Super-high-energy materials based on bis(2,2-dinitroethyl)nitramine

Article abstract of DOI:10.1039/c2jm15310f

Novel super-highly energetic bis(2,2-dinitroethyl)nitramine-based salts exhibiting excellent physical and detonation properties, such as low solubility in common solvents, moderate thermal stabilities, high densities, high detonation pressures and detonation velocities, were synthesized and fully characterized. The densities of the energetic salts range between 1.77 and 2.02 g cm^-3 as measured using a gas pycnometer. The detonation pressures and velocities as calculated by the EXPLO5 code are in the range 31.5-46.2 GPa and 8586-10004 m s^-1, which make them competitive super-highly energetic materials.

Full text of DOI:10.1039/c2jm15310f

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PAPER
Super-high-energy materials based on bis(2,2-dinitroethyl)nitramine†
a
ab
a
a
a
a
a
Jinhong Song, Zhiming Zhou,* Xiao Dong, Haifeng Huang, Dan Cao, Lixuan Liang, Kai Wang,
a
Jun Zhang, Fu-xue Chen and Yukai Wu
a
a
Received 19th October 2011, Accepted 7th December 2011
DOI: 10.1039/c2jm15310f
Novel super-highly energetic bis(2,2-dinitroethyl)nitramine-based salts exhibiting excellent physical
and detonation properties, such as low solubility in common solvents, moderate thermal stabilities,
high densities, high detonation pressures and detonation velocities, were synthesized and fully
ꢀ3
characterized. The densities of the energetic salts range between 1.77 and 2.02 g cm as measured using
a gas pycnometer. The detonation pressures and velocities as calculated by the EXPLO5 code are in the
ꢀ1
range 31.5–46.2 GPa and 8586–10 004 m s , which make them competitive super-highly energetic
materials.
Introduction
Currently, energetic nitrogen-rich salts, which are among the
most exciting developments, continue to attract more interest
than atomically similar non-ionic analogues, due to lower vapour
pressures, higher heats of formation, and enhanced thermal
The development of high-energy-density materials (HEDMs)
with improved performance has attracted considerable atten-
1–16
tion.
However, the demands of high energy and insensitivity
1
stabilities. Salt formation of the acidic precursor by direct
are quite often contradictory to each other, making the devel-
1
opment of novel HEDMs a difficult and challenging problem.
neutralization or metathesis reactions with alkaline nitrogen-rich
cations is a very effective method to increase the nitrogen
content, the heats of formation and the possibility for hydrogen
bonding, as a consequence of the densities and performances.
Up to now, there are only two compounds that possess the
ꢀ1
detonation velocities comparable to or higher than 10 000 m s .
2
In 1998, Ovchinnikov et al. reported a super-highly energetic
Recently, many new energetic salts have been developed.
1,5a–d
explosive—dinitrodiazenofuroxan—which exhibited the consid-
Examples include azolate N-anions
such as bis[3-(5-nitro-
ꢀ1
erably high calculated detonation velocity (10 000 m s ) and
1
imino-1,2,4-triazolate)]-based salts, N,N-bis[1H-tetrazol-5-yl]
ꢀ
3
density (2.02 g cm ). However, it is limited to practical appli-
5a,b
5f
5-azidotetrazole-based salts, 3,4,5-trini-
amine-based salts,
cation because of its high sensitivity and chemical instability. In
6a
tropyrazole-based salts, and nitroaminodiazido[1,3,5]triazine-
3
,4
2
000, Eaton et al. reported octanitrocubane (ONC) which was
6c
based salts; nitramide N-anions
7b
minotetrazole-based salts; dinitromethanide C-anions
7a,b
such as 2-methyl-5-nitra-
8a–f
such
ꢀ1
predicted to possess detonation velocity 10 100 m s based on
ꢀ3
the theoretical density of 2.1 g cm (experimental density 1.979 g
as dinitromethanide salts; and oxide O-anions such as nitro-
9
tetrazolate-2N-oxides. Among them, dihydrazinium N,N-bis
ꢀ3 4
cm ). However, the synthetic procedures are tedious, also, the
reaction agents are expensive, the conditions are too harsh, and
the overall yield is quite low.
(
1H-tetrazolate-5-yl)-amine (BTA) salt possesses the highest
ꢀ1
calculated detonation velocity (9926 m s ) of the reported
5b
energetic salts.
Generally, the energy of CHNO-type high energy simple
substance energetic materials can be improved by increasing the
densities, nitrogen contents or nitro group contents. However,
the chemical energy storage for this type of compounds is almost
close to its maximum, which makes the development of novel
highly energetic materials a considerably difficult problem.
