N-Trinitroethylamino functionalization of nitroimidazoles: A new strategy for high performance energetic materials

Article abstract of DOI:10.1039/c3ta11356f

An N-functionalized strategy, including N-amination and N-trinitroethylamination, was utilized for the synthesis of nitroimidazole-based energetic materials, giving rise to a new family of highly insensitive N-aminonitroimidazoles and oxygen-rich N-trinitroethylaminonitroimidazoles with good to excellent properties. These new energetic materials were fully characterized by IR, ¹H, and ¹³C NMR, elemental analysis, and some high performance compounds were further confirmed by ¹⁵N NMR (4a, 4d, 6a, 6b, and 6d), as well as single crystal X-ray diffraction (6a and 6b). N-Functionalization of nitroimidazoles not only gives rise to the N-aminonitroimidazoles as impact insensitive and thermally stable materials (IS > 40 J; T_d: 144-308 °C), but also provides a series of N-trinitroethylaminoimidazoles, which have favorable densities (1.75-1.84 g cm^-3), good detonation properties (P: 27.6-35.9 GPa; v_D: 7815-8659 m s^-1), and moderate thermal stabilities (136-172 °C). These properties are better than some known energetic compounds, such as TNT (P: 19.5 GPa; v_D: 6881 m s^-1) and TATB (P: 31.2 GPa; v _D: 8114 m s^-1), and are comparable to RDX (P: 35.0 GPa; v_D: 8762 m s^-1). The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3ta11356f

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N-Trinitroethylamino functionalization of
nitroimidazoles: a new strategy for high performance
Cite this: DOI: 10.1039/c3ta11356f
energetic materials†
Ping Yin,a Qinghua Zhang,a Jiaheng Zhang,a Damon A. Parrishb
a
*
and Jean'ne M. Shreeve
An N-functionalized strategy, including N-amination and N-trinitroethylamination, was utilized for the
synthesis of nitroimidazole-based energetic materials, giving rise to a new family of highly insensitive N-
aminonitroimidazoles and oxygen-rich N-trinitroethylaminonitroimidazoles with good to excellent
properties. These new energetic materials were fully characterized by IR, 1H, and 13C NMR, elemental
analysis, and some high performance compounds were further confirmed by 15N NMR (4a, 4d, 6a, 6b,
and 6d), as well as single crystal X-ray diffraction (6a and 6b). N-Functionalization of nitroimidazoles not
only gives rise to the N-aminonitroimidazoles as impact insensitive and thermally stable materials (IS >
40 J; Td: 144–308 ꢀC), but also provides a series of N-trinitroethylaminoimidazoles, which have favorable
densities (1.75–1.84 g cmꢁ3), good detonation properties (P: 27.6–35.9 GPa; vD: 7815–8659 m sꢁ1), and
moderate thermal stabilities (136–172 ꢀC). These properties are better than some known energetic
compounds, such as TNT (P: 19.5 GPa; vD: 6881 m sꢁ1) and TATB (P: 31.2 GPa; vD: 8114 m sꢁ1), and are
comparable to RDX (P: 35.0 GPa; vD: 8762 m sꢁ1).
Received 3rd April 2013
Accepted 10th May 2013
DOI: 10.1039/c3ta11356f
www.rsc.org/MaterialsA
(HMX),10 1,1-diamino-2,2-dinitroethene (FOX-7)11 and 2,4,6,8,10,
12-hexanitro-2,4,6,8,10,12-hexaazatetracyclododecane (CL-20).12
Introduction
In the past decade, the design and synthesis of new high-energy
density materials (HEDMs) with excellent performance charac-
teristics have attracted signicant interest in the eld of ener-
getic materials.1 In general, the most widely used strategy for the
design of HEDMs is to incorporate energy-containing groups
such as nitro,2 azido,3 diazo,4 amino,5 and N-oxido6 into the
molecular backbone of some nitrogen-rich heterocycles.
However, rational use of these functional groups in design of
energetic materials requires not only pursuing the highest
detonation velocity and pressure, but also addressing the prob-
lems of thermal stability and impact insensitivity in order to
obtain nal products with acceptable properties. Polynitro-
functionalized compounds are among the most signicant
structural motifs in HEDMs, and, as such, they are ideal targets
in the design of high performance energetic compounds. There
are many polynitro-explosives used for military purposes and
civilian applications, such as 2,4,6-trinitrotoluene (TNT),7 tri-
aminotrinitro benzene (TATB),8 1,3,5-trinitrotriazacyclohexane
(RDX),9 cyclo-1,3,5,7-tetramethylenene-2,4,6,8-tetranitramine
The presence of several nitro groups in these energetic
materials leads to high density and good oxygen balance. Of
these nitro-based functional groups, the trinitroethyl function-
ality is one of the most energetic groups for the construction of
HEDMs.13 Since the trinitroethyl fragment has high nitrogen
content, positive oxygen balance, and also high energy within
the molecule, these functionalized compounds are expected to
be excellent energetic materials with superior properties such as
high density, good thermal stability, low sensitivity, and posi-
tive oxygen balance.
Recently the N-functionalized chemistry of ve-membered
azoles has made great progress and many functional groups,
such as NO2,14 NH2,15 CH3,16 and CH2ONO2,17 have been
employed to develop new energetic materials with compre-
hensively good properties. While NO2 and CH2ONO2 could
improve performance with decreased stabilities, methyl-func-
tionalized compounds are more stable but display poorer
performances. Among the N-functionalized methodologies
above, N-amination has become one of the most attractive
strategies for preparing new energetic materials. The amino
products with the additional N–N bond(s) have higher heats of
formation, as well as improved detonation properties. More-
over, the amino group can undergo further functionalization,
such as nitration,18 diazotization,4 or trinitroethylation15a to
provide versatile energetic materials. In general, ve-membered
azoles or six-membered azines, with high heats of formation,
aDepartment of Chemistry, University of Idaho, Moscow, ID 83844-2343, USA. E-mail:
jshreeve@uidhao.edu; Fax: +1-208-885-9146
bNaval Research Laboratory, Code 603, Washington, D.C. 20375-5001, USA
† Electronic Supplementary Information (ESI) available. CCDC 927838 and
927839. For ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/c3ta11356f
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are considered to be favorable backbones for energetic process, O-tosylhydroxylamine was more suitable with electron-
materials. However, compared to linear trinitroethylamino poor nitroimidazoles, whereas hydroxylamine-O-sulfonic acid
compounds, studies on N-trinitroethylamino aromatic hetero- was preferred for some electron-rich nitrogen heterocycles.21 On
cycles are relatively rare and the contradictions between explo- the other hand, bases which could neutralize the acidic nitro-
sive performance and sensitivity still exist.15a,19 To achieve a imidazoles to form more active salts also played an important
valuable balance of them, it make sense to choose more role in the amination process. As a synthetic route shown in
insensitive backbones but with favorable energetic properties Scheme 1, reactions executed with aqueous ammonia gave rise
for N-trinitroethylamino functionalization. On the other hand, to the corresponding ammonium nitroimidazolates in nearly
it is likely that the N-trinitroethylamination strategy toward quantitative yield, which subsequently could be readily con-
high performance compounds continues to face the challenge verted to 1-aminonitroimidazoles (4a, 70% yield; 4b, 55% yield).
