Synthesis and Initiation Capabilities of Energetic Diazodinitrophenols

Article abstract of DOI:10.1002/zaac.201500703

The diazophenols 3-amino-6-diazo-2, 4-dinitrophenol (4) and 3-chloro-6-diazo-2, 5-dinitrophenol (8) were synthesized and comprehensively characterized. The regio-selectivity of nitration reactions with N,N′-(1,4-phenylene)dimethanesulfonamide (1) and N,N′-(1,4-phenylene)diacetamide (6) was investigated in detail. The purity of the products was confirmed via low temperature X-ray diffraction, multinuclear NMR spectroscopy, and elemental analysis. Moreover, the capability of 4 and 8 to initiate RDX (1,3,5-trinitro-1,3,5-triazinane) was tested, together with the two other recently presented diazophenols 4-diazo-2, 6-dinitrophenol (iso-DDNP) and 3-hydroxy-DDNP (HODDNP). The tests revealed superior properties of HODDNP compared to DDNP and the other tested diazophenols regarding its ability to initiate RDX.

Full text of DOI:10.1002/zaac.201500703

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DOI: 10.1002/zaac.201500703
Synthesis and Initiation Capabilities of Energetic Diazodinitrophenols
Dániel Izsák,[a] Thomas M. Klapötke,*[a] Andreas Preimesser,[a] and Jörg Stierstorfer[a]
Keywords: Nitrophenols; Diazonium salts; Primary explosives; Structure elucidation
Abstract. The diazophenols 3-amino-6-diazo-2,4-dinitrophenol (4)
and 3-chloro-6-diazo-2,5-dinitrophenol (8) were synthesized and com-
prehensively characterized. The regio-selectivity of nitration reactions
with N,NЈ-(1,4-phenylene)dimethanesulfonamide (1) and N,NЈ-(1,4-
phenylene)diacetamide (6) was investigated in detail. The purity of the
capability of 4 and 8 to initiate RDX (1,3,5-trinitro-1,3,5-triazinane)
was tested, together with the two other recently presented diazophenols
4-diazo-2,6-dinitrophenol
(iso-DDNP)
and
3-hydroxy-DDNP
(HODDNP). The tests revealed superior properties of HODDNP com-
pared to DDNP and the other tested diazophenols regarding its ability
products was confirmed via low temperature X-ray diffraction, multi- to initiate RDX.
nuclear NMR spectroscopy, and elemental analysis. Moreover, the
example, the addition of 2% tetrazene to LA lowers the stab
Introduction
initiation energy from 1000 mJ to 3 mJ.[8] However, TAT is
currently under investigation as LA replacement in the NOL-
130 stab mix employed in the M55 stab detonator,[9] owing to
its better initiation capability than LA.[10] Unfortunately, it suf-
fers from the major drawback of a high volatility due to the
non-ionic structure with only weak intermolecular interactions.
The recently presented,[11] and herein further investigated, 6-
diazo-3-hydroxy-2,4-dinitrophenol (HODDNP) and 4-diazo-
2,6-dinitrophenol (iso-DDNP) offer the zwitterionic nature of
DDNP coupled with a higher density. HODDNP with its ad-
ditional hydroxy group in comparison to DDNP is a non-vola-
tile metal-free primary explosive with superior initiation capa-
bility than DDNP itself.
Furthermore two diazophenols, namely 6-diazo-3-amino-
2,4-dinitrophenol (4) and 3-chloro-6-diazo-2,5-dinitrophenol
(8) were synthesized. During the synthesis of 4 the regio-selec-
tivity of the nitrations using N,NЈ-(1,4-phenylene)dimethane-
sulfonamide (1) and N,NЈ-(1,4-phenylene)diacetamide (6) as
starting materials was investigated and confirmed by single-
crystal X-ray diffraction and NMR spectroscopy. The nitration
of N,NЈ-(1,4-phenylene)dibenzenesulfonamide resulting in the
formation of three regio-isomers was already described by
K.-Y. Chu and J. Griffiths.[12] The use of the methanesulfonyl
protection group resulted in two advantages described herein.
Additionally, the initiation capability of these two compounds
(4 and 8) was also tested in combination with RDX.
