Nitrogen-rich polymers based on 5-bromo-1-vinyl-1H-tetrazole

Article abstract of DOI:10.1002/ejoc.200901226

Nitrogen-rich, polymers with contents of nitrogen between 50 and 60 % were synthesized by radical polymerization using 1 - ( 1 -vinyl-1H-tetrazol-5-yl) hydrazine and 1-methyl-1-( 1 -vinyl-lH-tetrazol-5-yl)hydrazine. The monomers were ob-tained by substitu

Full text of DOI:10.1002/ejoc.200901226

FULL PAPER
DOI: 10.1002/ejoc.200901226
Nitrogen-Rich Polymers Based on 5-Bromo-1-vinyl-1H-tetrazole
Thomas M. Klapötke*[a] and Stefan M. Sproll[a]
Keywords: Nitrogen heterocycles / Nitrogen-rich compounds / Tetrazole / Polymers / Polymerization
Nitrogen-rich polymers with contents of nitrogen between 50
and 60% were synthesized by radical polymerization using
1-(1-vinyl-1H-tetrazol-5-yl)hydrazine and 1-methyl-1-(1-
vinyl-1H-tetrazol-5-yl)hydrazine. The monomers were ob-
tained by substitution reactions of hydrazine derivatives and
5-bromo-1-vinyl-1H-tetrazole. Moreover, the poly-1-(1-vinyl-
1H-tetrazol-5-yl)hydrazine was converted into the corre-
sponding 5-azidotetrazolyl-containing polymer by the reac-
tion with sodium nitrite. The polymers were characterized
by measurements of the molecular weights, by vibrational
spectroscopy (IR) and elemental analysis. The thermal sta-
bility was determined by differential scanning calorimetry
and the sensitivity towards friction and impact were deter-
mined by BAM standards. The energetic properties were in-
vestigated by bomb calorimetric measurements and calcula-
tions with the EXPLO5 software. The high stability of the
polymers towards impact and friction, along with their suf-
ficient thermal stability (175–279 °C) and moderate energetic
characters renders these polymers into promising compounds
for an application as environmently friendly nitrogen-rich
polymers.
to be a versatile starting material. Since the intention of
this work was the synthesis of nitrogen-rich polymers, only
hydrazine and monomethylhydrazine were used.
Introduction
Tetrazoles claim an outstanding place among the group
of nitrogen-rich heterocycles. Their high content of nitrogen
along with a high thermal stability predestined them as
valuable building blocks for new energetic compounds.[1]
Besides their usage for military or civil explosives,[2] they
cover a wide field of applications ranging from pharmaceu-
ticals[3] over biomedical applications[4] and membranes[5] to
antifoggants in photographic materials.[6] Moreover, with a
content of nitrogen of 79% of 1H-tetrazole, these heterocy-
cles are promising candidates for environmentally friendly
propellants.[7]
Although tetrazoles are a well-investigated group of het-
erocycles, the number of polymers containing these hetero-
cycles is small. The first polymers based on tetrazoles were
1-poly(vinyltetrazole) and 1-poly(vinyl-5-aminotetrazole).[8]
Today, several approaches to synthesize 1-poly(vinyltetraz-
ole) are known, either by radical polymerization of 1-poly-
(vinyltetrazole)[8] or by the conversion of polyvinylnitrile
into the tetrazole moiety by a [2+3] cycloaddition reaction
with hydrazoic acid.[9] The disadvantage of these polymers
is their extremely low solubility in any solvent, preventing
them from any application. Therefore, they are used as co-
polymers with polystyrene.[10]
To further improve the energetic characteristics, the con-
version of polyvinyl tetrazolylhydrazine into the corre-
sponding 5-azidotetrazole-containing polymer was investi-
gated. The investigation of the physical stabilities of the
small number of known alkylated 5-azidotetrazoles proves
these energetic materials as very dangerous compounds
(sensitivity towards friction: Ͼ 5 N, sensitivity towards im-
pact: Ͼ 0.15 J).[11] Despite their high sensitivity towards
physical stress, their thermal stability (up to 170 °C) turns
these compounds into interesting building blocks for nitro-
gen-rich polymers. In the case of 5-azido-1H-tetrazole-con-
taining polymer, the long carbon chains of the polyvinyl
moiety could work as a protection against physical stress,
turning this polymer into a very interesting nitrogen-con-
taining polymer.
Results and Discussion
For the synthesis of 5-bromo-1-vinyl-1H-tetrazole (1),
the corresponding 5-bromo-1-(2-hydroxyethyl)tetrazole (2),
reported by Bayes,[12] proved to be a suitable starting mate-
rial (Scheme 1).
