Characterization of the energetic plasticizer methyl-NENA

Article abstract of DOI:10.1002/zaac.201100262

The energetic plasticizer N-methyl-N-(2-nitroxyethyl)nitramine (2) and its precursor N-methyl-N-(2-nitroxyethyl)ammonium nitrate (1) were synthesized by nitration of 2-(methylamino)ethanol and characterized by X-ray crystallography, multinuclear NMR spectroscopy (¹H, ¹³C, ¹⁴N), vibrational spectroscopy (IR and Raman), mass spectrometry and differential thermal analysis. The sensitivities were determined according to BAM methods and the detonation parameters were calculated with the EXPLO5 computer program to identify them as potentially explosive compounds. Copyright

Full text of DOI:10.1002/zaac.201100262

ARTICLE
DOI: 10.1002/zaac.201100262
Characterization of the Energetic Plasticizer Methyl-NENA
[a]
[a]
Dániel Izsák and Thomas M. Klapötke*
In Memory of Professor Manfred Held
Keywords: NENA; X-ray diffraction; Energetic materials; Plasticizer; Sensitivities
Abstract. The energetic plasticizer N-methyl-N-(2-nitroxyethyl)nitr- mass spectrometry and differential thermal analysis. The sensitivities
amine (2) and its precursor N-methyl-N-(2-nitroxyethyl)ammonium ni- were determined according to BAM methods and the detonation pa-
trate (1) were synthesized by nitration of 2-(methylamino)ethanol and
rameters were calculated with the EXPLO5 computer program to
identify them as potentially explosive compounds.
characterized by X-ray crystallography, multinuclear NMR spec-
1
13
14
troscopy ( H, C, N), vibrational spectroscopy (IR and Raman),
Introduction
acid and acetic anhydride in the presence of zinc chloride as
catalyst. 2 can also be synthesized in a two stage procedure,
[
1]
N-methyl-N-(2-nitroxyethyl)nitramine
(2),
commonly
where the first stage is the esterification of 2-(methylamino)
ethanol with nitric acid to N-methyl-N-(2-nitroxyethyl)ammo-
nium nitrate (1), which can be isolated as a colorless, fine crys-
talline solid upon mixing of the reaction mixture with diethyl
ether (Scheme 1).
known as Me-NENA, is an energetic plasticizer belonging to
the group of alkylated nitroxyethyl nitramines discovered in
the 1940ies.[ 2 is the simplest of the alkylated NENA com-
pounds, with other notable members being Et- and n-Bu-
NENA. These compounds incorporate the energetic nitramine
and nitroxy groups together with an alkyl chain of variable
length. Due to them being small molecules with raised energy
content and a non-polar moiety they find wide use as energetic
plasticizers for modern gun propellant formulations.[ Ener-
getic plasticizers are favorable over inert plasticizers like dibu-
tyl phthalate to compensate for as much loss of energy as pos-
sible due to other necessary, mostly inert, components.
1]
2]
Scheme 1. Synthesis of 1 and 2.
The intention of this paper is now to fill the gap of little
available analytical data in the open literature for Me-NENA,
including spectroscopic data, the molecular structure in the crys-
talline state, the sensitivities against various outer stimuli and
its energetic properties with regard to its potential explosiveness.
Crystal Structures
The crystal structures were determined by single-crystal X-
ray diffraction on an Oxford Diffraction Xcalibur 3 dif-
fractometer with a Sapphire CCD detector, four circle kappa
platform, Enhance Mo-K radiation source (λ = 71.069 pm)
α
Results and Discussion
and Oxford Cryosystems Cryostream cooling unit. Data collec-
tion and reduction were performed with the CrysAlisPro soft-
Syntheses
ware.[ The structures were solved with SIR97, refined with
4]
[5]
The syntheses are based on the original syntheses of
[6]
[7]
SHELXL-97 and checked with PLATON, all integrated in
the WinGX software suite. All non-hydrogen atoms were
[1]
Blomquist and Fiedorek from 1949, and the work up of 2 on
a publication by Plesch and Wiessler.[ For the synthesis of 2,
a colorless crystalline solid, the commercially available
[8]
3]
refined anisotropically, whereas hydrogen atoms were located
from difference Fourier electron density maps and refined iso-
2-(methylamino)ethanol was nitrated in a mixture of pure nitric
[9]
tropically. The finalized CIF files were checked with check-
CIF.[ Intra- and intermolecular contacts were analyzed with
10]
*
Prof. Dr. T. M. Klapötke
[11]
[12]
Mercury,
graph set patterns with RPluto.
