Synthesis, Characterization, and Properties of Pentanitrobenzene C6H(NO2)5

Article abstract of DOI:10.1002/zaac.201800471

The synthesis of the polynitroaromatic compound pentanitrobenzene was re-examined by modern spectroscopic, structural and physicochemical methods. Originally prepared in 1979, this material could exhibit interesting properties as an oxygen-rich energetic building block. The energies of formation were calculated with the GAUSSIAN program package and the detonation parameters were predicted using the EXPLO5 computer code. The performance data were determined and compared to the common oxidizer ammonium perchlorate. The crystal structure of pentanitrobenzene was determined by X-ray crystallography, and those of 2,3,4,6-tetranitroaniline and styphnic acid (trinitroresorcinol) were re-determined.

Full text of DOI:10.1002/zaac.201800471

Journal of Inorganic and General Chemistry
DOI: 10.1002/zaac.201800471
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
Synthesis, Characterization, and Properties of Pentanitrobenzene
C6H(NO2)5
Tanja Huber,[a] Chantal von der Heide,[a] Thomas M. Klapötke,*[a] and Burkhard Krumm*[a]
Dedicated to Professor Jean’ne M. Shreeve on the Occasion of her 85th Birthday
Abstract. The synthesis of the polynitroaromatic compound penta-
nitrobenzene was re-examined by modern spectroscopic, structural and
dicted using the EXPLO5 computer code. The performance data were
determined and compared to the common oxidizer ammonium perchlo-
physicochemical methods. Originally prepared in 1979, this material rate. The crystal structure of pentanitrobenzene was determined by X-
could exhibit interesting properties as an oxygen-rich energetic build- ray crystallography, and those of 2,3,4,6-tetranitroaniline and styphnic
ing block. The energies of formation were calculated with the
GAUSSIAN program package and the detonation parameters were pre-
acid (trinitroresorcinol) were re-determined.
1
in 1979;[7] characterization was achieved by H NMR, mass
Introduction
spectrum and elemental analysis. A little later in 1990, the 13
C
and 14N NMR spectroscopic data followed without assign-
ments.[8] Since then, no further reports with new information
regarding pentanitrobenzene appeared. In this contribution we
would like to re-investigate and study the properties of penta-
nitrobenzene.
New high energy dense oxidizers (HEDOs) are an ongoing
research topic in the synthesis and development of energetic
materials. Efforts are being conducted to find environmentally
friendly replacements for ammonium perchlorate (AP), which
is often used as oxidizer in composite rocket propellants. The
hazardous effects of AP include hypothyroidism and terato-
genic properties as well as the formation of acidic and chlo-
rine-containing gases during combustion. Further requirements
for new HEDOs are insensitivity, high densities and high de-
composition temperatures. As potential substitutes, the nitro
salts ammonium nitrate (AN) and ammonium dinitramide
(ADN) were investigated. However, they have some disadvan-
tages such as low thermal stabilities and hygroscopicity.[1,2]
Other possible alternatives were synthesized based on nitro-
carbamates containing trinitroethyl moieties,[3] polynitro-
carbamates[4] and dihydrazinium nitrates,[5] which often show
promising calculated properties and sensitivity data.
Results and Discussion
Synthesis and Characterization
The precursor material of pentanitrobenzene is the aniline
2,3,4,6-tetranitroaniline (2). This can be prepared by a one-pot
route starting from commercially available 3-nitroaniline (1)
(Scheme 1).[9]
The polynitro compound pentanitrobenzene, which is de-
scribed and investigated in this work, is based on the benzene
skeleton. Already several decades ago, the pernitro benzene,
hexanitrobenzene, was described as a powerful oxidizer with
high density, decomposition temperature and detonation
velocity. However, this material decomposes in moist air, mak-
ing further application difficult.[6] Similar to the synthesis of
hexanitrobenzene, pentanitrobenzene was first prepared from
the corresponding polynitroaniline derivative by Nielsen et al.
