Synthesis and characterization of perfluorinated nitriles and the corresponding sodium 5-perfluoroalkyltetrazolate salts

Article abstract of DOI:10.1016/j.jfluchem.2008.09.007

The high-yield syntheses of trifluoroacetonitrile (1a), pentafluoropropionitrile (1b) and heptafluorobutyronitrile (1c) under mild reaction conditions using readily available starting materials (trifluoroacetamide, pentafluoropropionamide, heptafluorobutanamide) are described. Furthermore, the reactions of the perfluoroalkyl nitriles with sodium azide in acetonitrile forming sodium 5-trifluoromethyltetrazolate (2a), sodium 5-pentafluoroethyltetrazolate (2b) and sodium 5-heptafluoropropyltetrazolate (2c) were undertaken. The 5-perfluoroalkyltetrazolate salts were characterized using vibrational (Raman and infrared) and multinuclear (¹³C, ^14/15N, ¹⁹F) NMR spectroscopy, differential scanning calorimetry, mass spectrometry and elemental analysis. Additionally, the single crystal X-ray structure of the monohydrate of 2a was determined. Crystal data: 2a·H₂O: monoclinic, C2/m, a = 18.8588(6) A?, b = 7.1857(2) A?, c = 9.3731(3) A?, β = 102.938(3)°, V = 1237.94(7) A?³, Z = 8, D_calc = 1.911 g cm^-3.

Full text of DOI:10.1016/j.jfluchem.2008.09.007

Journal of Fluorine Chemistry 129 (2008) 1199–1205
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Synthesis and characterization of perfluorinated nitriles and the corresponding
sodium 5-perfluoroalkyltetrazolate salts
*
Margaret-J. Crawford, Thomas M. Klapo¨tke , Hendrik Radies
Department of Chemistry and Biochemistry, Ludwig-Maximilian University of Munich, Butenandtstr. 5-13 (D), D-81377 Munich, Germany
A R T I C L E I N F O
A B S T R A C T
Article history:
The high-yield syntheses of trifluoroacetonitrile (1a), pentafluoropropionitrile (1b) and heptafluorobutyr-
onitrile (1c) under mild reaction conditions using readily available starting materials (trifluoroacetamide,
pentafluoropropionamide, heptafluorobutanamide) are described. Furthermore, the reactions of the
perfluoroalkyl nitriles with sodium azide in acetonitrile forming sodium 5-trifluoromethyltetrazolate (2a),
sodium 5-pentafluoroethyltetrazolate (2b) and sodium 5-heptafluoropropyltetrazolate (2c) were under-
taken. The 5-perfluoroalkyltetrazolate salts were characterized using vibrational (Raman and infrared) and
multinuclear (13C, 14/15N, 19F) NMR spectroscopy, differential scanning calorimetry, mass spectrometry
and elemental analysis. Additionally, the single crystal X-ray structure of the monohydrate of 2a was
Received 29 July 2008
Received in revised form 3 September 2008
Accepted 16 September 2008
Available online 25 September 2008
Keywords:
5-Perfluoroalkyltetrazolate
Vibrational spectroscopy
Multinuclear NMR spectroscopy
Differential scanning calorimetry
Mass spectrometry
˚
˚
˚
determined. Crystal data: 2aꢀH2O: monoclinic, C2/m, a = 18.8588(6) A, b = 7.1857(2) A, c = 9.3731(3) A,
3
˚
b
= 102.938(3)8, V = 1237.94(7) A , Z = 8, Dcalc = 1.911 g cmꢁ3
.
ß 2008 Elsevier B.V. All rights reserved.
Crystal structure
1. Introduction
One way to obtain literature known perfluorinated nitriles is
the reaction of the corresponding perfluorinated amide with
phosphorus pentoxide at a high temperature [10]. A second way to
synthesize trifluoroacetonitrile in high yields was developed by
Parker and is the reaction of a perfluorinated amide with a mixture
of pyridine and trifluoroacetic anhydride at ambient temperature.