Illustrations of
Fax: +49-89-2180-77492
[13]
E-Mail: tmk@cup.uni-muenchen.de
molecular structures were drawn with Diamond 2.
[
a] Department of Chemistry
Suitable single crystals could be obtained by slow diffusion
of diethyl ether into a concentrated solution of 1 in acetone
and by recrystallization of 2 from diethyl ether, respectively.
Ludwig Maximilian University
Butenandtstraße 5–13 (D)
81377 Munich, Germany
Z. Anorg. Allg. Chem. 2011, 637, (14-15), 2135–2141
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
2135

D. Izsák, T. M. Klapötke
ARTICLE
The crystallographic data of both compounds are given in
Table 1. The CIF files were deposited at the Cambridge Crys-
tallographic Data Centre and can be obtained free of charge
[14]
(1: CCDC-826319; 2: CCDC-826320).
Table 1. Crystallographic data of 1 and 2.
1
2
Formula –
M /g·mol 1
Color
C
3
H
9
N
3
O
6
C
3 7 3 5
H N O
183.13
colorless
block
165.12
colorless
block
Habit
Crystal size /mm
Crystal system
Space group
a /Å
b /Å
c /Å
0.25 ϫ 0.18 ϫ 0.10 0.20 ϫ 0.15 ϫ 0.10
orthorhombic monoclinic
Pca2 (No. 29) P2 /c (No. 14)
1
1
Figure 1. Molecular unit of N-methyl-N-(2-nitroxyethyl)ammonium
nitrate (1). Thermal ellipsoids are displayed at the 50% probability
level. Selected geometries: bond lengths /Å: O1–N1 1.400(2), O2–N1
12.5637(8)
5.5612(5)
11.2936(7)
90
9.7280(10)
7.3794(7)
11.7814(15)
90
1
1
.197(3), O3–N1 1.202(3), O1–C1 1.451(3), C1–C2 1.506(3), N2–C2
.483(3), N2–C3 1.488(3), O4–N3 1.251(2); bond angles /°: O1–N1–
α /°
β /°
90
90
125.816(11)
90
O2 112.2(2), O1–N1–O3 117.9(2), N1–O1–C1 113.7(2), O1–C1–C2
11.9(2), N2–C2–C1 111.2(2), C2–N2–C3 112.8(2), O4–N3–O5
γ /°
1
V /Å3
789.08(10)
4
685.82(16)
4
1
–
20.9(2); torsion angles /°: O2–N1–O1–C1 –179.5(2), N1–O1–C1–C2
80.6(2), O1–C1–C2–N2 –58.3(2), C1–C2–N2–C3 –177.8(2).
Z
ρ
calcd. /g·cm–3
1.542
1.599
T /K
173(2)
384
0.149
173(2)
344
0.152
F(000)–
Table 2. Distances and angles of the hydrogen bonds in 1.
μ /mm 1
D
H
A
D–H /Å
H···A /Å
D···A /Å
D–H···A /°
θ range /°
4.40–32.47
4.27–25.99
Dataset (h, k, l)
Reflections collected
Independent reflections 1469
–7:18; –8:8; –17:15 –11:11; –9:8; –14:14
N2 H5 O5 0.93(2)
N2 H5 O6 0.93(2)
2.39(2)
2.03(2)
2.09(2)
2.43(2)
3.016(2)
2.944(2)
2.914(2)
3.080(2)
124(2)
166(2)
166(2)
135(2)
5821
4540
1338
i
N2 H6 O4 0.84(2)
Observed reflections
790
878
i
N2 H6 O5 0.84(2)
R
int
0.0600
0.0338
Symmetry code: (i) –x + 3/2, y, z + 1/2.
Data
1469
1338
Restraints
Parameters
1
145
0
128
R
R
S
1
, wR
, wR
2
(obs.)
(all data)
0.0361, 0.0575
0.0855, 0.0651
0.804
0.0300, 0.0563
0.0554, 0.0605
0.869
–0.186, 0.155
multi-scan
826320
1
2
Δρmin/max /e·Å–3
–0.172, 0.202
Absorption correction multi-scan
CCDC 826319
1
crystallizes in the orthorhombic space group Pca2 with
1
four formula units in the unit cell and has a calculated density
–
3
of 1.542 g·cm . The asymmetric unit consists of a complete
ion pair and is shown in Figure 1.
