Synthesis of energetic polynuclear and polymeric nitroazole systems

Article abstract of DOI:10.1134/S1070427209100048

Interaction of cyanuric chloride and its mono and dichloro derivatives with ammonium or sodium 4-nitro-1,2,3-triazolates and polymer-analogous transformations of tetrazole-containing polymers were used to synthesize polynuclear systems and macromolecular

Full text of DOI:10.1134/S1070427209100048

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 10, pp. 1769−1775.  Pleiades Publishing, Ltd., 2009.
Original Russian Text  V.N. Kizhnyaev, F.A. Pokatilov, L.I. Vereshchagin, O.N. Verkhozina, T.L. Petrova, A.G. Prodaikov, G.V. Ratovskii, O.V. Tyukalova, 2009,
published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 10, pp. 1616−1622.
STUDIES IN THE FIELD OF CHEMISTRY OF NITRO COMPOUNDS
(TO 100TH BIRTHDAY ANNIVERSARY OF S. S. NOVIKOV)
Synthesis of Energetic Polynuclear
and Polymeric Nitroazole Systems
V. N. Kizhnyaev, F. A. Pokatilov, L. I. Vereshchagin, O. N. Verkhozina, T. L. Petrova,
A. G. Prodaikov, G. V. Ratovskii, and O. V. Tyukalova
Irkutsk State University, Irkutsk, Russia
Received April 29, 2009
Abstract—Interaction of cyanuric chloride and its mono and dichloro derivatives with ammonium or sodium
4-nitro-1,2,3-triazolates and polymer-analogous transformations of tetrazole-containing polymers were used to
synthesize polynuclear systems and macromolecular compounds with heterocyclic structures bearing explosophoric
groups.
DOI: 10.1134/S1070427209100048
In development of high-efficiency formulations
of solid-propellant, explosive, and gas-generating
formulations, particular attention is to be given to
polynitrous heterocyclic compounds, whose application
promise is determined by their high enthalpies of
formation, thermal stability, resistance to mechanical
shocks, and comparatively large content of nitrogen.
The increase in the energetic characteristics of these
compounds is favored by introduction of nitro groups
and other explosophoric substituents into heterocyclic
fragments [1–3]. Fairly promising energetic products
are polynuclear heterocyclic systems containing in their
structure nitro groups in addition to triazole, tetrazole, and
1,3,5-triazine rings. The results of syntheses of substances
of this kind are reflected in our communication.
radical polymerization of the corresponding monomer as
it was done in [9].
We synthesized 2,4,6-tri(4-nitro-1,2,3-triazol-
1-yl)-1,3,5-triazine as follows. To a solution of
a triethylammonium salt produced from 1.14 g (10 mmol)
of 4-nitro-1,2,3-triaziole and 1.02 g (10mmol) of
triethylamine in 10 ml of acetone was added dropwise at
room temperature 0.61 g (3mmol) of cyanuric chloride in
15 ml of acetone. The reaction mixture was agitated for
1 h and poured into 100 ml of cold water. The precipitate
was filtered off and dried in air. Yield 1.5 g, mp > 350°C.
IR spectrum, ν, cm–1: 1560 (NO2). 13C NMR spectrum, δ,
ppm, DMSO: 160.5 (3C-2,4,6 of triazine), 153.6 (3C-4
of triazole), 124.7 (3C-5 of triazole).
Similarly, we obtained 2-(4-nitro-1,2,3-triazol-1-yl)-
4,6-dimethoxytriazine from 1.4 g (8 mmol) of 2-chloro-
4,6-dimethoxytriazine, 1 g (8.8 mmol) of triethylamine in
10 ml of acetone. Yield 0.6 g (30%), mp 122–124°C. IR
spectrum, ν, cm–1: 1219 (–O–), 1565 (NO2), 1603 (C=N
of heteroring). 13C NMR spectrum, δ, ppm, DMSO: 173.2
(C-6 of triazine), 160.5 (2C-2,4 of triazine), 153.6 (2C-
4 of triazole), 124.7 (2C-5 of triazole), 56.6 (C, CH3).