In order to convert the hydroxyethyl group into the de-
sired vinyl group, several approaches were investigated. The
idea was the elimination of the hydroxy group, leading to
the formation of the desired vinyl group. A conversion of
the hydroxy group into the corresponding chlorinated com-
pound, as reported in literature for 1-(2-hydroxyethyl)-5-
amino-1H-tetrazole by Finnegan[13] and a subsequent elimi-
In order to improve their solubility and thus the applica-
tion of these polymers, the introduction of hydrazine moie-
ties was investigated. 5-Bromo-1-vinyltetrazole (1) proved
[a] Department of Chemistry and Biochemistry, University of
Munich (LMU),
Butenandtstr. 5-13, 81377 München, Germany
Fax: +49-89-2180-77492
E-mail: tmk@cup.uni-muenchen.de
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T. M. Klapötke, S. M. Sproll
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form the corresponding bromide by the reaction of 8 with
hydrobromic acid formed during the substitution reaction,
than compound 10 (Scheme 3).
Scheme 1. Synthesis of 2.
nation by potassium hydroxide proved not to be efficient,
due to a halogen exchange at the 5-position of 2 along with
side products, resulting in alkaline hydrolyses of the bro-
mine atom. Taking these results into account, two methods
for the preparation of 1 were developed. Method A
(Scheme 2) avoids the halogen exchange at the 5-position
by a bromination instead of the chlorination of the hydroxy
group by using PBr3 in dimethylformamide.[14] The follow-
ing elimination of the bromine atom was undertaken by tri-
ethylamine with a yield of 50%. In order to improve the
resulting overall yield of 21%, the hydroxy group was con-
verted into the corresponding tosylate by the reaction of
tosylchloride with 2 in dichloromethane[15] (method B,
Scheme 2). The yield of the tosylation with 80% exceeded
the yield of the bromination of the hydroxy group by 40%.
The elimination of the tosyl group of 7 by triethylamine at
100 °C gave higher yields (57%) than the elimination of the
bromine (Scheme 2). The overall yield of method A (21%)
could be improved to 46% in the case of method B.
Scheme 3. Synthesis of the nitrogen-rich monomers 8 and 10.
Besides the polymerization of the tetrazolylhydrazine, an-
other method for the synthesis of nitrogen-rich polymers
based on 1 would be a polymerization of 1 and a subse-
quent substitution of the bromine atom by a polymer ana-
logue reaction. Trials to polymerize 1 by using AIBN in
bulk at 80 °C resulted in a deflagration of 1 after 5 to
10 min in three of four experiments. Beside the radical poly-
merization in bulk, a radical polymerization in different sol-
vents and anionic and cationic polymerization in solution
were carried out, but only yielded starting material.
The polymerization of 8 and 10 was carried out in bulk
by using AIBN. A polymerization in solution only yielded
starting materials, like the experiments of the polymeriza-
tion of 1 in solution. Therefore, the polymerization had to
be performed in bulk at 90 °C. The AIBN had to be added
carefully in several steps over 15 min, because an addition
of more than 60 mg of AIBN resulted in a rise of tempera-
ture and a subsequent deflagration of 8 or 10. One problem
of the polymerization turned out to be the hydrazine moi-
ety. The hydrogen atoms act as radical interceptors, leading
to short chains along with starting material. To obtain a
complete conversion, several portions of AIBN had to be
added over 15 min (Scheme 4). Nevertheless, the yield of
the polymerization of 8 (25%–30%) was much lower than
the yield of the polymerization of 10 (85%). An explanation
could be the loss of the vinyl moiety at higher temperatures
along with a decomposition initiated by the AIBN.
Scheme 2. Synthesis of 5-bromo-1-vinyl-1H-tetrazole (1).
In order to increase the nitrogen content of the mono-
mer, the bromine atom was substituted by hydrazine and
methylhydrazine.[12b] The experiments showed that the for-
mation of the products 8 and 10 is dependent on the reac-
tion conditions. In contrast to the formation of 10, which
was performed at 60 °C, the formation of 8 was only pos-
sible at ambient temperature. Applying the same conditions
as for the synthesis of 10 resulted in a loss of the vinyl
group and only yielded 5-tetrazolylhydrazine 9. Moreover,
the purification of 8 was difficult, because of its high solu-
bility in water, along with a hygroscopic character. Beside
the impurities of water and hydrazine, 8 was more likely to Scheme 4. Polymerization of 8 and 10.
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Nitrogen-Rich Polymers Based on 5-Bromo-1-vinyl-1H-tetrazole
The investigation of the average molecular masses (Mn) is zig-zag-like along the y-axis. The structure is stabilized
of 11 and 12 showed the expected difference. Whereas the by an intermolecular interaction of the bromine atom with
polymer formed by the polymerization of 8 possessed a one oxygen atom of the tosyl moiety (Figure 2). The dis-
value for Mn corresponding to 10 molecular formulas in tance between the bromine atom and the oxygen atom O2
one chain, the polymer of 10 was much longer (about is found to be 3.0006(14) Å. The distance between a bro-
100 molecular formulas per chain). This effect can be ex- mine atom and an oxygen atom without any interactions
plained by the acidic NH-proton of 8 acting more efficiently is reported as 3.37 Å.[17] The distance found in the crystal
as a radical interceptor of the NH2-protons. Moreover the structure is by 12% shorter than the distance without inter-
shorter chains can also be explained by impurities of water action, allowing the assumption of an intermolecular bro-
or hydrazine, being always present in the samples of 8 along mine–oxygen interaction.
with the slow decomposition of 8 at increased temperature.