The bond lengths and angles are as expected.[15] In contrast Figure 2. Hydrogen bonding in 1. Thermal ellipsoids are displayed at
the 50% probability level. Symmetry code: (i) –x + 3/2, y, z + 1/2.
to the structure of 2 the atoms C1 to C3 are in one plane, with
the nitroxy group being rotated at 76° in the direction of the
nitrate. The latter is in one plane with N2 and almost horizontal
to the plane of the main chain. In the crystal structure both and are similar to other compounds containing nitramines and
Again, the bond lengths and angles meet the expectations
[
15,17]
nitrogen bonded hydrogen atoms participate in bifurcated hy- nitrate esters, like N,N-bis(2-nitroxyethyl)nitramine.
In
drogen bonds (see Table 2). One bifurcated bond is connecting contrast to 1 the bonds N2–C2 and N2–C3 are slightly shorter
the two ions of the formula unit, while the other one connects (about 0.03 Å) and the angle C2–N2–C3 is about 9° larger due
the cation with a nitrate of a neighboring formula unit. This to the electron withdrawing nitramine group. The latter lies
results in infinite chains along [001], a fragment of which is virtually in one plane with C2 and C3, whereas the nitroxy
illustrated in Figure 2. The graph set[16] for both bonds is group is in one plane with C1 and C2. The angle between the
R2,1(4) on the binary level.
two planes is about 73°. The part with the nitroxy group forms
Compound 2 crystallizes in the monoclinic space group P2 /c a layer structure parallel to [011], depicted in Figure 4. Due to
1
with four formula units in the unit cell. The calculated density the more acidic protons on C2 and C3 two of them build up
–
3
of 1.599 g cm is slightly higher than that of the precursor non-classical hydrogen bonds with the two nitramine oxygen
nitrate salt 1. The molecular structure is show in Figure 3. atoms of one neighboring molecule (see Table 3). This results
2
136
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 2135–2141

Characterization of the Energetic Plasticizer Methyl-NENA
Figure 3. Molecular structure of N-methyl-N-(2-nitroxyethyl)nitra-
mine (2). Thermal ellipsoids are displayed at the 50% probability
level. Selected geometries: bond lengths /Å: O1–N1 1.384(2), O2–N1
Figure 5. Hydrogen bonding in 2. Thermal ellipsoids are displayed at
the 50% probability level. Symmetry codes: (i) x, –y + 1/2, z + 1/2;
(
ii) x, –y + 1/2, z–1/2.
1
1
1
.205(2), O3–N1 1.210(3), O1–C1 1.453(2), C1–C2 1.508(2), N2–C2
.460(1), N2–C3 1.453(1), N2–N3 1.335(2), O4–N3 1.234(2), O5–N3
.240(1); bond angles /°: O1–N1–O2 112.6(1), O1–N1–O3 118.6(1), atoms show three signals in the 13C{ H} NMR spectrum at
1
N1–O1–C1 113.4(1), O1–C1–C2 105.3(1), N2–C2–C1 112.1(1), C2–
N2–C3 121.5(1), N3–N2–C3 117.7(1), O4–N3–N2 119.0(1), O5–N3–
N2 117.3(1); torsion angles /°: O1–C1–C2–N2 67.8(2), N1–O1–C1–
C2 –178.1(1), O2–N1–O1–C1 178.8(1), C1–C2–N2–C3 82.8(2), O5–
N3–N2–C3 –4.8(2).
3
4.2 (C3), 47.2 (C2) and 69.6 ppm (C1). All nitrogen atoms
14
are visible in the N NMR spectrum, with the ammonium
group exhibiting a broad signal at –346 ppm, the nitroxy group
a sharp signal at –40 ppm and the nitrate anion also a sharp
signal at 1 ppm.
1
2
shows three signals in its H NMR spectrum. The methyl
in infinite chains along [001] (see Figure 5) with the binary
descriptor of this chain of rings being C2,2(10)[R2,2(8)].
group C3 exhibits a singlet signal at 3.47 ppm, whereas the
two methylene groups show multiplet signals at 4.27 (C2) and
1
4
.87 ppm (C1). The 13C{ H} NMR spectrum shows also three
signals, with C3 having a shift of 39.9 ppm, C2 being at
5
0.7 ppm and C1 having a downfield shift of 70.8 ppm. The
N NMR spectrum exhibits two signals. One for the nitroxy
1
4
group at –38 ppm and one for the nitro group at –23 ppm.