Energetic materials containing trinitroethyl moieties typically
have high densities and good detonation performances, more-
over, they can be readily synthesized. Bis(2,2,2-trinitroethyl)
ꢀ1
nitramine (BTNENA) [detonation velocity (D) ¼ 8661 m s ;
ꢀ3
density (d) ¼ 1.97 g cm ] was ever used as the main ingredient in
some composite explosives in China. But this type of energetic
material is no longer used because of its high sensitivity and
8a–f
chemical instability. Recently, Shreeve, Klap o€ tke and Jalovy
a
School of Chemical Engineering and the Environment, Beijing Institute of
Technology, Beijing, 100081, P.R. China. E-mail: zzm@bit.edu.cn; Fax:
reported several gem-dinitro group containing energetic salts
+
b
86 10-68918982; Tel: +86 10-68918982
State Key Laboratory of Explosion Science and Technology, Beijing
Institute of Technology, Beijing, 100081, P.R. China
exhibiting impressive energetic properties, such as carbohy-
ꢀ1
drazidium 5-dinitromethyltetrazolate (D ¼ 9188 m s ) and
†
Electronic supplementary information (ESI) available: Ab initio
hydrazinium 1-amino-1-hydrazino-2,2-dinitroethenide (D
¼
computational data. CCDC reference number 822361. For ESI and
crystallographic data in CIF or other electronic format see DOI:
ꢀ
1
9
482 m s ), which drove us to design new gem-dinitro group
10.1039/c2jm15310f
containing energetic salts.
This journal is ª The Royal Society of Chemistry 2012
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Aiming at finding new super high-energy-density materials
with detonation velocity superior to CL-20, bis(2,2-dinitroethyl)
nitramine-based salts (BDNENA salts) were designed by
replacing the trinitro group with a gem-dinitro group. A
C-deprotonated anion could be obtained by deprotonation of
BDNENA to form salts paired with nitrogen–hydrogen-rich
cations. Such a design may provide the following advantages in
respect of enhancing the detonation velocity: (i) attaching more
NO
2
groups to the anion facilitates in improving the oxygen
balance (usually negative for energetic salts), directly increases
ꢀ
3
the density (group density of C(NO ) is 1.759 g cm , group
ꢀ
2
3 17,18,23
2
density of N–NO is 1.745 g cm ),
2
in particular, produces
more interaction sites for hydrogen bonding, therefore results in
higher density. (ii) Selecting appropriate nitrogen–hydrogen-rich
cations will provide more opportunities for the formation of H
prior to CO , hence more positive heats of formation.
2
O
2
Herein, we report the synthesis and characterization of novel
highly energetic BDNENA-based salts exhibiting excellent
physical and detonation properties, which were synthesized by
a simple and straightforward approach. The compounds
Scheme 2 Synthesis of BDNENA-based salts.
1
13
prepared were fully characterized by H and solid-state C NMR
solvents or slow decomposition for long evaporation times of the
(
nuclear magnetic resonance) spectroscopy and/or with solid-
dilute solution. The structures of the salts 1–9 were confirmed by
1
15
13 15
H NMR, solid-state C NMR and solid-state N NMR spec-
state N NMR spectroscopy, IR spectroscopy, elemental anal-
ysis and differential scanning calorimetry (DSC). Computational
calculations predicting energetic performances demonstrated
that modification of explosives containing trinitroethyl moieties
by replacing the trinitro group with a gem-dinitro group to form
a gem-dinitro group containing energetic salts is indeed an
effective method of improving energetic performances.
troscopy, IR spectroscopy, and elemental analysis. Because of
decomposition in DMSO, and low solubility in CHCl , CH OH,
3
3
1
CH CN, THF and acetone, H NMR spectra were recorded by
3
13
15
using D O as a locking solvent. Solid state C and N NMR
2
spectra were used as effective techniques to determine the
structure of the BDNENA salts.
1
In the H NMR spectra, the proton signals of the anion were
observed and easily assigned because only one signal occurred at
d z 5.3 ppm; it was shifted downfield compared to the parent
molecule (d z 4.8 ppm). The active proton signals of the cations
Results and discussion
BDNENA was prepared according to literature procedures:
oxidative nitration of the products of condensation of nitro-
methane and formaldehyde with sodium nitrite and silver nitrate
gives 2,2-dinitropropane-1,3-diol, followed by reaction with
KOH to form potassium 2,2-dinitroethanol, Mannich conden-
sation with ammonia, and finally nitration with fuming nitric
acid and conc. sulfuric acid. The X-ray quality single crystal of
the precursor BDNENA was obtained by slow evaporation of
were not observed because D O solvent was used.
2
13
In the C NMR spectra, two signals (d z 50 and 133 ppm) are
assigned to the anion, the other signals are associated with the
cations, and the C(NO2)2 peak (133 ppm) shifted downfield
compared to the parent molecule (118 ppm). These shifts sug-
gested anionic properties of BDNENA.
15
In the N NMR spectra of salts 4 and 7, signals d z 178, 346
and 356 ppm are assigned to the anion and signals d z 73 and
115 ppm are associated with the amino group of the cations. For
salts 1b and 7b, signals at d z 180, 352 and 357 ppm are assigned
to the anion, signals at d z 22, 71, 115 ppm are associated with
the amino group of cations (Fig. 1).