that nitro groups bonded to azoles improve their energy but As a result of our work, it was found that the yield of 4b was
make the N-amino groups inactive for further trinitroethylation. slightly improved using the ammonium salt rather than the
To the best of our knowledge, the N-trinitroethylamination of potassium salt.18 However, the other substituted ammonium
nitro-substituted azoles has remained undeveloped. In recent nitroimidazolates gave only trace amounts of product with O-
years, nitroimidazoles have attracted more attention as a new tosylhydroxylamine. Considering that aqueous ammonia is a
kind of energetic framework and various nitroimidazole deriv- weak base, other bases, such as K2CO3, KOH, NaOH, and NaH,
atives have been explored, such as 2,4-dinitroimidazole, 4,5- were chosen to form potassium or sodium nitroimidazolates for
dinitroimidazole, 2,4,5-trinitroimidazole, and 4,40,5,50-tetrani- amination. Aer optimization of reaction conditions, potas-
tro-2,20-biimidazole.20 In the continuation of our efforts to sium carbonate was found to result in better isolated yields than
search for new energetic materials, we are interested in devel- the other bases. Although 1-amino-4-nitroimidazole (4c) was
oping new strategies for the synthesis of trinitroethyl-derived obtained only in low yield (21%), 1-amino-5-azido-4-nitro-
heterocylic materials. Herein we report the synthesis of N-ami- imidazole (4d) and 1-amino-5-chloro-4-nitro-imidazole (4e)
nonitroimidazoles and the corresponding N-trinitroethyl- were obtained in moderate to good yields, 73% and 75%,
aminonitroimidazoles.
respectively. In addition, the attempt to aminate 2,4,5-trini-
troimidazole was unsuccessful, which may be a result of steric
hindrance.
With 1-amino-nitroimidazoles in hand (4a–4e), we focused
on further functionalization with trinitroethanol. In order to
Results and discussion
Syntheses
To study the detailed reaction activity and performance, a obtain N-trinitroethylaminoimidazoles, we chose 1-amino-2,4-
variety of substituted nitroimidazoles were chosen as starting dinitro-imidazole (4b) as the model substrate to determine
materials. Previous studies provided many options to achieve optimal conditions. The starting material was dissolved in
the amination of the NH group embedded in nitrogen hetero- water at room temperature, then trinitroethanol was added
cycles.15 The most common aminating reagents tested included to the dilute solution which resulted in trace amounts of
hydroxylamine-O-sulfonic acid, O-tosylhydroxylamine, 2,4,6-tri- 2,4-dinitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine (6b).
nitrophenyl-O-hydroxylamine, etc. Aer parallel tests, we found Considering that 4b was slightly soluble in water at room
that O-tosylhydroxylamine was the optimal aminating reagent temperature, the amount of solvent required was reduced by
ꢀ
in comparison with other reagents for these systems. In this preparing a saturated aqueous solution at 80 C. Although the
Scheme 1 Synthesis of N-amino and N-trinitroethylaminoimidazoles.
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higher concentration of reactant accelerated conversion of the For dinitro-biimidazole (1g), amination could be processed
starting material, impurities generated at high temperature from its potassium salt by using potassium carbonate with O-
precipitated from the aqueous solution. Therefore, the reaction tosylhydroxylamine. Based on the basicity of non-substituted
temperature was reduced slowly to room temperature aer biimidazole (1h), amination of 1h was performed with the use
addition of trinitroethanol. Aer stirring overnight at ambient of hydroxylamine-O-sulfonic acid. However, the attempted tri-
temperature, a white solid precipitated from the reaction to give nitroethylation of these diamino-biimidazoles did not yield the
6b in 61% yield. Likewise, treatment of other 1-amino-nitro- desired products. Compounds 4f, 4g, and 4h were veried by
imidazoles with trinitroethanol also gave the target products in NMR spectroscopic data and elemental analysis.
moderate to good yields (6a, 72%; 6c, 56%; 6d, 53%; 6e, 75%).
In the initial study, 5-azido-4-nitro-imidazole (1d) was
synthesized from 4,5-dinitro-1H-imidazole (1a) by the known
Structure and physical properties
method, including aminolysis, diazotation, and nucleophilic To assess the thermal stability of the new materials, differential
substitution with sodium azide.22 Because the separation of the scanning calorimetric (DSC) measurements was used for the new
sensitive diazonium salt was hard to handle and the overall compounds. Most of the N-aminonitroimidazoles melted
yield of 1d was very low, we combined the diazotation and with sharp endothermic peaks at low temperature (4a, 64 ꢀC; 4b,
following azido substitution as a one-pot procedure without 173 ꢀC; 4c, 93 ꢀC; 4d, 77 ꢀC; 4e, 123 ꢀC) and decomposed at
separation of the diazonium salt, and the overall yield of 1d was high temperature (4a, 264 ꢀC; 4b, 235 ꢀC; 4c, 211 ꢀC; 4d, 144 ꢀC;
increased to 51% (Scheme 2). We had also attempted to prepare 4e, 274 ꢀC). All N-trinitroethylaminonitroimidazoles decom-
5-azido-4-nitro-1H-imidazol-1-amine (4d) by the condensation posed without melting at moderate temperature (6a, 171 ꢀC; 6b,
of 5-chloro-4-nitro-1H-imidazol-1-amine (4e) and sodium azide 172 ꢀC; 6c, 139 ꢀC; 6d, 136 ꢀC; 6e, 156 ꢀC). For N-amino-
but failed to obtain the desired product.
imidazoles, all decomposed at high temperature (4f, 217 ꢀC; 4g,
The syntheses of N-amino-biimidazoles and their trini- 308 ꢀC; 4h, 292 ꢀC). In the IR spectra of the N-trini-
troethyl derivatives were undertaken (Scheme 3). When 4,40,5,50- troethylaminonitroimidazoles, characteristic absorption bands
tetranitro-1H,10H-2,20-biimidazole (1f) was treated with aqueous were observed at 1300–1600 cmꢁ1, which veried the multiple
ammonia and O-tosylhydroxylamine (3) the desired diamino nitro groups from the imidazole ring and the trinitroethylamine.
product was obtained as a yellow solid in a yield of 53%. In the 13C NMR spectra, the carbon atom bonded to three nitro
Because of the basicity of the non-substituted biimidazole (1g) groups was found at 125–128 ppm, while the carbon atoms of the
amination was performed using hydroxylamine-O-sulfonic acid. imidazole ring appeared between 120 and 150 ppm.