In order to overcome the above mentioned difficulties, we
extended the second method (dehydration of the corresponding
perfluorinated acetamide) for the in situ synthesis of trifluor-
oacetonitrile to prepare other perfluorinated nitriles [11]. The
nitriles generated by this method were then reacted in situ with
sodium azide to yield the series of sodium 5-perfluoroalkylte-
trazolates presented in this study. Here we present the details of
the modified synthetic method for the high-yield synthesis under
mild conditions of these materials from readily available, low-cost
amides. In addition, the spectroscopic and analytic characteriza-
tion of the corresponding series of sodium 5-perfluoroalkylte-
trazolate salts is discussed.
Perfluoroalkyltetrazolates were first synthesized in the late
1950s by W.G. Finnegan via the [2 + 3] cylcoaddition of sodium
azide with the corresponding perfluorinated nitrile [1] and in the
following decade, the syntheses and properties of a large variety of
salts of new 5-perfluoroalkyltetrazolates were published [2–4].
Some of these materials have been characterized by spectroscopic,
analytical and structural methods and have also found pharma-
ceutical applications as analgesic or an anti-inflammatory agents
[5,6].
5-Perfluoroalkyltetrazoles and their derivatives are not only of
interest to the pharmaceutical industry, but also for defense
applications as fluorine-rich components of magnesium-based
decoy flares. In this context, a more thorough investigation of the
properties of these materials was undertaken. However, the
synthesis of tetrazoles bearing an electron-withdrawing substi-
tuent such as a NO2 group is often complicated since hazardous or
inaccessible starting materials or side products are involved [7–9].
In particular, the perfluorinated nitriles required for the synthesis
of the 5-perfluoroalkyltetrazolates reported in this work are toxic,
difficult to obtain commercially and very expensive.
2. Results and discussion
2.1. Synthesis
The nitriles were synthesized by the drop-wise addition of a
mixture of pyridine and trifluoroacetic anhydride to the corre-
sponding perfluorinated amides (trifluoroacetamide, pentafluor-
* Corresponding author. Tel.: +49 89 2180 77491 fax: +49 89 2180 77492.
E-mail address: tmk@cup.uni-muenchen.de (T.M. Klapo¨tke).
0022-1139/$ – see front matter ß 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2008.09.007

1200
M.-J. Crawford et al. / Journal of Fluorine Chemistry 129 (2008) 1199–1205
Table 1
Crystal data and structure refinement for sodium 5-trifluoromethyltetrazolate
monohydrate.
Compound name
Sodium 5-trifluoromethyltetrazolate
monohydrate
Chemical formula
Formula weight (g molꢁ1
CSD deposit no.
Crystal size (mm)
Crystal system
C2H2F3N4NaO
178.07
)
419701
0.18 ꢂ 0.12 ꢂ 0.08
Monoclinic
C2/m
Space group
˚
a (A)
18.8588(6)
7.1857(2)
9.3731(3)
90
˚
b (A)
˚
c (A)
Scheme 1. Synthesis of perfluorinated nitriles 1a–c.
a
b
g
(8)
(8)
(8)
102.938(3)
90
3
˚
V (A )
1237.94(7)
8
Z
Dcalc (g cmꢁ3
(mmꢁ1
)
1.911
m
)
0.262
F (0 0 0), e
range (8)
Index ranges
704
u
3.92–26.50
ꢁ23 ꢃ h ꢃ 23
ꢁ9 ꢃ k ꢃ 9
ꢁ11 ꢃ l ꢃ 11
6556
Reflections collected
Reflections unique
Final R indicies (I > 2
R indicies (all data)
Goodness of fit (F2)
1376 (Rint = 0.0403)
R1 = 0.0342, wR2 = 0.0903
R1 = 0.0438, wR2 = 0.0962
1.079
s
(I))
Scheme 2. Synthesis of sodium 5-perfluoroalkyltetrazolates 2a–c.
Data/restraints/parameters
Large diff. peaks and hole
1376/1/132
0.364 and ꢁ0.461
opropionamide, heptafluorobutanamide) in pyridine solution at
room temperature. Addition of the pyridine–trifluoroacetic anhy-
dride mixture results immediately in the evolution of gas
(perfluorinated nitrile) and the reaction rate can therefore be
controlled by the rate of pyridine–trifluoroacetic anhydride
addition. The gas evolved was directly condensed into a cold trap
cooled by liquid nitrogen (Scheme 1).