The current and the future scope of research in the field of
energetic materials is the performance improvement of primary
and secondary explosives in general.[1,2] In addition it is a
common task to use heavy metal free compounds which are
mostly more environmentally benign.[3,4]
The main difference between primary and secondary explos-
ives is the unique ability of the former class to undergo the so
called deflagration-to-detonation transition (DDT), meaning
the acceleration of a subsonic heat based energy transfer of the
decomposition reaction into a supersonic shockwave, even in
an unconfined state. High performance primary explosives like
lead azide (LA) detonate virtually immediately when exposed
to heat even in the smallest quantities. Unfortunately, lead az-
ide is a highly toxic compound and liberates hydrazoic acid in
moist air due to the reaction with carbon dioxide, leading to
the development of more environmentally benign primary ex-
plosives like copper(I) 5-nitrotetrazolate (DBX-1),[5] or dipo-
tassium 1,1Ј-dinitramino-5,5Ј-bitetrazolate.[6] Another option
are metal-free primary explosives like 1-(5-tetrazolyl)-3-gua-
nyltetrazene hydrate (tetrazene), 2-diazo-4,6-dinitrophenol
(DDNP), or 2,4,6-triazido-1,3,5-triazine (TAT), but practically
most of them only undergo a DDT when confined and even
then rather large amounts (several hundred milligrams) are
necessary for the reliable initiation of a secondary explosive,
rendering them unserviceable for small initiation devices. As
a result of this and their high sensitivities toward mechanical
stimuli they are usually utilized either in (environmentally be-
nign) percussion caps,[7] or as sensitizers in detonators. For
Results and Discussion
Synthesis
* Prof. Dr. T. M. Klapötke
Fax: +49-89-2180-77482
A synthesis protocol is displayed in Scheme 1.
The first step was the protection of the free amines resulting
either in the formation of N,NЈ-(1,4-phenylene)dimethane
sulfonamide (1) or N,NЈ-(1,4-phenylene)diacetamide (6). After
that the regio-selectivity toward the nitration of 1 and 6 was
E-Mail: tmk@cup.uni-muenchen.de
[a] Department Chemie
Ludwig-Maximilians Universität München
Butenandtstr. 5–13
81377 München, Germany
Z. Anorg. Allg. Chem. 2016, 642, (1), 48–55
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Scheme 1. Syntheses of diazophenols 4 and 8.
intensively studied. 2a was synthesized via a two-step ni- was observed when using 4-amino-2,3,6-trinitrophenol, re-
tration. In the first step an isomeric mixture of twice nitrated sulting in the formation of HODDNP.[11] The mechanism how
species was obtained. This was confirmed by CHN analysis. 3 is converted into 4 could not be determined certainly. After
When the nitration is heated up to 65–75 °C the corresponding isolation of pure 3 and 4 DSC curves were recorded to deter-
trinitro-derivative (2a) was obtained. 2a could only be ob- mine their decomposition temperatures (displayed in Figure 1).
tained when methansulfonyl chloride was used as protection
group. When, for example, the benzenesulfonyl or the p-tol-
uenylsulfonyl protection groups were used only the twice ni-
trated species were formed. Too harsh nitration conditions re-
sulted in the cleavage of those protection groups or their ni-
tration. N,NЈ-(2,3-dinitro-1,4-phenylene)dimethane sulfon-
amide (2b) or N,NЈ-(2,3-dinitro-1,4-phenylene)diacetamide (7)
could also be synthesized selectively. Compound 2b was syn-
thesized using 100% nitric acid at low temperatures and 7 by
using acetylnitrate as nitrating reagent. The regio-selectivity
was confirmed by crystallization of the protected (for com-
pound 7) and the deprotected product (for compound 5). It was
also confirmed that 2b can be used as a more efficient starting
material for 2a achieving higher yields. In this case 2a was
synthesized by using 82.5% nitric acid at a reaction tempera-
ture of 45 °C resulting in an enhanced yield of 2a (70%). The
deprotection of 2a resulted in the formation of two different
compounds. As expected 1,4-diamino-2,3,5-trinitrobenzene (3)
is formed. Additionally the highly sensitive primary explosive
3-amino-6-diazo-2,4-dinitrophenol (4) is formed. This even
happens in all attempts to synthesize 1,4-diamino-2,3,5,6-tetra-
nitrobenzene with 3 as starting material. The same behavior Figure 1. DSC curves of 3 and 4 (heating rate β = 5 K·min–1).
Z. Anorg. Allg. Chem. 2016, 48–55
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Additionally, compounds 5 and 7 were crystallized from and data reduction was performed using the CRYSALISPRO
DMSO.
software.[14] The solution and refinement of all structures were
These two products differ dramatically in their thermal sta- performed using the programs sir-92[15], SHELXS-97[16] and
bility. Interesting to mention is the unexpected low thermal SHELXL-97[17] implemented in the WINGX software pack-
stability of 3 (125 °C). The literature known constitution iso- age[18] and finally checked with the PLATON software.[19] The
mer 1,3-diamino-2,4,6-trinitrobenzene for example is stable up non-hydrogen atoms were refined anisotropically and the
to 286 °C.[13] Compound 4 however shows the typical thermal
hydrogen atoms were located and freely refined when possible.
stability of 170 °C. The purity of 3 could only be confirmed
by CHN elemental analysis, high resolution mass spectrometry
and additionally by IR spectroscopy due to the conversion of
3 into 4 in organic polar solvents. The diazo vibration at
2195 cm–1 and the carbonyl vibration at 1593 cm–1 only appear
in the IR spectrum of 4. The N–H vibrations of the amino
groups appear at 3365 cm–1 and 3474 cm–1, whereas for 4 they
are located at 3282 cm–1 and 3390 cm–1. Finally, the nitration
of 4-chloroaniline resulted in the formation of 2-diazo-5-
chloro-3,6-dinitrophenol (8).