Scheme 2 Reaction optimization of 5-azido-4-nitro-imidazole.
Scheme 3 Amination of biimidazoles.
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In Fig. 1, the 15N NMR spectra of 4,5-dinitro-1H-imidazol-1- ꢁ30.78 (N6), ꢁ34.01 (N3), ꢁ135.32 (N2), ꢁ193.57 (N1), ꢁ309.71
amine (4a), 4,5-dinitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1- (N5) ppm, while the nitrogen signals of 4a are found in the
amine (6a) 2,4-dinitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine similar position at d ¼ ꢁ24.02 (N4), ꢁ34.08 (N3), ꢁ137.12 (N2),
(6b) and 5-azido-4-nitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1- ꢁ198.52 (N1), ꢁ308.11 (N5). In the spectra of 6b and 6d, the
amine (6d) are displayed as measured in CD3CN. The 15N nitrogen signals from NO2 are observed between ꢁ32.83 and
{H}NMR spectrum of 6a shows six signals at d ¼ ꢁ24.14 (N4), ꢁ23.38, as well as the typical nitrogen signals of NH, which are
Fig. 1 Selective 15N NMR spectra of N-aminoimidazoles and N-trinitroethylaminoimidazoles.
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Table 1 Properties of the N-aminonitroimidazoles and N-trinitroethylaminonitroimidazoles
Tm
Td
dc
DHf(g)d
DHsub
DHf
a
b
e
f
Comp.
[ꢀC]
[ꢀC]
[g cmꢁ3
]
[kJ molꢁ1
]
[kJ molꢁ1
]
[kJ molꢁ1]/[kJ gꢁ1
]
P g [GPa]
vDh [m sꢁ1
]
ISi [J]
OB j/OPk [%]
4a
4b
4c
4d
64
173
96
235
264
237
144
308
171
172
139
136
156
295
324
230
1.72
1.75
1.56
1.65
1.75
261.4
200.8
195.3
536.1
400.3
190.4
175.0
164.3
494.6
144.5
—
63.4
83.9
69.4
65.8
104.9
82.0
83.7
77.5
75.8
75.8
—
146.5/0.85
116.9/0.68
125.9/0.98
470.3/2.78
295.4/1.16
108.4/0.32
91.3/0.27
86.8/0.30
418.8/1.26
68.7/0.21
28.7
29.3
20.1
25.9
25.6
35.9
35.8
30.4
33.0
27.6
19.5
31.2
35.0
8137
8174
7363
8048
7939
8659
8649
8218
8513
7815
6881
8114
8762
>40
>40
>40
3.5
>40
2.5
7
10
2
7
ꢁ4.62/36.97
ꢁ4.62/36.97
ꢁ37.50/24.98
ꢁ23.66/18.92
ꢁ28.57/25.28
14.29/47.60
14.29/47.60
2.75/43.96
4.82/38.54
4.91/39.31
ꢁ24.66/42.27
ꢁ18.60/37.19
0.00/43.22
77
4g
285
163
—
—
—
6al
6bl
6c
1.83 (1.867m)
1.84 (1.869m)
1.75
6d
6e
TNT
TATB
RDX
1.79
1.76
1.65
1.93
—
80.4
324
205
ꢁ67.0/ꢁ0.30
ꢁ140/ꢁ0.54
80/0.36
15
50
7.5
—
192
—
112
1.80
a
Melting temperature. b Decomposition temperature. c Density measured by gas pycnometer (25 ꢀC). d Gas phase enthalpy of formation. e Enthalpy
f
g
h
of sublimation (calculated with Trouton's rule). Heat of formation. Detonation pressure (calculated with Explo 5.05). Detonation velocity
i
j
(calculated with Explo 5.05). Impact sensitivity. Oxygen balance (based on CO) for CaHbOcNd 1600(c ꢁ a ꢁ b/2)/Mw, Mw ¼ molecular
k
l
m
weight. Oxygen content. The calculation of detonation properties is based on crystal densities. Calculated density from single crystal X-ray
diffraction (20 ꢀC).
found at the highest eld (ꢁ309.37 and ꢁ304.19). The identi-
Densities of energetic materials, which represent one of
cation for each nitrogen atom is further conrmed by 1H, and the most important physical properties, were measured with a
15N-HMBC experiments (see ESI†).
gas pycnometer. The densities of N-amino-imidazoles are in
Table 2 Crystallographic data for 6a and 6b
6a
6b
Empirical formula
Formula weight
CCDC number
C5H4N8O10
336.16
927838
C5H4N8O10
336.16
927839
Crystal size [mmꢁ3
Crystal system
Space group
]
0.48 ꢂ 0.46 ꢂ 0.01 mm3
Monoclinic
P21/n
0.48 ꢂ 0.34 ꢂ 0.24 mm3
Orthorhombic
Pna21
11.1074(7)
9.5233(6)
10.9770(7)
90
90
90
˚
a [A]
8.3893(5)
˚
b [A]
10.0156(6)
14.3147(8)
90
103.532(2)
90
˚
c [A]
a [ꢀ]
b [ꢀ]
g [ꢀ]
3
˚
V [A ]
1169.39(12)
4
1161.14(13)
4
Z
T [K]
150(2) K
150(2) K
rcalcd [mg cmꢁ3
]
1.909 (ꢁ123 ꢀC) 1.867(20 ꢀC)
1.923 (ꢁ123 ꢀC) 1.869 (20 ꢀC)
m [mmꢁ1
F(000)
q [ꢀ]
]
0.185
680
0.187
680
2.51 to 26.39
ꢁ10 # h # 10,
ꢁ12 # k # 12,
ꢁ17 # l # 16
10 968
2396 [Rint ¼ 0.0235]
2396/0/211
1.044
2.82 to 26.40
ꢁ13 # h # 13,
ꢁ10 # k # 11,
ꢁ13 # l # 13
7852
2270 [Rint ¼ 0.0309]
2270/1/208
1.061
Index ranges
Reections collected
Independent reections (Rint
Data/restraints/parameters
Goodness-of-t on F2
R1 (I > 2d(I))a
)
0.0292
0.0750
0.0387
0.1071
wR2 (I > 2d(I))b
R1 (all data)
0.0337
0.0412
wR2 (all data)
0.0779
0.286 and ꢁ0.268
0.1096
0.424 and ꢁ0.418
Largest diff. peak and hole ([e Aꢁ3])
˚
R1 ¼ S||Fo| ꢁ |Fc||/S|Fo|. wR2 ¼ [Sw(Fo ꢁ Fc2)2/Sw(Fo2)2]1/2
.