The nitriles collected were then reacted with a suspension of
sodium azide in dry acetonitrile yielding the corresponding
sodium tetrazolate salts. These reactions were carried out at room
temperature. Compared to acetonitrile the reactivities of the
perfluorinated nitriles are higher, due to the electron-withdrawing
effect of the perfluorinated groups. Moreover, only the desired
products and no byproducts are observed. The water free
compounds obtained are very hygroscopic in consequence the
analytical data were collected as hydrates (Scheme 2).
2.2. Crystal structure
The molecular structure of 2a was determined using single
crystal X-ray diffraction. Crystals suitable for X-ray diffraction
were obtained by the slow evaporation of a solution of 2a in a
methanol at room temperature. The compound crystallized as a
monohydrate in the space group C2/m with 8 formula units in the
unit cell and a calculated density of 1.911 g cmꢁ3 at 200 K. The
asymmetric unit contains two crystallographically independent
ion pairs. The crystal and structure refinement data are given in
Table 1.
Fig. 1 shows an ORTEP plot of the distorted octahedral
coordination sphere of Na1 consisting of two water molecules
Fig. 1. ORTEP plot of 2aꢀH2O in the solid state showing the coordination sphere of the Na1 atom, with i = 1.5 ꢁ x, 0.5 + y, 2 ꢁ z; ii = 1.5 ꢁ x, ꢁ0.5 ꢁ y, 2 ꢁ z; iii = 1.5 ꢁ x, ꢁ0.5 + y,
2 ꢁ z; iv = x, ꢁ1 ꢁ y, z; = x, ꢁ1 + y, z; vi = 1 ꢁ x, y, 2 ꢁ z.
v

M.-J. Crawford et al. / Journal of Fluorine Chemistry 129 (2008) 1199–1205
1201
Fig. 2. ORTEP plot of 2aꢀH2O in the solid state showing the coordination sphere of the Na2 atom, with i = 1 ꢁ x, y, 2 ꢁ z; ii = 1 ꢁ x, ꢁy, 2 ꢁ z; iii = 1.5 ꢁ x, 0.5 + y, 2 ꢁ z;
iv = ꢁ0.5 + x, 0.5 + y, z; = x, ꢁy, z.
v
˚
˚
and four tetrazolate nitrogen atoms. The angles surrounding Na1
are between 80.44(6)8 (O1–Na1–N6(ii)) and 99.56(6)8 (O1–Na1–
N6). The sodium atoms form chains along the b-axis with the
sodium atoms connected via the O1 atoms, through the N1 atoms
and via a Na1–N6–N6–Na1 bridge.
The solid state structure of 2a shows two tetrazolate anions
with different coordination environments. One tetrazolate shows
the coordination of all ring N atoms to different sodium cations and
is shown in Fig. 1. Whereas, the N5 tetrazolate ring atoms show
coordination to Na2, the N6 atoms to Na1. The Na–N distances
range from 2.456(1) A to 2.666(2) A, whereas the Na1–O1 distance
˚
is shorter (2.403(1) A). Selected bond lengths and contact distances
for 2a are listed in Table 2.
Fig. 2 shows the coordination sphere of Na2 as an ORTEP plot.
The coordination sphere around Na2 can be described being
distorted trigonal bipyramid and comprises one water molecule
and four N atoms of four tetrazolates. The equatorial coordination
sites are occupied by one water molecule and the N2 and N3 atoms
of two tetrazolate anions. The N5 atoms of two further tetrazolates
occupy the axial coordination sites of Na2. The angles in the
Fig. 3. 13C NMR spectra in d6 DMSO of the perfluorinated tetrazolates (2a–c).

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M.-J. Crawford et al. / Journal of Fluorine Chemistry 129 (2008) 1199–1205
Table 2
Table 3
Selected bond lengths of substance 2a.
Computed isotropic magnetic shieldings (GIAO method [11,12], MPW1PW91/aug-
cc-pVDZ) and relative 14/15N NMR chemical shifts (ppm) referenced to MeNO2.
˚
˚
Distances (A)
Distances (A)
Abs.
Rel.
Exptl.