Found: C 28.95, H 1.03, N 46.24. С8Н5N11O5. Calculated:
C 28.66, H 1.49, N 45.97.
EXPERIMENTAL
Commercial cyanuric chloride of 99.5% purity was
used in the study. Its derivatives, 2,4-dichloro-6-methoxy,
2-chloro-4,6-dimethoxy-, 2,4-dichloro-6-diethylamino-
, 2-chloro-4,6-diaethylamino-, and 2-chloro-4,6-
dimorpholino-1,3,5-triazines, were synthesized using the
procedures reported in [4, 5]; 4(5)-nitro-1,2,3-triazole,
3-nitro- and 3-azido-1,2,4-triazoles, their N-chloromethyl
derivatives, and chloromethyl methylnitramine were
synthesized by the methods described in [6–8]. Poly-
5-vinyltetrazole (PVT) (M = 5  105) was produced by
We synthesized 2-(4-nitro-5-phenyl-1,2,3-triazol-1-
yl)-4,6-dimethoxy-1,3,5-triazine from 0.87 g (5 mmol)
of 2-chloro-4,6-dimethoxytriazine, 1 g (5.3 mmol) of
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KIZHNYAEV et al.
4-nitro-5-phenyl-1,2,3-triazole, and 0.59 g (5.3 mmol)
of triethylamine in 10 ml of acetone. Yield 0.75 g (47%),
mp 142–144°C. IR spectrum, ν, cm–1: 1600 (Ph), 1565
(NO2). 13C NMR spectrum, δ, ppm, DMSO: 173.2 (2C-
4,6 of triazine), 163.1 (C-2 of triazine), 151.5 (C-4 of
triazole), 130.3 (C-p of Ph), 129.1 (C-o of Ph), 126.3 (C-i
of Ph). Found: C 46.72, H 3.02, N 31.11. C13H11N7O4.
Calculated: C 47.42, H 3.34, N 29.79.
copper (2+) and nickel (2+) ions were produced by
pouring together, under agitation, aqueous-acetonitrile
solutions of nitrotriazole or its equimolar mixture of PVT
and a metal chloride in a solvent at room temperature. The
precipitates formed were washed with water to remove
unreacted salts and nitrotriazole. The precipitates obtained
in systems containing a polymer were additionally
treated with hot DMFA to remove homo complexes of
nitrotriazole with metal ions. The share of the fraction
soluble in DMFA did not exceed 3–4 wt % relative to
the total yield of metal complexes. The precipitates were
filtered off and dried in a vacuum to constant mass. The
composition of the products obtained was calculated from
elemental analysis data.
We synthesized 2,4-di(4-nitro-1,2,3-triazol-1-yl)-6-
methoxy-1,3,5-triazine as follows. To a solution of 0.5 g
(2.5 mmol) of 2,4-dichloro-6-methoxytriazine and 0.7 g
(6.1 mmol) of 4(5)-nitro-1,2,3-triazole in 10 ml of acetone
was added in portions, at 25°C under agitation, 0.51 g
(0.61 mmol) NaHCO3 in 1 ml of water. The mixture was
agitated for 2 h, allowed to stay overnight, and poured
into 50 ml of cold water. The precipitate was filtered of
and dried in air. Yield 0.62 g (69%), mp 131–133°C. IR
spectrum, ν, cm–1: 1219 (–O–), 1565 (NO2), 1603 (C=N
of heteroring). 13C NMR spectrum, δ, ppm, DMSO: 173.2
(C-6 of triazine), 160.5 (2 C-2,4 of triazine), 153.6 (2
C-4 of triazole), 124.7 (2 C-5 of triazole), 56.6 s (CH3).
