Derivatives of 5-nitro-1,2,3-2H-triazole-high performance energetic materials

Article abstract of DOI:10.1039/c2ta00136e

The energetic derivatives of 5-nitro-1,2,3-2H-triazole, which include 2-(methyl or amino)-4-(nitramino, azido, or nitro)-5-nitro-1,2,3-2H-triazoles, were prepared in moderate yields, and confirmed with NMR and IR spectroscopy, and elemental analysis. Their key properties, viz., melting and decomposition temperatures, densities, detonation pressures and velocities, and impact sensitivities, were measured or calculated. Among the new derivatives, 2-amino-4,5-dinitro-1,2,3-2H-triazole exhibits properties (T_m, 94 °C; T_d, 190 °C; ρ, 1.83 g cm^-3; P, 36.2 Gpa, v_D, 8843 m s^-1, IS, 24 J), comparable with RDX (T _m, 205 °C; T_d, 230 °C; ρ, 1.80 g cm ^-3; P, 35.0 Gpa, v_D, 8762 m s^-1, IS, 7.5 J), and may have potential as a high-performance energetic material.

Full text of DOI:10.1039/c2ta00136e

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Derivatives of 5-Nitro-1,2,3-2H-triazole – High Performance
Energetic Materials
Yanqiang Zhanga, Damon A. Parrishb, and Jean’ne M. Shreeve*a
a
Dr. Y. Zhang, Prof. Dr. J. M. Shreeve
Department of Chemistry, University of Idaho
Moscow, ID 83844-2343 (USA)
Fax: (+1) 208-885-9146
E-mail: jshreeve@uidhao.edu
b
Dr. D. A. Parrish
Naval Research Laboratory, Code 6030
Washington, D.C. 20375-5001 (USA)
Abstract: The energetic derivatives of 5-nitro-1,2,3-2H-triazole, which include 2-(methyl
or amino)-4-(nitramino, azido, or nitro)-5-nitro-1,2,3-2H-triazoles, were prepared in
moderate yields, and confirmed with NMR and IR spectroscopy, and elemental analysis.
Their key properties, viz., melting and decomposition temperatures, densities, detonation
pressures and velocities, and impact sensitivities, were measured or calculated. Among
the new derivatives, 2-amino-4,5-dinitro-1,2,3-2H-triazole exhibits properties (Tm, 94 °C;
Td, 190 °C; ρ, 1.83 gcm-3; P, 36.2 Gpa, vD, 8843 ms-1, IS, 24 J), comparable with RDX
(Tm, 205 °C; Td, 230 °C; ρ, 1.80 gcm-3; P, 35.0 Gpa, vD, 8762 ms-1, IS, 7.5 J), and may
have potential as a high-performance energetic material.
Introduction
The development of new high energy density materials (HEDM) continues to
focus on the synthesis of the derivatives of 5-membered nitrogen-containing heterocycles
(azoles) which are widely functionalized with energetic groups such as nitro, nitramino,
azido, etc, and are reported frequently.1 In order to achieve better detonation performance,
groups which are more energetic are bonded to azole rings, especially the fully C-
functionalized azoles such as 5-nitro-tetrazole,2 3,5-dinitro-triazole,3 4,5-dinitro-triazole,4
2,4,5-trinitro-imidazole,5 3,4,5-trinitro-pyrazole,6 and 2,3,4,5-tetranitro-pyrrole.7 Many of
the resulting azole compounds are very energetic, with high sensitivities (such as the
tetrazole derivatives including 5-azido-tetrazole,8 5-nitramino-tetrazole,9 and 5-nitro-
tetrazole2) and low thermal stabilities (such as pyrrole derivatives, e.g., tetranitro-pyrrole)
1

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which precludes their applications as explosives. Also, the resulting azoles tend to be
very acidic as a result of the electron withdrawing effect of the nitro group substitutents
on the azole ring upon the N-H group; this enhances the reactivity with metals increasing
the sensitivity and accelerating decomposition while concomitantly increasing the cost of
storage. Two routes to decrease the acidity include reaction with bases to form energetic
salts - a method which have been investigated extensively10 or the introduction of methyl
or amino groups via methylating or aminating reagents to replace the acidic proton.5,6
Compared with methylation, amination of energetic azoles is of greater value since while
the methyl group has a negative impact on detonation performance, the amino group has
a slight positive effect resulting in an increase in detonation performance.