Differential Thermal Analysis
The thermal behavior of both 1 and 2 was analyzed by
differential thermal analysis (DTA). The measurements were
conducted in open glass tubes (diameter 4 mm, length about
4
7 mm) at a heating rate of 5 °C·min–1 against SiO as inert
2
reference substance. Figure 6 shows the DTA plots for the two
compounds. While 1 has a melting point with an onset of 73 °C
and a decomposition starting at 134 °C, 2 begins to melt at
3
1 °C and to decompose at 180 °C. The minimum of the melt-
[
1]
ing peak is at 40 °C, which is in agreement with the literature.
Figure 4. Unit cell of 2, viewed along [0 0 1]. Thermal ellipsoids are
displayed at the 50% probability level.
Table 3. Distances and angles of the hydrogen bonds in 2.
D
H
A
D–H /Å
H···A /Å
D···A /Å
D–H···A /°
i
C2 H3 O4 0.98(2)
2.51(2)
2.52(2)
3.268(3)
3.480(3)
134(1)
174(2)
i
C3 H6 O5 0.96(3)
Symmetry code: (i) x, –y + 1/2, z + 1/2.
NMR Spectroscopy
1
The H NMR spectrum of 1 exhibits three signals. One for
the methyl group C3 in the form of a singlet signal at
2
.93 ppm, and two multiplet signals for the two methylene
–
1
groups at 3.67 (C2) and 4.99 ppm (C1). The three carbon Figure 6. DTA plots for 1 and 2 with a heating rate of 5 °C·min .
Z. Anorg. Allg. Chem. 2011, 2135–2141
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2137

D. Izsák, T. M. Klapötke
ARTICLE
Sensitivities
Table 6. Enthalpies of formation of the gas-phase species M.
Formula
H°(g)(M) /kJ·mol–1
M
Δ
f
Due to the elevated sensitivities of nitroxy and nitramine
compounds, with common candidates being nitroglycerin (NG)
and RDX when thinking of explosives, the sensitivities of both
+
+
C
NO
2
3
H
3
9
N
2
O
3
C
NO
3
C H N
3 7
3
H
9
N
2
O
3
510.9
–314.0
–91.1
–
–
3
O
5
1
and 2 against impact (E ), friction (F ) and electrostatic dis-
dr
r
[18]
charge (E ) were determined.
The sensitivities against im-
el
[
19]
pact and friction were determined according to BAM
(Bun-
The solid state enthalpy of formation (Table 8) of 2 was
desanstalt für Materialforschung und -prüfung) standards using calculated by subtracting the enthalpy of sublimation
a BAM drop hammer and a BAM friction apparatus.[
20–22]
–1
The (58.9 kJ·mol ), obtained by Trouton’s rule (ΔsubH = 188 ϫ
), from the gas-phase enthalpy.[ In the case of 1 the lattice
27]
compounds were classified in compliance with UN guide-
lines.[ The sensitivities against electrostatic discharge were energy (ΔU
T
m
23]
) and lattice enthalpy (ΔH ) were calculated from
L L
determined using an OZM Research ESD 2010 EN. Surpris- the corresponding molecular volume (Table 7) according to the
ingly both compounds are almost insensitive against impact, equations provided by Jenkins.[ With the calculated lattice
with 1 having a sensitivity of Ͼ 40 J and 2 decomposing at Ͼ enthalpy (Table 7) the gas-phase enthalpy of formation
28]
3
5 J. According to the UN guidelines 1 is therefore insensitive, (Table 6) was converted into the solid state (standard condi-
while 2 is less sensitive against impact. Concerning the sensi- tions) enthalpy of formation (Table 8).
tivities against friction, both compounds have to be classified
as “sensitive“, with 1 decomposing at 144 N and 2 at 120 N.
Table 7. Lattice energy and lattice enthalpy.
V
M
/nm3
0.197
ΔU
L
/kJ·mol–1
ΔH
L
/kJ·mol–1
The sensitivities against electrostatic discharge are 1.0 J and
.6 J, respectively. Both 1 and 2 never detonated, but only
0
1
506.8
511.8
decomposed.