Na1–O1
Na1–N1
Na1–N6
Na1–Na1
Na2–O2
Na2–N2
Na2–N3
Na2–N5
Na2–Na2
C1–N4
2.403(1)
2.666(2)
2.456(1)
3.593(1)
2.373(2)
2.500(2)
2.429(2)
2.512(2)
4.091(2)
1.322(3)
1.332(3)
1.490(3)
C2–F2
C2–F1
C3–N5
C3–C4
C4–F4
C4–F3
N1–N2
N2–N3
N3–N4
N5–N6
N6–N6
1.306(3)
1.317(2)
1.327(2)
1.488(3)
1.316(4)
1.326(2)
1.342(3)
1.309(3)
1.343(3)
1.343(2)
1.315(3)
anisostropic
shielding
shift,
14N/15N,
d
(ppm)
d (ppm)
MeNO2
ꢁ116.7
ꢁ65.0
0
0/0
ꢁ
F3C–CN4
N (N1, N4Ring
N (N2, N3Ring
)
)
ꢁ52
ꢁ60/ꢁ60.0
+14/+13.6
ꢁ139.0
+22
ꢁ
ꢁ
F5C2–CN4
N (N1, N4Ring
N (N2, N3Ring
)
)
ꢁ66.0
ꢁ51
ꢁ57/ꢁ57.9
ꢁ139.0
+22
+14/+14.0
F7C3–CN4
N (N1, N4Ring
N (N2, N3Ring
)
)
ꢁ65.5
ꢁ51
ꢁ57/ꢁ57.3
C1–N1
ꢁ139.1
+22
+15/+14.3
C1–C2
equatorial plane are 122.08(8)8 (O2–Na2–N3), 126.62(8)8 (O2–
Na2–N2(i)) and 111.29(8)8 (N3–Na2–N2(i)). The N5–Na–N50 angle
is not 1808 as expected for a perfect trigonal bipyramid but slightly
distorted to 162.87(8)8.
Each tetrazolate anion, shown in Fig. 2, shows coordination
through N1 to two sodium atoms (Na1). In addition, the tetrazolate
acts as a bridge between two sodium atoms (Na2) with the N2 and
N3 tetrazolate ring nitrogen atoms. The O2 atom of the H2O
molecule, however, shows only coordination to one sodium atom
(Na2) in contrast to the O1 atom of the H2O molecule in Fig. 1
which bridges two Na cations.
observed which corresponds to the coupling of the ring carbon
atom with the neighboring CF3 group. For tetrazolate salts 2b and
2c, a triplet (25.4 Hz and 25.2 Hz) is observed instead which
corresponds to the coupling of the ring carbon atom with the
fluorine atoms of the neighboring CF2 group. The CF3 group
resonances appear as quartets at 123.8 ppm (2a), 119.5 ppm (2b)
and 118.3 ppm (2c) with coupling constants of 267.5 Hz, 285.4 Hz
and 287.3 Hz, respectively. Additionally, the pentafluoroethyl-
and heptafluoropropyltetrazolates show a small coupling of the
carbon atom of the CF3 group to the neighboring CF2 group. The
NMR spectrum of 2b shows, as expected, a triplet of quartets at
112.3 ppm for the CF2 group. The coupling constants are 248.2 Hz
1
2
2.3. NMR spectroscopy
for the JCF and 39.0 Hz for the JCF. Sodium 5-heptafluoropro-
pyltetrazolate shows a triplet of triplets at 114.2 ppm with a
coupling constant of 250.7 Hz and 30.9 Hz corresponding to the
CF2 group directly bonded to the tetrazole ring. In contrast, the
second CF2 group shows a triplet of sextets at 109.1 ppm (264.6 Hz
The sodium 5-perfluoroalkyltetrazolates (2a–c) were charac-
terized using 13C{1H}, 19F and 15N NMR spectroscopy.
Fig. 3 shows a comparison of the 13C{1H} NMR spectra of the
sodium 5-perfluoroalkyltetrazolates in d6 DMSO. The signal
corresponding to the tetrazolate ring carbon atom shifts with
increasing fluorine content of the organic group from 154.0 ppm
to higher field (152.8 ppm). For sodium 5-trifluoromethylter-
2
and 37.2 Hz) indicating simular JCF coupling constants to the
adjacent CF2 and CF3 groups.