1,2,3-2H-Triazole is a surprisingly stable structure compared to other organic
compounds with three contiguous nitrogen atoms. With higher heats of formation, some
of the derivatives of 1,2,3-2H-triazole are reported to be more thermally stable than the
1,2,4-1H-triazole isomers, for example, compare 3-amino-5-nitro-1,2,4-1H-triazole (Td,
243 °C) and 4-amino-5-nitro-1,2,3-2H-triazole (Td, 297 °C).3,11 Although the derivatives
of 1,2,3-2H-triazole such as 4-amino-5-nitro-1,2,3-2H-triazole and 4,5-dinitro-1,2,3-2H-
triazole have been reported,4 1,2,3-2H-triazole-based energetic compounds have been
investigated to a lesser extent than the other azoles, such as tetrazole, 1,2,4-1H-triazole,
pyrazole, imidazole, and pyrrole. In this paper, a series of derivatives of 5-nitro-1,2,3-2H-
triazole including 4-nitramino-5-nitro-1,2,3-2H-triazole and its methyl derivative, 4-
azido-5-nitro-1,2,3-2H-triazole and its methyl and amino derivatives, and the methyl and
amino derivatives of 4,5-dinitro-1,2,3-2H-triazole, were prepared, and fully characterized
with 1H, 13C, and 15 N NMR, and IR spectroscopy, differential scanning calorimetry,
elemental analysis, hammer tests, and in some cases with single crystal X-ray structuring.
Their heats of formation and detonation properties were calculated by using Gaussian 03
and Explo 5.5, respectively. Some of these compounds show good detonation
performances and sensitivities. Considering that the multi-step preparation of derivatives
of 5-nitro-1,2,3-2H-triazole is costly, the development of short and efficient method for
preparation will be of value.
2

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Results and discussion
As the starting material for the series of new compound, 4-amino-5-nitro-1,2,3-
2H-triazole (1) was prepared by multi-step reactions from acetic anhydride and nitric acid
(100%) according to literature methods (Scheme 1).4,12
Scheme 1. Synthesis of 4-amino-5-nitro-1,2,3-2H-triazole, 1
4-Amino-5-nitro-1,2,3-2H-triazole (1) can be directly nitrated with mixed acid
(70% HNO3/concentrated H2SO4) to give 4-nitramino-5-nitro-1,2,3-2H-triazole (2) in
76% yield. Compound 1 has very poor solubility in common organic solvents, and
therefore was refluxed with dimethyl sulfate in H2O for 10 h to obtain 4-amino-2-methyl-
5-nitro-2H-triazole (3; yield 51%) (Scheme 2). Mixed acid was used to convert 3 to its 4-
nitramino analogue, 4.
Scheme 2. Synthesis of the 4-nitramino-5-nitro-1,2,3-2H-triazole (2) and its methyl
derivative.
4-Azido-5-nitro-1,2,3-2H-triazole (5) was prepared by the diazotation of 1 with
sodium nitrite in aqueous sulfuric acid (70%) followed by reaction with sodium azide. It
was neutralized with ammonia to form ammonium 4-azido-5-nitro-1,2,3-2H-triazolate
which was reacted with methyl iodide or O-picrylhydroxylamine (pic-O-NH2)13 in
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acetonitrile to yield 4-azido-2-methyl-5-nitro-1,2,3-2H-triazole (6; yield 61%) or 2-
amino-4-azido-5-nitro-1,2,3-2H-triazole (7; yield 75%), respectively (Scheme 3).
CH3
CH3I
N
N
N
(6)
H
H
N
N3
NO2
N
NH3 H2O
N
N
HNO2/NaN3
N
N
(1)
NH2
N
(5)
H2N
NO2
N3
NO2
N
N
pic-O-NH2
(7)
N3
NO2
Scheme 3. Synthesis of the 4-azido-5-nitro-1,2,3-2H-triazole (5), and its methyl and
amino derivatives.
Using the literature method, 4,5-dinitro-1,2,3-2H-triazole (8) was prepared by
oxidation of 1 with hydrogen peroxide (30%).4 With the methodology given in Scheme 3,
2-methyl-4,5-dinitro-1,2,3-2H-triazole (9; yield 51%) and 2-amino-4,5-dinitro-1,2,3-2H-
triazole (10; yield 55%) were obtained by reacting ammonium 4,5-dinitro-1,2,3-2H-
triazolate with methyl iodide and pic-O-NH2, respectively (Scheme 4).
Scheme 4. Synthesis of the 4,5-dinitro-1,2,3-2H-triazole (8), and its methyl and amino
derivatives.
In order to compare the properties of the derivatives of 1,2,3-2H-triazole with the
1,2,4-1H-triazole isomer, N-amino-dinitro-triazole was taken as an example since this is
among the most interesting derivatives of the triazole-based energetic compounds. 1-
Amino-3,5-dinitro-1,2,4-1H-triazole (13; yield, 69%) was prepared by diazotation,
neutralization, and amination of 3,5-diamino-1,2,4-1H-triazolate (Scheme 5). While this
work was underway, 13 was reported.14
Scheme 5. Synthesis of 1-amino-3,5-dinitro-1,2,4-1H-triazole, 13
4

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The structures of the resulting compounds are supported by 1H, 13C, and 15N
NMR, and IR spectroscopy, and elemental analysis. Compounds 2, 10 and 13 were
further confirmed by single-crystal X-ray structuring.
