Hydrogen bonding of 2-tetrazenes, 2. Synthesis and structural studies of hydroxyalkyl-substituted 2-tetrazenes

Article abstract of DOI:10.1515/znb-2002-0402

Five hydroxyethyl-2-tetrazenes (1 - 5) and their methyl ethers (6 - 10) have been synthesized and hydrogen bonding in these compounds has been investigated by theoretical and spectroscopic (IR, ¹H NMR, ¹⁵N NMR) methods. The structure of 1,1,4,4-tetrakis(2-hydroxyethyl)-2-tetrazene (4) was determined by X-ray diffraction analysis. Several conformations with intramolecular hydrogen bonds were investigated by ab initio B3LYP as well as semiempirical SCF calculations. In all cases, conformers with OH---N hydrogen bonds with azo nitrogen atoms as acceptors (conformers A, B, C) are found as most stable. In compounds with small or flexible N¹- and N⁴- substituents R besides the hydroxyethyl group (3, 4), hydrogen bonds forming six-membered rings, with the R groups taking syn positions at the N¹-N² and N³-N⁴ bonds (conformer A), are preferred over those with seven-membered rings and R taking anti positions (conformer B). Steric interaction in the other compounds (1, 2, 5) leads to destabilization of conformers A and conformers B become more stable. A special case is presented by compound 4 which has only hydroxyethyl substituents on the 2-tetrazene unit. In the most stable conformer (4C) there are two OH---O and one OH---N hydrogen bonds. By IR solution measurements intra- and intermolecular hydrogen bonds could be distinguished. Association shifts Δδ measured by ¹H NMR spectroscopy, indicate that the investigated compounds exhibit comparable association properties with intermolecular association clearly prevailing. ¹⁵N NMR spectra of compounds 1 - 10 in two solvents have been measured if solubility was sufficient. The data indicate that all nitrogen atoms of 1 - 5 participate in H bonding. In the crystalline state, molecules 4 adopt a conformation without intramolecular H bonds (4D) and are associated by intermolecular OH---O hydrogen bonds that form a three-dimensional network. An untypical decomposition pattern was discovered for benzyl derivatives 5 and 10.

Full text of DOI:10.1515/znb-2002-0402

Hydrogen Bonding of 2-Tetrazenes, 2 [1].
Synthesis and Structural Studies of Hydroxyalkyl-Substituted 2-Tetrazenes*
Bernd Poratha, Paul Rademachera, Roland Boeseb, and Dieter Bla¨serb
a
Institut fu¨r Organische Chemie, Universita¨t Essen,
Universita¨tsstrasse 5-7, D-45117 Essen, Germany
b Institut fu¨r Anorganische Chemie, Universita¨t Essen,
Universita¨tsstrasse 5, D-45117 Essen, Germany
Reprint requests to Prof. Dr. Paul Rademacher. Fax: +49-(0)201-183-4252.
E-mail: paul.rademacher@uni-essen.de
Z. Naturforsch. 57 b, 365–376 (2002); received January 30, 2002
Hydroxyalkyl-2-tetrazenes, Hydrogen Bonding, Conformational Analysis
Five hydroxyethyl-2-tetrazenes (1 - 5)and their methyl ethers ( 6 - 10)have been synthe-
sized and hydrogen bonding in these compounds has been investigated by theoretical and
spectroscopic (IR, 1H NMR, 15N NMR)methods. The structure of 1,1,4,4-tetrakis(2-hydroxy-
ethyl)-2-tetrazene (4)was determined by X-ray diffraction analysis. Several conformations with
intramolecular hydrogen bonds were investigated by ab initio B3LYP as well as semiempirical
SCF calculations. In all cases, conformers with OH---N hydrogen bonds with azo nitrogen
atoms as acceptors (conformers A, B, C)are found as most stable. In compounds with small
or flexible N1- and N4-substituents R besides the hydroxyethyl group (3, 4), hydrogen bonds
forming six-membered rings, with the R groups taking syn positions at the N1-N2 and N3-N4
bonds (conformer A), are preferred over those with seven-membered rings and R taking anti
positions (conformer B). Steric interaction in the other compounds (1, 2, 5)leads to destabi-
lization of conformers A and conformers B become more stable. A special case is presented
by compound 4 which has only hydroxyethyl substituents on the 2-tetrazene unit. In the most
stable conformer (4C)there are two OH---O and one OH---N hydrogen bonds. By IR solution
measurements intra- and intermolecular hydrogen bonds could be distinguished. Association
shifts
measured by 1H NMR spectroscopy, indicate that the investigated compounds exhibit
comparable association properties with intermolecular association clearly prevailing. 15N NMR
spectra of compounds 1 - 10 in two solvents have been measured if solubility was sufficient. The
data indicate that all nitrogen atoms of 1 - 5 participate in H bonding. In the crystalline state,
molecules 4 adopt a conformation without intramolecular H bonds (4D)and are associated by
intermolecular OH---O hydrogen bonds that form a three-dimensional network. An untypical
decomposition pattern was discovered for benzyl derivatives 5 and 10.
Introduction
time in 1878 by E. Fischer [12] and have since then
received considerable attention as sources of aminyl
radicals and products derived thereof [13, 14]. The
most important method to prepare 2-tetrazenes is
oxidative coupling of 1,1-disubstituted hydrazines
[3 - 5]. The parent compound, N4H4, was gener-
ated in 1975 from 1,1,4,4-tetrakis(trimethylsilyl)-
2-tetrazene [15].
2-Tetrazenes [2 - 5] are composed of a four nitro-
gen chain with a central double bond. They are iso-
electronic with the butadiene-dianion, which means
that in the planar structure there are three occupied
MOs, of which the highest (HOMO)is antibonding.
Therefore, their thermodynamic stability is closely
related to the shape and the energy of the MOs
[1, 6 - 11]. 2-Tetrazenes were described for the first
Recently, we have synthesized two members
of previously unknown hydroxyalkyl-2-tetrazenes
(1, 2)and investigated hydrogen bonding [16] of
these novel difunctional compounds by spectro-
Presented in part at the 5th Conference on Iminium
Salts (ImSaT-5), Stimpfach-Rechenberg (Germany),
September 11 - 13, 2001.
1
scopic (IR, H NMR, 15N NMR)and theoretical
methods [1]. The structures of 2 and its bis(tri-
c
¨
¨
0932–0776/02/0400–0365 $ 06.00
2002 Verlag der Zeitschrift fur Naturforschung, Tubingen www.znaturforsch.com
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B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
Table 1. Constitution of compounds 1 - 10.
Scheme 1. Synthesis of 2-tetrazenes 3 - 6, 8 - 10.
methylsilyl)ether were determined by X-ray analy-
sis. It was shown that OH---N hydrogen bonds of 2-
tetrazenes are medium strong. From (15N)data and
quantum chemical calculations it was concluded
that the amino-nitrogen atoms of a 2-tetrazene are
involved in intermolecular hydrogen bonding to a
larger extent than the azo-nitrogen atoms; the cor-
responding energy difference of the two types of H
bonds is about 3 kJ mol 1. This is in accordance
with a higher gas-phase basicity of the former ni-
trogen atoms [17].
We have now synthesized three additional hydr-
oxyalkyl-2-tetrazenes(3 -5)and investigatedhydro-
gen bonding in these compounds. Some additional
studies have been performed on compounds 1 and 2.
As reference systems without H bonding the corre-
sponding methyl ethers (6 - 10)were included in the
study. Structures 1 - 10 are summarized in Table 1.
8 - 10 were synthesized by oxidation of the cor-
responding 1,1-disubstituted hydrazines. The latter
compounds were obtained by N-nitrosation of the
corresponding secondary amines 11 followed by re-
duction according to literature methods [3-5]. The
procedure is outlined for compounds 3 - 6, 8 - 10 in
Scheme 1.