1
9–21
dichloromethane (DCM) at room temperature (Scheme 1).
Reactions of BDNENA with aqueous ammonia, ethylenedi-
amine, hydrazine hydrate, guanidine, aminoguanidine, dia-
minoguanidine,
triaminoguanidine,
3,4,5-triamino-1,2,4-
triazole, and N-carbamoylguanidine in DCM resulted in the
formation of salts 1–9 (Scheme 2).
In the IR spectra, several main absorption bands at approxi-
ꢀ1
All of the salts, which were isolated as powder materials in
good yields (>90%), are non-hygroscopic and stable in air.
Unfortunately, attempts to obtain the X-ray quality crystals of
the salts were unsuccessful due to the low solubility in common
mately 3020, 1610, 1490, 1460, 1360, 1334, 1280 and 1240 cm
are attributed to the C–H, N–NO and C–NO bonds of the
2
2
anion. The intense absorption bands in the range of 3100–3500
ꢀ1
cm are assigned to the N–H bonds of the nitrogen-rich cations.
Properties of BDNENA salts
The thermal stabilities of the BDNENA salts were determined by
differential scanning calorimetric (DSC) measurements
(
Table 1). All the salts decomposed without melting. Among the
BDNENA salts the decomposition temperatures fall in the range
ꢁ
from 94.2 (1) to 141.3 C (4), which are higher than the neutral
ꢁ
ꢁ
Scheme 1 Synthesis of BDNENA.
precursor BDNENA (T
¼ 103.5 C) and BTNENA (T
¼ 94.5 C)
d
d
3
202 | J. Mater. Chem., 2012, 22, 3201–3209
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15
Fig. 1
N NMR spectra of salts 4 (top) and 7 (bottom).
except for salt 1. Explosives containing trinitroethyl moieties
typically possess poor thermal stabilities. Interestingly, changing
the trinitro-group to a dinitro-group and salt formation led to an
increase in the thermal stability. Decomposition of explosives
may be caused by the reactions in or between molecules at
specific temperature. The decomposition of energetic salts
composed of cations and anions is possibly related to the
nucleophilic reactions of anions or electrophilic reactions of
cations. As observed in Table 1, the salts paired with conjugated-
ring-based cations which can delocalize the positive charge on
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Table 1 Properties of energetic salts 1–9
f
/
g
h
i
DHf cation
DHf L
kJ mol
/
DHf salt
kJ mol
/
DUf salt
kJ kg
/
a
m
ꢁ
b
d
ꢁ
c
ꢀ3
d
OB (%)
e
50 /cm, kg kJ mol
ꢀ1
ꢀ1
ꢀ1
ꢀ1
j
k
P /GPa D /m s
ꢀ1
Salt
T
/ C
T
/ C
d
mean /g cm
H
1
2
3
4
5
6
7
8
9
Dec
Dec
Dec
Dec
Dec
Dec
Dec
Dec
Dec
94.2
1.78
1.82
1.79
2.02
1.77
1.88
1.99
1.79
1.84
1.97
1.82
1.91
1.98 (b)
ꢀ19.3
ꢀ40.2
ꢀ22.1
ꢀ38.4
ꢀ39.4
ꢀ40.3
ꢀ41.1
ꢀ45.6
ꢀ41.4
+16.5
ꢀ21.6
ꢀ21.6
ꢀ11.0
—
624.4
1630.5
770.0
575.9
660.3
769.0
871.5
877.55
350.6
—
1289.5
1914.3
1250.5
1237.1
1149.6
1145.1
1146.0
1083.3
1114.9
—
ꢀ10.75
ꢀ257.85
315.48
59.40
79.6
ꢀ609.1
987.7
209.5
558.2
533.3
1352.7
1433.9
ꢀ663.4
47.0
36.4
33.6
39.0
42.8
33.4
37.8
46.2
33.7
31.5
35.5
34.8
39.2
41.4
44.6
8982
8751
9305
9587
8897
9314
10 004
8898
8568
8661
8748
9059
9319
9406
131.8
117.4
141.3
118.9
120.5
135.2
122.0
137.3
94.5
49.0, 2
20.9, 2
30.9, 5
—
35.0, 5
40.9, 5
40.7, 5
23.9, 5
44%
26.0, 5
32.0, 2.5
18.6, 5
196.95
418.83
622.93
697.70
ꢀ387.80
ꢀ13.97
l
BTNENA Dec
m
m
RDX
HMX
CL-20
Dec
Dec
Dec
230.0
287.0
210.0
—
—
—
—
—
—
92.60
417.0
357.0
414.5
468.2
m
m
104.80
431.00 (b)
377.40 (3)
m
m
m
2
.03 (3)
a
b
Melting point. Thermal degradation temperature. Measured density. Oxygen balance. Impact sensitivity. Calculated molar heat of formation
c
d
e
f
g
h
of the cation. Calculated molar lattice energy. Calculated heat of formation for the salt. Energy of formation. Calculated detonation pressure
i
j
k
Explo 5.05). Calculated detonation velocity (Explo 5.05). Probability of explosio n (firing rate). Ref. 1 and 29.
l
m
(
2
4
the cations typically possess better thermal stabilities (salts 4, 7
and 9). It is probable that a delocalized positive charge favors
lowering the electrophilicity of the cation, consequently, result-
ing in higher thermal stability.
thermodynamic properties of energetic salts. Heats of forma-
tion can be calculated for the salts with good accuracy
(including the heats of formation of the cations and anions and
22d
the lattice energy of the salts).