The 19F NMR spectra show the signal corresponding to the CF3
group of sodium 5-trifluoromethyltetrazolate at ꢁ59.7 ppm,
whereas sodium 5-pentafluoroethyltetrazolate shows signals at
2
azolate, a quartet with a JCF coupling constant of 33.8 Hz is
Fig. 4. 13C{19F} NMR spectra of 2a in d6 DMSO with selective 19F decoupling.

M.-J. Crawford et al. / Journal of Fluorine Chemistry 129 (2008) 1199–1205
1203
Fig. 5. DSC-thermograms of 2a–c (endo up).
Table 4
From the DSC measurements it is evident that the decomposi-
tion points decrease from 310 8C for 2a to 254 8C for 2c as the
fluorine content increases. For 2a a dehydration temperature of
169 8C was observed. Dehydration of 2b occurs at 186 8C and for 2c
at 144 8C. In all cases the sodium salts were hygroscopic.
Additionally, the sensitivity data of the sodium salts (2a–c)
were collected and listed in Table 4.
Properties of sodium perfluoroalkyltetrazolate salts.
2a
2b
2c
Friction (N)
>360
>100
310
>360
>100
265
>360
>100
254
Impact (J)
Decomposition point (8C)
Dehydration point (8C)
169
186
144
The sodium 5-perfluoroalkyltetrazolate salts (2a–c) show no
sensitivity toward friction and impact.
ꢁ83.9 ppm (quartet) for the CF3 group and at ꢁ110.4 ppm (triplet)
for the CF2 group. Sodium 5-heptafluoropropyltetrazolate shows
signals at ꢁ80.6 ppm, ꢁ109.1 ppm and ꢁ127.2 ppm in the 19F NMR
spectrum corresponding to the CF3 group, the ring neighbored CF2
group and the central CF2 group.
3. Conclusion
Trifluoroacetonitrile, pentafluoropropionitrile and heptafluor-
obutyronitrile were obtained at controllable rates from the
corresponding perfluorinated amides via dehydration with a
pyridine/trifluoroacetic anhydride mixture.
The assignment of the 19F NMR and 13C NMR signals and 13C, 19
F
coupling constants for 2a–c is based on a series of selectivily 19F
decoupled 13C{19F} NMR spectra, which are shown in Fig. 4.
On irradiation of the frequency of the CF3 group the signal at
188.3 ppm collapses to a triplet with a coupling constant of 31.4 Hz
(spectrum B). Irradiation at ꢁ109 ppm (CF2 group bonded to the
tetrazole ring) eliminates the C–F coupling of the ring carbon atom
(spectrum C). Correspondingly irradiation at ꢁ127 ppm (central
CF2 group) causes the 13C NMR signal of the CF3 group to appear as
a quartet only. The 13C NMR experiments with selective 19F
irradiation confirm the assigment of the 13C NMR signals.
All sodium 5-perfluoroalkyltetrazolates show two signals in the
14/15N NMR spectra. The signal for the nitrogen atom N1 is
observed at ꢁ60 ppm (2a), ꢁ57.9 ppm (2b) and ꢁ57.3 ppm (2c),
and for N2 chemical shifts at 13.6 ppm (2a), 14.0 ppm (2b) and
14.3 ppm (2c). Assignments were made by comparison to 15N
spectra of sodium 5-nitrotetrazolate.
Sodium 5-trifluoromethyltetrazolate (2a), sodium 5-pentafluor-
oethyltetrazolate (2b) and sodium 5-heptafluoropropyltetrazolate
(2c) were prepared from sodium azide and the corresponding
nitriles in dry acetonitrile and were characterized using vibrational
(Raman, infrared) and NMR spectroscopy (13C, 14/15N and 19F), DSC
measurements, mass spectrometry and elemental analysis. Addi-
tionally, the single crystal X-ray structure of the monohydrate of 2a
was determined. Crystal data: 2aꢀH2O: monoclinic, C2/m,
˚
˚
˚
˚
b
a = 18.8588(6) A, b = 7.1857(2) A, c = 9.3731(3) A,
V = 1237.94(7) A , Z = 8,
= 102.938(3)8,
s .
= 1.911 g cmꢁ3
3
4. Experimental
Trifluoroacetamide was supplied by ABCR GmbH & Co.KG.