Table 8. Solid state enthalpies and energies of formation.
Heats of Formation
Δ
f
H°(s)
/
Δn
Δ
f
U°(s) /kJ·mol–1 M /g·mol–1
Δ
f
U°(s) /kJ·kg–1
–
1
kJ·mol
All calculations were carried out using the Gaussian 09W
1
–314.9
–9
–292.6
183.12
165.10
–1598.0
–796.0
[24]
(
revision A.02) program package.
The enthalpies (H°) were 2 –150.0
–7.5 –131.4
calculated using the complete basis set (CBS) method of Pe-
tersson and co-workers in order to obtain very accurate ener-
The molar solid state enthalpies of formation (Δ H° ) were
f
(s)
gies. In this study we applied the modified CBS-4M method, used to calculate the molar solid state energies of formation
which is a reparametrization of the original CBS-4 method and (Δ U° ) according to Equation (2) (Table 8), with Δn being
f
(s)
also includes some additional empirical corrections.[ The en- the change of moles of gaseous components in the equation of
25]
thalpies of the gas-phase species M were calculated according formation.
to the atomization energy method (Equation (1), Table 4,
ΔU = ΔH – ΔnRT
(2)
Table 5, and Table 6).[
26]
Energetic Properties
Δ
f
H°(g)(M) = H°(M) – ∑H°(A) + ∑Δ
f
H°(g)(A)
(1)
The energetic properties of 1 and 2 were calculated to obtain
their Berthelot–Rot values (B ), which indicate if a substance
is possibly explosive or not and further allow a comparison of
the overall performance of explosives. Generally speaking, a
R
Table 4. CBS-4M results.
Point group Electronic state –H° /a.u.
NIMAG
+
1
substance is potentially explosive when its B
is higher than
R
C
NO
2
H
C
3
H
3
9
N
2
O
3
C
D
C
1
A
A
A
A
453.902330
280.080434
657.838290
0.500991
37.786156
54.522462
74.991202
0
0
0
0
0
0
0
–
1
1
2
that of the “Oppau salt” (55% NH NO , 45% (NH ) SO ;
3h
1
Ј
4
3
4 2
4
–3
1
B = 1193 kJ·m ), the explosion of which led to a catastrophe
R
[30]
1g
with over 1000 fatalities in 1921.
The calculation of the detonation parameters was performed
N
O
4A1g
with the EXPLO5 program (version 5.04),[
31,32]
using the cal-
culated energies of formation and the experimentally deter-
mined crystal densities. The results are summarized in Table 9.
–
1
–1
The detonation velocities (1: 7918 m·s ; 2: 8050 m·s ) and
detonation pressures (1: 242 kbar; 2: 259 kbar) are similar to
Table 5. Literature values for atomic enthalpies of formation.[29]
H°(g)(A) /kJ·mol–1
–1
Δ
f
NG (7813 m·s , 257 kbar). The Berthelot–Rot values
1: 11287 kJ·m ; 2: 11819 kJ·m ) are lower than that of RDX
(14665 kJ·m ), but higher than that of NG (10982 kJ·m ) and
much more powerful than the “Oppau salt”. Therefore both
compounds have to be considered as potentially explosive.
–3
–3
(
H
C
N
O
218.0
716.7
472.7
249.2
–3
–3
2
138
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 2135–2141

Characterization of the Energetic Plasticizer Methyl-NENA
Table 9. Physicochemical properties and detonation parameters of 1 described as “very strong” (vs), “strong” (s), “medium” (m) and
and 2 in comparison with the well-known explosives NG and RDX.
“weak” (w). Raman spectra were recorded using a Bruker RAM II
(
Nd:YAG laser, λ = 1064 nm) in open glass tubes. The intensities
1
2
NG *
RDX *
are reported as percentages of the most intense peak and are given in
parentheses. Low resolution mass spectra were recorded on a JEOL
MStation JMS-700 using the methods DEI and FAB. Intensities are
given as percentages of the most intense peak. The determinations
of the carbon, hydrogen and nitrogen contents were carried out by
combustion analysis using an Elementar Vario EL or an Elementar
Vario Micro. The calculated theoretical values are given in parenthe-
ses. Differential thermal analysis was conducted with an OZM Re-
search DTA 552-Ex, using about 30 mg substance in open glass tubes
Formula –
C
3
H
9
N
3
O
6
C
3
H
7
N
3
O
5
C
3
H
5
N
3
O
9
3 6 6 6
C H N O
222.12
7.5
120
0.2
1.80
–21.6
70
M /g·mol 1
183.12
Ͼ 40
144
1.0
1.54
165.11
Ͼ 35
120
0.6
1.60
–43.6
–150
–796
227.09
0.2
Ͼ 360
n.d.