a
b
2
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the range of 1.56–1.75 g cmꢁ3, while N-trinitroethylamino- 1.4396(16)). The atoms in the imidazole core with three
nitroimidazoles show higher densities lying between 1.75 and substituted nitrogen atoms are nearly planar with torsion angles
1.84 g cmꢁ3. The densities of 6a and 6b calculated based on (such as N(1)–C(2)–N(3)–C(4)–0.27(14), N(6)–N(1)–C(2)–N(3)–
the single-crystal X-ray diffraction areꢁ3slightly higher (6a, 179.27(11), and C(2)–N(3)–C(4)–N(18)–177.03(11)). However, the
1.867 g cmꢁ3 at 20 ꢀC; 6b, 1.869 g cm at 20 ꢀC) than the nitro groups bonded to imidazole are considerably twisted
ꢁ3
measured densities (6a, 1.83 g cmꢁ3 at 20 C; 6b, 1.84 g cm
relative to each other with a torsion angle of (C(4)–C(5)–N(21)–
O(22)–149.29(14), N(1)–C(5)–N(21)–O(23)–142.85(12), N(3)–C(4)–
N(18)–O(20)–158.46(11), C(5)–C(4)–N(18)–O(19)–162.58(12)).
Intermolecular hydrogenbonds are foundbetweenthe NH group
and imidazole in 6a (N(6)–H(6)/N(3)#1).
ꢀ
at 20 ꢀC).
Sensitivity and computational analyses
In order to obtain the detonation properties, the Gaussian 03
(Revision D.01) suite of programs was used to calculate the gas
phase enthalpies of formation of the resulting compounds.23
Employing Trouton's rule, the enthalpy of sublimation for each
compound was calculated. The heats of formation of these
energetic compounds fall between 68.7 kJ molꢁ1 and 470.1 kJ
molꢁ1. As shown in Table 1, 4d and 6d which contain an azido
group, not surprisingly, have higher heats of formation and
good detonation velocities (4d, 2.78 kJ gꢁ1, 8048 m sꢁ1; 6d, 1.26
kJ gꢁ1, 8513 m sꢁ1) than the other compounds in Table 1.
With the exception of 4d, all N-aminonitroimidazoles are
thermally stable (Td > 210 ꢀC) and insensitive to impact (IS > 40 J).
Among them, detonation propertiesof 4a (P, 28.7 GPa;vD, 8137 m
sꢁ1) and 4b (P, 29.3 GPa; vD, 8174 m sꢁ1) are higher than TNT
(P, 19.5 GPa; vD, 6881 m sꢁ1), and comparable to TATB (P, 31.2
GPa; vD, 8114 m sꢁ1). Compared with N-aminonitroimidazoles,
N-trinitroethylaminonitroimidazoles exhibit better detonation
performances due to their higher densities. Their calculated
detonation velocities lie in the range of 7815 to 8659 m sꢁ1, while
detonation pressures range from 27.6 to 35.9 GPa. Although the
heats of formation of N-trinitroethylaminonitroimidazoles
(0.21–1.26 kJ gꢁ1) are lower than the corresponding N-amino-
nitroimidazoles (0.68–2.78 kJ gꢁ1), most of them possess unique
positive oxygen balances (OB, 2.75–14.92) and good oxygen
content (OC, 37.19–47.60). The measurements of impact sensi-
tivities, obtained by using a BAM drop hammer apparatus,
indicated that N-trinitroethylaminonitroimidazoles are more
sensitive than the corresponding N-aminonitroimidazoles.
However, their densities and detonation performances are
superior with 2,4-dinitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-
Compared with 6a, 6b crystallizes in an orthorhombic
Pna21 space group with a calculated density of 1.869 g
cmꢁ3(20 ꢀC). The length of the C–N bonds joining the trini-
troethyl groups are also different from substituted nitro groups
joining the imidazole moieties [such as C(8)–N(9) 1.536(3),
C(8)–N(15) 1.503(4), and C(4)–N(21) 1.443(3)]. Interestingly, the
two nitro groups are planar with the imidazole ring with
torsion angles of N(3)–C(2)–N(18)–O(19) 6.7(4), N(1)–C(2)–
N(18)–O(20) 7.0(4), C(5)–C(4)–N(21)–O(23)–0.1(4), N(3)–C(4)–
N(21)–O(22) 1.6(4), while the two nitro groups of 6a are twisted
with imidazole. As a result, 6b could be more stable, which
may be reected by the values of their different impact
sensitivities (6a, 2.5 J; 6b, 7 J). In addition, the planar structure
tends to have a higher density, which can be seen in Table 2:
amine (6b) showing excellent overall properties (d, 1.869 g cmꢁ3
;
P, 35.8 GPa; vD, 8649 m sꢁ1; IS, 7 J; OB, 14.29; OC, 47.60), which is
comparable to RDX (d, 1.80 g cmꢁ3; P, 35.0 GPa; vD, 8762 m sꢁ1
;
IS, 7.4 J; OB, 0.00; OC, 43.22).
X-ray crystallography
Crystals of 6a and 6b suitable for crystal-structure analysis were
obtained by recrystallization from chloroform and acetonitrile.
Their crystallographic data are summarized in Table 2, and
structures are shown in Fig. 2 and 3, respectively. As can be seen
in Table 2, 6a crystallizes in the monoclinic P21/n space group
with a calculated density of 1.867 g cmꢁ3 (20 ꢀC). For C–NO2
groups, the length of the C–N bonds in the trinitroethyl groups
˚
˚
(1.5152(16) A–1.5220(16) A: C(8)–N(15), 1.5152(16); C(8)–N(12),
1.5218(16); C(8)–N(9), 1.5220(16)) are longer than the other two
C–N (C–NO2) bond distances in the substituted imidazole
Fig. 2 (a) Thermal ellipsoid plot (50%) and labeling scheme for 6a. Hydrogen
atoms are included but are unlabeled for clarity. (b) Ball and stick packing
diagram of 6a viewed down the a axis. The dashed lines indicate strong
˚
˚
(1.4396(16) A-1.4517(16) A: C(4)–N(18), 1.4517(16); C(5)–N(21), hydrogen bonding.
