Potassium 1,1′-dinitramino-5,5′-bistetrazolate: A primary explosive with fast detonation and high initiation power

Article abstract of DOI:10.1002/anie.201404790

Adequate primary explosives such as lead azide mostly contain toxic ingredients, which have to be replaced. A new candidate that shows high potential, potassium 1,1′-dinitramino-5,5′-bistetrazolate (K ₂DNABT), was synthesized by a sophisticated synthetic procedure based on dimethylcarbonate and glyoxal. It was intensively characterized for its chemical (X-ray diffraction, EA, NMR and vibrational spectroscopy) and physico-chemical properties (sensitivity towards impact, friction, and electrostatic, DSC). The obtained primary explosive combines good thermal stability with the desired mechanical stability. Owing to its high heat of formation (326 kJ mol^-1) and density (2.11 g cm^-3), impressive values for its detonation velocity (8330 m s^-1) and pressure (311 kbar) were computed. Its superior calculated performance output was successfully confirmed and demonstrated by different convenient energetic test methods.

Full text of DOI:10.1002/anie.201404790

Angewandte
Chemie
DOI: 10.1002/anie.201404790
Energetic Materials Hot Paper
Potassium 1,1’-Dinitramino-5,5’-bistetrazolate: A Primary Explosive
with Fast Detonation and High Initiation Power**
Dennis Fischer, Thomas M. Klapçtke,* and Jçrg Stierstorfer
Abstract: Adequate primary explosives such as lead azide
mostly contain toxic ingredients, which have to be replaced. A
new candidate that shows high potential, potassium 1,1’-
dinitramino-5,5’-bistetrazolate (K DNABT), was synthesized
2
by a sophisticated synthetic procedure based on dimethylcar-
bonate and glyoxal. It was intensively characterized for its
chemical (X-ray diffraction, EA, NMR and vibrational
spectroscopy) and physico-chemical properties (sensitivity
towards impact, friction, and electrostatic, DSC). The obtained
primary explosive combines good thermal stability with the
desired mechanical stability. Owing to its high heat of
Figure 1. Structures of lead styphnate and copper(I) 5-nitrotetrazolate
DBX-1).
(
À1
À3
formation (326 kJmol ) and density (2.11 gcm ), impressive
À1
values for its detonation velocity (8330 ms ) and pressure
[
10]
(
311 kbar) were computed. Its superior calculated perfor-
activity. More research is needed to determine long-term
storage and potential compatibility of the material with the
chemicals it would come in contact with in an energetic
formulation.
mance output was successfully confirmed and demonstrated by
different convenient energetic test methods.
P
rimary explosives are substances that show a very rapid
A “green” lead azide replacement needs to possess the
following properties: a) insensitivity to light; b) sensitivity to
detonation (but not too sensitive to handle and transport);
c) stability to at least 1808C; d) stability upon storage for long
periods of time; e) being free of toxic metals; f) being free of
toxic perchlorate; and g) ease and safety of synthesis.
Herein, we report the synthesis and characterization of
the new primary explosive potassium dinitraminobistetrazo-
transition from deflagration to detonation and generate
a shock-wave that makes transfer of the detonation to a less
[1,2]
sensitive secondary explosive possible. Lead azide and lead
styphnate are the most commonly used primary explosives
today. However, the long-term use of these compounds has
caused considerable lead contamination in military training
grounds and costly clean-up operations waste money that
could better be spent improving the defense capability of our
[
3,4]
[3]
late (K DNABT), which only contains potassium as the metal
2
[
5]
forces. A recent article published on December 4, 2012 in
the Washington Post entitled “Defense Dept. Standards On
and is an alternative to lead azide. Many tetrazoles have been
[
11]
described as energetic materials. While 5-nitriminotetra-
zoles are commonly known, 1-dinitramino-tetrazoles are very
[
6]
Lead Exposure Faulted” stated: “… it has found over-
whelming evidence that 30-year-old federal standards govern-
ing lead exposure at Department of Defense firing ranges and
other sites are inadequate to protect workers from ailments
associated with high blood lead levels, including problems with
the nervous system, kidney, heart, and reproductive system.”