1.59
3.5
E
F
E
dr /J
r
/N
el /J
–
3 a)
ρ /g·cm
Ω /%
Δ
Δ
b)
–39.3
H°(s) /kJ·mol–1 –315
f
–371
–1540
U°(s) /kJ·kg–1
–1598
417
f
–
1
EXPLO5 values:
(diameter 4 mm, length about 47 mm) at a heating rate of 5 °C·min
–
1 c)
Q
v
/kJ·kg
–5769
3619
242
7918
825
–5919
3769
259
8050
780
–6084
4553
257
7813
714
–6125
4236
349
8748
739
in a temperature range of 15 to 400 °C. The temperatures are given as
onset temperatures. Melting points were checked with a Büchi Melting
Point B-540 in open glass capillaries.
d)
Tex /K
e)
p
C–J /kbar
–
1 f)
D /m·s
V
B
–
1 g)
0
/L·kg
Caution! Although we had no problems during synthesis and handling,
proper protective equipment should be worn when working with both
1 and 2 on a larger scale due to the increased sensitivities against
friction and the potential explosive powers.
/kJ·m–3
11287
11819
10982
14665
R
a) Crystal density. b) Oxygen balance. c) Heat of explosion. d) Ex-
plosion temperature. e) Detonation pressure. f) Detonation velocity. g)
Volume of detonation gases. * Taken from the literature
EXPLO5 database. n.d.: not determined.
[
33]
and the
N-Methyl-N-(2-nitroxyethyl)ammonium Nitrate (1)
Conclusions
2
5
-(Methylamino)ethanol (3.76 g, 50.0 mmol) was added slowly to a
°C cold mixture of nitric acid (100%, 20.9 mL, 500 mmol) and water
The energetic plasticizer N-methyl-N-(2-nitroxyethyl)nitr-
amine (2) and its precursor N-methyl-N-(2-nitroxyethyl)ammo-
nium nitrate (1) were synthesized by the nitration of 2-(methyl-
amino)ethanol according to literature procedures. Their molec-
ular structures could be obtained by low-temperature single-
crystal X-ray diffraction. 1 crystallizes in the orthorhombic 87%). H NMR ([D ]acetone): δ = 4.99 (m, 2 H, CH ), 3.67 (m, 2
space group Pca2 with a density of 1.542 g·cm and 2 in the H, CH
monoclinic space group P2 /c with a density of 1.599 g·cm . (CH
The sensitivities against impact (E ), friction (F ) and electro-
(
0.5 mL), during which the temperature was maintained at 5 °C. After
the addition the solution was stirred for 20 min at 5 °C, then 1 h at
room temperature and slowly added to diethyl ether (250 mL). The
colorless precipitate was filtered, washed well with diethyl ether and
dried on air. Yield: colorless, fine crystalline solid (7.97 g, 43.5 mmol,
1
6
2
–
3
13
1
), 2.93 (s, 3 H, CH
3
). C{ H} NMR ([D
). 14N NMR ([D
6
]acetone): δ = 69.6
1
2
–3
–
), 47.2 (CH
2
), 34.2 (CH
3
6
]acetone): δ = 1 (NO
3
),
1
2
+
–40 (ONO
2
2
), –346 (NH ). IR (ATR): ν = 3050 (w), 2833 (w), 2362
dr
r
(
w), 1643 (s), 1613 (m), 1514 (w), 1477 (m), 1438 (m), 1387 (m),
static discharge (E ) were determined according to BAM
methods (1: Edr Ͼ 40 J, F = 144 N, E = 1.0 J; 2: E Ͼ 35 J,
el
1
1
327 (s), 1293 (s), 1280 (s), 1178 (w), 1158 (w), 1066 (w), 1038 (m),
000 (s), 912 (m), 850 (s), 826 (m), 814 (m), 750 (m), 720 (w), 663
r
el
dr
F = 120 N, E = 0.6 J). The detonation parameters were calcu-
r
el
–1
(
m) cm . Raman (300 mW): ν = 3053 (12), 3038 (15), 3015 (20),
lated with the EXPLO5 program based on the calculated
CBS-4M) energies of formation and the crystal densities. Al-
2
1
8
974 (58), 2837 (7), 1647 (6), 1471 (15), 1454 (8), 1429 (6), 1368 (5),
284 (36), 1181 (3), 1069 (7), 1046 (100), 1004 (9), 913 (4), 854 (22),
17 (6), 721 (9), 713 (6), 665 (9) cm . MS (FAB ): m/z = 121.0
(
–3
though the Berthelot–Rot values of 1 (11287 kJ·m ) and 2
–1
+
–
3
–3
+
–
–
(
11819 kJ·m ) are lower than RDX (14665 kJ·m ) they are [C H N O ]. MS (FAB ): m/z = 62.0 [NO ]. EA (C H N O ,
3 9 2 3 3 3 9 3 6
–1
–
3
still higher than NG (10982 kJ·m ) and much more powerful 183.13 g·mol ): C 19.61 (19.68), H 4.88 (4.95), N 22.54 (22.95)%.