The calculated heats of
Density is one of the most important physical properties of
energetic compounds. According to the Kamlet–Jacobs equa-
formation of the BDNENA anion were calculated by using the
25
Gaussian 03 (Revision D.01) suite of programs based on iso-
ꢀ1
22
tions, density (d) affects detonation performance. Detonation
pressure (P) is dependent on the square of the density, and the
detonation velocity (D) is proportional to the density. Densities
desmic reactions (Scheme 4) to be 26.0 kJ mol . The values for
5a,b,6a,26,27
the cations are available in the literature.
As shown in
Table 1, most of the salts exhibit positive heats of formation. As
shown in Table 1, the heats of formation of the salts are
calculated using Born–Haber energy cycles (Scheme 3). The
values of BDNENA salts fall in the range from ꢀ387.8 (9) to
ꢁ
for all the salts were measured with a gas pycnometer (25 C). As
shown in Table 1, the densities of BDNENA salts are in the range
ꢀ3
of 1.77 (5)–2.02 g cm (4). Particularly, the densities of salts 2, 4,
ꢀ
1
6, 7 and 9 fall in the range for new high-performance energetic
697.7 kJ mol (8).
ꢀ
3 1
materials (1.8–2.0 g cm ). To the best of our knowledge, the
The detonation pressures and velocities of the new highly
energetic salts, RDX, HMX and CL-20, were calculated with the
ꢀ3
density of the guanidinium BDNENA-based salt 4 (2.02 g cm )
is the highest of the reported energetic salts. These relatively high
densities are presumably caused by the high symmetry and value
of density contribution from the gem-dinitro group (1.759 g
28
program package EXPLO5 using the version 5.05. As shown in
Table 1, the calculated detonation pressures lie in the range
between 31.5 (9) and 46.2 Gpa (7), and the calculated detonation
ꢀ3
23
ꢀ1
cm ) of the anion and the extensive intra- and intermolecular
reticular structure through hydrogen bonds present in these salts.
Oxygen balance (OB) is an expression that is used to indicate
the degree to which an explosive can be oxidized. The sensitivity,
strength, and brisance of an explosive are all somewhat depen-
dent upon oxygen balance and tend to approach their maximum
values as the oxygen balance approaches zero. The oxygen
balances of the BDNENA salts were calculated to fall between
velocities fall in the range between 8568 (9) and 10 004 m s (7).
ꢀ1
Salts 1, 5 and 8 are comparable to RDX (8748 m s , 34.8 GPa)
ꢀ1
and BTNENA (8661 m s , 35.5 GPa), salts 3 and 6 are
ꢀ1
comparable or superior to HMX (9059 m s , 39.2 GPa), salts 4
ꢀ1
and 7 are comparable or even superior to CL-20 (9406 m s , 44.6
GPa). To the best of our knowledge, salt 7 exhibits the highest
ꢀ1
detonation velocity (10 004 m s ) of the reported energetic
5
salts, which makes it a competitive super-highly energetic
b
22
ꢀ
45.6 (8) and ꢀ19.3% (1). They are all better than TNT
material. According to the Kamlet–Jacobs equations, density
and heat of formation are two key factors affecting detonation
performance. It appears that the differences in detonation
properties for salts 4 and 7 are primarily derived from their
different heats of formation but possessing approximately the
same densities.
(
ꢀ74.0%). Salts 1 and 3 possess OBs similar to RDX and HMX.
Impact sensitivities of the synthesized salts were characterized
by H50 for BDNENA salts and measured using Fall Hammer on
an HGZ-19Z0991 apparatus (2.0 and/or 5.0 kg drop hammer;
5
0.0 mg sample). As shown in Table 1, the H50 values range from
2
0.9 (3) to 49.0 cm (2), most samples are less sensitive than HMX
29
(
32 cm, 2.5 kg); all samples are less sensitive than CL-20 (18.6
X-Ray crystallography
29
cm, 5 kg).