Found: C 28.95, H 1.03, N 46.24. C8H5N11O5. Calculated:
C 28.66, H 1.49, N 45.97.
The density of the polymers was found pycnometrically
[10]. Potentiometric measurements were made with an
EV-74 ion meter. 13C NMR spectra were recorded with
a Varian VXR-500S spectrometer (working frequency
126 MHz) in acetone and DMSO, with signals of their
methyl groups serving as the internal standard (29.5
and 39.5 ppm, respectively). IR spectra were recorded
on Infralum FT-801 and Specord M-80 instruments in
Vaseline oil on KBr glasses. The elemental analysis was
made on a FLASH BA 1112 Series CHN-analyzer. The
reactions were monitored by TLC on plates with a fixed
Silufol UF 254 layer, hexane–ethyl acetate as eluent,
development with iodine vapor.
In similar way we obtained 2,4-di(4-nitro-1,2,3-
triazol-1-yl) from 0.5 g (2.3 mmol) of 2,4-dichloro-6-
diethylaminotriazine, 0.52 g (4.5 mmol) of 4(5)-nitro-
1,2,3-triazole, and 0.38 g (4.5 mmol) of NaHCO3 in
10 ml of acetone and 1 ml of water. Yield 0.63 g (75%),
mp 206–208°C (from DMFA–ethanol). IR spectrum, ν,
cm–1: 1560 (NO2). 13C NMR spectrum, δ, ppm, DMSO:
163.2 (C-6 of triazine), 159.2 (2C-2,4 of triazine), 152.3
(2C-4 of triazole), 123.8 (2C-5 of triazole), 41.5 (2C,
CH2), 12.5 (2C, CH3). Found: С 35.11, H 3.44, N 44.21.
C11H12N12O4. Calculated: C 35.11, H 3.19, N 44.68.
As a starting compound for formation of polynuclear
systems serves 4-nitro-1,2,3-triazole (I), whose synthesis
and properties are reflected in a recently published review
[1]. Exhibiting properties of an N–H acid, nitrotriazole
(I) interacts with bases to give salts and, in the form of
a triazolate anion, reacts as a nucleophile with various
electrophilic reagents to give N-substitution products.
This property was used in synthesis of 4-nitro-1,2,3-
triazole-containing 1,3,5-triazines by reacting chloro-
substituted triazines with nitrotriazole (I) in a basic
medium (Scheme 1).
PVT was alkylated with chloromethyl derivatives of
triazoles and methylnitramine with an equimolar amount
of the corresponding alkylating agent gradually added
to a 1.5 M solution of a triethylammonium salt of PVT
in DMFA, with the reaction mixture then agitated at
a temperature of 60°C for 6 h. The resulting polymeric
products were precipitated into acidified water, washed
with distilled water, and dried in air at room temperature.
The samples obtained were washed with diethyl ether in
a Soxhlet apparatus and dried in a vacuum to constant
mass.
As demonstrated by experiments, cyanuric chloride
(II) actively reacts with three moles of nitrotriazole
(I) in an aqueous–acetone solution at 20–25°C in the
presence of sodium hydrocarbonate or triethanolamine
to give tris(4-nitro-1,2,3-triazolyl)-1,3,5-triazine (III).
Substitution of chlorine in 2,4-dichloro-6-methoxy- (IVa)
and 2-chloro-4,6-dimethoxy-1,3,5-triazines (Va), and
also in 2,4-dichloro-6-diethylamino-1,3,5-triazine (IVb),
requires a prolonged reaction. As a result, mono- (VIa,
Metal complexes of 4(5)-nitro-1,2,3-triazole and
mixed triazole-tetrazole polymeric complexes with
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SYNTHESIS OF ENERGETIC POLYNUCLEAR
1771
Scheme 1.
IV, VII: R = OM (a), R = N(Et)2 (b); V: R = OM (a), R = N(Et)2 (b), R = N(CH2)2O (c); VI: R = OM,
R1 = H (a), R = OM, R1 = Ph (b).