Scheme 1. Nitration of 3-nitroaniline (1) to 2,3,4,6-tetranitroaniline
(2).
Relatively harsh conditions are required for a triple nitration
of 1. After a simple aqueous work-up, 2 was obtained as a
dark yellow powder in good yield and also pure according to
1H and 13C NMR spectroscopy. As an alternative route with
milder conditions in each reaction, 2 is also accessible by a
four-step synthesis, which incorporates only single or double
nitration. Since this route is more laborious (acetylation, ni-
tration, de-acetylation, double-nitration[10]), more expensive
and much slower than the one-pot synthesis, it is not consid-
ered further.
* Prof. Dr. T. M. Klapötke
E-Mail: tmk@cup.uni-muenchen.de
http://www.hedm.cup.uni-muenchen.de/index.html
* Dr. B. Krumm
E-Mail: bkr@cup.uni-muenchen.de
[a] Energetic Materials Research
Department of Chemistry
Ludwig-Maximilian University Munich
Butenandtstr. 5–13 (D)
81377 Munich, Germany
For the conversion into pentanitrobenzene (3), strong oxid-
izing conditions are essential in order to oxidize the remaining
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amino into a nitro group. The powerful oxidant peroxodi- NMR Spectroscopy
sulfuric acid is generated in situ by using oleum and 98%
hydrogen peroxide (Scheme 2).[7]
2,3,4,6-Tetranitroaniline (2) and pentanitrobenzene (3) were
1
characterized by H, 13C, and 14N NMR spectroscopy, and for
3 the vibrational spectra (IR and Raman) were recorded. Most
soluble are both 2 and 3 in [D6]acetone, however, signals of
decomposition were observed after 1 h. Therefore, more suit-
able solvents for 3 are CDCl3 and CD2Cl2 despite lower solu-
bility.
1
For 2, in the H NMR spectrum the two resonances attrib-
Scheme 2. Oxidation of 2,3,4,6-tetranitroaniline (2) to pentanitro- uted to the aromatic hydrogen (δ = 9.30 ppm) and amino
benzene (3).
hydrogen atoms (δ = 8.88 ppm) are observed as expected at
lower field due to the electron-withdrawing nature of the
After extraction with dichloromethane and recrystallization
neighboring nitro groups. The 13C{1H} NMR spectrum dis-
from cold dichloromethane, pale yellow crystalline needles of
plays six resonances accordingly to the asymmetry with broad-
3 were obtained in good yield and were shown to be pure
ened signals for the CNO2 carbon atoms. Accordingly, the 14
N
1
according to H and 13C NMR spectroscopy.
NMR spectrum shows four resonances in a narrow range at
–18 to –27 ppm with the NH2 resonance detected at –294 ppm.
In moist environment, 3 decomposes by nucleophilic substi-
tution of the nitro groups in meta-(3-)position to the CH carbon
under formal elimination of nitrous acid. As was proven by
X-ray diffraction, the hydrolysis product is 2,4,6-trinitro-3-
hydroxyphenol (4), better known as trinitroresorcinol or styph-
nic acid (Scheme 3). At 25 °C solutions in polar solvents such
as acetone, approximately 50% is decomposed after 3 d into
4. Furthermore, already after storage at 0 °C of pure 3, the
odor of NO2 is noticeable after some days.
1
The H NMR spectrum of 3 shows the singlet for the aro-
matic hydrogen atom at δ = 9.69 ppm in [D6]acetone, 9.21 ppm
in CD2Cl2, and 9.12 ppm in CDCl3. This indicates a further
downfield shift upon introduction of the fifth nitro group com-
pared to 2. In the 13C{1H} and 13C NMR spectra of 3
(Figure 1), the four expected resonances are detected according
to the symmetry. Interestingly and as expected, the carbon
atoms display broadening/coupling due to the attached nitro
groups, and therefore require longer acquisition times to be
observed. Two of the three nitro-bound carbon atoms display
clear triplets due to coupling to 14N [1J(13C,14N) = 14.1 and
14.3 Hz], as also already mentioned in the earlier report.[8]
Based on the proton-coupled spectrum (insert Figure 1), a defi-
nite assignment of the ortho- and meta-carbon atoms (relative
to the CH carbon atom) was established. The signal at δ =
140.3 ppm is now split into a doublet of triplets due to ad-
Scheme 3. Hydrolysis of pentanitrobenzene (3) to styphnic acid (4).