than the “Oppau salt” (1193 kJ·m ), indicating highly explos- DTA: T
ive potentials.
–
3
m
= 73 °C, T
d r
= 134 °C. Sensitivities: Edr Ͼ 40 J, F = 144 N,
E
el = 1.0 J.
N-Methyl-N-(2-nitroxyethyl)nitramine (2)
Experimental Section
2
-(Methylamino)ethanol (3.76 g, 50.0 mmol) was slowly added to a
All chemicals were used as supplied (Acros Organics, AppliChem,
Riedel-de-Haën, Sigma–Aldrich, VWR).
suspension of nitric acid (100%, 4.17 mL, 100 mmol), acetic anhy-
dride (12.3 g, 120 mmol) and zinc chloride (300 mg, 2.20 mmol),
while the temperature was kept around 0 °C. After the addition was
complete the solution was stirred for 1 h at room temperature and for
30 min at 40 °C. The pale yellow solution was poured onto cracked
NMR spectra were recorded using a JEOL ECX 400 spectrometer. The
measurements were conducted in regular glass NMR tubes at 25 °C.
All chemical shifts are given in ppm relative to the external standards
1
13
tetramethylsilane ( H, 400.2 MHz; C, 100.6 MHz) and nitromethane ice (25 g) and the resulting colorless precipitate was filtered off,
N, 28.9 MHz). As additional internal standards the reference values washed with water (2 ϫ 20 mL) and dried on air. Yield: colorless
14
(
1
1
of the partially deuterated solvent impurity ( H) and the fully deuter-
crystalline solid (4.24 g, 25.7 mmol, 51%). H NMR ([D
Data analysis was performed using δ = 4.87 (m, 2 H, CH ), 4.27 (m, 2 H, CH ), 3.47 (s, 3 H, CH
]acetone): δ = 70.8 (CH ), 50.7 (CH ), 39.9 (CH
]acetone): δ = –23 (NNO ), –38 (ONO
ATR unit with neat samples. Transmittance values are qualitatively = 3043 (w), 3004 (w), 2967 (w), 2883 (w), 1728 (w), 1627 (m), 1613
6
]acetone):
1
3
[34]
ated solvent ( C) were used.
2
2
3
).
).
[
35]
13
1
the MestReNova software.
IR spectra were recorded using a Perki-
C{ H} NMR ([D
6
2
2
3
1
4
nElmer BX FT IR spectrometer on a Smiths DuraSamplIR II diamond
N NMR ([D
6
2
2
). IR (ATR): ν
Z. Anorg. Allg. Chem. 2011, 2135–2141
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2139

D. Izsák, T. M. Klapötke
ARTICLE
(
m), 1501 (s), 1476 (w), 1454 (m), 1440 (m), 1412 (m), 1386 (w), [12] W. D. S. Motherwell, G. P. Shields, F. H. Allen, Acta Crystallogr.,
Sect. B 2000, 56, 466–473.
1
1
365 (m), 1337 (m), 1269 (s), 1241 (s), 1170 (w), 1117 (w), 1072 (w),
039 (w), 1018 (s), 974 (w), 887 (s), 861 (s), 759 (s), 711 (m) cm .