In order to further increase the nitrogen content of the
polymer, the hydrazine moiety was converted into an azide
group. The conversion of 11 to the corresponding 5-azido-
1H-tetrazole-containing polymer (13) was carried out by
the reaction of sodium nitrite and the hydrazine moiety in
2 HCl. Being not soluble in aqueous media, a suspension
of 11 in the hydrochloric acid was used. To ensure a com-
plete conversion, an excess of sodium nitrite was applied
(Scheme 5).
Figure 1. Molecular structure of 7. Thermal ellipsoids are drawn
at the 50% probability level.
Scheme 5. Synthesis of 13.
The analysis of 13 showed a partial decomposition of
the tetrazolylhydrazine moieties. The determination of the
average molecular weight Mn was undertaken by GPC. One
problem was the insolubility even in DMF. The determi-
nation of Mn was carried out with the soluble parts of the
polymer whereas the insoluble parts were dismissed (insolu-
ble parts: ca. 15%). Using an IR and UV 275 nm detector
the average Mn was determined to be 1400 g/mol, corre-
sponding to ten monomers in a chain. The elemental analy-
sis (different charges of the polymer varied only little),
along with the average molecular weight, allowed an esti-
mated formula of C37H56N51O10. The calculated formula
for a chain of ten monomers (C30H30N70) differs signifi-
cantly from the experimentally obtained one. The main dif-
ferences are the reduced content of nitrogen and the in-
Figure 2. Intermolecular interaction of the bromine atom with the
oxygen atom O2.
creased content of oxygen. The reduced content of nitrogen
can be explained with a partial decomposition of the hy-
drazine and tetrazole moiety yielding amine-containing
parts. Taking this assumption into account, the oxygen con-
Compound 1 crystallizes in the orthorhombic space
tent can be explained by a nitration of the formed amines, group Pnma with four molecular formulas per unit cell
yielding primary or secondary nitramines, besides other im- (Figure 3). The geometry of the molecule is planar, allowing
purities. The nitro groups can be detected in the IR spectra the assumption, that the π-system is delocalized over the
of 13. Beside the strong vibration of the azide group around whole molecule. The molecules form zig-zag chains along
2100 cm–1, the commonly known vibrations of the nitro the x-axis, caused by intermolecular interactions of the bro-
group around 1600–1500 cm–1 and at 800 cm–1 can be inevi- mine atom and N4 of the tetrazole moiety (Figure 4). The
tably assigned.[16] The brown color of the polymer can be distance between Br1 and N4 in the crystal structure is
ascribed to the big amount of decomposition products, re- found to be 2.999(2) Å. The distance between a bromine
sults of the diazotization of the hydrazine moiety.
atom and a nitrogen atom without interactions is reported
Compound 7 crystallizes in the monoclinic space group to be 3.4 Å.[17] Due to the planar geometry of 1, the chains
P21/c with four molecular formulas per unit cell (Figure 1). form layers. Between these layers, no intermolecular interac-
The arrangement of the molecules in the crystal structure tions can be observed.
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T. M. Klapötke, S. M. Sproll
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C3 [D···A: 2.957(3) Å; ϽDHA: 124.9(17)°]. In addition to
the intramolecular hydrogen bridge, two other hydrogen
bridges are found. The first is formed by the first proton of
N6 to N4 and the second by the second proton of N6 to
N2 [D···A: 3.070(2) Å, 3.270(3) Å; ϽDHA: 158(2)°,
150(2)°; Figure 6]. The arrangement of the molecules leads
to a zig-zag pattern along the y-axis.
Figure 3. Molecular structure of 1. Thermal ellipsoids are drawn
at the 50% probability level.
Figure 5. Molecular structure of 7. Thermal ellipsoids are drawn
at the 50% probability level.
Figure 4. Intermolecular interactions of the bromine with N4 along
the x-axis.
Compound 10 crystallizes in the monoclinic space group
P21/n with four molecular forumulas per unit cell (Fig-
ure 5). The planar coordination geometry of N5 (the three
angles are 120° and the N6–N5–C1–N4 torsion angle is
found to be 177°) showing the sp2-hybridisation of the N5
nitrogen, with the free electron pair being part of the delo-
calized π-electron system of the molecule. The free electron
pair of N6 directly points towards the proton at C3 of the
vinyl groups. This finding leads to the assumption that N6
Figure 6. Inter- and intramolecular hydrogen bridges of 7. Thermal
forms an intramolecular hydrogen bridge to the proton at ellipsoids are drawn at the 50% probability level.