The absorptions were corrected with the SCALE3 ABSPACK
multi-scan method.[20] Selected data of the measurements and
the refinements are given in Table 1.
N,NЈ-(2,3,5-Trinitro-1,4-phenylene)dimethanesulfonamide
(2a) could only obtained crystalline with inclusion of DMSO.
The molecular unit consisting of one N,NЈ-(2,3,5-trinitro-1,4-
phenylene)dimethanesulfonamide and two dimethylsulfoxide
molecules is shown in Figure 2. The compound crystallizes in
–3
¯
the triclinic space group P1 with a density of 1.597 g·cm at
–100 °C. As expected all nitro groups are twisted out of the
ring plane.
The molecular unit of 3-amino-6-diazo-2,4-dinitrophenol (4)
is depicted in Figure 3. The compound crystallizes in the or-
thorhombic space group Pnma with four molecules in the unit
cell. Its density of 1.913 g·cm–3 at –100 °C is significantly
higher than that of the recently published HODDNP
Crystal Structures
Suitable single crystal of compounds 2a, 4, 5, 7, and 8 were
picked from the crystallization mixtures and mounted in
Kel-F oil, transferred to the N2 stream of an Oxford Xcalibur3
diffractometer with a Spellman generator (voltage 50 kV, cur- (1.837 g·cm–3).[11] The bond length N1–N2 of 1.098(3) Å
rent 40 mA) and a KappaCCD detector. The data collection clearly indicates a NϵN triple bond, whereas the C1–N1
Table 1. Crystallographic data and refinement parameters of compound 2a, 4, 5, 7, and 8.
2a
4
5
7
8
Formula
FW /g·mol–1
Crystal system
Space group
Color / habit
Size /mm
a /Å
b /Å
c /Å
α /°
β /°
C12H21N5O12S4
555.58
C6H3N5O5
225.13
C6H6N4O4
198.15
C10H10N4O6
282.22
C6HClN4O5
244.56
triclinic
orthorhombic
Pnma (no. 62)
orange block
0.15ϫ0.19ϫ0.20
16.2313(6)
10.6548(4)
4.5210(2)
90
90
90
781.87(5)
4
1.913
monoclinic
C2/c (no. 15)
yellow block
0.19ϫ0.21ϫ0.49
12.2042(6)
10.8478(4)
7.2959(4)
90
124.954(4)
90
791.66(8)
4
triclinic
monoclinic
Pc (no. 7)
yellow rod
0.08ϫ0.11ϫ0.23
6.5289(4)
6.9889(4)
9.7159(6)
90
97.723(6)
90
439.31(5)
2
¯
¯
P1 (no. 2)
P1 (no. 2)
colorless plate
0.03ϫ0.15ϫ0.20
10.1892(11)
10.5895(9)
11.6355(15)
97.918(9)
104.484(10)
103.643(8)
1155.1(2)
2
yellow needle
0.06ϫ0.14ϫ0.23
7.7535(16)
8.0847(11)
10.7662(19)
84.878(13)
70.272(17)
75.493(15)
615.0(2)
2
γ /°
V /Å3
Z
ρcalcd. /g·cm–3
μ /mm–1
F(000)
1.597
0.479
576
1.663
0.142
408
1.524
0.128
292
1.849
0.450
244
0.170
456
λ(Mo-Kα) /Å
T /K
0.71073
173
0.71073
173
0.71073
173
0.71073
298
0.71073
173
θ min-max /°
Dataset h; k; l
Reflect. coll.
Independ. refl.
Rint
4.2, 26.0
4.6, 27.0
5.1, 26.5
4.3, 26.0
4.2, 26.0
–8:8; –8:8; –11:11
5976
1704
0.025
1662
149
0.0212
0.0525
–12:12; –13:13; –14:14 –17:20; –13:13; –5:5 –15:15; –13:13; –9: 9 –9:9; –9:9; –11:13
8374
4506
0.047
3236
316
0.0868
0.1990
1.08
5595
891
0.023
822
88
0.0380
0.0947
1.20
–0.22, 0.27
Oxford XCalibur3
SIR-92
SHELXL-97
multi-scan
5627
823
0.023
742
76
0.0303
0.0891
1.05
–0.25, 0.19
Oxford XCalibur3
SIR-92
SHELXL-97
multi-scan
4029
2385
0.037
1352
221
0.0637
0.1770
1.01
0.22, 0.23
Oxford XCalibur3
SIR-92
SHELXL-97
multi-scan
Reflection obs.