Properties of the compounds
The thermal stabilities of the above compounds were determined by differential
scanning calorimetric (DSC) measurements scanning at 5 °C min-1 (Table 1). While
compounds 2, 4, and 5 decomposed without melting at 130, 112, and 149 °C, respectively,
other compounds melted prior to decomposing. Of the four methyl derivatives (3, 4, 6,
and 9), 3, 6, and 9 melt with sharp endothermic peaks. No sharp exothermic peaks which
would indicate decomposition are observed which may be a result of the compounds
vaporizing before decomposition. Also, in TGA measurements, weight loss occurs after
melting for 3, 6, and 9 making it very difficult to determine their decomposition points.
Among the new compounds, 2-amino-4,5-dinitro-1,2,3-2H-triazole (10) shows the
highest onset decomposition point at 190 °C.
Densities of these compounds were measured with a gas pycnometer, and found
to be in the range between 1.58 (3) and 1.87 (2) gcm-3 at 25 °C. Based on single-crystal
X-ray diffraction, the calculated densities of 4-nitramino-5-nitro-1,2,3-2H-triazole and 2-
amino-4,5-dinitro-1,2,3-2H-triazole (10) are 1.919 at 23 °C and 1.868 gcm-3 at 20 °C,
respectively, while the experimental data as 1.87 and 1.83 gcm-3 at 25 °C. Comparison of
the nitramino-, azido-, and nitro-based derivatives of 5-nitro-1,2,3-2H-triazole, the
nitramino- and nitro-based compounds have similar densities while not surprisingly the
corresponding azido-based compounds have the lowest densities.
The gas phase enthalpies of formation of the above compounds were calculated
using the Gaussian 03 (Revision D. 01) suite of programs.15 The enthalpy of sublimation
was estimated according to Trouton’s rule.16 The resulting heats of formation of these
compounds vary between 0.87 (3) and 3.50 (7) kJg-1. Because of the high enthalpy of
formation of the azido group (9.86 kJg-1), the azido-based compounds show higher heats
of formation than the corresponding nitramino- and nitro- compounds. Moreover, the 2-
amino derivatives possess more positive heats of formation than their corresponding
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parents; in contrast the heats of formation of the 2-methyl derivatives are lower than
those of their corresponding parents.
With the data for molecular weight, density, and heat of formation in hand, the
detonation pressure (P) and velocity (vD) of the resulting compounds were calculated
with Explo 5.05.17 For compounds 10 and 13, two groups of detonation performance data
were obtained by using the measured density and calculated density, respectively. The
impact sensitivities were determined by BAM Fallhammer measurements with a 10 kg
drop weight. As can be seen in Table 1, the amino derivatives 7 (P, 33.0 Gpa; vD, 8756
ms-1; IS, 3 J) and 10 (P, 36.2 Gpa; vD, 8843 ms-1, IS, 24 J) exhibit higher detonation
performance and are more impact sensitive than their corresponding methyl derivatives 6
(P, 26.3 Gpa; vD, 8096 ms-1; IS, 8 J) and 9 (P, 28.5 Gpa; vD, 8126 ms-1; IS, 35 J).
Although 4-nitramino-5-nitro-1,2,3-2H-triazole (2, P, 36.9 Gpa, vD, 8876 ms-1), 4-azido-
5-nitro-1,2,3-2H-triazole (5, P, 32.9 Gpa; vD, 8669 ms-1) and its amino derivative (7, P,
33.0 Gpa; vD, 8756 ms-1) show good detonation properties, their impact sensitivities are
3.5, 4, and 3 J, respectively, which tends to preclude their further applications. 2-Amino-
4,5-dinitro-1,2,3-2H-triazole (10) is competitive with the performance properties of RDX
(P, 35.0 Gpa; vD, 8762 ms-1) and it is more than 3X less impact sensitive (24 J). Thus it
is the most promising energetic material among the nitramino and nitro derivatives.
The thermal stabilities of 2-amino-4,5-dinitro-1,2,3-2H-triazole (10) and its
isomer 1-amino-3,5-dinitro-1,2,4-1H-triazole (13) are shown in Figure 1. It can be seen
that 10 with the onset decomposition temperature (Td,onset) as 190 °C is more stable
thermally than 13 (Td,onset, 165 °C). Moreover, with the higher heat of formation (1.58 vs
1.21 kJg-1) and the same experimental densities (1.83 vs 1.83 gcm-3), 10 exhibits a
somewhat better detonation performance than 13 (P, 36.2 vs 34.9 Gpa; vD, 8843 vs 8725
ms-1) while their impact sensitivities are similar at 24 vs 30 J.