The two benzyl derivatives 5 and 10 were found
to be so unstable that only small amounts could
be isolated. The decomposition products indicate
a way of fragmentation uncharacteristic for 2-
tetrazenes, with benzyl (17)and hydroxyethyl ( 16)
or methoxyethyl radicals as reactive intermediates
(Scheme 2). Thus, bibenzyl (19)and 3-phenyl-
propanol (18)or 3-methoxypropylbenzene ( 20), re-
spectively, were detected as by-products together
with several other compounds. To our knowledge,
Results and Discussion
Syntheses
Compounds 1 [1], 2 [1], and 7 [9] were pre- such a decomposition pattern of a 2-tetrazene has
pared as described previously. Compounds 3 - 6, not been observed previously.
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B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
367
Table 3. Structure parameters of O-H---N hydrogen
bonds in conformers A - C of 2-tetrazenes 1 - 5.
Con-
former
O-H
[pm]
OH---N
[pm]
N---O
[pm]
O-H---N
[ ]
1A
1B
1C
2A
2B
2C
3A
3B
3C
4A
4B
4C
5A
5B
5C
97.1
96.9
96.8
97.2
97.5
97.6
97.0
97.4
97.6
97.4
97.2
97.8
96.9
97.2
98.0
216.8
220.9
287.5
210.3
196.0
196.0
210.9
196.5
192.8
194.3
208.7
188.4
217.4
201.2
180.8
277.7
287.4
309.2
291.0
287.2
280.4
270.5
286.7
277.5
277.2
291.9
275.8
293.0
288.9
272.4
135.2
141.7
93.7
139.4
154.5
143.3
134.1
153.0
143.7
141.4
142.6
147.2
133.9
149.1
154.1
weak van der Waals interactions are not adequately
taken into account [18].
Scheme 2. Decomposition of 2-tetrazene 5.
For all compounds four conformations (A - D,
Scheme 3)were considered. In A the intramolecular
OH---N hydrogen bonds form six-membered rings,
while in B they exhibit seven-membered rings. In
conformation C there is an intramolecular OH---O
hydrogen bond and in D there are no hydrogen
bonds. The geometry of the respective conform-
ers was optimized; the absolute and relative ener-
gies are summarized in Table 2. We refrain from
presenting excessive data, but will discuss the re-
sults mainly with respect to intramolecular hydro-
gen bonding. Structure parameters of the O-H---N
hydrogen bonds in conformers A - C are presented
in Table 3. As an example, these conformers are de-
picted for compound 4 as ball and stick diagrams in
Fig. 1. Some additional structure parameters are re-
ported for 4 together with experimental results (see
below).
Quantum chemical computations
In the previous communication [1] we have
shown that all N atoms of a 2-tetrazene can act
as an acceptor of hydrogen bonds with the amino
nitrogen atoms being preferred over the azo nitro-
gen atoms. For compounds 1 - 5, various structures
with intramolecular hydrogen bonds are possible.
We have studied these conformations with the aid
of B3LYP calculations with special consideration
of intramolecular OH---N and OH---O hydrogen
bonds. This hybrid density functional method is
well suited for studying hydrogen bonds although
Table 2. Absolute energies [au] and relative energies
[kJ mol 1] of conformers A - D of 2-tetrazenes 1 - 5
(B3LYP/6-31+G** results).
2-Tetra-
zene
— Conformer —
B
For all compounds, conformers with intramolec-
ular OH---N hydrogen bonds were found as
most stable, and these conformers are about 10
A
C
D
1 –991.156902 –991.167500 –991.164956 –991.162300
27.82 0.00 6.68 13.65
2 –762.523346 –762.527020 –762.524264 –762.519650
9.64 0.00 7.23 19.34
3 –607.672539 –607.668549 –607.667958 –607.663746
0.00 10.47 12.03 23.08
4 –836.737928 –836.733899 –836.741772 –836.736499
10.09 20.67 0.00 13.84
5 –1069.794301–1069.794640–1069.792329–1069.790015
0.89 0.00 6.07 12.14
1
- 20 kJ mol more stable than those without H
bonds (D). In compounds with small or flexible sub-
stituents R (3, 4), the hydrogen bonds forming six-
membered rings (A)are preferred over those with
seven-membered rings (B), whereas in the other
compounds (1, 2, 5)the former conformation is ster-
ically destabilized so that B becomes most stable.
Steric destabilization in A may become so large that
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368
B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
Scheme 3. Conforma-
tions A - D of com-
pounds 1 - 10.
as indicated in Scheme 3, the other two are only
linked by an O-H---O hydrogen bond (Fig. 1). In the
latter grouping, the OH---O distance has a value of
210.7 pm and the O-H---O angle is 160.9 . In com-
pound 5, the two types of conformations with in-
tramolecular OH---N hydrogen bonds forming six-
or seven-membered rings, respectively, are of simi-
lar strength. In 5B the OH---N distance (201.2 pm)
is shorter than in 5A (217.4 pm), and the O-H---N
angle is larger in 5B (149.1 )than in 5A (133.9 ) . In
all structures, the phenyl groups are approximately
perpendicular to the plane of the N4 chain. In this
orientation repulsive interactions between the hy-
droxyethyl groups and the phenyl rings are avoided.
Finally, a short comment is given for the OH---O
bond in conformation C of 1 - 5. The OH---O
distance varies between 202 and 215 pm and the
O---O distance between 294 and 307 pm which
corresponds to an O-H---O angle of 147 to 162 .
For the methyl ethers 6 - 10, structures similar
to those of the corresponding 2-tetrazene alcohols
without intramolecular hydrogen bonds (1D - 5D)
were calculated as the most stable conformers.
Fig. 1. Conformers A - C of compound 4.
conformation C or even D may be more stable. The
main reason for this destabilization is that in A both
substituents R are in syn positions of the N-N bonds
of the 2-tetrazene unit, whereas in B they are in anti
positions. In conformer C this holds only for one
substituent R. Compound 4 with four hydroxylethyl
substituents on the 2-tetrazene unit clearly presents
a special case with conformer C being most stable
(see below).
Conformer 1A differs in the orientation of the
phenyl groups relative to the 2-tetrazene unit from
the other conformers. While in 1B - 1D the phenyl
groups take nearly coplanar positions, in 1A they
are approximately perpendicular to this group so
that -conjugation is removed. In conformer 1C
the OH---N interaction is rather weak as indi-
cated by the unfavourable O-H---N angle and the
Spectroscopic investigations
It has been shown by spectroscopic measure-
1
large N---O distance (Table 3). This is compensated ments (IR, H, 15N NMR)that hydroxyalkyl-2-
by the OH---O interaction with a relatively short tetrazenes form intra- and intermolecular hydrogen
OH---O distance (201.9 pm)and a wide O-H----O bonds [1]. In their IR spectra (liquid film or in KBr),
angle (156.2 ). Since there are four hydroxyethyl compounds 1 - 5 exhibit strong and broad absorption
1
groups in compound 4, additional conformations bands at 3300 - 3500 cm that are characteristic
are possible with intramolecular OH---O hydrogen for hydroxy groups intermolecularly associated by
bonds. 4A has a symmetric tetracyclic structure with hydrogen bonds. Compounds 2, 3 and 5 are suffi-
two OH---N and two OH---O hydrogen bonds. The ciently soluble in chloroform so that IR spectra at
most stable conformer (4C)is unsymmetrical with a different concentrations up to high dilution (50.0
tricyclic structure. While two hydroxyethyl groups - 0.1%)could be measured. With increasing dilu-
form an O-H---N and an O-H---O hydrogen bond tion, the intensity of the afore-mentioned band de-
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B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
369
1
tained from 15N chemical shifts (15N)of the hydr-
oxyalkyl-2-tetrazenes compared with their methyl
ethers [1]. We have measured the
Table 4. H chemical shifts [ppm] of hydroxy groups
and associations shifts
in [D6]DMSO and CDCl3.
