Synthesis of 1,3-bis(1,2,4-triazol-3-amino)-2,4,6-trinitrobenzene and its thermal and explosive behaviour

Article abstract of DOI:10.1039/b003139i

1,3-Bis(1,2,4-triazol-3-amino)-2,4,6-trinitrobenzene (BTATNB) has been synthesized by condensing 1,3-dichloro-2,4, 6-trinitrobenzene and 3-amino-1,2,4-triazole in dimethyl formamide (DMF) at 125 ± 2 °C. The product has been characterized by elemental analysis, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and mass spectrometry. The data on thermal and explosive properties indicate that BTATNB is slightly more thermally stable than 3-picrylamino-1,2,4-triazole (PATO). At the same time, it is safer towards impact and friction.

Full text of DOI:10.1039/b003139i

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Synthesis of 1,3-bis(1,2,4-triazol-3-amino)-2,4,6-trinitrobenzene and
its thermal and explosive behaviour
J. P. Agrawal,* Mehilal, U. S. Prasad and R. N. Surve
High Energy Materials Research L aboratory, Sutarwadi, PuneÈ411 021, India
Received (in Montpellier, France) 17th April 2000, Accepted 27th April 2000
Published on the Web 5th July 2000
1,3-Bis(1,2,4-triazol-3-amino)-2,4,6-trinitrobenzene (BTATNB) has been synthesized by condensing 1,3-dichloro-2,4,
6-trinitrobenzene and 3-amino-1,2,4-triazole in dimethyl formamide (DMF) at 125 ^ 2 ¡C. The product has been
characterized by elemental analysis, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and
mass spectrometry. The data on thermal and explosive properties indicate that BTATNB is slightly more thermally
stable than 3-picrylamino-1,2,4-triazole (PATO). At the same time, it is safer towards impact and friction.
Safety, reliability and stability are given prime consideration
when developing explosives and propellants. Of course, in
recent times, cost-e†ectiveness, eco-friendliness and the
hazards involved in demilitarization are also being given due
consideration, in addition to better explosive performance.1,2
The mechanical integrity of conventional explosive composi-
tions is disturbed by aerodynamic heating, thereby a†ecting
the performance of warheads and shells. In order to obviate
these shortcomings, there is a need to develop explosives with
high melting points and as a result, better stability.3
From an analysis of the structures of a large number of
thermally stable explosives reported so far in the literature,
Agrawal4 suggested that there are four general approaches to
impart thermal stability to explosive molecules, these being (i)
introduction of amino groups in aromatic nitro compounds,
(ii) condensation of triazole ring to aromatic nitro compounds,
(iii) salt formation and (iv) introduction of conjugation.
With the use of concept (ii), 3-picrylamino-1,2,4-triazole
(PATO) was synthesized by condensing picryl chloride with
3-amino-1,2,4-triazole5,6 or by condensing tetryl with 3-
amino-1,2,4-triazole.7 It was initially thought that PATO
would replace 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), a
well-known and the most thermally stable explosive,8,9 but its
performance is inferior to TATB. With these ideas in mind, a
new explosive molecule, 1,3-bis(1,2,4-triazol-3-amino)-2,4,6-tri-
nitrobenzene (BTATNB), not reported so far in the literature,
was conceived, designed and synthesized by the condensation
of 1,3-dichloro-2,4,6-trinitrobenzene with 3-amino-1,2,4-tri-
azole (Scheme 1).
In the present paper, we report the synthesis and character-
ization of BTATNB along with its thermal as well as explosive
properties. Furthermore, its properties have been compared to
those of PATO.
Experimental
Materials
1,3-Dichloro-2,4,6-trinitrobenzene10 (prepared from styphnic
acid by treatment with pyridine and phosphorus oxychloride),
m.p. 128È129 ¡C, and 3-amino-1,2,4-triazole11 (prepared by
condensing amino guanidine bicarbonate and formic acid),
m.p. 152È156 ¡C, were used as starting materials. Dimethyl-
formamide, SQ grade from Glaxo, was used as a solvent.
To a one-litre 4-necked round bottom Ñask, placed in an oil
bath and equipped with a mechanical stirrer, reÑux condenser
and thermometer pocket, 500 ml of dimethylformamide
(DMF) was transferred and 25 g (0.09 mole) of 1,3-dichloro-
2,4,6-trinitrobenzene was added slowly with stirring. After
this, 37 g (0.44 mole) of 3-amino-1,2,4-triazole was added
slowly over a period of 10 min with vigorous stirring. On
complete addition, the temperature of the reaction mixture
was raised to and maintained at 125 ^ 2 ¡C for 10 h. As the
BTATNB product is insoluble in the reaction medium, a pale
yellow solid started precipating slowly. The reaction mixture
was cooled down to ambient temperature and the product
was Ðltered on a Buchner funnel. It was washed thoroughly
with hot DMF and Ðnally with acetone, followed by drying.
The yield of BTATNB as pale yellow, free Ñowing crystals was
25.27 g (76%) and its melting point 319È321 ¡C (decomp.).
Characterization
The melting point was recorded on a Veego melting point
apparatus and is uncorrected.
Structural aspects. Elemental analysis was performed on a
Carlo Erba elemental analyzer, model EA 1108. The Fourier
transform infrared (FTIR) spectrum was recorded at room
temperature by the KBr matrix method on a PerkinÈElmer