Pentafluoropropionamide and heptafluorobutyramide were
obtained from Apollo Scientific. Acetonitrile (analytical grade)
was supplied by Acros Organics and was dried over P4O10 and
freshly distilled before use. The remaining reagents were also
supplied by Acros Organics and were used as supplied.
In order to compute the 14/15N NMR chemical shifts for all three
anions, the isotropic magnetic shieldings were computed using
the GIAO (Gauge-Independent Atomic Orbital) method imple-
mented in G03 [12,13]. The NMR shielding tensors were
calculated at the MPW1PW91/aug-cc-pVDZ level of theory using
the GIAO method [13]. Table 3 summarizes the computed
isotropic magnetic shieldings and relative 14/15N NMR chemical
shifts (ppm) referenced to MeNO2.
The crystallographic data were collected using an Oxford
Xcalibur3 diffractometer with a Spellman generator (voltage
50 kV, current 40 mA) and a Kappa CCD area detector with
˚
a radiation (l = 0.71073 A). The
graphite-monochromated Mo K
data were collected using CRYSALIS CCD software [14] and
reduced with CRYSALIS RED [15]. The structure was solved by
direct methods (SHELXS-97) [16] and refined using SHELXL-97
[17]. Finally, the structure was checked using PLATON [18]. A
multi-scan empirical absorption correction using spherical
harmonics was applied using SCALE3 ABSPACK [19]. All non-
2.4. Properties
The DSC data (Fig. 5) provide a comparison between the sodium
salts of trifluoromethyl- (2a), pentafluoroethyl- (2b) and hepta-
fluoropropyltetrazolate (2c).

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M.-J. Crawford et al. / Journal of Fluorine Chemistry 129 (2008) 1199–1205
hydrogen atoms were refined anisotropically. The H1a and H1b
atoms were found from Fourier difference maps and freely
refined. The H2a atom was found Fourier difference maps and
(N1Ring). 19F NMR (376.5 MHz, d6 DMSO):
FAB–(C2F3N4ꢁ), m/z: 137.1 [M]ꢁ (100). IR (KBr):
(m), 1508 (s), 1417 (w), 1234 (vs), 1171 (vs), 1141 (vs), 1042 (s),
973 (w), 775 (w), 750 (m), 582 (w) cmꢁ1. Raman: (200 mW):
1516 (70), 1245 (13), 1177 (55), 1159 (31), 1054 (81), 996 (26), 754
(90), 422 (28), 394 (67), 171 (100) cmꢁ1
Anal. calcd. for
d
ꢁ59.7 (3F, s, –CF3);
3418 (s), 1642
y
˚
refined with the O2–H2a distance restrained to 0.9(5) A. All Ortep
y
plots show thermal ellipsoids with 50% probability for the non-
hydrogen atoms.
.
Further details of the crystal structure investigation may
be obtained from Fachinformationszentrum Karlsruhe, 76344
Eggenstein-Leopoldshafen, Germany (fax: +49 7247 808 666,
e-mail: crysdata@fizkarlsruhe.de, http://www.fiz-karlsruhede/
request_for_deposited_data.html) on quoting the appropriate
CSD number: 419701
NaC2F3N4ꢀ0.33H2O: C, 14.47; H, 0.40; N, 34.33. Found: C, 14.77;
H, 0.48; N, 34.34. Sensitivity data: friction > 360 N; impact >100 J.
4.4. Sodium 5-pentafluoroethyltetrazolate 2b
m.p.: –, dehydr. p.: 186 8C, decomp. p.: 265 8C. 13C NMR
1
2
The DSC data were obtained using a Linseis DSC PT10 in closed
(100.6 MHz, d6 DMSO): d 112.3 (tq, JCF = 248.2 Hz, JCF = 39.0 Hz,
1
2
aluminium containers with a hole (1
m
m) on the top for gas release
–CF2–CF3), 119.5 (qt, JCF = 285.4 Hz, JCF = 37.9 Hz, –CF3), 152.8 (t,
in a nitrogen atmosphere (nitrogen flow 5 mL/min). The used
heating rate was 5 8C/min. Additionally, the melting points were
also independently determined using Bu¨chi B-540.