6

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Table 1. Properties of the derivatives of 5-nitro-1,2,3-2H-triazole, 1-amino-3.5-diniro-
1,2,4-1H-triazole, and RDX.
[a]
[b]
[e]
Tm
Td,onset
[ºC]
ρ[c]
ΔHf(g)[d]
ΔHsub
ΔHf[f]
P[g]
νD[h]
IS[i]
[J]
Comp.
[ºC]
[gcm-3]
1.87
[kJmol-1]
[kJmol-1]
75.8
[kJmol-1]/[kJg-1] [Gpa]
[ms-1]
2
-
130
302.4
226.6/1.30
36.9
8876
3.5
(1.919)[j]
1.58
1.74
1.77
1.65
1.75
3
4
5
6
7
9
169
-
208.2
268.5
602.4
568.6
670.8
240.2
83.1
72.4
79.4
74.7
76.2
66.2
125.1/0.87
196.1/1.04
523.0/3.37
493.9/2.92
594.6/3.50
174.0/1.01
20.8
30.0
32.9
26.3
33.0
28.5
7497
8350
8669
8096
8756
8126
> 40
25
4
112
149
-
124
132
79
8
141
190
3
1.70
35
1.83
10
94
343.6
69.0
274.6/1.58
36.2
8843
24
(1.868)[j]
1.83
13
131
205
165
230
286.7
192[k]
76.0
112[k]
210.7/1.21
80/0.36
34.9
35.0
8725
8762
30
(1.855)[j]
1.80
RDX
7.5
[a] Melting temperature. [b] Decomposition temperature (onset). [c] Density (25 °C) [d] Gas phase
enthalpy of formation. [e] Enthalpy of sublimation according to Trouton’s rule. [f] Heat of formation. [g]
Detonation pressure. [h] Detonation velocity. [i] Impact sensitivity. [j] Calculated density from single-
crystal X-ray diffraction.[k] Data from NIST Chemistry WebBook
Figure 1. The DSC curves of 2-amino-4,5-dinitro-1,2,3-2H-triazole (10) and 1-amino-
3,5-dinitro-1,2,4-1H-triazole (13).
X-ray Crystallography:
Crystals of 2, 10 and 13, suitable for single-crystal X-ray diffraction, were
obtained by slow evaporation of ethyl acetate/benzene, ethyl acetate/benzene, and ethanol
solutions, respectively. Their structures are shown in Figures 2, 3, and 4, and
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2a
2b
Figure 2. 2a) Thermal ellipsoid plot (50%) and labeling scheme for 4-nitramino-5-nitro-
1,2,3-2H-triazole (2). Hydrogen atoms are included but are unlabeled for clarity. 2b) Ball
and stick packing diagram of 2 viewed down the b axis. Dashed lines indicate strong
hydrogen bonding.
3a
3b
Figure 3. 3a) Thermal ellipsoid plot (50%) and labeling scheme for 2-amino-4,5-dinitro-
1,2,3-2H-triazole (10). Hydrogen atoms are included but are unlabeled for clarity. 3b)
Ball and stick packing diagram of 10 viewed down the b axis. Dashed lines indicate
strong hydrogen bonding.
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4a
4b
Figure 4. 4a) Thermal ellipsoid plot (50%) and labeling scheme for 2-amino-3,5-dinitro-
1,2,4-1H-triazole (13). Hydrogen atoms are included but are unlabeled for clarity. 4b)
Ball and stick packing diagram of 13 viewed down the b axis. Dashed lines indicate
strong hydrogen bonding.
crystallographic data are summarized in Table 2. Crystals 2 and 10 crystallize in the
monoclinic P21/c space group, while 13 crystallizes in the triclinic P1 space group. For 2,
the nitro group is twisted out of the triazole ring plane with torsion angles of N(1)-C(5)-
N(10)-O(11), 6.1(4); C(4)-C(5)-N(10)-O(11), -174.5(3); N(1)-C(5)-N(10)-O(12), -
173.1(2); C(4)-C(5)-N(10)-O(12), 6.3(4). There are two groups of intermolecular
hydrogen bonds N(2)-H(2)...N(3) and N(6)-H(6)...O(12). For crystals 10 and 13, the big
differences between the two isomers are their torsion angles of the nitro groups out of the
triazole ring plane. For crystal 10, the twisted angles of the two nitro groups are as
follows: N(5)-C(1)-N(6)-O(8), 145.88°; C(2)-C(1)-N(6)-O(8), -25.3°; N(5)-C(1)-N(6)-
O(7) , -31.6°; C(2)-C(1)-N(6)-O(7) , 157.26°; N(3)-C(2)-N(9)-O(11) , 149.86°; C(1)-
C(2)-N(9)-O(11) , -26.9°; N(3)-C(2)-N(9)-O(10) , -29.5°; C(1)-C(2)-N(9)-O(10) , 153.8°,
while those of crystal 13 are as follows: N(1A)-C(5A)-N(10A)-O(11A), 169.5°; N(1B)-
C(5B)-N(10B)-O(11B), 153.1°; N(4A)-C(5A)-N(10A)-O(12A), 165.7°; N(4B)-C(5B)-
N(10B)-O(12B), 155.4°; N(2A)-C(3A)-N(7A)-O(9A), -178.1°; N(2B)-C(3B)-N(7B)-
O(9B), -176.4°; N(4A)-C(3A)-N(7A)-O(8A), -177.1°; N(4B)-C(3B)-N(7B)-O(8B), -
177.0°. From Figures 2b and 3b, it can be clearly seen that the intermolecular hydrogen
bonds are formed in the triazole-based energetic compounds, such as N(12)-
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H(12A)...N(12) for 10, and N(6A)-HAA...O(9A) for 13. The extensive hydrogen
bonding interactions contribute to an increase in density and decrease in sensitivity of the
two compounds. Further details are provided in the ESI.