The heats of formation are other important parameters to be
considered in the design of energetic salts. Recently, significant
progress has been made in the theoretical prediction of
An X-ray quality crystal of BDNENA was obtained by slow
evaporation of DCM at room temperature. The structures are
shown in Fig. 2, and crystallographic data are summarized in
3
204 | J. Mater. Chem., 2012, 22, 3201–3209
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Table 2 Crystallographic data for BDNENA
BDNENA
Formula
CCDC number
4 6 6 10
C H N O
822361
298.15
M
Crystal size/mm
r
ꢀ
3
0.24 ꢂ 0.20 ꢂ 0.12
Colorless prism
Monoclinic
C2/c
12.363(13)
5.876(5)
15.136(16)
0.71073
90
90.31(8)
90
1099.6(19)
4
113(2)
Crystal color and habit
Crystal system
Space group
ꢀ
a/A
ꢀ
b/A
ꢀ
c/A
ꢀ
Ka)/A
L (M
ꢁ
o
a/
ꢁ
b/
ꢁ
g/
V/A
ꢀ
3
Z
T/K
ꢀ
3
r/Mg m
1
1.801
0.018
ꢀ
m/mm
F
000
ꢁ
608
2.7 to 27.9
ꢀ16 # h # 16
q/
Index ranges
ꢀ
7# k # 7
ꢀ19 # l # 19
Reflections collected
5096
Independent reflections (Rint
Data/restraints/parameters
GOF on F2
)
1293(0.0928)
1293/0/92
1.08
0.0507
0.0995
a
R
1
(I > 2s(I))
uR (I > 2s(I))
b
2
Fig. 2 (a) Thermal ellipsoid plot (30%) and labeling scheme for
R1 (all data)
wR2 (all data)
0.0622
0.0967
BDNENA. Hydrogen atoms are included but are unlabelled for clarity.
(b) Ball and stick packing diagram of BDNENA viewed down the b axis.
ꢀ
ꢀ3
Largest diff. peak and hole/e A
PkF
0.36 and ꢀ0.35
Dashed lines indicate strong hydrogen bonding.
R
1
¼
o
| ꢀ |F
c
k/P
|F
o
2
¼ [P
u(F
ꢀ F
c o
) / u(F ) ] .
P
a
b
|. uR
2
o
2
2
2
2 1/2
Table 2. BDNENA crystallizes in monoclinic C2/c with 4
molecules in the unit cell, and with a calculated density of 1.801 g
ꢀ
3
cm . Bond lengths: [O1–N1 1.2295(18); O2–N3 1.207(2); O3–N3
.207(2); O4–N4 1.216(2); O5–N4 1.221(2); N1–O1 1.2294(18);
N1–N2 1.363(3); N2–C1 1.450(2); N2–C1 1.450(2); N3–C2 1.506
2); N4–C2 1.510(2); C1–C2 1.525(3); C1–H1A 0.9900; C1–H1B
The DH value could be predicted by the formula suggested by
L
1
31
Jenkins et al. (eqn (2)), where UPOT is the lattice potential
+
energy and nM and nX depend on the nature of the ions M and
p
(
ꢀ
X
q
, respectively, and are equal to three for monoatomic ions,
0
.9900; C2–H2 1.0000]. Symmetry codes: (i) x, y, z; (ii) ꢀx, y, ꢀz
five for linear polyatomic ions, and six for nonlinear polyatomic
ions.
+
1/2; (iii) x + 1/2, y + 1/2, z; (iv) ꢀx + 1/2, y + 1/2, ꢀz + 1/2; (v)
x, ꢀy, ꢀz; (vi) x, ꢀy, z ꢀ 1/2; (vii) ꢀx + 1/2, ꢀy + 1/2, ꢀz; (viii)
ꢀ
x + 1/2, ꢀy + 1/2, z ꢀ 1/2.
DH
L
¼ UPOT + [p((n
M
/2) ꢀ 2) + q((n
X
/2) ꢀ 2)]RT
(2)
The equation for the lattice potential energy, UPOT, takes the
ꢀ3
Theoretical study
form of eqn (3), where r
is the density (g cm ), M is the
m m
chemical formula mass of the ionic material (g), and the coeffi-
ꢀ1
Calculations were carried out by using the Gaussian 03 (Revision
ꢀ1
ꢀ1
ꢀ1
cients g (kJ mol cm) and d (kJ mol ) are assigned literature
31
values.
25
E.01) suite of programs. The geometric optimization of the
structures and frequency analyses were carried out by using the
30
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.
Based on the Born–Haber energy cycle (Scheme 3), the heat of
formation of a salt can be simplified according to eqn (1), where
DH
L
is the lattice energy of the salt.
o
o
DH
f
(ionic salt, 298 K) ¼ DH
f
(cation, 298 K)
o
+
DH
f
(anion, 298 K) ꢀ DH
L
(1)
Scheme 3 Born–Haber cycle for the formation of energetic salt.
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Scheme 4 Isodesmic reactions for calculations of heats of formation.
ꢀ1
ꢀ1
1/3
UPOT (kJ mol ) ¼ g(r /M ) + d
(3)
m
m
The remaining task was the determination of the heats of
formation of the cations and anions, which were computed by
using the method of isodesmic reactions (Scheme 4). The
o
f 298
Fig. 3 Optimized structure and charge distribution in salt 4 as found
enthalpy of an isodesmic reaction (DH
) is obtained by
with NBO analysis (B3LYP/6-311+G (d,p)).
combining the MP2(full)/6-311++G** energy difference for the
reaction and the scaled zero-point energies (B3LYP/6-31+G**).