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Experimental section
Safety precautions
Although we have encountered no difficulties in preparing all of
the compounds in this work, manipulations must be carried out
by using appropriate standard safety precautions. Eye protec-
tion and leather gloves must be worn. Mechanical actions of
these energetic materials involving scratching or scraping must
be avoided.
General methods
All chemicals were pure analytical grade materials obtained
from Aldrich or Acros Organics and used as received. 1H and 13
C
NMR spectra were recorded on a Bruker 300 MHz nuclear
magnetic resonance spectrometer operating at 300 MHz and 75
MHz, respectively. 15N NMR spectra were recorded on a Bruker
500 MHz nuclear magnetic resonance spectrometer operating at
50.7 MHz. Chemical shis in 1H, and 13C NMR spectra are
reported relative to Me4Si and in 15N NMR to MeNO2. To obtain
the 15N spectrum for 6b required ꢃ48 h, while the others were
recorded in ꢃ12 h. CD3CN was used as a locking solvent unless
otherwise stated. Elemental analyses (C, H, N) were performed
on a CE-440 Elemental Analyzer. Impact sensitivity tests were
carried out using the BAM fallhammer method. Melting and
decomposition points were recorded on a differential scanning
ꢀ
calorimeter (DSC, TA Instruments Q10) at a scan rate of 5 C
minꢁ1. IR spectra were recorded using KBr pellets with a Biorad
Model 3000 FTS spectrometer. Densities were determined at
room temperature by employing a Micromeritics AccuPyc 1330
gas pycnometer.
Fig. 3 (a) Thermal ellipsoid plot (50%) and labeling scheme for 6b. Hydrogen
atoms are included but are unlabeled for clarity. (b) Ball and stick packing diagram
of 6b viewed down the a axis.
X-ray crystallography
ꢁ3
6a, 1.867 g cmꢁ3 (20 C),ꢁ13.909 g cm (ꢁ123 C); 6b, 1.869 g
ꢀ
ꢀ
A yellow plate of dimensions 0.48 ꢂ 0.46 ꢂ 0.01 mm3 for 6a and
a colorless plate of dimensions 0.48 ꢂ 0.34 ꢂ 0.24 mm3 for 6b
were mounted on a MiteGen MicroMesh using a small amount
of Cargille Immersion Oil. Data were collected on a Bruker
three-circle platform diffractometer equipped with a SMART
APEX II CCD detector. The crystals were irradiated using
graphite monochromated MoKa radiation (l ¼ 0.71073). An
Oxford Cobra low temperature device was used to keep the
crystals at a constant 150(2) K during data collection. Data
collection was performed and the unit cell was initially rened
using APEX2 [v2010.3-0].24 Data reduction was performed using
SAINT [v7.68A]25 and XPREP [v2008/2].26 Corrections were
applied for Lorentz, polarization, and absorption effects using
SADABS [v2008/1].27 The structure was solved and rened with
the aid of the programs in the SHELXTL-plus [v2008/4] system of
programs.28 The full-matrix least-squares renement on F2
included atomic coordinates and anisotropic thermal parame-
ters for all non-H atoms. The H atoms were included using a
riding model.
cmꢁ3 (20 C), 1.923 g cm (ꢁ123 C).
ꢀ
ꢀ
Conclusion
N-Trinitroethylaminoimidazoles were obtained from ammo-
nium or potassium nitroimidazolates by
a facile linear
synthesis, including N-amination followed by N-trini-
troethylation. These new compounds were characterized by IR,
and NMR spectroscopic data and elemental analysis.
Compounds 6a and 6b were structured using single-crystal
X-ray diffraction which allowed correlation of conguration
relationships with densities and impact sensitivities. N-Ami-
nonitroimidazoles with excellent thermal stabilities and impact
sensitivities are better than TNT and comparable to TATB.
Moreover, all of the N-trinitroethylaminonitroimidazole
compounds have positive oxygen balances and good oxygen
content, best exemplied by 6b which exhibits high density,
good oxygen content, moderate thermal stability, and high
detonation performance and may serve as a promising alter-
native to some known explosives such as RDX. Detailed prop-
erties of these imidazole-based compounds show good
Theoretical study
compatibilities
with
N-trinitroethylamination,
thereby Computations were performed by using the Gaussian 03
providing a promising N-functionalized strategy toward high (Revision D.01) suite of programs. The geometric optimization
performance energetic materials.
of the structures and frequency analyses were carried out by
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using the B3-LYP functional with the 6-31+G** basis set 19, and (100 : 35). Yellow solid (947 mg, 55%); M.p. 173 ꢀC, 265 ꢀC
1
single-point energies were calculated at the MP2/6-311++G** (dec.); H NMR: d 8.12 (s, 1H), 6.22 (s, 2H); 13C NMR: d 141.6,
level. All of the optimized structures were characterized to be 141.2, 126.1; IR (KBr pellet): 3343, 3267, 3205, 3148, 1548, 1494,
true local energy minima on the potential-energy surface 1342, 1315,1145, 1025, 857, 821 cmꢁ1; elemental analysis (%)
without imaginary frequencies.
calcd for C3H3N5O4 (173.09): C, 20.82; H, 1.75; N, 40.46; found:
According to the method of isodesmic reactions, the gas C, 21.19; H, 1.76; N, 39.67. Density: 1.75 g cmꢁ3. Impact sensi-
phase enthalpies of formation were computed and the enthalpy tivity: >40 J.
of reaction is obtained by combining the MP2/6-311++G**
4-Nitro-1H-imidazol-1-amine (4c). 4-Nitro-1H-imidazol-1-
energy difference for the reactions, the scaled zero point ener- amine was prepared by using the potassium salt. To a 200 mL
gies, and other thermal factors. Thus, the gas phase enthalpy of round bottomed ask, 4-nitro-1H-imidazole (1.13 g, 10 mmol)
the species being investigated can be readily extracted. The and potassium hydroxide (728 mg, 13 mmol) were added to
ꢀ
enthalpy of sublimation was calculated by using Trouton's 20 mL MeOH. The mixture was stirred at 50 C for 0.5 h. The
rule.29 Solid-state heats of formation of the resulting solvent was removed by evaporation and DMF (20 mL) was
compounds were calculated with eqn (1) in which Tm is the added to the residue. Freshly prepared O-tosylhydroxylamine in
melting temperature.