Table 1. Energetic properties of 11, 12 and 13.
11
12
13
GAP[j]
Molecular formula
Tdec [°C]
C31N56H65O2
203
1254
1.45
360
35
4460
23384
1754
C413N575H760O14
276
13990
1.45
360
C37N51H56O10
174
1375
1.45
160
(C3N3H5O)20
216
2000
1.3
360
7
–
–
Mn [gmol–1]
Density [g cm–3][a]
Sensitivity towards friction [N]
Sensitivity towards impact [J]
–∆Ucomb. [calg–1][b]
–∆Hcomb [kJmol–1][c]
∆fHm [kJmol–1][d]
Values calculated by EXPLO5 V5.02
–∆EUm° [kJkg–1][e]
TE [K][f]
45
7
4650
272630
–30
4464
25656
2962
–
2621
2015
154
7074
792
166
243
1160
1249
100
6005
764
126
234
4324
2957
173
7205
721
200
247
4444
2860
135
6629
738
195
248
pC–J [kbar][g]
D [ms–1][h]
Gas vol. [Lkg–1][i]
Is [s][k]
Is [s][l]
[a] Estimated from a structure determination. [b] Experimental (constant volume) combustion energy. [c] Experimental molar enthalpy
of combustion. [d] Molar enthalpy of formation. [e] Energy of explosion. [f] Explosion temperature. [g] Detonation pressure. [h] Detona-
tion velocity. [i] Assuming only gaseous products. [j] Obtained from the database of EXPLO5 V5.02. [k] Specific impulse (isobaric
combustion, chamber pressure 60 bar, frozen expansion). [l] Specific impulse of a mixture containing 75% ammonium dinitramide as
oxidizer.
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Nitrogen-Rich Polymers Based on 5-Bromo-1-vinyl-1H-tetrazole
towards heat and impact. Although we had no problems in synthe-
sis, proper protective measures (safety glasses, face shield, leather
coat, grounded equipment and shoes, Kevlar® gloves and ear
plugs) should be used when undertaking work involving these com-
pounds.
Comparing the values of ∆EUm° (an indication of the
work performed by the explosive) of the polymers, 13
showes the highest energetic properties, due to the 5-azido-
tetrazole moieties (11: –2621 kJkg–1, 12: –1160 kJkg–1 and
13: –4324 kJkg–1; Table 1). As expected, polymer 12 pos-
sesses the lowest energetic properties, due to the methyl
moiety stabilizing the tetrazolylhydrazine (∆EUm° only 25%
of ∆EUm° of 13). The energetic character of polymer 11 lies
General: All chemical reagents and solvents of analytical grade
were obtained from Sigma–Aldrich or Acros Organics and used as
supplied. All chemical reagents and solvents of analytical grade
between the ∆EUm° values of 12 and 13. The value of were obtained from Sigma–Aldrich or Acros Organics and used
as supplied. 2-(5-Bromo-1H-tetrazol-1-yl)ethanol (2) was prepared
according to Bayes.[12] 1H, 13C and 15N NMR spectra were re-
corded using a JEOL Eclipse 400 instrument. The spectra were
measured in [D6]DMSO, CDCl3 or D2O. The chemical shifts are
given relative to tetramethylsilane (1H, 13C) or nitromethane (15N)
as external standards. Coupling constants (J) are given in Hertz
(Hz). Infrared (IR) spectra were recorded using a Perkin–Elmer
Spectrum One FT-IR instrument and KBr pellets or NaCl plates
at room temperature. Raman spectra were recorded using Perkin–
Elmer Spectrum 2000R NIR FT-Raman instrument equipped with
∆EUm° is in the case of 13 almost equal to that of glycidyl
azide polymer (GAP, a common energetic binder). Another
important value for the evaluation of energetic characteris-
tics is the detonation velocity D. A comparison of these
values of polymers 11 to 13 shows, that polymer 11 and 13
exceed the detonation velocity of GAP by 400 ms–1 in case
of 11 and 600 ms–1 in the case of 13. The specific impulse,
an indication of the qualification as propellant, is only in
the case of 13 comparable with the value of GAP.
The thermal stability was determined by DSC measure- a Nd:YAG laser (1064 nm). The intensities are reported in percent-
ages relative to the most intense peak and are given in parentheses.
Elemental analyses were performed with a Netsch Simultaneous
Thermal Analyzer STA 429. Melting points were determined using
differential scanning calorimetry (Linseis DSC PT-10 instrument).