The heats of formation of the cations and anions being investi-
gated can then be extracted readily.
Detonation pressure (P) and detonation velocity (D) were
calculated with the program package EXPLO5 using the version
5
.05, in which several parameters have been modified. The input
was made using the sum formula, energy of formation, and the
experimental densities measured by a gas pycnometer. The
program is based on the chemical equilibrium, steady state model
of detonation. It uses the Becker–Kistiakowsky–Wilson’s equa-
tion of state (BKW EOS) for gaseous detonation products and
29,31–35
Cowan–Fickett’s equation of state for solid carbon.
The
calculation of the equilibrium composition of the detonation
products is done by applying the modified White, Johnson, and
Dantzig’s free energy minimization technique. The program is
designed to enable the calculation of detonation parameters at
the CJ point. The BKW equation in the following form was used
with the BKWN set of parameters (a ¼ 0.5, b ¼ 0.096, k ¼ 17.56,
q ¼ 4950) as stated below the equations, X being the molar
i
th
fraction of i gaseous product, and k being the molar covolume
i
th
of the i gaseous product:
P
bx
a
pV/RT ¼ 1 + xe , x ¼ (k X k )/[V(T + q)]
(4)
i
i
In order to obtain a better understanding of the structure of
the salt, the structure optimization and natural bond orbital
(
NBO) and the molecular orbital analyses of salt 4 were carried
Fig. 4 HOMO (top) and LUMO (bottom) of salt 4.
25
out by using Gaussian 03. As shown in Fig. 3, the NBO analysis
indicated that the positive charge is delocalized over the guani-
dinium group in which the positive charges of H (19) (0.450e) and
H (16, 17, 19, 20, 22, 23, 37, 38, 40, 41, 43, 44) (0.399e z 0.450e)
are significantly higher than those of the other hydrogen atoms H
and the N7 and O24 atoms of the N–NO group occupy the
2
LUMO. The negative charge is not delocalized over the anion.
The non-conjugated charge distribution likely causes the
moderate thermal stabilities.
(
11, 32) (0.243e) and H (12, 33) (0.254e).
In the anion, O atoms (1, 2, 3, 4, 5, 24, 25, 26, 27, 28) (ꢀ0.433e
to 0.536e) carry negative charges, the charge distribution implies
that the O atoms in the anion can form hydrogen bonds with the
hydrogen atoms in the cation. The negative charge of O (3, 5, 26,
Conclusions
In summary, novel super-high-energy materials of BDNENA-
based salts were successfully synthesized and fully characterized.
The new salts exhibit excellent physical and detonation proper-
ties, such as low solubility in common solvents, moderate
thermal stabilities, high densities, positive heats of formation,
high detonation pressures and detonation velocities, and lower
impact sensitivities than the parent. The comprehensive proper-
ties of most salts are better than BTNENA (see Table 1). Salt 4
2
8) and the positive charge of H (11, 12, 32, 33), as well as the
steric effect, suggest an intramolecular hydrogen bond. High
symmetry in the structure and strong hydrogen bonds likely
increase the density of the salt.
The highest occupied molecular orbitals (HOMOs) and lowest
unoccupied molecular orbitals (LUMOs) of salt 4 (Fig. 4) further
reveal that the N–NO
2
group of the anion occupies the HOMO,
3
206 | J. Mater. Chem., 2012, 22, 3201–3209
This journal is ª The Royal Society of Chemistry 2012

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ꢀ
3
possesses the highest density (2.02 g cm ) and salt 7 exhibits the
3,4,5-Triamino-1,2,4-triazole, triaminoguanidinium hydro-
ꢀ
1
unprecedented detonation properties (10 004 m s , 46.2 GPa),
which are better than those of the reported energetic salts.
Specifically, detonation properties of salts 3 and 6 are compa-
chloride and N-carbamoylguanidinium hydrochloride were
38–40
synthesized according to the literature.
ꢀ1
rable to HMX (9059 m s , 39.2 GPa), salts 4 and 7 are
Bis(2,2-dinitroethyl)nitroamine (BDNENA)
ꢀ1
comparable or even superior to CL-20 (9406 m s , 44.6 GPa),
which place these salts in the competitive super-high-energy
performance class. The results also suggest the potential to serve
as a series of promising alternatives to some conventional ener-
getic materials such as HMX and CL-20.
Bis(2,2-dinitroethyl)nitroamine was synthesized according to the
19–21
literature:
oxidative nitration of the condensation products
from nitromethane and formaldehyde with sodium nitrite and
silver nitrate; a subsequent reaction with KOH formed potas-
sium 2,2-dinitroethanol, followed with a Mannich condensation
with ammonia, and finally nitration with fuming nitric acid and
1
conc. sulfuric acid. White solid. H NMR (500 MHz, CDCl , d):
Experimental section
3
13
6
1
1
.67 (t, 2H), 4.81 (d, 4H) ppm; C NMR (100 MHz, CD CN, d):
3
Caution! Although none of the compounds described herein have
exploded or detonated in the course of this research, these
materials should be handled with extreme care using the best
safety practices.