CH2Cl2 (100 mL, prepared by the procedure described above)
was added to the DMF solution at 0 ꢀC. Aer addition the
temperature was allowed to rise to room temperature and stir-
red for 12 h. The organic solvent was removed by rotary evap-
oration. Ethyl acetate (50 mL) was added to dissolve the
aminoimidazole remaining and the mixture was ltered; the
ltrate was washed with brine, and dried over Na2SO4. The ethyl
acetate solution was evaporated and the crude product was
puried by chromatography with hexane–ethyl acetate (100 : 50)
DHf ¼ DHf(g) ꢁ DHsub ¼ DHf(g) ꢁ 188[J molꢁ1
K
ꢁ1] ꢂ Tm (1)
With densities and heats of formation in hand, the detona-
tion pressure (P) and velocity (vD), were calculated using the
program package EXPLO 5.05.
General procedure
O-Tosylhydroxylamine. O-Tosylhydroxylamine was prepared to give 4c. White solid (268 mg, 21%). M.p. 96 ꢀC, 237 ꢀC (dec.);
by the literature method.15a Freshly prepared ethyl O-p-tolyl- 1H NMR: d 7.87 (s, 1H), 7.69 (s, 1H), 5.63 (s, 2H); 13C NMR: d
sulphonylacetohydroximate (15 mmol, 3.86 g) was added to 142.9, 139.2, 132.0; IR (KBr pellet): 3304, 3206, 3133, 1655, 1532,
25 mL of 60% HClO4. The mixture was stirred at room 1468, 1382, 1271, 1111, 1002, 853, 824, 649 cmꢁ1; elemental
temperature for 2 h. Hydrolysis of ethyl O-p-tolylsulphonylaceto- analysis (%) calcd for C3H4N4O2 (128.09): C, 28.13; H, 3.15; N,
hydroximate was monitored by thin layer chromatography 43.74; found: C, 28.13; H, 3.11; N, 42.91. Density: 1.56 g cmꢁ3
(TLC). When the reaction was completed, the white slurry was Impact sensitivity: >40 J.
.
poured into ice and extracted with CH2Cl2 (4 ꢂ 25 mL). The
organic portions were combined, dried over Na2SO4, and used 1H-imidazole was prepared from 4,5-dinitroimidazole in two
for N-amination reactions. steps. 4,5-Dinitroimidazole (15.8 g, 0.1 mol) was dissolved in
5-Azido-4-nitro-1H-imidazol-1-amine (4d). 5-Azido-4-nitro-
4,5-Dinitro-1H-imidazol-1-amine (4a). 4,5-Dinitroimidazole aqueous ammonia (200 mL) and stirred at 100 ꢀC for 15 h. The
was prepared based on the literature.30 To a 200 mL round yellow solution was concentrated to appropriate 20 mL by
bottomed ask, 4,5-dinitroimidazole (1.58 g, 10 mmol) was passing air over the liquid surface. The precipitate was then
dissolved in excess aqueous ammonia. The solvent was removed removed by ltration and 5-amino-4-nitroimidazole was
by blowing air over the liquid surface and the residue was dried obtained, which was used for the next step without purication.
in vacuo. Acetonitrile (100 mL) was added to the ammonium salt 1H NMR: d 7.32 (s, 2H), 7.23 (s, 1H).
and followed by the freshly prepared O-tosylhydroxylamine in
5-Amino-4-nitroimidazole was dissolved in H2SO4 (70%, 200
ꢀ
CH2Cl2 (100 mL, prepared as above). The mixture was stirred at mL) and the solution was cooled to 0 C. A solution of sodium
room temperature for 12 h. The solvent was removed by rotary nitrite (6.90 g, 0.1 mol) in water (30 mL) was added to the stirred
evaporation and ethyl acetate (50 mL) was added. The white solution. Aer addition, the reaction mixture was stirred at
ꢀ
precipitate was ltered and ethyl acetate was removed. The room temperature for 1 h, cooled to 0 C and diluted with 500
residue was puried by chromatography with hexane–ethyl mL H2O. Urea (3.03 g, 0.05 mol) was added, and then NaN3 (6.50
acetate (100 : 50), to give 4a. Yellow solid (1.21 g, 70%); M.p. g, 0.1 mol) was added in small portions and the reaction was
1
64 C, 235 C (dec.); H NMR: d 7.66 (s, 1H), 5.80 (s, 2H); 13C stirred for additional 3 h. The nal yellow aqueous solution was
NMR: d 138.8, 136.8, 133.1; 15N NMR: d ꢁ24.02, ꢁ34.08, ꢁ137.12 extracted with ethyl ether (5 ꢂ 100 mL), and the ether solution
(d, J ¼ 12.68 Hz), ꢁ198.52 (dt, J ¼ 6.59 Hz, 1.52 Hz), ꢁ308.11 (t, was evaporated under reduced pressure to give 5-azido-4-nitro-
J ¼ 73.01 Hz); IR (KBr pellet): 3358, 3250, 3203, 3140, 1558, 1526, 1H-imidazole. Yellow solid (7.81 g, 51% overall yield). 1H NMR:
1489, 1363, 1314, 1209, 1154, 954, 812, 643 cmꢁ1; elemental d 7.32 (s, 2H), 7.23 (s, 1H).
ꢀ
ꢀ
analysis (%) calcd for C3H3N5O4 (173.09): C, 20.82; H, 1.75; N,
5-Azido-4-nitro-1H-imidazole (1.54 g, 10 mmol) was dis-
solved in 30 mL DMF. Potassium carbonate (2.07 g, 15 mmol)
was added and stirred at 50 ꢀC for 2 h. To the reaction mixture
40.46; found: C, 20.99; H, 1.78; N, 39.77. Density: 1.72 g cmꢁ3
Impact sensitivity: >40 J.
.