Figure 1. 13C{1H} and 13C (red box) NMR spectrum of 3 in CD2Cl2.
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Table 1. Crystal data, details of the structure determinations, and refinement of 2–4.
2
3
4
Formula
FW /g·mol–1
T /K
C6H3N5O8
273.13
103(2)
C6HN5O10
303.10
143(2)
C6H3N3O8·2/3H2O
257.12
143(2)
λ /Å
0.71073
monoclinic
P21/c
0.40ϫ0.30ϫ0.10
colorless platelet
7.1929(4)
11.0332(6)
12.0424(7)
90
97.724(2)
90
947.02(9)
4
1.916
0.181
0.71073
triclinic
P1
0.71073
crystal system
Space group
Crystal size /mm
Crystal habit
a /Å
b /Å
c /Å
α /°
β /°
trigonal
¯
¯
P3c1
0.20ϫ0.10ϫ0.05
pale yellow block
8.1268(5)
13.1290(8)
20.3142(15)
88.676(5)
79.512(6)
81.601(5)
2108.4(2)
8
0.30ϫ0.15ϫ0.15
pale yellow block
12.5856(7)
12.5856(7)
9.9705(8)
90
90
120
1367.71(19)
2
1.873
γ /°
V /Å3
Z
ρcalcd. /g·cm–3
μ
1.910
0.187
0.181
F(000)
552
1216
784
2Θ range /°
Index ranges
6.800–50.700
–8 Յ h Յ 8
–13 Յ k Յ 13
–14 Յ l Յ 14
6864
8.678–52.000
–9 Յ h Յ 10
–14 Յ k Յ 16
–25 Յ l Յ 24
17766
8.992–52.736
–11 Յ h Յ 13
–8 Յ k Յ 15
–6 Յ l Յ 12
3061
Reflections collected
Reflections unique
Parameters
1728
180
8229
757
931
91
GooF
1.073
1.052
1.081
R1 / wR2 [I Ͼ 2σ(I)]
R1 / wR2 (all data)
Largest diff. peak / hole /e·Å–3
0.0460 / 0.0935
0.0777 / 0.1033
0.291 / –0.267
0.0490 / 0.0970
0.0848 / 0.1130
0.276 / –0.255
0.0402 / 0.0931
0.0611 / 0.1117
0.241 / –0.242
3
ditional coupling to 1H with J(13C,1H) = 7.5 Hz, whereas that
at δ = 141.8 ppm remains virtually unchanged. Because of the
generally larger C–H coupling constant in benzenes at meta
position compared to ortho position the assignment for 3 was
made.
The 14N NMR spectrum of 3 shows three signals at
–33.5 ppm [ortho-(C1/C5)], –36.6 ppm [meta-(C2/C4)], and
–37.2 ppm [para-(C3)] with the assignments. Definite distinc-
tion between those nitro groups at ortho-(C1/C5) and meta-
1
(C2/C4) position is based on the H-15N-HMBC experiment,
which shows one cross peak derived from the 1H-15N coupling
to the ortho-(C1/C5) nitro group at –33.5 ppm.
Single Crystal Structure Analysis
Single crystals suitable for X-ray structure determination
were obtained for the polynitrobenzenes 2–4 (Table 1).
Single crystals of 2 were obtained by recrystallization from
dichloromethane. 2,3,4,6-Tetranitroaniline (2) crystallizes in
the monoclinic space group P21/c with four molecules per unit
cell. The calculated density is 1.916 g·cm–3 and the volume of
the unit cell is 947.02(9) Å3 at 103 K (Figure 2).