18.4, 53.9 ppm; IR (KBr): n ¼ 3217, 3035, 1487, 1422, 1356,
ꢀ1
322, 1240, 1151, 1111, 1078, 926, 906, 755, 733, 664, 645 cm .
General procedure for the synthesis of the salts 1–9
General methods
To a solution of BDNENA (1 mmol) in DCM (50 mL), 2 eq. of
2
5% aqueous ammonia, 99% hydrazine hydrate, guanidine,
1
13
15
H, C and N NMR spectra were recorded on a 500 MHz
nuclear magnetic resonance spectrometer operating at 400.18,
00.63 and 50.69 MHz, respectively. Chemical shifts are reported
aminoguanidine, diaminoguanidine, triaminoguanidine, 3,4,5-
triamino-1,2,4-triazole, N-carbamoylguanidine, or 1 eq. ethyl-
enediamine was added. The mixtures were stirred at room
temperature for 1 h and the yellow precipitate was filtered off,
washed with DCM, and dried at RT for 2 h.
1
1
2
in ppm relative to TMS. The locking solvent was D O for H
1
3
15
NMR spectra. Solid state C and N NMR spectra were used as
effective techniques to determine the structure of the salts. The
melting and decomposition points were recorded on a DSC at
Diammonium bis(2,2-dinitroethanide)nitroamine salt (1)
ꢁ
ꢀ1
a scan rate of 10 C min . IR spectra were recorded by using
KBr pellets. Densities were measured at room temperature using
a Micromeritics Accupyc II 1340 gas pycnometer. Elemental
analyses were obtained on an Elementar Vario MICRO CUBE
1
Yellow powder (314 mg, 96%); H NMR (500 MHz, D
O, d):
2
13
5.26 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 132.1, 53.5
ppm; IR (KBr): n ¼ 3217, 3035, 1487, 1422, 1356, 1322, 1240,
ꢀ1
(
Germany) elemental analyzer.
1151, 1111, 1078, 926, 906, 755, 733, 664, 645 cm ; elemental
4 12 8
analysis (%) calcd for C H N O10: C 14.46, H 3.64, N 33.73;
found: C 14.23, H 3.82, N 33.46.
X-Ray crystallography
Crystals of bis(2,2-dinitroethyl)nitramine were removed from
the flask and covered with a layer of hydrocarbon oil. A suit-
able crystal was selected, attached to a glass fiber, and placed in
the low-temperature nitrogen stream. Data for bis(2,2-dini-
troethyl)nitramine were collected at 113(2) K using a Rigaku
Saturn724 CCD diffractometer equipped with a graphite-
Ethylenediammonium bis(2,2-dinitroethanide)nitroamine salt (2)
1
Yellow powder (331 mg, 94%); H NMR (500 MHz, DMSO-d
6
,
13
d): 7.576 (s, br, 3H), 5.242 (s, 2H), 2.978 (s, 2H) ppm; C NMR
100 MHz, solid-state, d): 132.1, 52.9, 37.4 ppm; IR (KBr): n ¼
145, 3024, 1610, 1495, 1462, 1367, 1334, 1288, 1247, 1203, 1160,
(
3
ꢀ1
ꢀ
1129, 1069, 924, 906,779, 740, 674, 642 cm ; elemental analysis
%) calcd for C 10: C 20.12, H 3.94, N 31.28; found: C
0.30, H 4.04, N 31.01.
monochromatized MoKa radiation (l ¼ 0.71073 A) using
(
6 14 8
H N O
omega scans. Data collection and reduction were performed
and the unit cell was initially refined by using CrystalClear-SM
Expert 2.0 r2 (ref. 36) 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 the
2
Dihydrazinium bis(2,2-dinitroethanide)nitroamine salt (3)
1
Yellow powder (350 mg, 99%); H NMR (500 MHz, D
2
O, d):
37
SHELXTL-97 system of programs. Structures were solved in
the space group C2/c for BDNENA by analysis of systematic
absences. In this all-light-atom structure the value of the Flack
parameter did not allow the direction of the 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 2.
13
.266 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 132.1,
5
5
1
3.5 ppm; IR (KBr): n ¼ 3525, 3332, 3112, 1602, 1475, 1422,
ꢀ1
360, 1310, 1246, 1175, 1085, 945, 906, 736, 644 cm ; elemental
analysis (%) calcd for C H N O : C 13.26, H 3.90, N 38.67;
4 14 10 10
found: C 12.96, H 4.12, N 38.89.