Measurements were performed at a heating rate of 5 °C min–1 in
closed aluminium containers with a hole (1 µm) on the top for gas
release with a nitrogen flow of 5 mLmin–1. The reference sample
was a closed aluminium container. The molecular weights were
measured by Fa. PSS, Mainz using a TSP P1000 HPLC pump with
1.0 mLmin–1 flow, a TSP AS3000 injection system with 50 µL vol-
ments. Polymer 12 possesses the highest thermal stability of
276 °C. Polymers 11 and 13 are in the range of GAP
(203 °C and 174 °C), whereas the decomposition point of
13 is about 30 °C lower than that of 11. The sensitivity
towards impact and friction was determined by BAM meth-
ods.[18] Polymers 11 and 12 proved to be insensitive towards
friction and less sensitive towards impact. Polymer 13 was
sensitive towards friction and sensitive towards impact. The
physical stability of polymers 11 and 12 is much higher than
that of GAP, whereas the values of 13 are in the same range. ume of injection and a Showdex Differentialrefractometer RI 71 as
detector. The analysis was done using PSS-WinGPC Unity Version
7.2. As column were used PSS-GRAM, 10 µm 30 Å, ID
8.0 mmϫ50 mm, PSS-GRAM, 10 µm 30 Å, ID 8.0 mmϫ300 mm,
PSS-GRAM, 10 µm 100 Å, ID 8.0 mmϫ300 mm and -GRAM,
10 µm 3000 Å, ID 8.0 mmϫ300 mm. DMF containing 0.01 
LiNO3 or DMSO containing 5 g L–1 was used as eluent. The cali-
bration was done using a polystyrene standard.
The difference of the sensitivity towards friction of 13 and
GAP can be explained by the consistency of the polymers
(solid in the case of 13, viscous oil in the case of GAP).
The advantage of polymer 13 is its comparable value of
∆EUm° with the value of GAP, along with a much higher
detonation velocity. Moreover, 13 is a solid, in contrast to
GAP, which has to be cured if applied as binder.
2-(5-Bromo-1H-tetrazol-1-yl)ethyl 4-Methylbenzenesulfonate (7): p-
Toluenesulfonyl chloride (18.0 g, 94 mmol), triethylamine (9.8 g,
98 mmol) and 4-(dimethylamino)pyridine (5.7 g, 47 mmol) were
added to a solution of 2-(5-bromo-1H-tetrazol-1-yl)ethanol (18.0 g,
94 mmol) in dichloromethane at 0 °C. After stirring for 3 h at am-
bient temperature, the reaction mixture was washed three times
with saturated ammonium chloride solution. The organic phase
was dried with sodium sulfate and the solvent was removed under
reduced pressure. The product was obtained as brownish solid
Conclusions
Three nitrogen-rich polymers were synthesized and char-
acterized. Poly-1-vinyl(5-hydrazinyl)-1H-tetrazole (11),
poly-1-vinyl(5–1-methylhydrazinyl)-1H-tetrazole (12) and
the 5-azido-1H-tetrazole-containing polymer (13) proved to
be moderate to good explosives along with sufficient ther-
mal and physical stabilities. Their content of nitrogen is lo-
cated between 50 and 60%, turning them into promising
materials for the development of new gas generating com-
positions. The synthesis of 11, 12 and 13 was carried out
using 5-bromo-1-vinyltetrazole 1 as starting material. The
polymers were investigated by vibrational spectroscopy (IR)
and the energetic properties were determined by bomb
calorimetric measurements. The polymers 11 and 12 are sol-
uble in DMSO and in acids.
(25.7 g, 74.3 mmol, 79%). m.p. 91 °C. IR (KBr): ν = 3977 (vw),
˜
2975 (vw), 2973 (vw), 1597 (w), 1454 (m), 1436 (m), 1412 (m), 1395
(m), 1355 (vs), 1293 (w), 1241 (w), 1190 (vs), 1177 (vs), 1135 (m),
1094 (m), 1052 (m), 1005 (s), 906 (s), 809 (m), 776 (m), 776 (s), 664
1
(s), 578 (m), 554 (s), 489 (w) cm–1. H NMR (CDCl3): δ = 2.42 (s,
3
3
3 H, CH3), 4.46 (t, J = 4.95 Hz, 2 H, CH2), 4.63 (t, J = 4.95 Hz,
3
3
2 H, CH2), 7.29 (d, J = 7.97 Hz, 2 H, CH), 7.61 (d, J = 8.25 Hz,
2 H, CH) ppm. 13C NMR (CDCl3): δ = 21.8 (CH3), 47.3 (CH2),
66.1 (CH2), 127.8 (CH), 130.3 (CH), 141.7 (Cq), 145.9 (Cqtetrazol
)
ppm. m/z (DCI+): 348.0 (10), 346.0 (10) (M), 284.1 (22), 282.1 (22),
240.1 (5), 238.1 (5), 198.1 (7), 175.2 (12), 171.1 (4), 155.1 (36), 131.2
(7), 91.1 (100), 90.2 (24), 89.2 (7), 65.2 (23), 63.2 (5), 39.1 (5).