The structure of 2,3,4,6-tetranitroaniline (2) consists of an
almost completely planar benzene ring. The distance between
N4 and C1 [1.318(4) Å] is quite short compared to the other
C–N bond lengths [1.456(3)–1.478(3) Å], which is due to the
electron-donating effect of the NH2 group pushing electron
Figure 2. X-ray molecular structure of 2,3,4,6-tetranitroaniline (2). Se-
lected bond lengths /Å: C2–C1 1.429(4), C6–C1 1.423(4), C3–C4
1.383(4), C4–C5 1.382(4), C3–C2 1.379(4), C6–C5 1.378(4), N4–C1
1.318(4), N2–C4 1.456(3), C3–N5 1.478(3), O7–N5 1.220(3), O8–N5
1.223(3), C5–H5 0.9500; Selected bond angles /°: C6–C1–C2
114.3(2), C3–C2–C1 122.7(2), C2–C3–C4 120.0(2), C5–C4–C3
119.7(2), C6–C5–C4 120.4(2), C5–C6–C1 122.6(2), N4–C1–C2
121.5(2); Selected torsion angles /°: C2–C3–N5–O8 64.9(3), C3–C2–
density into the bond and thereby shortens the distance. In ac- N1–O2 41.0(3), C5–C6–N3–O5 –0.9(3), O3–N2–C4–C3 15.5(4).
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cordance to this, the C–C bonds in direct vicinity to the amino
group (C2–C1 and C6–C1) are longer than the other C–C
bonds in the ring. The bond angles of the benzene ring have
values between 114.3(2)° and 122.7(2)°, whereby the angle in
direct vicinity to the amino group (C6–C1–C2) is the smallest.
The nitro group (N5) in meta position to C1 is significantly
twisted out of the plane by 64.9(3)°, since there is no “stabili-
zation” possible by a neighboring hydrogen atom. The two
nitro groups in ortho position to the carbon atom carrying the
aromatic hydrogen atom (C5) are the most “stabilized”,
whereas the nitro moiety at C2 shows a distortion as well
[41.0(3)°]. The distances between the weak intramolecular in-
teracting hydrogen and oxygen atoms are 2.30 Å for O5–H5,
2.42 Å for O4–H5, 1.86 Å for O6–H41, and 2.02 Å for O1–
H42.
A room temperature (298 K) determination of the crystal
structure of 2,3,4,6-tetranitroaniline was reported in 1966 with
a density of 1.86 g·cm–3.[11]
Figure 3. X-ray molecular structure of pentanitrobenzene (3). Selected
Based on the crystal structure, the sensitivity towards moist-
ure of 2 (as also is the case for 3) could be explained. Due to
the strong twist of the N5-nitro group, the molecule is labile
towards nucleophilic attack at this position, provided that the
free rotation is restricted in solution as well. This assumption
was confirmed by treating 2,3,4,6-tetranitroaniline (2) in re-
fluxing water/acetone resulting in 3-amino-picric acid,[9]
which agrees with the observations from the NMR experiments
in [D6]acetone of 2.
bond lengths /Å: C1–C2 1.388(4), C4–C5 1.388(4), C2–C3 1.384(4),
C4–C3 1.383(3), C5–C6 1.378(4), C1–C6 1.377(4), N1–C1 1.481(3),
N1–O1 1.216(3), N1–O2 1.223(3), C6–H6 0.9500; Selected bond
angles /°: C1–C6–C5 119.0(2), C6–C5–C4 121.3(2), C3–C4–C5
118.7(2), C4–C3–C2 120.9(2), C3–C2–C1 119.0(2), C6–C1–C2
121.1(2), O1–N1–C1 116.9(2), O1–N1–O2 125.7(2); Selected torsion
angles /°: O2–N1–C1–C2 –8.3(4), O4–N2–C2–C3 –74.5(3), O6–N3–
C3–C4 –42.9(3).