FTIR spectrophotometer, model 1600. The 1H NMR spec-
trum was recorded with Bruker 90 MHz, model WG-90
spectrometer using sulfuric acid-d (97 ^ 1% sulfuric acid-
2
d
solution in D O, 99.5 ] atom% D, Acros, Belgium) as a
2
2
solvent and tetramethylsilane (TMS) as an internal standard.
The electron impact mass spectrum (EIMS) was recorded on a
Scheme 1
DOI: 10.1039/b003139i
New J. Chem., 2000, 24, 583È585
583
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double focussing JEOL-DS mass spectrometer at 70 eV
usingthe direct insertion technique.
data of BTATNB are given in Table 2. The FTIR spectrum of
BTATNB shows characteristic absorption bands at 3240,
3102, 2860, 1614, 1518 and 1324 cm~1.
Thermal and explosive properties. The deÑagration tem-
perature was determined by heating 0.02 g of the sample in a
glass tube in a WoodÏs metal bath12 at a heating rate of 5 ¡C
min~1. The temperature at which the sample ignited was
recorded as the deÑagration temperature. Di†erential thermal
analysis (DTA) was recorded on a DTA apparatus by heating
10 mg of the sample at a heating rate of 10 ¡C min~1, in the
presence of static air. The activation energy of decomposition
was determined by the Ozawa13 and Kissinger14 methods.
The impact sensitivity was determined by the fall hammer
method using a 2.0 kg drop weight and friction sensitivity on
a Julius PeterÏs apparatus by standard methods.15 The veloc-
ity of detonation16 (VOD) and detonation pressure17 (DP)
were calculated by methods reported in the literature.
The title compound is insoluble in almost all common
organic solvents, hence the only choice left to us was to record
the 1H NMR spectrum in deuterated sulfuric acid with
TMS as an internal standard. Since the D SO used for
2
4
recording the spectrum is not 100% deuterated, the residual
signal was also recognized at d 11.0 from the blank spectrum
and accordingly, chemical shifts of the remaining protons were
assigned. In the spectrum, there are only two sharp singlets at
d 9.63 and 9.37, which correspond to one picryl proton and
two C-5 protons of the triazole rings, respectively. A notice-
ably high deshielding e†ect could be attributed to the highly
polar solvent in which the spectrum was recorded and
involved hydrogen bonding. In the NMR spectrum, the
signals for the secondary NH protons are absent because of
rapid exchange with the acidic solvent. The chemical shifts
reported here are the results from two independent NMR
spectra recorded at di†erent time intervals and therefore,
support the chemical stability of the compound in D SO .
Results and discussion
Synthesis and structure
2
4
The molecular structure shown in Scheme 1 is also well-
supported by the IR, mass spectral and elemental analysis
data. (Values reported herein are the results of three indepen-
dent analyses).
The synthesis of the title compound requires a temperature of
125 ^ 2 ¡C and a period of 10 h, compared to 100 ¡C and 5 h
for PATO. PATO is soluble in DMF while the title com-
pound is insoluble in almost all common organic solvents.
Therefore, as the reaction proceeds, it starts precipitating in
the reaction medium and it is very difficult to recrystallise.
However, it was washed thoroughly with hot DMF to remove
any adhering impurities. Some physical properties of
BTATNB are given in Table 1. The compound has been char-
acterized by spectral data and elemental analysis. The spectral
The electron impact mass spectrum of BTATNB shows a
negligible abundance of the molecular ion peak at m/z 377.
The [M [ NO ]` ion at m/z 331 is characteristic of the
2
EIMS of nitroaromatic compounds. The low intensity ion at
m/z 314 probably arises from consecutive loss of NO and
2
OH radicals from the M` peak. The ion at m/z 286 is formed
as a result of the loss of 2NO with protonation while the loss
2
of 3NO with protonation produces an ion at m/z 240 from
2
Table 1 Some physical properties of BTATNB
M`. The ion at m/z 213 is the stable trinitrobenzene species.
The ion at m/z 91, which constitutes the base peak in the spec-
trum, arises most probably from the molecular ion by the loss
of 286 mass units. Another signiÐcant ion at m/z 83 corre-
sponds to the 3-imino-1,2,4-triazole ion.
Property
Value
Melting point/¡C
Density/g cm~3
Calcd.a
Exptl. (Ñotation method)
Particle size/lm
Decomp. at 325
2.03
1.98
6È7
Thermal and explosive properties
The title compound deÑagrates or ignites at 325 ¡C. The DTA
curve shows an exotherm at 320È321 ¡C, indicating a good
a Calculated density from ref. 18.
Table 2 Spectral data and elemental analysis of BTATNB
Peak/cm~1
Assignment
3240
3102
2860
1614
NH (stretching)
ArÈH (stretching)
N2CHÈN (triazole ring)
C2N (stretching)
1518 and 1324
1238
1100
NO (asym. and sym. stretching)
2
NÈN (stretching)
CÈN (ring bending)
980
N]O (stretching)
870
738
Penta-substituted benzene ring
NO (out-of-plane wagging
2
CH bending vibration)
1H NMR (D SO )
2
4
d
Assignment
9.37 (2H, s)
9.63 (1H, s)
CÈH protons of triazole ring
ArÈH proton
EIMS (70 eV) m/z
377, 331(7), 314(1.5), 286(100), 240(28),
213(32), 91(100), 83(52)
Elemental analysis
For C H N
Calcd. %
Found %
O (MW 377)
10
7 11 6
C 31.83, H 1.85, N 40.84
C 32.01, H 1.93, N 40.76
584
New J. Chem., 2000, 24, 583È585