[ppm] of 2-tetrazenes 1, 3 - 5
(15N)values
of compounds 1 - 10 in [D6]DMSO and CDCl3 so-
lutions (Table 5). For compounds 1 and 4 solubility
in CDCl3 is insufficient for 15N NMR spectroscopic
measurements, and the same holds for compound 6
Compound [D6]DMSO (1 M)CDCl
(0.02 M)
3
1
3
4
5
4.9
4.6
4.5
4.7
1.8
3.1
2.6
2.9
2.6
2.0
1.6
2.1
and [D6]DMSO. In [D6]DMSO, the
(15N)val-
ues are always smaller than in CDCl3 indicating
that in the former solvent associations of the hy-
droxy groups with solvent molecules are prevail-
ing. The larger (15N)values measured for CDCl 3
solutions can thus be attributed to OH---N hydro-
gen bonds. In order to estimate the significance of
these values, the data are compared with protonation
shifts [1, 22 - 25]. While tertiary amines show pos-
itive protonation shifts of about 10 - 20 ppm, those
of imines are negative and numerically much larger
Table 5. 15N chemical shifts [ppm] of amino and azo
nitrogen atoms of 2-tetrazenes 1- 5and their methylethers
6 - 10 and
(15N)values in [D 6]DMSO and CDCl3.
2-Tetrazene
CDCl3 (1 M)[D
(amino-N) (azo-N)
6]DMSO (1 M)
(amino-N) (azo-N)
–230.5
–8.3
–231.9
–8.4
–230.7
–234.3
11.5
16.3
–235.2
–236.0
13.1
13.6
(
–100 ppm). As an example, Schiff bases with
strong intramolecular phenolic OH---N hydrogen
bonds are mentioned for which
(15N)values of
(
(
(
-
-
-
)3.6
)1.1
)0.1
)1.1
–4.8
0.8
0.4
–0.5
–256.1
–257.1
13.4
15.1
–256.8
–257.2
14.1
13.9
about –20 to –30 ppm have been measured [26].
Since the (15N)values observed for CDCl 3 so-
lutions (Table 5)are rather small, in particular for
compounds 3/8 and 5/10, no detailed interpretation
regarding the strength of the different OH---N hy-
drogen bonds seems to be possible. However, the
fact that numerically smaller values are found for
[D6]DMSO than CDCl3 solutions, is in accordance
with mainly OH---O association in the former sol-
–1.7
0.2
–252.7
–252.8
6.9
6.7
–252.4
7.5
0.2
–246.3
–247.4
7.0
8.4
–247.1
–247.7
7.8
7.6
(
-
–1.4
0.6
0.2
Not determined because of too low solubility.
1
creases and its position is shifted by about 75 cm
vent. Only for compounds 2/7 the
(15N)values
to higher frequencies. Simultaneously, sharp bands
at 3630 and 3155 cm 1 appear corresponding to O-
H vibrations of free and intramolecularly associated
hydroxy groups, respectively.
By 1H NMR spectroscopy inter- and intramolec-
ular hydrogen bonds can be distinguished [19 - 21].
While chemical shifts of hydrogen atoms in in-
termolecular hydrogen bonds are characterized by
strong variations with concentration, the corre-
sponding shifts for intramolecular hydrogen bonds
are only small. We have measured 1H NMR spectra
of compounds 1, 3 - 5 in [D6]DMSO (1 M)and in
CDCl3 (0.02 M)and have determined association
measured in CDCl3 are significantly larger than in
[D6]DMSO which is an indication of stronger par-
ticipation of both amino and azo nitrogen atoms in
hydrogen bonding in compound 2 [1]. The differ-
ent behaviour of this chiral compound can certainly
be explained with a more rigid structure favouring
OH---H interactions.
X-ray structure analysis of 4
Compound 4 was analysed by X-ray crystallog-
raphy. The crystallographic data and the results are
given in Table 6. A structure diagram with the atom
numbering scheme is depicted in Fig. 2. The pack-
ing of the molecules is shown in Fig. 3. The com-
pound crystallizes in the monoclinic space group
P21/n with two formula units in the unit cell.
shifts
(Table 4). The data indicate that the inves-
tigated compounds exhibit comparable association
properties with intermolecular association clearly
prevailing.
Important indications about the nitrogen atoms
Selected structure parameters from the X-ray
to act as acceptors in hydrogen bonds can be ob- structure analysis are summarized in Table 7 to-
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370
B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
Table 6. Crystallographic data of 2-tetrazene 4.
Table 7. Selected structure parameters of 2-tetrazene 4
from X-ray crystal structure analysis (XRA)and quantum
chemical calculations (B3LYP, PM3).
Formula
C8H20N4O4
236.28
pale yellow
block
0.52, 0.47, 0.43
monoclinic
P21/n
Mr
XRA
B3LYPa PM3a
Colour
Crystal description
Crystal size [mm]
Crystal system
Space group
Bonds lengths (pm)
N(1)-N(1A)
N(1)-N(2)
N(2)-C(1)
N(2)-C(3)
C(1)-C(2)
C(3)-C(4)
O(1)-C(2)
O(2)-C(4)
124.7(2)
136.6(2)
145.1(2)
143.9(2)
149.8(2)
150.0(2)
140.2(2)
141.1(2)
125.5
137.9
147.1
146.8
152.8
152.9
142.3
142.9
123.4
140.6
150.4
150.3
153.6
153.4
140.9
140.2
˚
a [A]
5.1915(13)
6.834(2)
16.745(3)
92.264(11)
593.6(2)
2
˚
b [A]
˚
c [A]
3
˚
V [A ]
Z
1
[g cm
]
1.3222
calcd
Bond angles ( )
˚
[A]
T [K]
0.71073
293(2)
N(1A)-N(1)-N(2)
N(1)-N(2)-C(1)
N(1)-N(2)-C(3)
C(1)-N(2)-C(3)
113.90(2)
114.5
116.9
118.8
110.6
112.5
1
119.01(12) 119.0
111.07(11) 110.8
120.14(12) 118.3
[mm
]
0.105
F(000)256
2 Range [ ]
4.86 < 2 < 60.00
Torsional angles ( )
Collected reflections
Independent reflections
Obsvd. reflections
3065
1732
N(2A)-N(1A)-N(1)-N(2) 180.00(2)
180.0
180.0
39.6
171.9
1343
N(1A)-N(1)-N(2)-C(1)
14.14(0.20) 18.8
Parameters refined
Goodness-of-fit on F2
R1/wR2 [I > 2 (I)]
74
N(1A)-N(1)-N(2)-C(3) 160.12(0.14) 161.2
1.040
a
Conformer 4D.
0.0585 / 0.1650
R1/wR2 (all data)0.0707 / 0.1767
3
˚
Resid. el. density [e A
]
0.206/–0.195
Fig. 3. Packing of molecules 4 in the crystal.
found previously for compound 1 [1]. The data in
Table 6 indicate that the molecular structure of com-
pound 4, as calculated for the conformation without
intramolecular hydrogen bonds (4D), is reproduced
fairly well by both quantum chemical methods.
However, deviations from the observed parameters
are considerably smaller for the ab initio (B3LYP)
Fig. 2. Molecular structure of 2-tetrazene 4 with atom
numbering.
gether with the results of B3LYP and PM3 calcula-
tions obtained for conformation 4D.
The structure parameters determined for the 2- than the semi-empirical method (PM3). While for
tetrazene unit are in good agreement with those the former method bond lengths are uniformly too
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B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
371
large by 0.8 - 3.0 pm, for the latter method devi- a BIORAD FTIR spectrometer FTS 135. Only the most
significant absorptions are given. Electron impact mass
spectra (MS)were obtained with a Fisons VG Prospec
instrument (70 eV). The intensities are reported as a per-
centage relative to the base peak after the corresponding
m/z value. GC/MS analyses were carried out making use
of a gas chromatograph HP 5890 Series II of Hewlett-
Packard that was connected with a quadrupol mass spec-
trometer HP 5971A MSD. Elemental analyses were per-
formed with a Carlo Erba EA 1110 CHNS-O instrument.