Single crystals of 3 were obtained by recrystallization from
cold dichloromethane. Pentanitrobenzene (3) crystallizes in the
¯
triclinic space group P1 with eight molecules per unit cell and
four molecules per asymmetric unit. The molecules in the
asymmetric unit are slightly different to each other regarding
their bond lengths, bond angles and torsion angles which is
presumably due to intra- and intermolecular interactions of the
nitro groups. The calculated density of 3 is 1.910 g·cm–3 and
the volume of the unit cell is 2108.4(2) Å3 at 143 K. Figure 3
shows one of the four molecules of the asymmetric unit.
The structure of pentanitrobenzene (3) consists of an almost
completely planar benzene ring, similar as observed for 2. The
respective bonds (C1–C2 and C4–C5, C2–C3 and C4–C3, C5–
C6 and C1–C6) have each the same or a very similar bond
length. The shortest C–C bond lengths [1.378(4) Å and
1.377(4) Å] are observed for the carbon atom carrying the
hydrogen atom (C6). The C–N bond lengths are in the typical
range of C–N single bonds. The bond angles in the ring are
alternating between around 119° and 121°. Regarding the tor-
sion angles, it is obvious that the nitro groups in meta position
to C6 (N2 and N4) are strongly twisted out of the plane with
–74.5(3)° (Figure 4). The N3-nitro group is with –42.9(3)°
slightly twisted as well, whereas the nitro groups in ortho-
position to C6 are almost unaffected. Similar as in 2, this is due
to weak stabilizing interactions between the aromatic hydrogen
atom and the oxygen atoms of the adjacent nitro moieties. The
distance between O1 and H6 is 2.37 Å and the distance be-
tween O10 and H6 is 2.47 Å.
Figure 4. View along the x,y axis and the benzene plane showing the
twist of the NO2 groups in the structure of pentanitrobenzene (3).
N4-nitro groups, as was similarly described for 2. Accordingly,
3 is also sensitive to moisture regioselectively at the meta posi-
tions to C6. This was proven by reacting 3 in cold water yield-
ing the corresponding dihydroxy product, styphnic acid (4), in
addition to observations during NMR experiments of 3.
Single crystals of 4 were obtained from aqueous solution at
5 °C. Styphnic acid (4) crystallizes in the trigonal space group
¯
P3c1 with two molecules per unit cell and with two-thirds
equivalents of crystal water. The calculated density is
1.873 g·cm–3 and the volume of the unit cell is 1367.71(19) Å3
at 143 K (Figure 5).
Styphnic acid (4) is a highly symmetric molecule with an
almost planar benzene ring. The C–C bonds directly adjacent
to the carbon atoms C2 bound to the hydroxyl groups are
slightly longer than the C1–C3 bonds. A similar effect was
observed for the bonds adjacent to the electron-donating amino
group in the aniline 2. The bond angles in the benzene ring
range from 116.6 to 124.1°, whereby the smallest angles are
located at C2. The N1-nitro and the hydroxyl groups are al-
most planar to the benzene ring. The N2-nitro group in para
Also in this case, the sensitivity of 3 towards nucleophilic position to the unsubstituted carbon atom C3 is twisted out of
attack can be explained due to the distortion of the N2- and the plane by around 64.9°. Moreover, the compound contains
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Table 2. Physical and sensitivity data of 3 in comparison with AP.
