306 mg, 89%; FI-IR (KBr pellet, cm-1):
3625, 3410, 3262, 3175, 2872, 2809, 2651, 1697, 1670, 1525,
1511, 1455, 1399, 1343, 1418, 1319, 1288, 1261, 1171, 1108,
Conclusions
6 | J. Name., 2012, 00, 1-3
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In this work, a series of new energetic compounds 2-9 were
synthesized through a simple, safe and efficient route. N,N'-
(Methylenebis(1,2,4-oxadiazole-3,5-diyl))dinitramide (3) and
its energetic salts (4-9) were fully characterized by
multinuclear NMR (1H, 13C), IR spectroscopy and elemental
analysis, and salt 4 was further confirmed by single-crystal X-
ray diffraction. Except for salt 5, salts 4-9 show excellent
3
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o
thermal stabilities of 183 (8) to 209 C (4), which are much
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better than their parent compound 3 (Td=152 oC). Their
densities were measured to be in the range of 1.568 g cm-3 (6)
and 1.763 g cm-3 (4). Among them, the diammonium salt (4)
shows the highest density (d=1.763 g cm-3). Their impact
sensitivities and friction sensitivities were determined to be in
the range of 3 J (5) and 14 J (9) and 96 N (5) to >360 N (6),
respectively. And their detonation pressures and detonation
velocities were calculated according to Kamlet-Jacobs
equations to be between 19.1 (6) and 27.1 (5) GPa and 6845
(6) and 7962 (5) m s-1, respectively. Among them, the
dihydrazinium salt (5) shows the best detonation performance
performances (5: P=27.1 GPa; vD=7962 m s-1).
4
5
6
7
8
H. Wei, C. He, J. Zhang and J. M. Shreeve. Angew. Chem.
Int. Ed. 2015, 54, 9367 –9371
Conflicts of interest
The authors declare no conflict of interest.
G. Zhao, C. He, P. Yin, G. H. Imler, D. A. Parrish and J. M.
Shreeve. J. Am. Chem. Soc. 2018, 140, 3560−3563.
Y. Liu, C. He, Y. Tang, G. H. Imler, D. A. Parrish and J. M.
Shreeve. Dalton Trans. 2018, 47, 16558–16566.
Acknowledgements
This work was financially supported by National Natural
Science Foundation of China (NSFC, Grant. No. 21602241).
Y. Cao, H. Huang, X. Lin, J. Yang and X. Gong. New J.
Chem. 2018, 42, 11390-11395.
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J. 2017, 23, 1–9. b) Y. Cao, H. Huang, X. Lin, J. Yang and X.
Gong. New J. Chem. 2018, 42, 11390–11395.
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