C10H11BrN4O3S (347.19): calcd. : C 34.59, H 3.19; N 16.14; found
C 34.73, H 3.03, N 16.26: Friction sensitivity: Ͼ360 N; impact sen-
sitivity: Ͼ100 J.
Experimental Section
CAUTION! Tetrazoles, bromotetrazoles, tetrazolylhydrazines and
azidotetrazoles are highly energetic compounds with sensitivity
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T. M. Klapötke, S. M. Sproll
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5-Bromo-1-vinyl-1H-tetrazole (1): Benzenesulfonate
7
(10.3 g, tained as colorless solid after filtration (130 mg, 19%); dec. 203 °C.
29.3 mmol) was suspended in 20 mL of triethylamine and refluxed
for 4 h. After addition of 200 mL of 2 HCl, the aqueous phase
was then extracted 3 times with ethyl ether. The combined organic
phases were then extracted with 80 mL of 2 HCl, saturated so-
dium carbonate solution and 100 mL of brine. After removal of
the solvent in slightly reduced vacuum, the product was recovered
by sublimation from the dark brown residue and obtained as color-
less crystals (2.9 g, 17 mmol, 57%). m.p. 57 °C, dec. 136 °C. IR
IR (KBr): ν = 3431 (m), 3250 (m), 3086 (m), 2978 (m), 2926 (m),
˜
1608 (vs), 1520 (m), 1434 (m), 1402 (m), 1374 (m), 1337 (m), 1314
(w), 1262 (w), 1082 (m), 948 (vw), 879 (vw), 821 (vw), 804 (vw),
733 (vw), 697 (vw), 660 (vw). 553 (vw) cm–1. ([C3H6N6]x) calcd. C
28.57, H 4.80, N 66.64; found C 27.20, H 5.03, N 61.35. Friction
sensitivity: Ͼ360 N; impact sensitivity: Ͼ35 J.
Poly-1-vinyl(5–1-methylhydrazinyl)-1H-tetrazole (12): Hydrazine
derivative 10 (300 mg, 2.1 mmol) was molten at 78 °C and AIBN
(15 mg) was added carefully. Additional 15 mg of AIBN was added
two times over 20 min. After 4 h, the polymer was cooled to ambi-
ent temperature and washed with hot dichloromethane and 20 mL
of water. The polymer was obtained as colorless solid (260 mg,
(KBr): ν = 3128 (vw), 3100 (vw), 2944 (vw), 1734 (vw), 1638 (s),
˜
1424 (s), 1401 (s), 1373 (s), 1259 (w), 1227 (m), 1200 (w), 1108 (vs),
1053 (m), 1017 (m), 962 (w), 944 (m), 962 (m), 802 (w), 720 (vw),
1
669 (m), 637 (w), 550 (vw), 532 (vw) cm–1. H NMR (CDCl3): δ =
1
3
1
5.50 (d, J = 1.92, Jcis = 8.79 Hz, 1 H, CH2), 6.19 (d, J = 1.92,
87%); dec. 276 °C. IR (KBr): ν = 3430 (vs), 3341 (vs), 3225 (m),
˜
3Jtrans = 15.39 Hz, 1 H, CH2), 7.92 (dd, Jtrans = 15.39, Jcis
=
3
3
3010 (m), 2964 (m), 2927 (m), 2873 (w), 2801 (vw), 1646 (vw), 1554
(vw), 1412 (m), 1382 (m), 1323 (w), 1261 (m), 1216 (m), 1099 (m),
1040 (m), 987 (w), 909 (m), 802 (w), 735 (w), 693 (vw), 658 (vw),
617 (vw) cm–1. [C4H8N6]x (1254.23): calcd. C 34.28, H 5.75, N
59.97; found C 35.44, H 5.45, N 57.49. Friction sensitivity:
Ͼ360 N; impact sensitivity: Ͼ45 J.
8.79 Hz, 1 H, CH) ppm. 13C NMR (CDCl3): δ = 111.8 (CH2), 125.1
(CH), 131.9 (Cq) ppm. m/z (DCI+): 175.0 [M + H], 69. C3H3BrN4
(174.99): calcd. C 20.59, H 1.73, N 32.02; found N 31.82, C 20.92,
H 1.91. Friction sensitivity: Ͼ120 N; impact sensitivity: Ͼ35 J.
1-(1-Vinyl-1H-tetrazol-5-yl)hydrazine (8): Tetrazole
1
(2.0 g,
11.6 mmol) was dissolved in 20 mL of 2-propanol. Hydrazine mon-
ohydrate (2.3 g, 46.4 mmol) was added and the reaction mixture
stirred for 12 h. The formed hydrazinium hydrobromide was fil-
tered off and the solvent removed under reduced pressure. The
product was obtained as slightly impure oil, which solidified over
several hours (0.4 g, 3.2 mmol, 27%). m.p. 70 °C, dec. 207 °C. IR
5-Azido-1H-tetrazole-Containing Polymer (13): Poly-1-vinyl(5-
hydrazinyl)-1H-tetrazole (11) (200 mg) was suspended in 15 mL of
2  HCl. Saturated sodium nitrite solution was added dropwise at
0 °C over 10 min, until the formation of NO2 was observed. After
10 min, the solid was filtered off and washed with 200 mL of water.