Bis(guanidinium) bis(2,2-dinitroethanide)nitroamine salt (4)
Reactants: nitromethane, formaldehyde (37%), aqueous
ammonia (28–30%), hydrazine (99%), ethylenediamine, guani-
dinium hydrochloride (99%), aminoguanidinium hydrochloride
1
Pale yellow powder (403 mg, 98%); H NMR (500 MHz, D O, d):
2
13
5.284 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 159.1,
15
(
98.5%), diaminoguanidinium hydrochloride (98.5%), and silver
133.8, 53.3 ppm; N NMR (50 MHz, solid-state, d): 355.33,
345.59, 178.58, 73.14 ppm; IR (KBr): n ¼ 3462, 3414, 3375, 3197,
nitrate (99.95%, Salt Lake Metals) were used as received.
This journal is ª The Royal Society of Chemistry 2012
J. Mater. Chem., 2012, 22, 3201–3209 | 3207

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3
9
011, 1674, 1643, 1563, 1491,1462, 1347, 1304, 1236, 1161, 1092,
(no. 20091101110033), National Defense 973 Program (no.
3100021210901) and the National Natural Science Fund Project
(no. 21172020).
ꢀ
1
08, 738, 680, 646, 583 cm ; elemental analysis (%) calcd for
C H N O : C 17.15, H 4.80, N 39.99; found: C 17.15, H 4.67,
16 12 10
6
N 39.55.
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I. V. Ovchinnikov, N. N. Makhova, L. I. Khmel’nitskii,
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Orange powder (410 mg, 92%); H NMR (500 MHz, D
2
O, d):
13
5
1
1
.296 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 158.8,
3
4
35.3, 52.9 ppm; IR (KBr): n ¼ 3434, 3340, 3290, 1682, 1568,
ꢀ1
476, 1291, 1241, 1163, 1007, 642, 532 cm ; elemental analysis
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(
%) calcd for C H N O : C 16.15; H 4.07; N 43.94; found: C
6 18 14 10
1
6.00; H 3.97; N 43.24.
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1
Yellow powder (409 mg, 85%); H NMR (500 MHz, D
2
O, d):
13
5
1
1
.304 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 159.9,
35.3, 52.9 ppm; IR (KBr): n ¼ 3434, 3340, 3290, 1682, 1568,
6
7
(a) Y. Zhang, Y. Guo, Y.-H. Joo, D. A. Parrish and J. M. Shreeve,
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ꢀ1
476, 1291, 1241, 1163, 1007, 642, 532 cm ; elemental analysis
(
6 20 16
%) calcd for C H N O10: C 15.13, H 4.23, N 47.05; found: C
1
5.33, H 4.13, N 46.90.
1
538–1546.
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salt (7)
1
458.
1
Yellow powder (485 mg, 96%); H NMR (500 MHz, D
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2
O, d):
13
5
1
3
3
.428 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 159.9,
15
35.3, 52.9 ppm; N NMR (50 MHz, solid-state, d): 357.23,
47.58, 177.20, 115.66, 71.99 ppm; IR (KBr): n ¼ 3434, 3340,
ꢀ1
290, 1682, 1568, 1476, 1291, 1241, 1163, 1007, 642, 532 cm ;
elemental analysis (%) calcd for C
6 22 18
H N O10: C 14.23; H 4.38;
N 49.79; found: C 13.90; H 4.17; N 49.24.
9
M. Go o€ bel, K. Karaghiosoff, T. M. Klap o€ tke, D. G. Piercey and
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nitroamine salt (8)
1
1
1
Yellow powder (253 mg, 93%); H NMR (500 MHz, D O, d):
2
1
3
5
1
1
6
1
.219 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 152.0,
33.9, 50.9 ppm; IR (KBr): n ¼ 3386, 3322, 3264, 3101, 1635,
591, 1554, 1421, 1295, 1222, 1147, 1091, 1004, 954, 819, 715,
1
1
1
1
1
ꢀ1
70, 619 cm ; elemental analysis (%) calcd for C
8 18 18
H N O10: C
5 Y. Gao, C. Ye, B. Twamley and J. M. Shreeve, Chem.–Eur. J., 2006,
1
8.26, H 3.45, N 47.90; found: C 18.36, H 3.56, N 47.56.
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Yellow powder (519 mg, 95%); H NMR (500 MHz, D O, d):
2
1
3
5
1
1
7
.335 (s, 1H) ppm; C NMR (100 MHz, solid-state, d): 156.2,
55.5, 131.8, 52.7 ppm; IR (KBr): n ¼ 3348, 3192, 3028, 1730,
698, 1634, 1593, 1487, 1354, 1309, 1256, 1167, 1113, 899, 851,
1
ꢀ1
75, 761, 740, 677, 642 cm ; elemental analysis (%) calcd for
12: C 19.13, H 3.61, N 39.04; found: C 19.10, H 3.69,
8 18 14
C H N O
N 38.83.
2
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2
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This journal is ª The Royal Society of Chemistry 2012
J. Mater. Chem., 2012, 22, 3201–3209 | 3209