The most prominent and most promising lead azide
replacement today is copper(I) 5-nitrotetrazolate (DBX-1,
Figure 1) which was developed by Fronabarger, Williams,
[
12]
rare, which is due to their hard accessibility.
unprotected 1,1’-diamino-5,5’-bistetrazole
In theory,
could be
[
12]
nitrated, but the amination of 5,5’-bistetrazole is a procedure
with low yield and high effort, so an alternative route was
developed. Looking for better starting materials, the bisni-
trileimine seems to be a suitable precursor for this molecule.
Unfortunately unprotected bisnitrilimine is only known as its
[
13]
diphenyl derivative,
so another more easily removable
[7–9]
et al. at PSEMC.
alternative for lead azide, DBX-1 has shown a tendency to
decompose with periodate salts, thus inhibiting its explosive
Despite its promise as a “greener”
protecting group than a phenyl moiety was chosen. The
following synthetic process describes the synthesis of
K DNABT starting from commercially available dimethyl
2
carbonate. The carbonate reacts with hydrazine hydrate to
[
14]
methyl carbazate 1. The condensation reaction with half an
[
*] D. Fischer, Prof. Dr. T. M. Klapçtke, Dr. J. Stierstorfer
Ludwig Maximilian University Munich, Department of Chemistry
Butenandtstrasse 5–13, Haus D, 81377 Mꢀnchen (Germany)
E-mail: tmk@cup.uni-muenchen.de
[15]
equivalent of glyoxal forms 2,
which is subsequently
oxidized with NCS (N-chlorosuccinimide) to the correspond-
ing chloride. Substitution with sodium azide offers the diazide
(in only 38% yield), which is then cyclized with hydrochloric
Homepage: http://www.hedm.cup.uni-muenchen.de
acid in a diethyl ether suspension. The N-methoxycarbonyl-
[**] Financial support of this work by the Ludwig-Maximilian University
of Munich (LMU), ARDEC, and ONR is gratefully acknowledged.
protected 1,1’-diamino-5,5’-bistetrazole (5) is gently nitrated
with N O . An alkaline aquatic work-up with KOH precip-
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201404790.
2
5
itates dipotassium K DNABT (Scheme 1).
2
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Scheme 1. Synthetic pathway towards K DNABT.
2
All of the intermediate products can be used as obtained;
no column chromatography is required. Fortunately
K DNABT shows low water solubility, which facilitates
2
isolation and purification. The toxicity of K DNABT in
2
water was determined using the known luminous bacteria
[
16]
method with Vibrio fischeri NRRL-B-11177.
The EC50
concentration of this compound after 30 min of incubation
À1
À1
time is higher than 1.4 gl . With a value above 1 gl ,
a compound can basically be considered as nontoxic.
The molecular structure of K DNABT in the solid state
2
(
Figure 2) was determined by low-temperature single-crystal
[
17]
X-ray diffraction. It crystallizes in the triclinic space group
À3
¯
P1 with a density of 2.172 gcm at 100 K. The potassium
atoms are coordinated irregularly by either the nitrogen
atoms N2, N3, N5 or the nitro oxygen atoms O1 and O2. Both
tetrazole rings as well as atom N5 are almost planar to each
other. The nitro groups are twisted out of this plane by almost
Figure 2. Molecular structure of K DNABT with cation coordination.
Ellipsoids are set at 50% probability. Selected bond lengths [ꢁ]: C1–C1
2
i
1
1
.453(4), N1–C1 1.352(3), N4–C1 1.322(3), N1–N2 1.355(2), N1–N5
.394(2), N5–N6 1.332(3), O1–N6 1.248(2), O2–N6 1.261(2); selected
i
torsion angles [8]: C1-N1-N5-N6 75.3(3), N1-C1-C1-N4 À1.5(4), O1-
7
58.