Semi-empirical PM3 [27] calculations were performed
with the MOPAC 93 [28] program package, Becke3LYP
[29] HF/DFT calculations with the program GAUSSIAN
98 [30]. In the latter method the basis set 6-31+G(d,p)was
used. Geometries were fully optimized at the respective
levels of theory.
The X-ray structure determination of compound 4
was carried out with a Siemens P4 diffractometer. The
computer controlled instrument used graphite monochro-
mated Mo-K radiation. The structure was solved by di-
rect methods and all atoms except hydrogen atoms were
refined anisotropically. Scattering factors were corrected
for anomalous dispersion by Cromer and Lieberman [31].
The refinements based on F2 were performed by the full-
matrix least-squares method with the crystallographic
software SHELXL-97 [32]. Hydrogen atoms were treated
with a riding model on idealized geometries with the 1.2
fold isotropic displacement parameters of the equivalent
Uij of the corresponding carbon atom. Hydroxy hydro-
gen atom positions were taken from a Fourier-map and
also refined as riding groups. Further details of the crys-
tal structure investigations have been deposited with the
Cambridge Crystallographic Data Centre as Supplemen-
tary Publication no. CCDC-177474. These include lists
of atomic coordinates, selected bond lengths and angles
and equivalent isotropic displacement parameters. Copies
of the data can be obtained free of charge on applica-
tion to The Director, CCDC, 12 Union Road, Cambridge
CB25Z, UK (Fax: Int. code + 44(1223)336-033; e-mail:
deposit@ccdc.cam.ac.uk).
ations between –1.3 and +6.4 pm are found. Both
theoretical methods confirm the slightly pyramidal
configuration of the amino nitrogen atoms. The sum
of the bond angles at these atoms was calculated as
348.1 (B3LYP)and 341.9 (PM3)and observed as
350.2 (XRA). For the torsional angles, the PM3 re-
sults too deviate more than the B3LYP values which
are in excellent agreement with the experimental
ones.
In the crystalline state, molecules 4 are associ-
ated by OH---O hydrogen bonds. It is obvious from
energetic reasons that no intramolecular OH---N
bonds are present. The molecules form a three-
dimensional network. The 2-tetrazene units are
ordered centrosymmetrically parallel above each
other, and all hydroxy groups act as hydrogen
donors as well as acceptors in the hydrogen bonds.
In this way, a ladder-like motive is built with the
N4 chains as steps. These strands are connected
at both sides with two other strands which are in-
verted and displaced by a half step width. Thus, each
2-tetrazene molecule is associated with six other
molecules by hydrogen bonds.
Conclusions
2-Tetrazenes with hydroxyalkyl groups are well
suited to study in detail some important aspects of
hydrogen bonding. In the liquid and solid state, the
pure compounds are associated by intermolecular
OH---O hydrogen bonds, while isolated molecules
form intramolecular OH---N hydrogen bonds. In
the latter, mainly for steric reasons the azo nitrogen
atoms are preferred as acceptors over the amino
nitrogen atoms.
Experimental Section
General methods
(2-Hydroxyethyl)methylnitrosamine (12a)
Melting points (uncorrected)were determined with
an Electrothermal 9100 apparatus. The H, 13C and 15N
Butyl nitrite (43.3 g, 0.450 mol)was added dropwise
1
NMR spectra were recorded on a Bruker Avance DRX to a solution of 2-methylamino-ethanol (11a)(30.0 g,
500 spectrometer. The following frequencies were used: 0.400 mol)in absolute THF (250 ml)at a temperature of
500.13 MHz (1H), 125.76 MHz (13C), and 50.6 MHz 0 C. Stirring continued at 20 C for 2 d. The solvent and
(15N). The spectra were measured as solutions in a 5 mm butanol were removed in vacuo in an evaporator at a bath
tube at 20 C with the solvents CDCl3 or [D6]DMSO. temperature below 40 C. The yellow crude material was
The chemical shifts are reported in units of parts per distilled in high vacuum. Yield 37.7 g (91%); b. p. 105 C
1
million ( )relative to tetramethylsilane ( H, 13C)or ni-
tromethane (15N)as internal standard. Coupling constants
J are given in Hz. Infrared (IR)spectra were recorded on
/ 0.04 hPa. The compound forms a syn / anti mixture
3:1). – 1H NMR (500 MHz, CDCl3): = 3.07 (s, 3 H,
CH3), 3.3 - 3.6 (br, 1 H, OH), 3.7 - 3.8 (m, 4 H, NCH2,
(
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B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
OCH2), 3.83 (s, 3 H, CH3), 3.91 (t, 3J = 6 Hz, 2 H, NCH2), Bis(2-hydroxyethyl)nitrosamine (12b)
4.17 (t, J = 6 Hz, 2 H, OCH2) . –13C NMR (126 MHz,
3
By the procedure described for 12a, diethanolamine
CDCl3): = 32.6 (CH3), 40.5 (CH3), 47.9 (NCH2), 56.0
(NCH2), 58.3 (OCH2), 60.0 (OCH2). – IR (liquid film):
= 3385 (s, O-H), 2941 (s, C-H), 2878 (s, C-H), 1437
(11b)(42.1 g, 0.400 mol)was reacted with butyl ni-
trite (51.6 g, 0.500 mol)in absolute THF (200 ml)at
a temperature of 0 C. Stirring continued at 20 C for
5 h and then at 50 C for 36 h. The solvent and butanol
were removed in vacuo in an evaporator. Last traces of
butanol were removed by stirring the crude material at
1
(m, N=O), 1387 (m), 1332 cm (s, (O-H)).
1-(2-Hydroxyethyl)-1-methylhydrazine (13a)
1
80 C/0.1 hPa for 6 h. Yield 52.0 g (97%). – H NMR
Under argon, LiAlH4 (11.4 g, 0.300 mol)is suspended
in absolute THF (200 ml)at reflux temperature. At 50 -
55 C, a solution of nitrosamine 12a (26.0 g, 0.250 mol)
in absolute THF (80 ml)is added slowly. The mixture is
refluxed for 2.5 h. Excess LiAlH4 is hydrolysed with a
solution of sodium hydroxide (4.8 g)in water (20 ml.)
The hydroxide precipitate is filtered off and extracted
with THF (100 ml). The combined filtrates are dried over
sodium sulfate. The solvent is removed in an evaporator
below 30 C (bath temperature). The crude material is
distilled through a 20 cm Vigreux column in high vacuum.
Yield 12.1 g (54%); b. p. 45 - 46 C / 0.03 hPa. – 1H NMR
(500 MHz, CDCl3): = 2.51 (s, 3 H, CH3), 2.56 (t, 3J =
5 Hz, 2 H, NCH2), 3.77 (t, 3J = 5 Hz, 2 H, OCH2), 3.0 -
3.5 (br, 3 H, OH, NH2) . –13C NMR (126 MHz, CDCl3):
= 51.4 (CH3), 61.5 (NCH2), 62.2 (OCH2). – IR (liquid
film): = 3312 (s, O-H, NH2), 2945 (s, C-H), 2838 (s,
C-H), 2788 (m, C-H), 1610 (m, (NH2)), 1458 cm 1 (m).
3
(500 MHz, [D6]DMSO): = 3.45 (t, J = 5 Hz, 2 H,
3
NCH2), 3.6 - 3.8 (m, 4 H, NCH2, OCH2), 4.18 (t, J =
5 Hz, 2 H, OCH2), 4.6 - 5.2 (br, 2H, OH). – 13C NMR
(126 MHz, [D6]DMSO): = 46.4 (NCH2), 54.9 (NCH2),
56.7 (OCH2), 58.7 (OCH2)- IR (liquid film):
= 3381
(s, O-H), 2945 (s, C-H), 2878 (s, C-H), 1440 (w, N=O),
1
1386 (m), 1335 (s), 1120 cm (s, C-O).