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Table 3 Some thermal and explosive properties of BTATNB and
PATO
also thankful to Dr. A. K. Sikder for his valuable suggestions
during the spectral analysis.
Property
BTATNB
PATO
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DeÑagration temperature/¡C
DTA/¡C
325
320È321
(exotherm)
318
318
(exotherm)
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135.8
134.1
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50.43
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137
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Calc. DP/GPa
4
5
[36
[36
7609
29.8
7469
27.0
6
7
thermal stability of the compound. The activation energies of
decomposition (AED) of the title compound and PATO have
been determined by the Ozawa and Kissinger methods and
the data are given in Table 3. The results show that the activa-
tion energy of decomposition of BTATNB is higher than that
of PATO, suggesting that BTATNB is more thermally stable
than PATO. This is also supported by the higher deÑagration
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9
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temperature and T of 321 ¡C derived from the DTA curve.
max
The study on explosive properties of the title compound
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indicates that it is very insensitive towards impact and friction
(Table 3), being less sensitive to impact than PATO. The cal-
culated VOD and DP of BTATNB are 7609 m s~1 and 29.8
GPa while those of PATO are 7469 m s~1 and 27.0 GPa,
respectively. Thus, it is more energetic than PATO.
In conclusion, a comparison of the properties of BTATNB
and PATO indicates that BTATNB is a slightly more ther-
mally stable explosive than PATO. At the same time, it is also
more powerful and insensitive to impact.
Acknowledgements
The authors are thankful to Dr. Haridwar Singh, Director of
HEMRL, for permission to publish this work. The authors are
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