3
AP
Formula
C6HN5O10
303.10
143
220
5
NH4ClO4
117.49
–
240
20
FW /g·mol–1
a)
Tm /°C
a)
Tdec /°C
b)
IS /J
b)
FS /N
96
63
360
–
b)
ESD /mJ
ρ /g·cm–3 c)
1.91
52.8
18.5
–13.2
66.4
1.95
54.5
+34.0
+34.0
–295.8
d)
O /%
e)
ΩCO /%
e)
ΩCO2 /%
ΔfHm /kJ·mol–1 f)
Vdet /m s–1 g)
9090
251
259
234
6368
157
235
261
h)
Isp /s
h)
Isp /s (15% Al)
Isp /s (15% Al, 14% binder)
h)
Figure 5. X-ray molecular structure of styphnic acid (4) with two-
a) Onset melting Tm and decomposition point Tdec from DTA measure-
ments, heating rate 5 K·min–1. b) Sensitivity towards Impact IS, Fric-
tion FS and electrostatic discharge ESD. c) Recalculated X-ray density
at room temperature. d) Oxygen content. e) Oxygen balance assuming
formation of CO and CO2. f) Energy of formation calculated by the
CBS-4M method using Gaussian 09[13]. g) Predicted detonation veloc-
ity. h) Specific impulse Isp of the neat compound and compositions
with aluminum or aluminum and binder (6% polybutadiene acrylic
acid, 6% polybutadiene acrylonitrile, and 2% bisphenol A ether) using
the EXPLO5 (Version 6.03) program package (70 kbar, isobaric com-
bustion, equilibrium expansion).[14]
thirds of crystal water. Selected bond lengths /Å: C1–C2 1.404(3), C4–
C2 1.389(2), C1–C3 1.379(2), N1–C1 1.450(3), N2–C4 1.467(4), N1–
O1 1.240(2), N1–O2 1.224(2), N2–O4 1.2231(19), C3–H3 1.01(3),
O3–C2 1.331(2), O3–H30 0.84(3); Selected bond angles /°: C1–C3–
C1 119.8(3), C2–C4–C2 124.1(3), C3–C1–C2 121.5(2), C4–C2–C1
116.57(19), C2–C1–N1 120.47(18), O1–N1–C1 118.14(17); Selected
torsion angles /°: O1–N1–C1–C2 2.118(31), C1–C2–O3–H30
–0.906(26), C2–C4–N2–O4 64.853(22).
two-thirds equivalents of crystal water (O5 and H51), which
is disordered.
Conclusions
The crystal structure of styphnic acid containing two-thirds
of crystal water at room temperature (298 K) with a density of
1.84 g·cm–1 was described in 1982, after an initial report from
1931.[12] Now, with this low-temperature data set, there is an
improved quality styphnic acid crystal structure available.
The polynitrobenzene pentanitrobenzene (3) can be prepared
now via a two-step route and is now fully characterized. The
starting material 3-nitroaniline (1) is easily available and in-
expensive. Important experimental and calculated properties
such as sensitivities, thermal stability, and energetic parameters
were determined and discussed. Pentanitrobenzene exhibits a
relatively high decomposition temperature, detonation velocity,
density and specific impulse for the neat compound. The mo-
lecular structure of 3 in the crystalline state was determined
and discussed. Furthermore, the crystal structures of 2,3,4,6-
tetranitroaniline (2) and styphnic acid/trinitroresorcinol (4)
were improved by low-temperature X-ray crystallography. Un-
fortunately, the moisture sensitivity of pentanitrobenzene (3)
restricts some further applications and chemistry, but ad-
ditional studies as a synthetic building block from freshly pre-
pared material will be subject of future studies.
Thermal Stabilities and Energetic Properties
The physical properties of pentanitrobenzene (3) were deter-
mined or calculated and compared with those of ammonium
perchlorate (AP) (Table 2).
The thermal stability was investigated by differential ther-
mal analysis (DTA) with a temperature range of 15–400 °C
and a heating rate of 5 K·min–1. It was found that pentanitro-
benzene (3) melts at 143 °C before decomposition occurs at
220 °C. Sensitivity measurements against impact, friction and
electrostatic discharge show that 3 is sensitive against these
stimuli (IS = 5 J, FS = 96 N, ESD = 63 mJ). Furthermore, 3 has
a positive oxygen balance regarding the formation of carbon
monoxide and an oxygen content comparable with that of AP.
The detonation velocity is significantly higher than in the com-
mon oxidizer ammonium perchlorate (AP) and the calculated
density approaching that of AP. The specific impulse for the
neat compound as well as with aluminum is higher than for
AP. However, mixed with 15% aluminum and 14% binder, the
oxygen balance seems not to be sufficient to obtain a higher
specific impulse than in compositions with AP. Lower binder
content might be more adequate for an optimal combustion
behavior.