1,1-Bis(2-hydroxyethyl)hydrazine (13b)
By the procedure described for 13a, nitrosamine 12b
(26.8 g, 0.200 mol)is reduced with LiAlH (11.5 g,
4
0.300 mol) in absolute THF (250 ml). Yield 3.7 g (15%);
4
b. p. 90 C/7*10 hPa. – 1H NMR (500 MHz, CDCl3):
3
3
= 2.62 (t, J = 5 Hz, 4 H, NCH2), 3.64 (t, J = 5 Hz,
4 H, OCH2), 3.8 - 5.0 (br, 4 H, OH, NH2) . –13C NMR
(126 MHz, CDCl3): = 59.9 (NCH2), 62.6 (OCH2) . – IR
(liquid film): = 3400 (m, O-H), 3343 (m, N-H), 2927 (s,
C-H), 2879 (s, C-H), 2816 (s, C-H), 1608 (m, (NH2)),
1
1458 (m), 1118 cm (s, C-O).
1,4-Bis(2-hydroxyethyl)-1,4-dimethyl-2-tetrazene (3)
1,1,4,4-Tetrakis(2-hydroxyethyl)-2-tetrazene (4)
Under argon, hydrazine 13a (3.15 g, 35.0 mmol)is
dissolved in absolute diethyl ether (40 ml). With stirring,
yellow mercury(II)oxide (8.67 g, 40.0 mmol)is added
in several portions at 20 C. Stirring is continued for 1 h.
Mercury and mercury oxide are filtered off and the filtrate
is dried over sodium sulfate. The solvent is removed in
an evaporator in vacuo. The crude material is purified
by chromatography on neutral aluminium oxide with a
mixture of CH2Cl2-CH3OH (50:1)as eluent. Yield 1.38 g
By the procedure described for 3, hydrazine 13b
(4.33 g, 36.0 mmol)is oxidized with yellow mercury(II)
oxide (10.83 g, 50.0 mmol)in THF (50 ml). The crude ma-
terial is purified by chromatography on neutral aluminium
oxide with a mixture of CH2Cl2-CH3OH (50:1)as eluent.
Recrystallization from CH2Cl2-CH3OH (20:3)afforded
colourless crystals. Yield 0.78 g (18%); m. p. 68 - 70 C.
– 1H NMR (500 MHz, [D6]DMSO): = 3.23 (t, 3J = 5 Hz,
8 H, NCH2), 3.47 (q, 3J = 5 Hz, 8 H, OCH2), 4.53 (t, 3J =
6 Hz, 4 H, OH) . –13C NMR (126 MHz, [D6]DMSO):
= 54.8 (NCH2), 58.9 (OCH2). – IR (KBr): = 3301 (s,
O-H), 2925 (s, C-H), 2881 (s, C-H), 1455 (s), 1332 (s,
(OH)), 1139 cm 1 (s, C-O). – MS (70 eV, EI): m/z = 236
(45%); colourless oil. – 1H NMR (500 MHz, CDCl3):
2.57 (s, 6 H, CH3), 3.24 (t, 3J = 5 Hz, 4 H, NCH2), 3.73
(t, 3J = 5 Hz, 4 H, OCH2), 3.0 - 3.2 (br, 2 H, OH). - 13
=
C
NMR (126 MHz, CDCl3): = 38.4 (CH3), 61.5 (NCH2),
62.2 (OCH2). – IR (liquid film): = 3368 (s, O-H), 2962
(s, C-H), 2879 (s, C-H), 1608 (w, N=N), 1466 (m), 1271
+
+
(48)[M +], 104 (7)[C 4H10NO2 ], 74 (97)[C 4H11NO2
-
1
(s, (O-H)), 1040 cm (s, C-O). - MS (70 eV, EI):
CH3O], 56 (100)[C H6N+], 45 (51)[C H5O+], 30 (55)
3
2
m/z = 176 (35)[M +], 149 (8)[M + - HCN], 145 (12)[M +
+
[CH2NH2 ], 28 (32)[N 2+]. – C8H20N4O4 (236.27): calcd.
+
- CH2OH], 102 (20)[M - CH2OH - C2H5N], 116 (38)
C 40.67, H 8.53, N 23.71; found C 40.62, H 8.77, N 23.99.
[M+ - 2 (C2H4O)], 56 (26) [C3H6N+], 45 (25)[C 2H5O+],
44 (100)[C H6N+], 28 (22)[N +], 15 (21)[CH +]. –
2
2
3
Benzyl-(2-hydroxyethyl)nitrosamine (12c)
MS (high resolution): m/z = 176.1254 (calcd. 176.1273).
– C6H16N4O2 (176.22): calcd. C 40.90, H 9.15, N 31.79;
found C 41.24, H 9.24, N 29.42.
By the procedure described for 12a, 2-(benzylamino)-
ethanol (11c)(60.5 g, 0.400 mol)was reacted with butyl
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373
nitrite (43.3 g, 0.450 mol)in chloroform(250 ml). Stirring
(Car). – IR (KBr): = 3369 (s, O-H), 3086 (m, Ar-H),
continued at 20 C for 5 h and then at 50 C for 72 h. 3062 (m, Ar-H), 3029 (m, Ar-H), 2930 (s, C-H), 2885
Yield 72.7. g (100%, crude material, used without further (s, C-H), 1603 (s, C=C), 1495 (s), 1355 (s, (O-H)),
1
purification). The compound forms a syn/anti mixture 1046 (s, C-O), 699 (s, (Ar-H)o o p ), 734 cm (s, (Ar-
( 3:1). – 1H NMR (500 MHz, CDCl3): = 2.72 (t, 3J = H)o o p). – MS (70 eV, EI): m/z = 328 (68)[M +], 150 (60)
5 Hz, 2 H, NCH2), 3.18 (br, 3 H, NCH2, OH), 3.55 (t, 3J = [C6H5CH2NC2H4OH+], 120 (42)[C 6H5CH2NC2H4OH+
5 Hz, 2 H, NCH2), 3.62 (t, 3J = 5 Hz, 2 H, OCH2), 3.75 - CH3O], 106 (28)[C H5CH2NC2H4OH+ - C2H5O], 91
6
(s, 2 H, NCH2), 4.13 (t, 3J = 5 Hz, 2 H, OCH2), 7.0 - 7.5 (100)[C 6H5CH2 ], 77 (5)[C 6H5 ], 65 (20)[C 5H5 ], 45
+
+
+
(m, 5 H, ArH) . –13C NMR (126 MHz, CDCl3): = 46.0 (20)[C H5O+], 28 (10)[N +]. – C18H24N4O2 (328.41):
2
2
(NCH2), 47.3 (NCH2), 53.7 (NCH2), 57.3 (NCH2), 59.0 calcd. C 65.83, H 7.37, N 17.06; found C 65.52, H 7.17,
(OCH2), 59.0 (OCH2), 127.8 (CarH), 128.1 (CarH), 128.2 N 17.50.
(CarH), 128.5 (CarH), 128.8 (CarH), 128.9 (CarH), 134.8
(Car), 135.0 (Car). – IR (liquid film): = 3401 (s, O-H),
3065 (m, Ar-H), 3032 (m, Ar-H), 2943 (m, C-H), 2884
(m, C-H), 1451 (s, N=O), 1341 cm (s, (O-H)).
N-Nitroso-N-(2-hydroxyethyl)aniline (12d)
1
By the procedure described for 12a, N-(2-hydroxy-
ethyl)aniline (11d)(54.8 g, 0.400 mol)is reacted with
butyl nitrite (43.3 g, 0.450 mol)in diethyl ether (250 ml).