163 ppm. Signals characteristic of the C5 carbon atom are
observed at 122–124 ppm, and signals of the C4 carbon
atom of the triazole ring bonded to a nitro group, at
around 153.5 ppm. Thus, 13C NMR spectroscopic data
demonstrate that nitrotriazole moieties exist in the
polynuclear systems we isolated, supposedly in the
(4-nitro-1,2,3-triazol-1-yl)-isomeric form.
VIb), and di(nitrotriazolyl)triazines (VIIa, VIIb) are
formed. 2-Chloro-4,6-diethylamino-1,3,5-triazine (Vb)
and 2-chloro-4,6-dimorpholino-1,3,5-triazine (Vc) could
not at all be introduced into a reaction with nitrotriazole
(I), even with sodium hydroxide used as a base. Probably,
the presence of two amino groups in compounds Vb, Vc
substantially diminishes the mobility of the chlorine atom
in position 6 of the triazine ring.
Nitrotriazole (I) in the form of a triazolate anion can
react as a nucleophile with macromolecular electrophilic
reagents having at their backbone substituents capable
of substitution under the action of nucleophilic reagents.
For example, the reaction of halogen substitution in vinyl
chloride moieties has been used to synthesize highly
energetic nitrotriazole-tetrazole–containing polymeric
products, which cannot be obtained by polymerization.
These copolymers VIII have been obtained by reacting
sodium 4-nitro-1,2,3-triazolate with a copolymer of
vinyl chloride with 2-methyl-5-vinyltetrazole in DMFA
at 120–150°C [11] (Scheme 2).
Reactions of substitution of the chlorine atom in the
triazine ring with nitrotriazole moieties can yield isomeric
compounds via formation of a C–N bond involving
various nitrogen atoms of the triazole ring. However,
the reaction, as a rule, predominantly yields one of
isomers, which is isolated by fractional crystallization of
the reaction products. This is also confirmed by spectral
studies of the polynuclear compounds obtained.
The IR spectra of the nitro compounds obtained, VIa,
VIb and VIIa, VIIb, show absorption bands related to
stretching vibrations of the nitro group (1565 cm1) and
stretching-deformation vibrations of C=N bonds of the
heterorings (1603 cm–1). The 13C NMR spectra show
signals characteristic of nuclei of the triazine rings bound
to the methoxy group at 171–173 ppm and signals of
carbons having nitrotriazole rings as substituents at 159–
In contrast to the low-molecular-weight polynuclear
compounds considered above, the copolymers obtained
contain two isomeric vinylnitrotriazole monomer units.
The ratio between the isomeric fragments characterized
in 1H NMR spectra by signals at 9.1 (H4) and 8.59 ppm
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KIZHNYAEV et al.
Scheme 2.
Scheme 3.
(H5) (5-nitro-1,2,3-triazol-1-yl isomer and 4-nitro-1,2,3-
triazol-1-yl isomer, respectively) is 1 : 3.
1,2,4-triazole, and methylnitramine as alkylating
electrophilic agents. We used the reaction on Scheme
3 to synthesize N-substituted tetrazole-containing
polymeric products bearing nitroazole and other
energetic moieties as substituents from polymer IX. The
conditions and results of the reaction are listed in Table 1.
Under the chosen conditions, the degree of substitution
did not exceed 85%, i.e., the resulting polymeric products
(Xa–Xd) are copolymers containing monomer units of
substituted and unsubstituted 5-vinyl-terazoe. Raising the
concentration of chloromethyl reagents and elevating the
process temperature resulted in that, already in the early
stages of the reaction, gelation leading to a decrease in the
Polymeric products combining nitrotriazole and
tetrazole moieties in their structure can synthesized
using another approach based on the ability of
compounds with N–H unsubstituted tetrazole rings
to form salts in interaction with bases and to react
in the form of a tetrazolate anion as a nucleophile
with various electrophilic reagents. The role of such
nucleophilic substrates can be played in the presence of
bases, e.g., triethylamine, by monomer units of poly-5-
vinyltetrazole (IX). In this study, we used chloromethyl
derivatives of nitro-1,2,3- and 1,2,4-triazoles, azido-
Table 1. Conditions and results of modification of poly-5-vinyltetrazole. Poymer : alkylating agent = 1 : 1, DMFA, 60°C, 6 h
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SYNTHESIS OF ENERGETIC POLYNUCLEAR
1773
degree of substitution of tetrazole units in the modification
product was observed in the system.