Several energetic tests were performed ensuring the
N6-N5-N1 1.6(3). Symmetry codes: (i) 1Àx, 1Ày, 1Àz; (ii)Àx, 1Ày,
1
Àz; (iii) x, y, 1+z; (iv) 1Àx, Ày, 1Àz; 1; (v) 1+x, y, 1+z; (vi) 1+x, y,
z; (vii) 1Àx, 1Ày, Àz; (viii) x, 1+y, z; (ix) Àx, 1Ày, Àz; (x) Àx, Ày,
Àz.
suitability of K DNABT as a primary explosive. The friction
2
1
and impact sensitivity is comparable to Pb(N ) . Along with
3
2
the successful ignition of one gram of RDX by 40 mg of
K DNABT, a flame test (Figure 3d) and a “hot needle test”
2
(
see the Supporting Information for videos) indicated the
demonstrated by a detonation (Figure 3b) against an alumi-
num block in comparison with the commonly used lead azide.
Owing to their good flowability, both compounds were simply
poured into the steel block and ignited unpressed. The
indentation is 1.4 mm, whereas lead azide reaches only
0.2 mm, using 500 mg of each compound (Figure 3c). Addi-
instant detonation of the material in contact with a flame or
a hot metal needle.
Several detonation parameters were calculated using the
[
19]
EXPLO5 code in its latest version 6.02 using a calculated
heat of formation and density (recalculated from the X-ray
structure 100 K value to room temperature). It can be seen
tionally, K DNABT shows excellent thermal stability. The
2
from Table 1 that K DNABTeasily outperforms lead azide in
all critical detonation parameters, while the sensitivities
compound was heated up to 1008C and the temperature was
held for 48 h. No loss of mass or any decomposition was
observed (the TGA plot is shown in the Supporting Informa-
tion). A violent decomposition was observed at 2008C using
2
(
impact, friction, and electrostatic discharge) are in the
same range. The experimental explosive work released was
2
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À1
a DSC experiment (heating rate of 5 degmin ). All tests
point to the fact that this material is a suitable and non-toxic
replacement for lead azide, with a straightforward synthesis
from commonly available chemicals.
Experimental Section
The detailed experimental description of the whole synthetic
procedure is shown in Scheme 1; the general methods are given in
the Supporting Information.
Dipotassium dinitraminobistetrazolate (K DNABT): Compound
2
5
(1 g, 3.52 mmol) was suspended in 50 mL dry acetonitrile and
cooled to 0–58C. N O (1.5 g, 13.9 mmol) was added and the mixture
2
5
was stirred at this temperature. After all of the starting material was
dissolved (1–2 h), the solution was stirred for additional 30 min. Then
2
m KOH (14 mL) was added and the mixture was stirred vigorously at
ice bath temperature. Additional KOH solution was added until the
pH of the aqueous phase stayed constantly at 12 or above. The
precipitated solid was filtered and suspended in 20 mL of ice water,
stirred for 5 min, and filtered again, yielding 720 mg (61%) of finely
powdered colorless K DNABT.
2
À1
DSC (58Cmin ): 2008C (dec); IR (KBr): n˜ = 3450 (m), 1635 (w),
1
1
3
440 (s), 1382 (w), 1360 (w), 1300 (vs), 1256 (m), 1163 (w), 1124 (w),
031 (w), 998 (w), 872 (w), 773 (w), 729 cm (w); Raman (1064 nm,
00 mW, 258C): n˜ = 1610 (100), 1455 (9), 1270 (12), 1251 (19), 1142
À1
(
3
6), 1084 (14), 1016 (34), 992 (4), 889 (2), 750 (2), 732 (3), 512 (7),
À1
01 cm (4); EA (C K N O 334.30): C 7.19, N 50.28%; found:
2
2
12 4,
Figure 3. A) Setup of explosive work test; B) moment of detonation;
À
À
4
C 7.62, N 47.95%; m/z (FAB ): 257 (C HN O ); BAM drop
2
12
C) result of explosive work test (left: Pb(N ) , right: K2DNABT);
3
2
hammer: 1 J; friction tester: < 5N; ESD: 3 mJ.
D) flame test of K DNABT at the moment of detonation.
2
Received: April 29, 2014
Published online: && &&, &&&&
Keywords: explosives · heterocycles · synthetic methods ·
tetrazoles · X-ray diffraction
.
Table 1: Comparison of the energetic properties and calculated perfor-
mance data of lead azide and K DNABT.