Yield 65.1 g (98%, crude material, used without further
purification). – 1H NMR (500 MHz, CDCl3): = 2.72 (br,
1-Benzyl-1-(2-hydroxyethyl)hydrazine (13c)
By the procedure described for 13a, nitrosamine 12c
3
4
1 H, OH), 3.77 (t, J = 5 Hz, 2 H, NCH2), 4.17 (t, 3J =
(36.0 g, 0.200 mol)is reduced with LiAlH (9.5 g,
0.250 mol)in THF (300 ml). Yield 26.8 g (81%, crude
5 Hz, 2 H, OCH2), 7.35 - 7.50 (m, 3 H, ArH), 7.55 - 7.70
(m, 2 H, ArH) . –13C NMR (126 MHz, CDCl3): = 47.9
(OCH2), 58.8 (NCH2), 120.4 (CarH), 127.7 (CarH), 129.5
(CarH), 142.0 (Car). – IR (liquid film): = 3422 (s, O-H),
3067 (m, Ar-H), 2945 (s, C-H), 2885 (s, C-H), 1596 (s,
1
material, used without further purification). – H NMR
(500 MHz, CDCl3): = 2.69 (t, 3J = 5 Hz, 2 H, NCH2),
2.8 - 3.1 (br, 3 H, NH, OH), 3.68 (s, 2 H, NCH2), 3.82 (t,
3J = 5 Hz, 2 H, OCH2), 7.2 - 7.4 (m, 5 H, ArH). – 13C
NMR (126 MHz, CDCl3): = 59.6 (NCH2), 62.4 (OCH2),
68.1 (NCH2), 127.6 (CarH), 128.6 (CarH), 129.2 (CarH),
136.6 (Car). – IR (liquid film): = 3327 (s, O-H, NH2),
3062 (s, Ar-H), 3028 (s, Ar-H), 2940 (s, C-H), 2822 (s,
C-H), 1602 (m, (NH2)), 1453 (s), 1048 (m, C-O).
1
C=C), 1450 (s, N=O), 1076 cm (s, C-O).
N-Nitroso-N-(2-methoxyethyl)aniline (14d)
By the procedure described for 14a, N-nitroso-N-(2-
hydroxyethyl)aniline (12d)(41.5 g, 0.250 mol)is reacted
with iodomethane (42.6 g, 0.300 mol)and sodium hydride
(7.2 g, 0.300 mol)in absolute THF (400 ml). Yield 42.6 g
(95%, crude material, used without further purification).
1,4-Dibenzyl-1,4-bis(2-hydroxyethyl)-2-tetrazene (5)
Under argon, hydrazine 13c (8.32 g, 50.0 mmol)is dis-
solved in absolute ethanol (200 ml)and cooled to –15 C.
A solution of 1,4-benzoquinone (6.50 g, 60.0 mmol)in
absolute ethanol (200 ml)is added dropwise so that the
temperature does not rise above –10 C. Stirring is con-
tinued for 1 h at this temperature. The solvent is removed
in an evaporator in vacuo below 40 C (bath temperature).
The black residue is treated with chloroform (300 ml)and
washed five times with sodium hydroxide solution (5%,
100 ml). The organic solution is dried with potassium
carbonate. The solvent is removed in vacuo in an evap-
orator. The brown residue is purified by chromatography
on neutral aluminium oxide with a mixture of CH2Cl2-
CH3OH (50:1)as eluent. Recrystallization (four times)
1
– H NMR (500 MHz, CDCl3): = 3.28 (s, 3 H, CH3),
3.53 (t, 3J = 5 Hz, 2 H, NCH2), 4.17 (t, 3J = 5 Hz, 2 H,
OCH2), 7.3 - 7.5 (m, 3 H, ArH), 7.6 - 7.7 (m, 2H, ArH).
–
13C NMR (126 MHz, CDCl3): = 45.4 (OCH2), 58.8
(CH3), 68.3 (NCH2), 120.3 (CarH), 127.3 (CarH), 129.3
(CarH), 142.2 (Car). – IR (liquid film): = 3060 (m, Ar-
H), 3019 (m, Ar-H), 2986 (s, C-H), 2894 (s, C-H), 2831
(s, C-H), 1592 (s, C=C), 1457 (s, N=O), 1380 (s), 1127
1
cm (s, C-O).
1-(2-Methoxyethyl)-1-phenylhydrazine (15d)
By the procedure described for 13a, N-nitroso-N-(2-
methoxyethyl)aniline (14d)(44.2 g, 0.245 mol)is reduced
from petrol ether/ethyl acetate (3:2)afforded fine brown-
1
ish needles. Yield 1.22 g (15%); m. p. 52 - 53 C. – H with LiAlH4 (9.5 g, 0.250 mol)in THF (300 ml). Yield
NMR (500 MHz, CDCl3): = 2.3 - 2.5 (br, 2 H, OH), 3.33 13.82 g (34%); b. p. 98 - 102 C/6*10 hPa. – 1H NMR
5
(t, 3J = 5 Hz, 4 H, NCH2), 3.69 (t, 3J = 5 Hz, 4 H, OCH2), (500 MHz, CDCl3): = 3.36 (s, 3 H, CH3), 3.61 (t, 3J =
4.45 (s, 4 H, NCH2), 7.1 - 7.4 (m, 10 H, ArH). – 13C NMR 5 Hz, 2 H, NCH2), 3.68 (t, J = 5 Hz, 2 H, OCH2), 3.7
3
(126 MHz, CDCl3): = 54.5 (NCH2), 56.8 (NCH2), 61.0 - 3.9 (br, 2 H, NH2), 6.78 (t, 3J = 7 Hz, 1 H, ArH), 6.99
(OCH2), 127.1 (CarH), 128.1 (CarH), 128.4 (CarH), 137.7 (d, 3J = 8 Hz, 2 H, ArH), 7.25 (t, 3J = 8 Hz, 2 H, ArH) .
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–
13C NMR (126 MHz, CDCl3): = 55.1 (OCH2), 58.9 (OCH2), 58.7 (OCH2), 68.7 (OCH3), 70.6 (OCH3) . – IR
(CH3), 70.5 (NCH2), 112.9 (CarH), 117.9 (CarH), 128.9 (liquid film): = 2986 (s, C-H), 2930 (s, C-H), 2894 (s,
1
(CarH), 151.3 (Car). – IR (liquid film): = 3340 (s, N-H), C-H), 2831 (s, C-H), 1457 (s, N=O), 1380 (s), 1127 cm
3059 (m, Ar-H), 3021 (m, Ar-H), 2928 (s, C-H), 2880 (s, (s, C-O).
C-H), 2830 (s, C-H), 1597 (m, (NH2)), 1497 (s, C=C),
1
1452 (m), 1117 cm (s, C-O).
1-(2-Methoxyethyl)-1-methylhydrazine (15a)
By the procedure described for 13a, nitrosamine 14a
1,4-Bis(2-methoxyethyl)-1,4-diphenyl-2-tetrazene (6)
(17.7 g, 0.150 mol)is reduced with LiAlH (7.6 g,
4
By the procedure described for 3, 1-(2-methoxyethyl)-
1-phenylhydrazine (15d)(4.99 g, 30.0 mmol)is oxidized
with yellow mercury(II)oxide (8.66 g, 40.0 mmol)in
diethyl ether (40 ml). The product is obtained as fine
yellowish needles by recrystallization from diethyl ether.
Yield 2.41 g (49%); m. p. 107 C. – 1H NMR (500 MHz,
0.200 mol) in THF (250 ml). Yield 7.70 g (49%); b. p.
55 C/30 hPa. – 1H NMR (500 MHz, CDCl3): = 2.43 (s,
3 H, NCH3), 2.55 (t, 3J = 5 Hz, 2 H, NCH2), 2.90 (b, 2 H,
NH2), 3.28 (s, 3 H, OCH3), 3.48 (t, 3J = 5 Hz, 2H, OCH2).
