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New Journal of Chemistry
Journal Name
μm). IR (ATR), ṽ (cm−1) = 3329 (m), 3156 (w), 3051 (w), 2801
ARTICLE
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Conclusions
DOI: 10.1039/C8NJ05266B
Our findings are important for a reliable approach towards
facile accumulation of nitro functionalities at the pyrazole
platform. C-nitrations at the 4,4-bipyrazole (1), were
(w), 1639 (w), 1549 (m), 1512 (m), 1478 (m), 1400 (s), 1334
(vs), 1298 (s), 1260 (m), 1228 (m), 1212 (m), 1167 (m), 1100
(m), 995 (m), 945 (w), 871 (w), 847 (s), 834 (s), 764 (m), 685
(vs), 629 (m), 604 (m), 587 (m), 546 (w), 518 (vw). Raman
(1064 nm, 200 mW, 25 °C): ṽ (cm−1) = 1640 (31), 1562 (5),
1544 (7), 1426 (11), 1399 (100), 1390 (13), 1340 (11), 1299
(5), 1265 (9), 1227 (6), 1210 (10), 947 (9), 833 (15), 754 (5),
performed
environmentally benign reaction conditions. The step-wize
nitration causes significant change increasing impact
under
very
simple,
cost-effective
and
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sensitivity and density and therefore energetic performance.
Compounds 2–4 are especially promising intermediates, while
exhibiting excellent thermal stability and low sensitivity
towards external stimuli. Moreover, compounds 5 and 6 can be
already classified as explosive materials showing excellent
1
519 (2), 360 (4), 316 (3), 270 (6), 237 (5), 209 (28). H NMR
(d6-DMSO, 400 MHz, ppm) δ = 14.27 (br, 1H), 10.34 (br, 1H),
8.31 (s, 1H). 13C NMR (d6-DMSO, 101 MHz, ppm) δ = 153.2,
149.0, 134.4, 103.5, 102.6. 14N NMR (d6-DMSO, 29 MHz,
ppm) δ = −24. 15N NMR (d6-DMSO, 41 MHz, ppm) δ = −20.3,
−25.8, −82.8, −121.9, −170.5. Anal. Calcd for C6H3N6O6: C
26.78, H 1.12, N 36.43 %. Found: C 26.82, H 1.23, N 36.15 %.
m/z (DEI+): 269 (4) [M]+, 239 (14), 223 (31), 93 (34), 77 (100).
thermals
stability
and
good
sensitivities.
Further
functionalization of the 4,4-bipyrazole scaffold is currently
under investigation in our laboratories.
3,3,5,5-Tetranitro-4,4-bipyrazole (6): Fuming HNO3 (43.7
mL, 98%, d = 1.501 g cm-3) was added to a warm solution of 1
(8.04 g, 60 mmol) in 91% H2SO4 (350 mL, d = 1.820 g cm-3).
The mixture was placed into pre-heated oil bath and the clear
solution formed was stirred at 98-100 oC (bath temperature) for
8 h. After cooling, the mixture containing colorless solid
Conflicts of interest
There are no conflicts to declare.
Acknowledgements
reaction product was poured into 1.2 kg of crushed ice and left Financial support of this work by the Ludwig-Maximilian
o
overnight at 5-10 C. Crystalline deposit of 6H2O (18.32 g, University of Munich (LMU) and the Office of Naval Research
92%) was filtered, washed with 40 mL of ice water and dried. It (ONR) under grant no. ONR.N00014-16-1-2062 is gratefully
was purified by crystallization from boiling water (45.0 g per 1 acknowledged. We thank Dr. Burkhard Krumm for NMR
L). The compound crystallizes as monohydrate 6H2O from a measurements and Stefan Huber for his help with the sensitivity
variety of wet solvents (alcohols, ethylacetate, aceton, 1,4- testing.
dioxane etc.). Anhydrous material
6 was obtained by
crystallization from hot 1,2-dichlorobenzene (3.0 g per 1 L).
6H2O: Colorless prisms. DTA (5 °C min−1): 115 °C (H2O),
292 °C (melt.), 298 °C (exo.); BAM: drop hammer: 9 J (100–
500 μm); friction tester: 324 N (100–500 μm); ESD: 0.40 J
(100–500 μm). IR (ATR), ṽ (cm−1) = 3619 (w), 3520 (w), 3096
(w), 2954 (w), 2352 (w), 1844 (vw), 1574 (m), 1544 (s), 1512
(s), 1488 (s), 1421 (s), 1352 (s), 1329 (s), 1310 (s), 1288 (m),
1215 (m), 1198 (w), 1022 (m), 1004 (m), 951 (w), 839 (vs), 814
(m), 798 (m), 772 (m), 691 (m), 643 (vw), 613 (vw), 589 (vw),
514 (w). Raman (1064 nm, 200 mW, 25 °C): ṽ (cm−1) = 1660
(7), 1565 (5), 1423 (4), 1400 (100), 1370 (4), 1313 (2), 1289
(2), 1226 (9), 1200 (2), 1007 (2), 829 (16), 756 (4), 590 (4), 374
(2), 269 (4). 1H NMR (d6-DMSO, 400 MHz, ppm) δ = 10.07 (s,
2H). 13C NMR (d6-DMSO, 101 MHz, ppm) δ = 149.7, 101.0.
14N NMR (d6-DMSO, 29 MHz, ppm) δ = −18. 15N NMR (d6-
DMSO, 41 MHz, ppm) δ = −25.9, −114.8. Anal. Calcd for
C6H2N8O8H2O: C 21.70, H 1.21, N 33.74 %. Found: C 21.89,
H 1.46, N 33.57 %.
6: Colorless needles. DTA (5 °C min−1): 292 °C (melt.), 298
°C (exo.); BAM: drop hammer: 4.5 J (100–500 μm); friction
tester: 192 N (100–500 μm); ESD: 0.30 J (100–500 μm). IR
(ATR), ṽ (cm−1) = 3740 (vw), 3208 (m), 2967 (w), 1567 (s),
1519 (vs), 1482 (s), 1416 (s), 1348 (s), 1320 (vs), 1274 (w),
1207 (m), 1018 (w), 994 (m), 842 (vs), 758 (m), 744 (m), 712
(m), 675 (m), 635 (m), 580 (w), 518 (m). Anal. Calcd for
C6H2N8O8: C 22.94, H 0.64, N 35.67 %. Found: C 23.04, H
0.85, N 35.66 %.
Notes and references
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