No. parameters
R1 (obs)
wR2 (all data)
S
1.07
Resd. dens. /e Å–3 –0.49, 1.63
–0.13, 0.15
Oxford XCalibur3
SIR-92
SHELXL-97
multi-scan
Device type
Solution
Refinement
Absorpt. corr.
Oxford XCalibur3
SIR-92
SHELXL-97
multi-scan
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[1.367(3) Å] and C2–O1 [1.324(4) Å] bonds are also signifi-
cantly shorter than typical C–N (1.47 Å) and C–O (1.43 Å)
single bonds.
1,4-Diamino-2,3-dinitrobenzene (5), depicted in Figure 4,
crystallizes in the monoclinic space group C2/c with four mol-
ecules in the unit cell. Its density at –100 °C is 1.663 g·cm–3
which is slightly lower than that of 1,3-diamino-2,4-dinitro-
benzene (1.74 g·cm–3 at 298 K)[21] and 1,2-diamino-4,5-dini-
trobenzene (1.725 g·cm–3 at –100 °C).[22] The molecular unit
is shown in Figure 4.
Figure 2. Molecular unit of 2a. Ellipsoids of non-hydrogen atoms in
all structures are drawn at the 50% probability level. Selected bond
lengths /Å: C7–N5 1.479 (7), C2–N2 1.471 (8), 1.471 (8), C1–N1
1.411 (9), C4–N4 1.381 (9), S1–N1 1.628 (6), S2–N4 1.645 (6), S1–
O1 1.434 (7), S1–O2 1.428 (8), S2–S8 1.426 (5), S1–C8 = S2–C5
1.745 (8); Selected bond angles /°: C2–C3–N3 117.87 (6), C3–C2–N2
119.22 (6), C6–C7–N5 115.64 (6), C4–N4–S2 125.93 (5), C1–N1–S1
124.31 (5), O1–S1–N1 107.67 (3), O2–S1–N1 105.19 (4), C8–S1–
N1 105.68, O2–S1–O1 121.04 (4), O7–S2–O8 120.02 (3), C5–S2–N4
107.09 (3), O8–S2–N4 104.27 (3), O7–S2–N4 107.66 (3); Selected
torsion angles /°: C3–C2–N2–O3 57.3 (1), C2–C3–N3–O6 55.9 (1),
C6–C7–N5–O10 46.9 (1), C2–C1–N1–S1 75.9 (1), C6–C4–N4–S2 9.4
(1).
Figure 4. Molecular unit of 5. Ellipsoids of non-hydrogen atoms in all
structures are drawn at the 50% probability level. Selected bond
lengths /Å: C1–N1 1.332 (2), C2–N2 1.411 (2), N2–O1 1.254 (2), N2–
O2 1.239 (2); Selected bond angles /°: O1–N2–O2 120.8 (2). Selected
torsion angles /°: C2–C2i–N2–O2 15.1 (2), C2–C1–N1–H1B 6.8 (2);.
The twice N-protected N,NЈ-(2,3-dinitrophenyl)1,4-diacet-
¯
amide (7) crystallizes in the triclinic pace group P1 with two
molecular units (Figure 5) in the unit cell. Its density
(1.524 g·cm–3) is significantly lower than that of 5.
Figure 3. Molecular unit of 4. Ellipsoids of non-hydrogen atoms in all Figure 5. Molecular unit of 7. Selected bond lengths /Å: C1–N1 1.423
structures are drawn at the 50% probability level. Selected bond (4), C2–N2 1.464 (4), C3–N3 1.475 (4), C4–N4 1.411 (4), N2–O2
lengths /Å: C1–N1 1.367 (3), N1–N2 1.098 (3), C2–O1 1.324 (4), C3– 1.217 (3), N2–O3 1.222 (3), N3–O4 1.215 (3), N3–O5 1.221 (3), C7–
N3 1.441 (2), N3–O3 1.235 (2), C4–N4 1.321 (3), O3–N4 2.59 (1);
Selected bond angles /°: C1–N1–N2 177.7 (3), N3–O3–O2 121.3, O3–
O1 1.219 (4), C9–O6 1.223 (4). Selected bond angles /°: N1–C1–O1
122.3 (3), O2–N2–O3 123.8 (3), O4–N3–O5 125.5 (3), N4–C9–O6
N3–O2 121.3; Selected torsion angles (°): C2–C3–N3–O2 11.8 (2), 122.4 (3). Selected torsion angles /°: C3–C4–N4–C9 50.2 (5), C6–C1–
C3–C4–N4–H 2.9 (2.9).
N1–C7 42.9 (5), C4–C3–N3–O5 51.5 (5), C3–C2–N2 O3 48.5 (4).
Z. Anorg. Allg. Chem. 2016, 48–55
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