–
1
[13] K. Brandenburg, Diamond 2.1c, Crystal Impact GbR, Bonn, Ger-
many, 1999.
Raman (300 mW): ν = 3043 (23), 3028 (27), 3004 (54), 2971 (100),
888 (13), 2851 (8), 1632 (22), 1523 (9), 1503 (9), 1448 (20), 1417
25), 1388 (22), 1366 (12), 1335 (10), 1301 (9), 1280 (33), 1238 (42),
172 (57), 1075 (13), 1040 (33), 1022 (9), 973 (28), 898 (16), 860
[
14] CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: +44-
223-336033; E-Mail: deposit@ccdc.cam.ac.uk).
2
(
1
1
[
15] F. H. Allen, O. Kennard, D. G. Watson, L. Brammer, A. G. Orpen,
R. Taylor, J. Chem. Soc. Perkin Trans. 2 1987, S1–S19.
–1
+
(62), 817 (68), 713 (17), 639 (23), 605 (21) cm . MS (DEI ): m/z = [16] a) M. C. Etter, J. C. MacDonald, J. Bernstein, Acta Crystallogr.,
+
+
165.0 (10) [M ], 103.0 (25) [M
–
NO
65.10 g·mol ): C 21.97 (21.82), H 4.18 (4.27), N 25.18 (25.45)%.
= 31 °C, T = 180 °C. Sensitivities: Edr Ͼ 35 J, F = 120 N,
el = 0.6 J.
3
]. EA (C
3
H
7
N
3
O
5
,
Sect. B 1990, 46, 256–262; b) J. Bernstein, R. E. Davis, L. Shi-
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1
1
573.
17] J. Halfpenny, R. W. H. Small, Acta Crystallogr., Sect. B 1978, 34,
452–3454.
18] M. Su c´ eska, Test Methods for Explosives, Springer, New York,
Berlin, Heidelberg, 1995.
19] http://www.bam.de/de/index.htm.
DTA: T
E
m
d
r
[
[
[
3
Acknowledgement
[20] a) NATO Standardization Agreement 4489, September 17, 1999;
b) WIWeB-Standardarbeitsanweisung 4–5.1.02, November 8,
2
002.
Financial support of this work by the Ludwig-Maximilian University
of Munich (LMU), the U.S. Army Research Laboratory (ARL), the
Armament Research, Development and Engineering Center (ARDEC),
the Strategic Environmental Research and Development Program
[
21] a) NATO Standardization Agreement 4487, August 22, 2002; b)
WIWeB-Standardarbeitsanweisung 4–5.1.03, November 8, 2002.
22] Reichel & Partner GmbH, http://www.reichel-partner.de/.
23] Impact: insensitive Ͼ 40 J, less sensitive Ն 35 J, sensitive Ն 4
J, very sensitive Ն 3 J; Friction: insensitive Ͼ 360 N, less sensi-
tive = 360 N, sensitive Ͻ 360 N and Ͼ 80 n, very sensitive Յ
80 n, extremely sensitive Յ 10 N; According to: Recommenda-
tions on the Transport of Dangerous Goods, Manual of Tests and
[
[
(SERDP) and the Office of Naval Research (ONR Global, title: “Syn-
thesis and Characterization of New High Energy Dense Oxidizers
(HEDO) – NICOP Effort” under contracts W911NF-09–2-0018
(ARL), W911NF-09–1-0120 (ARDEC), W011NF-09–1-0056 (AR-
th
DEC) and 10 WPSEED01–002 / WP-1765 (SERDP) is gratefully ac-
knowledged. 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 Su c´ eska (Brodarski Institute, Croatia) in the development
of new computational codes to predict the detonation and propulsion
parameters of novel explosives. We are indebted to and thank Dr. Betsy
M. Rice and Dr. Brad Forch (ARL, Aberdeen Proving Ground, MD)
and Mr. Gary Chen (ARDEC, Picatinny Arsenal, NJ) for many helpful
and inspired discussions and support of our work. Dr. Jörg Stierstorfer
is thanked for computational work and Mr. Stefan Huber for per-
forming the sensitivity tests.
Criteria, 4 edition, United Nations, New York, Geneva, 1999.
[
24] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A.
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Characterization of the Energetic Plasticizer Methyl-NENA
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
2141