Experimental Section
General: Solvents were dried and purified with standard methods. The
starting material 3-nitroaniline (1) is commercially available and used
without further purification. Raman spectra were recorded in a glass
tube with a Bruker MultiRAM FT-Raman spectrometer with a Klaas-
tech DENICAFC LC-3/40 laser (Nd:YAG, 1064 nm, up to 1000 mW)
in the range of 4000–400 cm–1. IR spectra were recorded with a Per-
kin–Elmer Spectrum BX-FTIR spectrometer coupled with a Smiths
ATR DuraSample IRII device. Measurements were recorded in the
range of 4000–650 cm–1. All Raman and IR spectra were measured at
ambient temperature and their intensities are qualitatively described as
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“very strong” (vs), “strong” (s), “medium” (m), “weak” (w) and “very Pentanitrobenzene (3):[7] 2,3,4,6-Tetranitroaniline (2) (500 mg,
weak” (vw). NMR spectra were recorded with JEOL Eclipse and 1.83 mmol) was dissolved in oleum (25.0 mL, 20–25 wt% SO3) and
Bruker TR 400 MHz spectrometers at 25 °C. Chemical shifts were de-
termined in relation to external standards Me4Si (1H, 399.8 MHz; 13C,
the solution was cooled to 5 °C. H2O2 (2.70 mL, 98%) was added
dropwise keeping the temperature below 25 °C. The suspension was
100.5 MHz); MeNO2 (14N, 28.9 MHz) and are given in parts per mil- stirred for 24 h at 25–30 °C and for 1 h at 0 °C. Afterwards, the reac-
lion (ppm). Elemental analyses (CHN) were obtained with
Vario EL Elemental Analyzer.
a
tion mixture was extracted with DCM (5ϫ50 mL) and the solvent was
evaporated. The resulting yellow solid was recrystallized from cold
DCM (15 mL) to afford pale yellow crystalline needles (295 mg, 53%)
which were filtered, washed with ice-cold DCM and dried in vacuo
for 5 h. 1H NMR (CDCl3): δ = 9.12 (s, 1 H, CH). 1H NMR (CD2Cl2):
The sensitivity data were acquired by measurements with a BAM
drophammer and a BAM friction tester.[1] Melting and decomposition
points were determined by differential thermal analysis (DTA) using
an OZM Research DTA 552-Ex instrument with Meavy 2.1.2 software.
The samples (3–15 mg) were measured in open glass tubes (diameter
4 mm, length about 47 mm) at a heating rate of 5 K·min–1 in the range
of 15–400 °C. The temperatures are given as onset temperatures.
1
δ = 9.21 (s, 1 H, CH). H NMR ([D6]acetone): δ = 9.69 (s, 1 H, CH).
13C{1H} NMR (CDCl3): δ = 141.4 (br., ortho-C rel. to CH), 139.8 [t,
1J(C-14N) = 14.3 Hz, meta-C rel. to CH], 137.8 [t, 1J(C-14N) =
14.1 Hz, para-C rel. to CH], 125.9 (s, CH). 13C NMR (CD2Cl2): δ =
1
1
141.8 (br., ortho-C rel. to CH), 140.3 [dt, J(C-H) = 7.5, J(C-14N) =
14.3 Hz, meta-C rel. to CH], 138.2 [t, 1J(C-14N) = 14.1 Hz, para-C rel.
to CH], 127.1 [d, J(C-H) = 183.5 Hz, CH]. 14N NMR (CD2Cl2): δ =
Crystal Structure Determination: The crystal structure data were
obtained with an Oxford Xcalibur CCD Diffractometer with a
KappaCCD detector at low temperature (143 K and 103 K). Mo-Kα
radiation (λ = 0.71073 Å) was delivered by a Spellman generator (volt-
age 50 kV, current 40 mA). Data collection and reduction were per-
formed using the CRYSALIS CCD[15] and CRYSALIS RED[16] soft-
ware, respectively. The structures were solved by SIR92/SIR97[17] (di-
rect methods) and refined using the SHELX-97[18] software, both im-
plemented in the program package WinGX22.[19] Finally, all structures
were checked using the PLATON software.[20] Structures displayed
with ORTEP plots are drawn with thermal ellipsoids at 50% prob-
ability level.