Table 2. Crystallographic data for 2, 10, and 13.
2
10
13
formula
CCDC number
Mr
C2H2N6O4
897415
174.10
0.11 x 0.07 x 0.06
Monoclinic
P21/c
11.430(7)
5.989(4)
8.915(5)
90
C2H2N6O4
879779
174.10
0.18 x 0.16 x 0.05
Monoclinic
P21/c
8.044(4)
16.110(6)
4.998(2)
90
C2H2N6O4
879777
174.10
0.50 x 0.37 x 0.20
Triclinic
P1
8.3290(10)
11.4808(15)
13.6457(17)
78.002(4)
77.916(4)
89.974(4)
1246.8(3)
8
Crystal size [mm3]
crystal system
space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
99.043(8)
90
602.6(6)
4
107.119(5)
90
619.0(5)
4
γ [°]
V [Å3]
Z
T [K]
296(2)
1.919
0.180
352
293(2) K
1.868
0.176
293(2)
1.855
0.174
704
ρcalcd [Mg/m3]
μ [mm-1]
F(000)
352
θ [°]
index ranges
1.80 to 26.47
-14<=h<=14,
-7<=k<=6,
-11<=l<=11
5068
2.53 to 26.25
-9<=h<=9,
-19<=k<=0,
-6<=l<=6
2355
1.56 to 26.48
-10<=h<=10,
-14<=k<=14,
-17<=l<=17
12125
reflections collected
independent reflections
(Rint)
1242 [Rint = 0.0692]
1218 [Rint = 0.0393]
8734 [0.0145]
data / restraints /
parameters
1242 / 0 / 109
1218 / 2 / 115
8734 / 19 / 913
GOF on F2
1.007
0.0551
0.1402
0.0841
1.086
0.0376
0.0889
0.0587
1.063
0.0339
0.0773
0.0403
R1 (I > 2δ (I))[a]
wR2 (I > 2δ (I))[b]
R1 (all data)
wR2 (all data)
0.1600
0.1015
0.0821
Largest diff. peak and
0.325 and -0.339
0.159 and -0.237
0.159 and -0.202
hole [e.Å-3]
[a]
[b]
;
1/2
wR2 = ∑w(F 2 − F 2 )2 / ∑w(F
[
)
]
2
2
R1 = ∑ Fo − Fc / ∑ Fo
o
c
o
Conclusion
The energetic 5-nitro-1,2,3-2H-triazole-based compounds, including 4-nitramino-5-nitro-
1,2,3-2H-triazole (2) and its methyl derivative (4), 4-azido-5-nitro-1,2,3-2H-triazole (5)
and its methyl (6) and amino (7) derivatives, and the methyl (9) and amino (10)
derivatives of 4,5-dinitro-1,2,3-2H-triazole, were synthesized, and fully characterized
with 1H, 13C, and 15N NMR, and IR spectroscopy, differential scanning calorimetry,
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elemental analysis, and hammer tests. The heats of formation and detonation properties
of the resulting compounds were calculated by Gaussian 03 and Explo 5.05 programs,
respectively. The amino derivatives exhibit higher detonation performances and are more
impact sensitive than the corresponding methyl derivatives. Although 4-azido-5-nitro-
1,2,3-2H-triazole (5) and its methyl (6) and amino (7) derivatives show excellent
detonation performances, their high impact sensitivities discourage their actual
applications. Among the 4-nitramino and 4-nitro-5-nitro-1,2,3-2H-triazole-based
products, 4-nitramino-5-nitro-1,2,3-2H-triazole (2) and 2-amino-4,5-dinitro-1,2,3-2H-
triazole (10) exhibit identical detonation performances, viz., P, 36.9 Gpa; vD, 8876 ms-1
and P, 36.2 Gpa; vD, 8843 ms-1, respectively, which are comparable with RDX (P, 35.0
Gpa; vD, 8762 ms-1). Compound 10 with good thermal stability (Td,onset, 190 °C) and
impact insensitivity (24 J) is the most promising high-performance energetic material
prepared in this work.