The polymer was obtained as brown solid (120 mg, 60%); dec.
(KBr): ν = 3426 (vs), 2956 (m), 2918 (m), 2853 (w), 1645 (m), 1580
˜
174 °C. IR (KBr): ν = 3432 (vs), 2963 (w), 2929 (w), 2851 (vw),
˜
(m), 1393 (w), 1312 (vw), 1260 (w), 1168 (w), 1099 (m), 1017 (w),
2164 (m), 1697 (w), 1625 (m), 1531 (s), 1442 (w), 1384 (w), 1261
(w), 1177 (w), 1093 (m), 1020 (w), 803 (w), 721 (vw), 581 (vw), 523
(vw) cm–1. C37H56N51O10 (1375.19): calcd. C 32.32, H 4.10, N
51.95; found C 31.46, H 3.99, N 50.53. Friction sensitivity:
Ͼ160 N; impact sensitivity: Ͼ7 J.
1
972 (m), 800 (m), 735 (w) cm–1. H NMR ([D6]DMSO): δ = 4.55
(br. s, 2 H, NH2), 5.16 (d, 3Jcis = 8.91 Hz, 1 H, CH2), 5.70 (d, 3Jtrans
3
3
= 15.73 Hz, 1 H, CH2), 7.30 (dd, Jtrans = 15.73, Jcis = 8.91 Hz, 1
H, CH), 8.44 (s, 1 H, NH) ppm. 13C NMR ([D6]DMSO): δ = 105.6
(CH2), 126.6 (CH), 157.2 (Cq) ppm. m/z (DEI+): 126.2 [M] (18),
99.2 (43), 91.2 (9), 84.2 (18), 82.1 (11), 80.1 (11), 69.2 (10), 68.2
(15), 57.2 (17), 44.1 (15), 43.2 (100), 42.2 (53), 41.2 (18), 39.2 (11),
30.2 (11), 29.1 (24), 28.2 (76), 27.1 (17). C3H6N6·0.2HBr (126.12):
calcd. C 25.32, H 4.39, N 59.06; found C 24.94, H 4.70, N 59.37.
Friction sensitivity: Ͼ360 N; impact sensitivity: Ͼ50 J.
Table 2. Selected crystal data for 1, 7 and 10.
1
7
10
Formula
Mr [gmol–1]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C3H3BrN4
175.00
orthorhombic monoclinic
C10H11BrN4O3S C4H8N6
347.20
140.16
monoclinic
P21/n
1-Methyl-1-(1-vinyl-1H-tetrazol-5-yl)hydrazine (10): Tetrazole
1
Pnma
P21/c
(2.0 g, 11.6 mmol) was dissolved in 30 mL of 2-propanol. Mono-
methylhydrazine (1.1 g, 23.2 mmol) was added and the reaction
mixture was refluxed for 12 h. The solvent was removed under re-
duced pressure and the residue was washed with dichloromethane.
The residue was extracted using acetonitrile. After removal of the
solvent, the product was obtained as colorless solid (1.4 g,
7.4368(2)
6.4442(3)
11.8738(3)
90
6.9438(2)
26.6687(5)
7.6877(2)
90
7.1943(3)
12.6152(5)
7.8085(3)
90
β [°]
90
90
569.04(3)
4
113.713(3)
90
1303.43(6)
4
91.199(3)
90
708.53(5)
4
γ [°]
V [Å3]
9.9 mmol, 85%). m.p. 56 °C, dec. 203 °C. IR (KBr): ν = 3430 (s),
˜
Z
3341 (s), 300 (w), 2964 (m), 2927 (m), 2870 (w), 2801 (vw), 1646
(vs), 1554 (w), 1441 (m), 1421 (s), 1412 (s), 1323 (w), 1261 (m),
1216 (m), 1159 (m), 1099 (m), 1040 (m), 988 (w), 909 (m), 802 (m),
735 (m), 693 (vw), 661 (vw), 617 (vw) cm–1. 1H NMR ([D6]DMSO):
F(000)
336
2.043
7.11
53.99
696
1.769
3.323
54.00
296
1.314
0.13
52.00
ρcalcd. [gcm–3]
µ [mm–1]
2θ [°]
3
δ = 3.19 (s, 3 H, CH3), 5.03 (s, 2 H, NH2), 5.05 (d, Jcis = 8.91 Hz,
Index range
–9ՅhՅ9
–8ՅkՅ8
–15ՅlՅ15
0.71073
200(2)
–8ՅhՅ8
–34ՅkՅ34
–9ՅlՅ9
0.71073
200(2)
–8ՅhՅ8
–15ՅkՅ15
–9ՅlՅ9
0.71073
200(2)
3
3
1 H, CH2), 5.63 (d, Jtrans = 15.73 Hz, 1 H, CH2), 7.92 (dd, Jtrans
= 15.73, Jcis = 8.91 Hz, 1 H, CH) ppm. 13C NMR ([D6]DMSO):
3
δ = 44.3 (NCH3), 104.9 (CH2), 129.6 (CH), 157.2 (Cq) ppm. m/z
(DCI+): 141.2 [M], 87.1, 75. C4H8N6 (140.14): calcd. C 34.28, H
5.75, N 59.97; found C 34.41, H 5.80, N 59.76. Friction sensitivity:
Ͼ360 N; impact sensitivity: Ͼ100 J.