2JCF = 25.4 Hz, CRing). 14N NMR (40.5 MHz, d6 DMSO):
d 14 (N2Ring),
ꢁ57 (N1Ring). 15N NMR (40.5 MHz, d6 DMSO):
14.0 (N2Ring), ꢁ57.9
d
(N1Ring). 19F NMR (376.5 MHz, d6 DMSO):
d
ꢁ83.9 (3F, t, 3JFF = 3.0 Hz,
The 13C, 14/15N and 19F NMR spectra were measured with a Jeol
Eclipse 400 spectrometer operating at 100.6 MHz for 13C, 40.5 MHz
for 15N and 376.5 MHz for 19F. Chemical shifts (in ppm) are given
–CF3), ꢁ110.4 (2F, q, JFF = 3.0 Hz, –CF2–CF3); FAB–(C3F5N4ꢁ), m/z:
3
187.1 [M]ꢁ (100). IR (KBr):
y 3423 (s), 1639 (w), 1486 (w), 1416 (w),
1342(s), 1342(s), 1210(vs), 1159(vs), 1086(m), 1067(m), 1040 (w),
975 (vs), 750 (m), 636 (w), 544 (w), 499 (w) cmꢁ1. Raman:
with respect to TMS (13C), MeNO2
external standards.
(
14/15N) and CFCl3
(
19F) as
(200 mW):
y 2943 (14), 1490 (75), 1344 (24), 1222 (24), 1169
IR spectra were obtained using
BX FT-IR System and Raman spectra were measured using a
PerkinElmer Spectrum 2000 FT-Raman spectrometer fitted with
a
PerkinElmer Spectrum
(19), 1150 (27), 1092 (14), 1070 (42), 1040 (8), 986 (21), 919 (7), 770
(16), 752 (100), 640 (19), 601 (18), 546 (21), 399 (31), 379 (33), 358
(42), 343 (52), 266 (33), 189 (24), 153 (20) cmꢁ1. Anal. calcd. for
NaC3F5N4ꢀ0.5H2O: C, 16.45; H, 0.46; N, 25.58. Found: C, 16.85; H,
0.84; N, 25.76. Sensitivity data: friction >360 N; impact >100 J.
a Nd-YAG-laser (l = 1064 nm) as solids at room temperature
(resolution = 4 cmꢁ1).
The friction and impact sensitivity data were obtained using a
BAM drophammer and friction tester, in accordance with the BAM
methods [20,21]. A description of the sensitivity test apparatus can
be found in reference [22].
4.5. Sodium 5-heptafluoropropyltetrazolate 2c
m.p.: –, dehydr. p.: 144 8C, decomp. p.: 254 8C. 13C NMR
1
(100.6 MHz, d6 DMSO):
d
109.1 (tsextet, JCF = 264.6 Hz,
1
2
2JCF = 37.2 Hz, –CF2–CF3), 114.2 (tt, JCF = 250.7 Hz, JCF = 30.9 Hz,
4.1. General preparation of perfluorinated nitriles (1a–c)
1
2
–CF2–CF2–CF3), 118.3 (qt, JCF = 287.3 Hz, JCF = 34.5 Hz, –CF3),
152.8 (t, 2JCF = 25.2 Hz, CRing). 14N NMR (40.5 MHz, d6 DMSO):
d
15
14.3
ꢁ80.6
A mixture of 6.95 mL (10.5 g, 0.05 mol) trifluoroacetic anhy-
dride and 8.5 mL (8.3 g, 0.10 mol) pyridine was added drop-wise to
a solution of perfluorinated amide (0.05 mol) in 26 mL pyridine.
The gas obtained was condensed into a cooling trap at ꢁ196 8C
under a low stream of dried nitrogen gas [11]. The yield of
perfluorinated nitrile obtained was not determined because it was
reacted with sodium azide in situ to form the corresponding
sodium 5-perfluoroalkyltetrazolate salts as described below in
yields of 95–99%.
(N2Ring), ꢁ57 (N1Ring). 15N NMR (40.5 MHz, d6 DMSO):
d
(N2Ring), ꢁ57.3 (N1Ring). 19F NMR (376.5 MHz, d6 DMSO):
d
3
(3F, 2JFF = 9.2 Hz, JFF = 0.9 Hz, –CF3), ꢁ109.1 (2F, m, CF2–CF2–CF3),
ꢁ127.2 (2F, m, –CF2–CF3); FAB–(C4F7N4ꢁ), m/z: 237.0 [M]ꢁ (100).