Experimental Part:
Cautions: Although none of the compounds described herein exploded or detonated in
the course of this research, these materials should be handled with care using the best
safety practices.
General methods: 1H, and 13C spectra were recorded on a 300 MHz (Bruker AVANCE
300) nuclear magnetic resonance spectrometer operating at 300.13, and 75.48 MHz , and
a 500 MHz (Bruker AVANCE 500) nuclear magnetic resonance spectrometer operating
at 50.69 MHz for 15N spectra, respectively, using [D6]DMSO as a locking solvent unless
otherwise stated. Chemical shifts in 13C and 15N NMR spectra were reported relative to
Me4Si and MeNO2, respectively. The melting and decomposition points were recorded
on a differential scanning calorimeter (DSC, TA Instruments Q10) at a scan rate of 5 ºC
min-1 in closed aluminum containers with a small hole in the lids. IR spectra were
recorded by using KBr pellets. Densities were measured at room temperature using a
Micromeritics Accupyc 1330 gas pycnometer. Elemental analyses were obtained on a
CE-440 elemental analyzer (EAI Exeter Analytical).
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X-ray crystallography:
An irregular colorless crystal of dimensions 0.11 x 0.07 x 0.06 mm2 (2), an orange
plate crystal of dimensions 0.18 x 0.16 x 0.05 mm2 (10), and an irregular colorless crystal
of dimensions 0.50 x 0.37 x 0.20 mm2 (13) 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 MoKα radiation (λ = 0.71073).
An Oxford Cobra low temperature device was used to keep the crystals at a constant
293(2)°K during data collection.
Data collection was performed and the unit cell was initially refined using APEX2
[v2010.3-0].18 Data Reduction was performed using SAINT [v7.60A]19 and XPREP
[v2008/2].20 Corrections were applied for Lorentz, polarization, and absorption effects
using TWINABS [v2008/2].21 The structure was solved and refined with the aid of the
programs in the SHELXTL-plus [v2008/4] system of programs.22 The crystal of 10 was a
two-component twin and all refinements were performed on the only the major twin
component. The full-matrix least-squares refinement on F2 included atomic coordinates
and anisotropic thermal parameters for all non-H atoms. The H atoms were included
using a riding model.
Theoretical study: Calculations were performed with the Gaussian 03 (Revision D.01)
suite of programs.15 The geometric optimization of the structures based on single-crystal
structures, where available, and frequency analyses were carried out using the B3LYP
functional with 6-31+G** basis set,23 and single energy points were calculated at the
MP2/6–311++G** level. All of the optimized structures were characterized to be true
local energy minima on the potential energy surface without imaginary frequencies.
The gas phase enthalpies of formation of the resulting compounds were computed
by using the method of isodesmic reactions. The enthalpy of reaction (ΔHr298o) is
obtained by combining the MP2/6-311++G** energy difference for the reaction, the
scaled zero point energies, and other thermal factors. Thus, the gas phase enthalpy
[ΔHf(g)] of the species being investigated can be readily extracted. The enthalpy of
sublimation (ΔHsub) was estimated by using Troutons rule.16 The heat of formation (ΔHf)
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of the resulting compounds were calculated with Equation (1), in which Tm is the melting
temperature.
ΔH f = ΔH f (g) − ΔHsub = ΔH f (g) − (188[Jmol−1K−1]×T m)
(1)
With values of the heats of formation and densities, the detonation pressure (P)
and velocity (νD), and specific impulse (Isp) were calculated based on the traditional
Chapman-Jouget thermodynamic detonation theory using Explo 5.5.
4-Amino-5-nitro-1,2,3-2H-triazole (1): Prepared according to the reference method.4
4-Nitramino-5-nitro-1,2,3-2H-triazole (2): 4-Amino-5-nitro-1,2,3-2H-triazole (645 mg,
5 mmol) was added in portions to a mixture of HNO3 (70%; 5 mL) and concentrated
H2SO4 (5 mL) under stirring and cooling at 0 °C. The mixture was stirred for 2 h and
then warmed slowly to room temperature. After stirring for additional 2 h, the reaction
mixture was poured into ice water (80 mL), and extracted with ethyl ether (4 × 25 mL).