2,4-Dinitro-1H-imidazol-1-amine (4b).18 Aer using the same in an ice bath was added freshly prepared O-tosylhydroxylamine
procedure as for 4a, 2,4-dinitro-1H-imidazol-1-amine (4b) in CH2Cl2 (100 mL, prepared as above) cooled below 10 ꢀC. The
was obtained by chromatography with hexane–ethyl acetate reaction mixture was allowed to warm, and stirred at room
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temperature for 24 h. The organic solvent was removed by rotary NMR: d 134.5, 125.0, 120.9; IR (KBr pellet): 3267, 3180, 3119,
evaporation. Ethyl acetate (50 mL) was added to dissolve the 1637, 1504, 1437, 1411, 1327, 1294, 1106, 1023, 751 cmꢁ1
;
aminoimidazole and the mixture was ltered, washed with elemental analysis (%) calcd for C6H8N6 (164.17): C, 43.90; H,
brine, and dried over Na2SO4. The ethyl acetate solution was 4.91; N, 51.19; found: C, 44.04; H, 4.86; N, 50.88.
evaporated and the crude product was puried by chromatog-
4,5-Dinitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine (6a).
raphy with hexane–ethyl acetate (100 : 40) to give 4d. Yellow A suspension of 4,5-dinitro-1H-imidazol-1-amine (4a, 173 mg, 1
solid (1.23 g, 73%). M.p. 77 ꢀC, 144 ꢀC (dec.); 1H NMR: d 7.61 (s, mmol) in distilled water (30 mL) was stirred at 80 ꢀC for 1 h. The
1H), 5.64 (s, 2H); 13C NMR: d 141.4, 140.4, 126.6; 15N NMR: d resulting clear yellow solution was allowed to cool to 50 ꢀC and
ꢁ27.26, ꢁ140.50, ꢁ141.65, ꢁ144.93 (d, J ¼ 11.66 Hz), ꢁ205.04, 2,2,2-trinitroethanol (362 mg, 2 mmol) was added. Then the
ꢁ285.43, ꢁ307.38 (t, J ¼ 70.98 Hz); elemental analysis (%) calcd reaction was stirred overnight at ambient temperature. The
for: C3H3N7O2 (169.10): C, 21.31; H, 1.79; N, 57.98; found: C, precipitate was ltered, washed with water, and dried under
21.37; H, 1.82; N, 57.61; IR (KBr pellet): 3375, 3307, 3120, 2143, vacuo. Pale yellow solid (243 mg, 72%). M.p. 163 ꢀC, 171 ꢀC
1
1541, 1501, 1461, 1417, 1360, 1329, 1177, 1146, 948, 839 cmꢁ1
Density: 1.65 g cmꢁ3. Impact sensitivity: 3.5 J.
.
(dec.); H NMR: d 8.13 (s, 1H), 7.21 (s, 1H), 5.04 (d, J ¼ 5.4 Hz,
2H); 13C NMR: d 140.7, 138.2, 131.2, 127.5, 54.4; 15N NMR: d
5-Chloro-4-nitro-1H-imidazol-1-amine (4e). 5-Chloro-4-nitro- ꢁ24.14, ꢁ30.78 (t, J ¼ 2.03 Hz), ꢁ34.01, ꢁ135.32 (d, J ¼ 6.08 Hz),
1H-imidazole was prepared based on the literature.31 Aer using ꢁ193.57, ꢁ309.71 (d, J ¼ 85.68 Hz); IR (KBr pellet): 3210, 3119,
the same procedure as for 4d, 5-chloro-4-nitro-1H-imidazol-1- 3019, 1616, 1590, 1542, 1463, 1344, 1305, 1207, 1111, 849, 807
amine (4e) was obtained by chromatography with hexane–ethyl cmꢁ1; elemental analysis (%) calcd for C5H4N8O10 (336.13): C,
acetate (100 : 50 to 100:100). White solid (1.22 g, 75%). M.p. 17.87; H, 1.20; N, 33.34; found: C, 18.25; H, 1.27; N, 32.51.
1
123 C, 274 C (dec.); H NMR: d 8.01 (s, 1H), 5.20 (s, 2H); 13C Density: 1.83 g cmꢁ3. Impact sensitivity: 2.5 J.
ꢀ
ꢀ
NMR: d 144.0, 134.7, 125.1; elemental analysis (%) calcd for
2,4-Dinitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine (6b).
C3H3ClN4O2 (162.53): C, 22.17; H, 1.86; N, 34.47; found: C, A suspension of 2,4-dinitro-1H-imidazol-1-amine (4b, 173 mg, 1
22.15; H, 1.82; N, 33.52.
mmol) in distilled water (40 mL) was stirred at 80 ꢀC for 1 h. The
4,40,5,50-Tetranitro-1H,10H-2,20-biimidazole-1,10-diamine (4f).32 resulting clear yellow solution was allowed to cool to 50 ꢀC and
Compound 4f was obtained by using the same procedure as for 2,2,2-trinitroethanol (362 mg, 2 mmol) was added. The reaction
4a. 4,40,5,50-Tetranitro-1H,10H-2,20-biimidazole-1,10-diamine (4f) was stirred overnight at ambient temperature. The precipitate
was isolated by chromatography with hexane/ethyl acetate was ltered, washed with water and dried under vacuum. White
(100 : 50). White solid (1.82 g, 53%). M.p. 206 ꢀC, 217 ꢀC (dec.); solid (204 mg, 61%), 172 ꢀC (dec.); 1H NMR: d 8.13 (s, 1H), 7.21
1H NMR (d6-DMSO): d 8.55 (s, 2H), 6.87 (s, 4H); 13C NMR (d6- (s, 1H); 5.04 (d, J ¼ 5.4 Hz, 2H); 13C NMR: d 141.4, 140.9, 127.3,
DMSO): d 137.0, 134.8, 131.6; IR (KBr pellet): 3360, 3259, 1532, 125.8, 54.5; 15N NMR: d ꢁ23.38, ꢁ30.75, ꢁ32.83, ꢁ130.14,
1504, 1389, 1366, 1312, 1147, 849, 816 cmꢁ1; elemental analysis ꢁ192.82, ꢁ304.19 (d, J ¼ 84.67 Hz); IR (KBr pellet): 3275, 3140,
(%) calcd for C6H4N10O8 (344.16): C, 20.94; H, 1.17; N, 40.70; 3008, 1597, 1552, 1512, 1340, 1308, 853, 802 cmꢁ1; elemental
found: C, 21.09; H, 1.17; N, 40.09.
analysis (%) calcd for C5H4N8O10 (336.13): C, 17.87; H, 1.20; N,
4,40-Dinitro-1H,10H-2,20-biimidazole-1,10-diamine (4g). The 33.34; found: C, 17.88; H, 1.21; N, 32.60. Density: 1.84 g cmꢁ3
starting material (4,40-dinitro-1H,10H-2,20-biimidazole) was Impact sensitivity: 7 J.