(Table 1). Owing to the amphoteric nature of N–H-
unsubstituted tetrazole ring, the starting polyvinyltetrazole
(IX) is soluble in all of the liquids mentioned above.
Most of its modification products lose the ability to be
dissolved and acquire a property of limited swelling.
Possibly, this is due to side processes of “cross-linking”
of macromolecular chains, with nitro and azido groups
involved. The possibility of substitution of these groups
in the triazole ring with the tetrazolate anion was found
for reactions involving model compounds, N-substituted
nitro and azido triazoles, in which only nitro and azido
groups are subject to nucleophilic substitution. The
involvement of these groups in the substitution reactions
could be reliably confirmed only for systems in which
NaI was used as a catalyst. However, occurrence of
side reactions involving nitro and azido groups cannot
be fully ruled out under the conditions of the reaction
of alkylation of polyvinyltetrazole (IX) without
a catalyst, because the number of intermacromolecular
“cross-links,” which can lead to loss of solubility by
a polymeric sample is within the error of their analytical
determination.
The structure of polymeric products formed in
modification of polymer IX was confirmed by spectral
methods and results of potentiometric titration. The
IR spectra of samples Xc, Xd contain high-intensity
absorption bands at 1300–1310 and 1550–1560 cm–1,
associated with symmetric and antisymmetric vibrations
of the nitro group, and a band at 830–840 cm–1, related
to its deformation vibrations. Strong bands at 1515
and 1520 cm–1 are associated with vibrations of,
respectively, 1,2,4- and 1,2,3-triazole rings containing
a nitro group. The IR spectrum of sample Xb shows
a strong absorption band at 2140 cm–1, related to
antisymmetric vibrations of the azide group, and a band
at 1530 cm–1, characterizing vibrations of the triazole
ring. As a rule, the absorption bands of the tetrazole
ring at 1500–1540 cm–1 have low intensity and are
overlapped with neighboring high-intensity bands. The
broad high-intensity bands in the IR spectrum of sample
Xa at 1265, 1295, and 1540 cm–1 are due to symmetric
and antisymmetric vibrations of the nitramine group,
and vibrations of the tetrazole ring are characterized
by a low-intensity absorption band at 1540 cm–1, and
vibrations of the tetrazole ring are characterized by
a low-intensity absorption band at 1540 cm–1.
The presence of residual monomer units with
N–H-unsubstituted tetrazole rings in modified poly-
vinyltetrazoles Xa–Xd favors manifestation of
polyelectrolyte properties by these samples and, in
particular, ability to swell in aqueous alkali solutions.
The reaction of alkylation of a 5-substituted tetrazole
ring in a basic medium always yields two isomeric
1,5- and 2,5-disubstituted products [12]. A similar
pattern was also observed in alkylation of a polymeric
substrate IX with chloromethyl derivatives of triazoles
and nitramines. For example, the presence of two
signals from the carbon atom of the tetrazole ring, with
chemical shifts of 167.8 and 163.0 ppm, and two signals
from carbon atoms of the methylene bridges connecting
the triazole and tetrazole rings, at 62.67 and 57.6 ppm,
indicates that the macromolecule contains two isomeric
1,5- and 2,5-disubstituted tetrazole rings. The triazole
ring is characterized by a singlet with a chemical shift
of 157.0 ppm, related to the signal of a cyclic carbon
bonded to the nitro group, and by a doublet at 148.3 ppm,
associated with the cyclic CH moiety. To the hydrocarbon
backbone correspond broadened signals at 37 and 30 ppm,
associated with the CH and CH2 groups.