IR (KBr):
y 3421 (m), 1642 (w), 1485 (w), 1418 (w), 1382 (w), 1345
(m), 1286 (m), 1232 (vs), 1194 (s), 1185 (s), 1158 (m), 1121 (s),
1051 (w), 1030 (w), 935 (m), 891 (vs), 765 (w), 741 (s), 675 (w), 600
(w), 563 (w), 535 (w) cmꢁ1. Raman: (200 mW):
y 1485 (74), 1348
(16), 1284 (28), 1211 (31), 1154 (47), 1089 (14), 1053 (42),894
(29), 766 (20), 743 (100), 677 (34), 604 (23), 537 (15), 399 (34), 379
4.2. General preparation of the sodium 5-perfluoroalkyltetrazolates
(34), 348 (46), 310 (71), 287 (39), 205 (18), 178 (21), 92 (12) cmꢁ1
.
(2a–c)
Anal. calcd. for NaC4F7N4ꢀ0.5H2O: C, 17.86; H, 0.37; N, 20.82.
Found: C, 17.71; H, 0.70; N, 21.20. Sensitivity data: friction >360 N;
impact >100 J.
Sodium azide (3.25 g, 0.05 mol) was suspended in 50 mL of dry
acetonitrile in a 1 L round bottomed flask equipped with a Young
valve and a magnetic stirrer bar. The perfluorinated nitrile
prepared according to the described method above was then
condensed into the reaction vessel at ꢁ196 8C. The flask containing
the reaction mixture was then evacuated and then the Young valve
closed. The reaction vessel was subsequently warmed slowly to
room temperature and the reaction mixture stirred for 48 h. The
suspension was then filtered and the solvent removed under
reduced pressure, yielding the sodium 5-perfluoroalkyltetrazolate
as a white solid (yield: 90–97%).
Acknowledgments
Financial support of this work by the Ludwig-Maximilian
University of Munich (LMU), the Fonds der Chemischen Industrie
(FCI), the European Research Office (ERO) of the U.S. Army
Research Laboratory (ARL) and ARDEC (Armament Research,
Development and Engineering Center) under contract nos. N
62558-05-C-0027, R&D 1284-CH-01, R&D 1285-CH-01, 9939-AN-
01 & W911NF-07-1-0569 and the Bundeswehr Research Institute
for Materials, Explosives, Fuels and Lubricants (WIWEB) under
contract nos. E/E210/4D004/X5143 & E/E210/7D002/4F088 is
gratefully acknowledged. The authors acknowledge collabora-
tions Dr. M. Krupka (OZM Research, Czech Republic) in the
development of new testing and evaluation methods for energetic
4.3. Sodium 5-trifluoromethyltetrazolate 2a
m.p.: –, dehydr. p.: 169 8C, decomp. p.: 310 8C. 13C NMR
1
2
(100.6 MHz, d6 DMSO):
33.8, CRing). 14N NMR (40.5 MHz, d6 DMSO):
(N1Ring). 15N NMR (40.5 MHz, d6 DMSO):
13.6 (N2Ring), ꢁ60.0
d
123.8(q, JCF 267.5, –CF3), 154.0 (q, JCF
d
14 (N2Ring), ꢁ60
d
´
materials and with Dr. M. Suceska (Brodarski Institute, Croatia) in

M.-J. Crawford et al. / Journal of Fluorine Chemistry 129 (2008) 1199–1205
1205
Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P. Salvador,
J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas,
D.K. Malick, A.D. Rabuck, K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G.
Baboul, S. Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I.
Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A.
Nanayakkara, M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong,
C. Gonzalez, J.A. Pople, Gaussian, Inc., Gaussian 03, Revision A.1, Pittsburgh, PA,
2003.
the development of new computational codes to predict the
detonation parameters of high-nitrogen explosives. We are
indebted to and thank Dr. Betsy M. Rice (ARL, Aberdeen, Proving
Ground, MD) for many helpful and inspired discussions and
support of our work.
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