The combined organic phase was dried over anhydrous Na2SO4 and filtered. After
removing the solvent, the crude product was recrystallized from ethyl acetate and hexane
1
(1/4) to get orange solid (661 mg, 76%). H NMR: δ = 14.18 ppm (s, 2H; NH); 13C NMR:
δ = 144.7, 136.2 ppm; 15N NMR: δ = -25.8, -29.7, -49.4, -76.1, -107.4, -197.8 ppm;
IR(KBr pellet):3430, 3292, 3211, 2940, 1615, 1570, 1449, 1348, 1317, 1295, 1198, 1140,
982, 814, 763, 567 cm-1; elemental analysis (%) calcd for C2H2N6O4 (174.08): C, 13.80;
H, 1.16; N, 48.28; found: C, 13.80; H, 1.10; N, 47.75.
4-Amino-2-methyl-5-nitro-1,2,3-2H-triazole (3): 4-Amino-5-nitro-1,2,3-2H-triazole
(1.548 g, 12 mmol) was added to 15 mL aqueous NaOH (0.96 g, 24 mmol). After stirring
for 5 min at room temperature, dimethyl sulfate (1.513 g, 12 mmol) was added drop wise,
and the reaction mixture was stirred at reflux for 10 h. The reaction mixture was slowly
cooled to room temperature. The resulting yellow needles (0.876 g, 51% yield) were
filtered, washed with a small amount of cold H2O, and dried. The needles can be
1
recrystallized with hot water. H NMR: δ = 6.72 (s, 2H; NH2), 4.05 ppm (s, 3H; CH3);
13C NMR: δ = 149.2, 137.4, 42.9 ppm; IR(KBr pellet): 3442, 3316, 1639, 1576, 1474,
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1451, 1354, 1300, 1211, 1111, 868, 784, 642 cm-1; elemental analysis (%) calcd for
C3H5N5O2 (143.10): C, 25.18; H, 3.52; N, 48.94; found: C, 25.21; H, 3.46; N, 48.54.
2-Methyl-4-nitramino-5-nitro-1,2,3-2H-triazole (4): After using the same procedure as
for 2, the crude product was purified via chromatography with ethyl acetate/hexane (2/5)
to obtain a yellow solid (564 mg, 60%), which can be recrystallized from ethyl
acetate/hexane (1/3). 1H NMR: δ = 11.90 (s, 1H; NH), 4.32 ppm (s, 3H; CH3); 13C NMR:
δ = 145.5, 135.3 44.0 ppm; 15N NMR: δ = -27.6, -33.1, -49.8, -137.8, -208.0 ppm;
IR(KBr pellet): 3428, 3285, 1602, 1578, 1511, 1485, 1375, 1336, 1292, 1160, 927, 812,
759 cm-1; elemental analysis (%) calcd for C3H4N6O4 (188.10): C, 19.16; H, 2.14; N,
44.68; found: C, 19.46; H, 2.22; N, 43.93.
4-Azido-5-nitro-1,2,3-2H-triazole (5): 4-Amino-5-nitro-2H-triazole (1.032 g, 8 mmol)
was dissolved in H2SO4 (70%, 20 mL) at room temperature. The solution was cooled in
an ice-bath and NaNO2 (0.607 g, 8.8 mmol) was added in small portions with stirring.
After addition, the reaction mixture was stirred in room temperature for 50 min and
placed in an ice-bath again and diluted with 80 mL H2O. A small portion of urea was
added, and then NaN3 (0.650 g, 10 mmol) in small portions. After stirring for 1 h, the
reaction mixture was extracted with ethyl ether (4 × 30 mL), and the collected ether phase
was dried with anhydrous Na2SO4. The ethyl ether solution was evaporated under air to
obtain a white solid (1.005 g, 81%), which was recrystallized with hexane/ethyl acetate
(2/1) to yield colorless plates. 1H NMR: δ = 11.8 ppm (s, 1H; NH); 13C NMR: δ = 142.4,
139.8 ppm; 15N NMR: δ = -25.8, -51.2, -75.0, -120.8, -144.4, -145.7, -298.8 ppm;
IR(KBr pellet): 3172, 2995, 2928, 2149, 1578, 1518, 1434, 1339, 1260, 1219, 1173, 991,
847, 785 cm-1; elemental analysis (%) calcd for C2HN7O2 (155.08): C, 15.49; H, 0.65; N,
63.23; found: C, 15.51; H, 0.66; N, 62.82.
4-Azido-2-methyl-5-nitro-1,2,3-2H-triazole (6): 4-Azido-5-nitro-1,2,3-2H-triazole (310
mg, 2 mmol) was neutralized with excess aqueous ammonia. After removing the volatile
materials, the resulting ammonium 4-azido-5-nitro-2H-triaozolate was dried in vacuo.