2
Pb(N
3
)
2
K
2
DNABT
C K N O
4
Formula
N Pb
6
2
2
12
[
[
[
[
[
1] N. Mehta, K. Oyler, G. Chemg, A. Shah, J. Marin, K. Yee, Z.
À1
M [gmol
]
291.3
2.5–4
0.1–1
<0.005
28.9
À11.0
ca. 315
4.8
334.3
1
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Mater. 2012, 9, 293 – 327.
[
a]
IS [J]
[
b]
FS [N]
ꢀ1
[
c]
ESD [J]
0.003
50.3
À4.8
200
[
d]
N [%]
[
e]
W [%]
TDec. [8C]
[
f]
À3 [g]
1
[gcm
]
2.172 (100 K)
.11 (298 K)
326.4
5] T. M. Klapçtke, N. Mehta, Propellants Explos. Pyrotech. 2014,
[
18]
2
3
9, 7 – 8.
À1 [h]
D H 8 [kJmol
]
450.1
th
f
m
[
[
6] S. Vogel in Washington Post, December 4 , 2012, p. 23.
7] J. W. Fronabarger, M. D. Williams, W. B. Sanborn, J. G. Bragg,
D. A. Parrish, M. Bichay, Propellants Explos. Pyrotech. 2011, 36,
À1 [i]
D U8 [kJkg
]
1574.9
1036.1
f
EXPLO5 6.02 (BKWG-S)
541 – 550.
À1 [j]
ÀD U8 [kJkg
]
1569
3401
338
5920
252
4959
3424
317
8330
489
Ex
[
8] N. Mehta, K. D. Oyler, G. Cheng, Proceedings of the Interna-
tional Pyrotechnics Seminar 2012, 38th, 433 – 443.
[
k]
T
det
[K]
[
l]
PCJ [kbar]
[
9] T. M. Klapçtke, D. G. Piercey, N. Mehta, K. D. Oyler, M.
Jorgensen, S. Lenahan, J. S. Salan, J. W. Fronabarger, M. D.
Williams, Z. Anorg. Allg. Chem. 2013, 639, 681 – 688.
[
m]
Vdet [ms]
[
n]
V0 [Lkg]
[
6
a] Impact sensitivity according to the BAM drop hammer (method 1 of
). [b] Friction sensitivity according to the BAM friction tester (method 1
[10] T. M. Klapçtke, N. Mehta, D. Piercey, J. Sabatini, K. Oyler, Z.
Naturforsch. B 2014, 69, 125 – 127.
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À1
[
g] Density at RT. [h] Heat of formation. [i] Energy of formation. [j] Heat of
detonation. [k] Temperature of detonation. [l] Detonation pressure.
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[
volume after detonation.
Angew. Chem. Int. Ed. 2014, 53, 1 – 5
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
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Communications
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charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
¯
[
17] Selected X-ray data: colorless plate, triclinic, P1, a = 5.0963(6),
[18] The room-temperature value was calculated by the volume
expansion equation 1298K = 1 /(1+a (298ÀT)); a = 1.5 ꢁ
b = 6.8248(8), c = 8.4271(8) ꢀ, a = 7.56(1), b = 86.15(1), g =
T
v
v
3
À3
À4
À1
7
1.02(1)8, V= 255.65(5) ꢀ , Z = 1, 2.172 gcm , wR2 6.57%,
10
K .
S = 1.09, CCDC 999474 contains the supplementary crystallo-
[19] M. Su c´ eska, EXPLO5 6.02 program, Zagreb, Croatia, 2014.
4
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Communications
Energetic Materials
Fast and furious: The picture shows the
moment of detonation of the new primary
explosive potassium 1,1’-dinitramino-
5,5’-bistetrazolate, which can be synthe-
sized by a safe and sustainable proce-
dure. It shows faster detonation with
greater initiation power than lead azide
while simultaneously being environmen-
tally compatible.
D. Fischer, T. M. Klapçtke,*
J. Stierstorfer
&&&& — &&&&
Potassium 1,1’-Dinitramino-5,5’-
bistetrazolate: A Primary Explosive with
Fast Detonation and High Initiation
Power
Angew. Chem. Int. Ed. 2014, 53, 1 – 5
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!