.
prepared according to literature.33 Compound 4g was obtained
4-Nitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine (6c).
by using the same procedure as for 4d and isolated by chro- 2,2,2-Trinitroethanol (543 mg, 2 mmol) was added to a solution
matography with hexane–ethyl acetate (100 : 100 to 10 : 100). of 4-nitro-1H-imidazol-1-amine (4c, 128 mg, 1 mmol) in water
1
ꢀ
ꢀ
Yellow solid (1.07 g, 42%). M.p. 285 C, 308 C (dec.); H NMR (30 mL) at 50 ꢀC. The resulting solution was stirred at 50 ꢀC until
(d6-DMSO): d 8.57 (s, 2H), 6.87 (s, 4H); 13C NMR (d6-DMSO): d a white precipitate formed. The reaction mixture was cooled
143.3, 133.4, 123.6; IR (KBr pellet): 3330, 3266, 3127, 1541, 1498, and stirred overnight at room temperature. The precipitate was
1399, 1344, 1298, 1001, 820 cmꢁ1; elemental analysis (%) ltered, washed with water and dried under vacuum. White
calcd for C6H6N8O4 (254.16): C, 28.35; H, 2.38; N, 44.09; found: solid (163 mg, 56%), 139 ꢀC (dec.); 1H NMR: d 7.95 (s, 1H), 7.65
C, 28.55; H, 2.44; N, 43.89. Density: 1.75 g cmꢁ3. Impact sensi- (s, 1H), 6.94 (s, 1H), 4.93 (d, J ¼ 5.1 Hz, 2H); 13C NMR: d 143.8,
tivity: >40 J.
138.5, 133.1, 128.1, 55.0; IR (KBr pellet): 3142, 1590, 1535, 1510,
1H,10H-2,20-Biimidazole-1,10-diamine (4h). A suspension of 1381, 1119, 808 cmꢁ1; elemental analysis (%) calcd for
1H,10H-2,20-biimidazole (1h, 134 mg, 1 mmol) in aqueous KOH C5H5N7O8 (291.14): C, 20.63; H, 1.73; N, 33.68; found: C, 20.81;
(560 mg of KOH in 20 mL of distilled water) was stirred at 90 ꢀC H, 1.74; N, 33.27. Density: 1.75 g cmꢁ3. Impact sensitivity: 10 J.
for 0.5 h. The reaction temperature was allowed to cool to 40 ꢀC
5-Azido-4-nitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine
and hydroxylamine-O-sulfonic acid (684 mg, 6 mmol) was added (6d). 2,2,2-Trinitroethanol (543 mg, 3 mmol) was added to the
over 20 min with the temperature maintained below 50 ꢀC. Aer solution of 5-azido-4-nitro-1H-imidazol-1-amine (4d, 169 mg, 1
ꢀ
stirring at 50 C overnight, the mixture was extracted by ethyl mmol) in water (50 mL) at 50 ꢀC. The resulting solution was
ꢀ
ether (5 ꢂ 10 mL). The organic portions were combined, dried stirred at 50 C until a white precipitate was formed. The reac-
over Na2SO4, and concentrated under reduced pressure. The tion mixture was cooled and stirred overnight at room
residue was puried by chromatography with hexane/ethyl temperature. The precipitate was ltered, washed with water
acetate (20 : 100). White solid (39 mg, 24%). M.p. 154 ꢀC, 292 ꢀC and dried under vacuum. White solid (177 mg, 53%), 136 ꢀC
1
(dec.); 1H NMR: d 7.24 (s, 2H), 6.96 (s, 2H), 6.87 (s, 4H); 13C (dec.). H NMR: d 7.59 (s, 1H), 6.90 (s, 1H), 4.88 (d, J ¼ 4.5 Hz,
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2H); 13C NMR: d 142.5, 141.1, 128.0,125.2, 55.0; IR (KBr pellet):
4 (a) C. Qi, S. H. Li, Y. C. Li, Y. Wang, X. X. Zhao and S. P. Pang,
Chem.–Eur. J., 2012, 18, 16562–16570; (b) C. Qi, S. H. Li,
Y. C. Li, Y. A. Wang, X. K. Chen and S. P. Pang, J. Mater.
Chem., 2011, 21, 3221–3225; (c) Y. C. Li, C. Qi, S. H. Li,
H. J. Zhang, C. H. Sun, Y. Z. Yu and S. P. Pang, J. Am.
Chem. Soc., 2010, 139, 12172–12173.
3303, 2136, 1605, 1555, 1525, 1408, 1362, 1323, 1175, 803, 775
cmꢁ1
;
15N NMR: d ꢁ28.57, ꢁ30.25 (t, J ¼ 2.03 Hz), ꢁ34.01,
ꢁ139.31, ꢁ142.55, ꢁ143.14 (d, J ¼ 6.08 Hz), ꢁ199.06, ꢁ283.43,
ꢁ309.37 (d, J ¼ 84.67 Hz); elemental analysis (%) calcd for
C5H4N10O8 (332.15): C, 18.08; H, 1.21; N, 42.17; found: C, 18.09;
H, 1.22; N, 41.11. Density: 1.79 g cmꢁ3. Impact sensitivity: 2 J.
5-Chloro-4-nitro-N-(2,2,2-trinitroethyl)-1H-imidazol-1-amine
(6e). A suspension of 5-chloro-4-nitro-1H-imidazol-1-amine (4e,
163 mg, 1 mmol) in distilled water (30 mL) was stirred at 80 ꢀC
for 1 h. The resulting clear yellow solution was allowed to cool to
50 ꢀC and 2,2,2-trinitroethanol (362 mg, 2 mmol) was added.
The reaction was stirred overnight at ambient temperature. The
precipitate was ltered, washed with water, and dried under
5 (a) V. M. Boddu, D. S. Viswanath, T. K. Ghosh and
R. Damavarapu, J. Hazard. Mater., 2010, 181, 1–8; (b)
R. D. Schmidt, G. S. Lee, P. R. Pagoria, A. R. Mitchell and
R. Gilardi, J. Heterocycl. Chem., 2001, 38, 1227–1230.
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1
ꢀ
vacuum. White solid (140 mg, 43%), 156 C (dec.); H NMR: d
8.12 (s, 1H), 6.69 (s, 1H), 4.95 (s, 2H); 13C NMR: d 144.3, 134.5,
127.6, 123.9, 54.2; IR (KBr pellet): 3215, 3171, 2994, 1604, 1557,
1471, 1381, 1302, 1279, 1124, 997, 801 cmꢁ1; elemental analysis
(%) calcd for C5H4ClN7O10 (325.58): C, 18.45; H, 1.24; N, 30.11;
found: C, 18.52; H, 1.16; N, 29.43. Density: 1.76 g cmꢁ3. Impact
sensitivity: 7 J.
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Acknowledgements
The authors gratefully acknowledge the support of ONR
(N00014-12-1-0536); and (N00014-11-AF-0-0002).
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