1
–33.5 (ortho-NO2 rel. to CH), –36.6 (meta-NO2 rel. to CH), –37.2
(para-NO2 rel. to CH) ppm. IR (ATR): ν˜ = 3080 (w, νCH), 1606 (w),
1555 (vs, νNO2), 1393 (w), 1325 (vs, νNO2), 1307 (m), 1167 (w), 926
(m), 890 (s), 832 (w), 817 (m), 804 (m), 789 (w), 769 (w), 725 (m),
716 (w) cm–1. Raman (502 mW): ν˜ = 3083 (w), 1610 (w), 1593 (w),
1569 (m), 1360 (s), 1338 (m), 1201 (w), 833 (vs) cm–1. C6HN5O10
(303.10 g·mol–1): calcd.: C 23.78, H 0.33, N 23.11%; found: C 23.84,
H 0.47, N 22.82%. Melting point: 143 °C; Dec. point: 220 °C. Sensi-
tivities (BAM): IS:5 J, FS: 96 N, ESD: 63 mJ (grain size 100–500 μm).
Acknowledgements
The theoretical calculations were achieved by using the Gaussian 09
program package[13] and were visualized by using GaussView 5.08.[21]
Optimizations and frequency analyses were performed at the B3LYP
level of theory (Becke’s B3 three parameter hybrid functional by using
the LYP correlation functional) with a cc-pVDZ basis set. After cor-
recting the optimized structures with zero-point vibrational energies,
the enthalpies and free energies were calculated on the CBS-4M (com-
plete basis set) level of theory.[22] The detonation parameters were
obtained by using the EXPLO5 (V6.03) program package.[14,23]
We would like to thank the following co-workers for X-ray determi-
nation measurements and refinements: Prof. Konstantin Karaghiosoff,
Dr. Peter Mayer, as well as M.Scs. Cornelia Unger and Jörn Martens.
Financial support of this work by the Ludwig-Maximilian University
of Munich (LMU), the Office of Naval Research (ONR) under grant
no. ONR.N00014–16–1-2062, and the Bundeswehr – Wehrtechnische
Dienststelle für Waffen und Munition (WTD 91) under grant no.
E/E91S/FC015/CF049 is gratefully acknowledged. The authors
acknowledge collaborations with Dr. Mila Krupka (OZM Research,
Czech Republic) in the development of new testing and evaluation
methods for energetic materials and with Dr. Muhamed Suceska (Brod-
arski Institute, Croatia) in the development of new computational
codes to predict the detonation and propulsion parameters of novel
explosives. We thank Evonik Industries AG for a generous gift of 98%
hydrogen peroxide.
Crystallographic data (excluding structure factors) for the structures in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting the
depository numbers CCDC-1866511 (for 2), CCDC-1866506 (for 3),
and CCDC-1866507 (for 4) (Fax: +44-1223-336-033; E-Mail:
deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
CAUTION! The benzene derivatives 2–4 are energetic materials and
show sensitivities in the range of secondary explosives! They should
be handled with caution during synthesis or manipulation and ad-
ditional protective equipment (leather jacket, face shield, ear protec-
tion, Kevlar gloves) is strongly recommended.
Keywords: Energetic materials; Oxidizer; Polynitrobenzenes;
NMR spectroscopy; X-ray diffraction
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Z. Anorg. Allg. Chem. 0000, 0–0
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Journal of Inorganic and General Chemistry
ARTICLE
Zeitschrift für anorganische und allgemeine Chemie
T. Huber, C. von der Heide, T. M. Klapötke,*
B. Krumm* ........................................................................ 1–8
Synthesis, Characterization, and Properties of Pentanitro-
benzene C6H(NO2)5
Z. Anorg. Allg. Chem. 0000, 0–0
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