–
13C NMR (126 MHz, CDCl3): = 50.3 (NCH3), 58.7
(OCH3), 61.8 (NCH2), 70.6 (OCH2). – IR (liquid film):
= 3327 (s, N-H), 2944 (s, C-H), 2882 (s, C-H), 2835 (s,
C-H), 1604 (m, (NH2)), 1459 (m), 1127 cm 1 (s, C-O).
3
CDCl3): = 3.39 (s, 6 H, CH3), 3.71 (t, J = 6 Hz, 4
3
H, OCH2), 4.26 (t, J = 6 Hz, 4 H, NCH2), 6.9 - 7.0
(m, 2 H, ArH), 7.2 - 7.4 (m, 8 H, ArH). – 13C NMR
(126 MHz, CDCl3): = 46.6 (OCH2), 59.1 (CH3), 68.4
(NCH2), 114.7 (CarH), 120.7 (CarH), 129.1 (CarH), 145.9
(Car). – IR (KBr): = 3057 (s, Ar-H), 3040 (m, Ar-H),
2978 (s, C-H), 2933 (s, C-H), 2898 (s, C-H), 1594 (s,
1,4-Bis(2-methoxyethyl)-1,4-dimethyl-2-tetrazene (8)
By the procedure described for 3, hydrazine 15a
(2.60 g, 25.0 mmol)is oxidized with yellow mercury(II)
oxide (6.50 g, 30.0 mmol)in diethyl ether (40 ml). The
crude material is purified by high-vacuum distillation.
1
C=C), 1491 (s), 1037 cm (s, C-O). – MS (70 eV, EI):
+
+
+
m/z = 328 (23)[M ], 300 (3)[M - N2], 255 (3)[M
-
1
+
Yield 1.77 g (69%); b. p. 75 C / 0.02 hPa. – H NMR
N2 - C2H5O], 151 (7)[C H5NHC2H4OCH3 ], 150 (9)
6
+
+
(500 MHz, CDCl3): = 2.75 (s, 6 H, NCH3), 3.27 (s, 6
[C6H5NC2H4OCH3 ], 106 (36)[C 6H5NC2H4OCH3
H, OCH3), 3.30 (t, 3J = 5 Hz, 4 H, NCH2), 3.50 (t, 3J =
+
C2H5O], 77 (22) [C6H5 ], 45 (100)[C H5O+], 28 (6)
2
5 Hz, 4 H, OCH2) . –13C NMR (126 MHz, CDCl3):
=
+
[N2 ]. – C18H24N4O2 (328.41): calcd. C 65.83, H 7.37, N
38.2 (NCH3), 54.6 (NCH2), 58.6 (OCH3), 70.4 (OCH2).
– IR (liquid, film): = 2963 (s, C-H), 2917 (s, C-H), 2877
(s, C-H), 1601 (w, N=N), 1464 (m), 1121 cm 1 (s, C-O).
– MS (70 eV, EI): m/z = 204 (48)[M +], 176 (4)[M +-N2],
159 (22)[M + - C2H5O], 131 (8)[M + - C3H7NO], 116 (38)
[M+ - 2 (C2H4O)], 73 (12) [C3H7NO+], 56 (26)[C3H6N+],
45 (100)[C 2H5O+], 44 (55)[C 2H6N+], 28 (22)[N 2+]. –
MS (high resolution): m/z = 204.1578 (calcd. 204.1586).
– C8H20N4O2 (204.27): calcd. C 47.04, H 9.87, N 27.43;
found C 46.56, H 9.90, N 26.91.
17.06; found C 66.07, H 7.27, N 17.10.
(2-Methoxyethyl)methylnitrosamine (14a)
Under argon, iodomethane (35.5 g, 0.250 mol)is added
to a solution of (2-hydroxyethyl)methylnitrosamine(12a)
(18.2 g, 0.175 mol)in absolute THF (300 ml.) The so-
lution is cooled to –60 C and sodium hydride (7.2 g,
0.300 mol)is added. The mixture is vigorously stirred
and allowed to warm to 20 C. When the exothermic re-
action has ended, stirring is continued for 30 min. Then
excess sodium hydride is destroyed with water (10 ml).
The solvent is removed in vacuo in an evaporator and
the residue is treated with dichloromethane (100 ml)and
Bis(2-methoxyethyl)nitrosamine (14b)
By the procedure described for 14a, nitrosamine 12b
water (100 ml). The layers are separated and the aque- (26.8 g, 0.200 mol)is methylated with iodomethane
ous solution is extracted two times with dichloromethane (71.0 g, 0.500 mol)and sodium hydride (14.4 g,
(75 ml). The combined organic phases are dried with 0.600 mol)in absolute THF (400 ml). Yield 30.3 g (95%,
1
sodium sulfate, and the solvent is removed in an evapora- crude material, used without further purification). – H
tor. The residue is distilled in vacuo. Yield 18.5 g (86%); NMR (500 MHz, CDCl3): = 3.25 (s, 3 H, CH3), 3.32 (s,
b. p. 90 - 92 C/18 hPa. The compound forms a syn / anti 3 H, CH3), 3.40 (t, 3J = 5 Hz, 2 H, NCH2), 3.68 (t, 3J =
1
mixture ( 1.5:1). – H NMR (500 MHz, CDCl3):
=
5 Hz, 2 H, OCH2), 3.81 (t, 3J = 5 Hz, 2 H, OCH2), 4.32 (t,
3.06 (s, 3 H, NCH3), 3.24 (s, 3 H, NCH3), 3.31 (s, 3 H, 3J = 5 Hz, 2H, NCH2) . –13C NMR (126 MHz, CDCl3):
OCH3), 3.43 (t, 3J = 5 Hz, 2 H, NCH2), 3.70 - 3.75 (m,
= 44.5 (NCH2), 52.9 (NCH2), 58.7 (CH3), 58.8 (CH3),
3
4 H, NCH2, OCH2), 3.78 (s, 3 H, OCH3), 4.26 (t, J = 68.8 (OCH2), 70.7 (OCH2). – IR (liquid film): = 2986
5 Hz, 2H, OCH2) . –13C NMR (126 MHz, CDCl3):
=
(s, C-H), 2933 (s, CH), 2895(s, C-H), 2830 (s, C-H), 1454
1
32.3 (CH3), 40.4 (CH3), 44.9 (NCH2), 53.2 (NCH2), 58.6 (s, N=O), 1357 (s), 1119 cm (s, C-O).
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375
1,1-Bis(2-dimethoxyethyl)hydrazine (15b)
1-Benzyl-1-(2-methoxyethyl)hydrazine (15c)
By the procedure described for 13b, nitrosamine 14c
By the procedure described for 13b, nitrosamine 14b
(35.3 g, 0.181 mol)is reduced with LiAlH (9.5 g,
4
(29.6 g, 0.200 mol)is reduced with LiAlH (11.5 g,
4
0.250 mol)in THF (300 ml). Yield 30.1 g (92%, crude
0.300 mol) in THF (250 ml). Yield 13.1 g (44%); b. p.
1
3
1
material, used without further purification). – H NMR
50-53 C/1*10 hPa. – H NMR (500 MHz, CDCl3):
(500 MHz, CDCl3): = 2.73 (t, 3J = 5 Hz, 2 H, NCH2),
2.8 - 3.0 (br, 2 H, NH2), 3.34 (s, 3 H, CH3), 3.60 (t, 3J =
5 Hz, 2 H, OCH2), 3.71 (s, 2 H, NCH2), 7.2 - 7.4 (m,
5 H, ArH) . –13C NMR (126 MHz, CDCl3): = 58.7
(CH3), 59.0 (NCH2), 66.5 (NCH2), 70.8 (OCH2), 127.2
(CarH), 128.2 (CarH), 129.2 (CarH), 137.2 (Car). – IR (liq-
uid film): = 3339 (m, NH2), 3062 (m, Ar-H), 3028 (m,
Ar-H), 2925 (s, C-H), 2816 (s, C-H), 1602 (m, (NH2)),
3
= 2.69 (t, J = 5 Hz, 4 H, NCH2), 2.8 - 3.1 (br, 2 H,
NH2), 3.28 (s, 6 H, CH3), 3.53 (t, 3J = 5 Hz, 4 H, OCH2).