The dried 4-azido-5-nitro-2H-triaozolate was suspended in CH3CN (25 mL) at room
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temperature and excess methyl iodide (853 mg, 6 mmol) was added. After stirring for 4 h
at 40 °C, the precipitate was filtered, and the solvent was removed. The crude product
was purified by chromatography with ethyl acetate/hexane (1/3) to obtain the white solid
(206 mg, 61%), which was crystallized from ethyl acetate/hexane (1/3) to yield very thin
white plates. 1H NMR: δ = 4.2 ppm (s, 3H; CH3); 13C NMR: δ = 141.5, 140.6, 43.6 ppm;
15N NMR: δ = -27.1, -49.7, -63.0, -141.6, -144.4, -145.3, -298.2 ppm; IR(KBr pellet):
3443, 2144, 1566, 1445, 1337, 1222, 1080, 872, 797, 761, 617cm-1; elemental analysis
(%) calcd for C3H3N7O2 (169.10): C, 21.31; H, 1.79; N, 57.98; found: C, 21.65; H, 1.85;
N, 57.34.
2-Amino-4-azido-5-nitro-1,2,3-2H-triazole (7): 4-Azido-5-nitro-1,2,3-2H-triazole (310
mg, 2 mmol) was neutralized with excess aqueous ammonia. After removing the volatile
materials, the resulting ammonium 4-azido-5-nitro-2H-triazolate was dried in vacuo. The
dried 4-azido-5-nitro-2H-triazolate was suspended in CH3CN (25 mL) at room
temperature and Pic-O-NH2 (488 mg, 2 mmol) was added. After stirring for 8h at room
temperature, the yellow precipitate (ammonium picrate) was filtered off, and the solvent
was removed. The crude product was purified by chromatography with ethyl
acetate/hexane (1/3) to obtain a yellow solid (255 mg, 75%), which was crystallized from
ethyl acetate/hexane (1/3) to yield thin yellow plates. 1H NMR: δ = 7.92 ppm (s, 2H;
NH2); 13C NMR: δ = 138.8, 137.9 ppm; 15N NMR: δ = -27.3, -66.0, -74.3, -124.3, -144.3,
-144.8, -274.4, -297.8 ppm; IR(KBr pellet): 3448, 3348, 3273, 2147, 1564, 1506, 1406,
1339, 1223, 924, 795 cm-1; elemental analysis (%) calcd for C2H2N8O2 (170.09): C, 14.12;
H, 1.19; N, 65.88; found: C, 14.17; H, 1.13; N, 65.37.
4,5-Dinitro-1,2,3-2H-triazole (8): Prepared according to the reference method.4
2-Methyl-4,5-dinitro-1,2,3-2H-triazole (9): After using the same procedure as for 6, 9
was purified by chromatography with ethyl acetate/hexane (1/4) to yield a white solid
(176 mg, 51%). 1H NMR: δ = 4.41 ppm (s, 2H; NH2); 13C NMR: δ = 143.6, 44.5 ppm;
15N NMR: δ = -32.2, -48.6, -138.8 ppm; IR(KBr pellet): 3447, 1629, 1560, 1437, 1362,
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1317, 1138, 865, 813 cm-1; elemental analysis (%) calcd for C3H3N5O4 (173.09): C, 20.82;
H, 1.75; N, 40.46; found: C, 21.01; H, 1.70; N, 40.12.
2-Amino-4,5-dinitro-1,2,3-2H-triazole (10): After using the same procedure as for 7, 10
was purified by chromatography with ethyl acetate/hexane (1/3) to yield an amber solid
(191 mg, 55%). 1H NMR (CD3CN): δ = 7.13 ppm (s, 2H; NH2); 13C NMR (CD3CN): δ =
142.7 ppm; 15N NMR (CD3CN): δ = -32.60, -57.78, -127.62,-278.1 ppm; IR(KBr pellet):
3328, 3141, 1625, 1559, 1535, 1456, 1366, 1325, 1142, 997, 872, 814, 752, 669 cm-1;
elemental analysis (%) calcd for C2H2N6O4 (174.08): C, 13.80; H, 1.16; N, 48.28; found:
C,14.00; H, 1.11; N, 47.80.
3,5-Dinitro-1,2,4-1H-triazole (12): Prepared according to the reference method.3
1-Amino-3,5-dinitro-1,2,4-1H-triazole (13): After using the same procedure as for 7, 13
was purified by chromatography with ethyl acetate/hexane (1/3) to yield a white or pale
yellow solid (240 mg, 69%); 1H NMR (CD3CN): δ = 7.05 ppm (s, 2H; NH2); 13C NMR
(CD3CN): δ = 154.9, 147.4 ppm; 15N NMR (CD3CN): δ = -30.39, -35.53, -81.05, -144.45,
-155.41, -286.13 ppm; IR(KBr pellet): 3336, 3280, 1566, 1516, 1342, 1323, 1132, 937,
860, 827, 648 cm-1; elemental analysis (%) calcd for C2H2N6O4 (174.08): C, 13.80; H,
1.16; N, 48.28; found: C,13.88; H, 1.14; N, 47.88.
Acknowledgements
The authors gratefully acknowledge the support of ONR (N00014-10-1-0097).
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