One more way to combine tetrazole and nitrotriazole
moieties in a polymeric structure consists in that N–H-
unsubstituted derivatives of tetrazole and 1,2,3-triazole
to be involved in complexation reactions with metal ions.
For example, polyvinyltetrazole (IX) directly forms,
upon mechanical mixing of solutions of the polymer and
copper and nickel chlorides at room temperature, salt-like
complexes with Cu2+ and Ni2+ ions of composition L :
M2+ = 2 : 1, in which tetrazolate anions acts as a ligand
(L) [13]. It was found that nitrotriazole I behaved in about
the same way in reactions with copper and nickel salts to
give ionic complexes of similar composition exclusively
with nitrotriazolate ligands (Table 2). According to
elemental analysis data, the metal complexes contain no
chlorine. In contrast to polymeric tetrazole-containing
complexes, which are insoluble in organic solvents and
water, products of reactions with nitrotriazole are soluble
in DMFA. Taking into account that tetrazole- and triazole-
containing compounds similarly behave in reactions
with metal salts and the acidity constants of these N–H
acids are close {pKa of nitrotriazole (I) is 4.8 [14], and
The resulting N-substituted polyvinyltetrazoles
(Xa–Xd) are uncolored powder-like substances with
a comparatively high density and limited solubility
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KIZHNYAEV et al.
Table 2. Complexation of 4(5)-nitro-1,2,3-triazole (I) and its 1 : 1 mixture with poly-5-vinyltetrazole (IX) with metal salts
(MCl2)
pK0 of polyvinyltetrazole (IX) is 4.65 [11]}, we made an
attempt to form mixed metal complexes simultaneously
containing tetrazolate and nitroazolate ligands. By mixing
aqueous-acetonitrile solutions of 1 : 1 mixtures of the
polymer and nitrotriazole with solutions of copper and
nickel chlorides, we obtained, in nearly quantitative
yield, insoluble colored powder-like products containing
no elementary chlorine according to elemental analysis
data (Table 2).
CONCLUSIONS
(1) Various energetic polynuclear and polymeric
compounds bearing nitro groups were synthesized on the
basis of 4(5)-nitro-1,2,3-triazole.
(2) A method for “linking” of nitrotriazole rings
to macromolecular compounds by introduction of
anchor electrophilic groups capable of reacting with
nucleophilic moieties of polymers into triazole rings
was developed.
An analysis of the IR spectra of the compounds
synthesized demonstrated that products formed an
equimolar mixture of a tetrazole-containing polymer (IX)
and nitrotriazole (I) contains both types of heterorings.
This is indicated by the presence of absorption bands
characteristic of model homo complexes of, respectively,
polyvinyltetrazole and nitrotriazole with Cu2+ and Ni2+
ions. To the absorption by the nitrotriazolate moiety
belong bands at 1650–1655, 1240–1255, 1290–1295,
and 825–830 cm–1, associated with various kinds of
vibrations of the nitro group, and the absorption band
of the nitroazolate anion at 1535 cm–1. Vibrations of
the tetrazolate ring give rise to the absorption band
at 1060 cm–1 (other bands related to vibrations of
tetrazole and triazole rings in the IR spectra coincide in
frequency). Taking into account the aforesaid, elemental
analysis data, and absence of solubility in the products
synthesized, we can suggest that a macromolecular
compound containing in their structure fragments of
a “mixed” metal complex of composition (L1 + L2) :
M2+ = 2 : 1 (Scheme 4).
(3) It was shown that nitrotriazole and tetrazole
moieties can be combined in the structure of a polymeric
compound via the reaction of joint complexation of
nitrotriazole and a tetrazole-containing polymer with
metal ions.
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