λ
T [K]
Reflections col-
lected
Unique reflections 678
7395
14131
2829
216
5187
1391
111
Parameter
58
Poly-1-vinyl(5-hydrazinyl)-1H-tetrazole (11): Hydrazine derivative 8
(700 mg, 5.5 mmol) was molten at 85 °C and AIBN (15 mg) was
added carefully. Additional 15 mg of AIBN was added two times
over 20 min. After 4 h, the polymer was cooled to ambient tem-
perature and washed with 20 mL of water. The polymer was ob-
S
Rint
1.154
0.0494
1.054
0.0312
0.978
0.0286
R1/wR2 [IϾ2σ(I)] 0.0197/ 0.0457 0.0347/0.0538 0.0731/0.1321
R1/wR2
0.0249/0.0516
0.0224/0.0496 0.0441/0.1160
1174
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 1169–1175

Nitrogen-Rich Polymers Based on 5-Bromo-1-vinyl-1H-tetrazole
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Crystal Structure Analysis: The crystallographic data were collected
using an Oxford Xcalibur3 diffractometer with a Spellman genera-
tor (voltage 50 kV, current 40 mA) and a Kappa CCD area detector
with graphite-monochromated Mo-Kα radiation (λ = 0.71073 Å).
The structure was solved by direct methods (SHELXS-97)[19] and
refined using SHELXL-97.[20] All non-hydrogen atoms were refined
anisotropically. ORTEP plots showing thermal ellipsoids with 50%
probability for the non-hydrogen atoms (Table 2).
[5] P. N. Gaponik, O. A. Ivashkevich, V. P. Karavai, A. Lesnikov-
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1,245,614, 1971.
CCDC-742853 (for 1), -742852 (for 7) and -742851 (for 10) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from the Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data request/cif.
[7]
T. M. Klapoetke, C. M. Sabate, Chem. Mater. 2008, 20, 3629–
3637.
Acknowledgments
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C. G. Miller, G. K. Williams, U. S. Patents 264982, 2007.
N. V. Tsarevsky, K. V. Bernaerts, B. Dufour, F. E. Du Prez, K.
Matyjaszewski, Macromolecules 2004, 37, 9308–9313.
T. M. Klapötke, S. M. Sproll, Eur. J. Org. Chem. 2009, 25,
4284–4289.
Financial support of this work by the Ludwig-Maximilians Uni-
versität (LMU) of Munich, the European Research Office (ERO)
of the U.S. Army Research Laboratory (ARL), the Armament Re-
search, Development and Engineering Center (ARDEC) and the
Strategic Environmental Research And Development Program
(SERDP) under contract numbers W911NF-09-2-0018 (ARL),
W911NF-09-1-0120 (ARDEC), W011NF-09-1-0056 (ARDEC)
and 10 WPSEED01-002/WP-1765 (SERDP) is gratefully acknowl-
edged. 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 Sucesca (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 Drs. Betsy M. Rice and Brad Forch (ARL, Aberdeen,
Proving Ground, MD) and Dr. Gary Chen (ARDEC, Picatinny
Arsenal, NJ) for many helpful and inspired discussions and support
of our work. We also thank Mr. Stefan Huber for sensitivity mea-
surements.
[9]
[10]
[11]
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a) D. E. Bayes, Eu. Patent EP011736 8A1, 1982; b) J. Heppe-
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J, sensitive Ͼ 4, very sensitive Ͼ 3 J; friction: insensitive Ͼ 360
N, less sensitive = 360 N, sensitive Ͻ 360 N Ͼ80 N, very sensi-
tive Ͻ 80 N, extremely sensitive Ͻ 10 N; according to the UN
Recommendations on the Transport of Dangerous Goods (+)
indicates: not safe for transport.
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[20] G. M. Sheldrick, SHELXS-97, Program for the Refinement of
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Received: October 28, 2009
Published Online: January 8, 2010
Eur. J. Org. Chem. 2010, 1169–1175
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1175