–
13C NMR (126 MHz, CDCl3): = 58.8 (CH3), 60.7
(NCH2), 70.8 (OCH2). – IR (liquid film): = 3344 (m,
NH2), 2977 (s, C-H), 2926 (s, C-H), 2877 (s, C-H), 2815
1
(s, C-H), 1607 (m, (NH2)), 1458 (m), 1119 cm (s,
C-O).
1
1453 (s), 1118 cm (m, C-O).
1,1,4,4-Tetrakis(2-methoxyethyl)-2-tetrazene (9)
1,4-Dibenzyl-1,4-bis(2-methoxyethyl)-2-tetrazene (10)
By the procedure described for 3, hydrazine 15b
(5.20 g, 35.0 mmol)is oxidized with yellow mercury(II)
oxide (10.83 g, 50.0 mmol)in THF (50 ml). The crude
material is purified by chromatography on neutral alu-
minium oxide with a mixture of hexane and ethyl acetate
(5: 2)as eluent. Yield 3.52 g (69%). – 1H NMR (500 MHz,
By the procedure described for 5, hydrazine 15c
(9.02 g, 50.0 mmol)is oxidized with benzoquinone
(6.50 g, 60.0 mmol)in ethanol (400 ml). After removal
of the solvent the brown crude material was crystallized
at -20 C. Recrystallization from little petrol ether (five
times)afforded brownish needles. Yield 1.17 g (13%;)
m. p. 29 - 30 C. – 1H NMR (500 MHz, CDCl3): = 3.28
3
CDCl3): = 3.30 (s, 12 H, CH3), 3.43 (t, J = 5 Hz, 8
H, NCH2), 3.50 (t, 3J = 5 Hz, 8 H, OCH2) . –13C NMR
(126 MHz, CDCl3): = 52.2 (NCH2), 58.7 (CH3), 70.5
(OCH2). – IR (liquid, film): = 2977 (s, C-H), 2923 (s,
C-H), 2888, (s, C-H), 2815 (s, C-H), 1577 (w, N=N), 1460
(s), 1119 cm 1 (s, C-O). – MS (70 eV, EI): m/z = 292 (12)
[M+], 88 (14)[C H10NO+], 45 (100)[C H5O+)], 31 (9)
3
(s, 6 H, CH3), 3.37 (t, J = 6 Hz, 4 H, NCH2), 3.48 (t,
3J = 6 Hz, 4 H, OCH2), 4.46 (s, 4 H, NCH2), 7.1 - 7.4
(m, 10 H, ArH) . –13C NMR (126 MHz, CDCl3):
=
60.0 (NCH2), 56.4 (NCH2), 58.7 (CH3), 70.5 (OCH2),
126.8 (CarH), 128.1 (CarH), 128.3 (CarH), 138.4 (Car) . –
IR (KBr): = 3061 (m, Ar-H), 3026 (m, Ar-H), 2975 (s, C-
H), 2882 (s, C-H), 2845 (s, C-H), 1603 (s, C=C), 1503 (s),
4
2
[CH3O+], 29 (16)[C 2H5 ], 28 (7)[N 2 +], 15 (7)[CH 3+].
– C12H28N4O4 (292.38): calcd. C 49.30, H 9.65, N 19.16;
found C 48.04, H 9.26, N 17.54.
+
1
1118 (s, C-O), 733 (s, (Ar-H)o o p ), 699 cm (s, (Ar-
H)o o p ). – MS (70 eV, EI): m/z = 356 (66)[M +], 164 (76)
+
[C6H5CH2NC2H4OCH3 ], 120 (10)[C 6H5CH2NHCH2],
Benzyl-(2-methoxyethyl)nitrosamine (14c)
+
+
+
91 (100[C6H5CH2 ]), 77 (3) [C6H5 ], 65 (11)[C H5 ],
5
59 (39)[C 3H7O+], 45 (25)[C 2H5O+], 29 (12)[C 2H5 ]. –
+
By the procedure described for 14b, nitrosamine 13c
(36.0 g, 0.200 mol)is methylated with iodomethane
(35.5 g, 0.250 mol)and sodium hydride (6.0 g, 0.250 mol)
in THF (350 ml). Yield 36.4 g (94%, crude material,
used without further purification). The compound forms
C20H28N4O2 (356.47): calcd. C 67.39, H 7.92, N 15.72;
found C 66.91, H 7.81, N 16.14.
Oxidation of hydrazine 13c with mercury(II) oxide
1
a syn / anti mixture ( 1.5:1). – H NMR (500 MHz,
By the procedure described for 3, hydrazine 13c
(4.99 g, 30.0 mmol)is oxidized with yellow mercury(II)
oxide (8.66 g, 40.0 mmol)in absolute diethyl ether
(40 ml). After removal of the solvent, a crude material
(4.26 g)was obtained. GC/MS analysis indicated a com-
plex mixture of decomposition products with only a small
amount of 2-tetrazene 5 (m/z = 328). The main compo-
nents were 3-phenylpropanol (18)and bibenzyl ( 19).
3-Phenylpropanol (18). MS (70 eV, EI): m/z = 136 (37)
[D6]DMSO): = 3.16 (s, 3 H, CH3), 3.20 (s, 3 H, CH3),
3.31 (t, 3J = 5 Hz, 2 H, NCH2), 3.6 - 3.7 (m, 4 H, NCH2,
3
OCH2), 4.29 (t, J = 5 Hz, 2 H, OCH2), 4.83 (s, 2 H,
OCH2), 5.36 (s, 2 H, NCH2), 7.0 - 7.5 (m, 5 H, ArH).
–
13C NMR (126 MHz, [D6]DMSO): = 42.1 (NCH2),
46.4 (NCH2), 51.1 (NCH2), 55.6 (NCH2), 57.7 (CH3),
57.8 (CH3), 67.3 (OCH2), 68.8 (OCH2), 127.1 (CarH),
127.4 (CarH), 128.0 (CarH), 128.3 (CarH), 128.5 (CarH),
128.6 (CarH), 134.7 (Car), 135.3 (Car). – IR (liquid film):
= 3065 (m, Ar-H), 3032 (m, Ar-H), 2931 (s, C-H), 2895 [M+], 118 (58)[M - OH], 117 (100)[M - H2O], 105
+
+
(s, C-H), 2831 (m, C-H), 1455 (s, N=O), 1118 cm (s, (16)[M + - CH3O], 92 (48)[C 7H8 ], 91 (80)[C 7H7 ], 77
1
+
+
+
C-O).
(15)[C 6H5 ].
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376
B. Porath et al. · Hydrogen Bonding of 2-Tetrazenes, 2
+
Bibenzyl (19). MS (70 eV, EI) :m/z = 182 (35)[M ], (4.59 g)was obtained. GC/MS analysis indicated a com-
+
+
91 (100)[C 7H7 ], 65 (9)[C 5H5 ].
plex mixture of decomposition products of 2-tetrazene
10 (m/z = 328). The main components were 3-methoxy-
propylbenzene (20)and bibenzyl ( 19).
Oxidation of hydrazine 15c with mercury(II) oxide
3-Methoxypropylbenzene (20). MS (70 eV, EI) :m/z =
By the procedure described for 3, hydrazine 15c
(5.41 g, 30.0 mmol)is oxidized with yellow mercury(II)
oxide (8.66 g, 40.0 mmol)in absolute diethyl ether
(40 ml). After removal of the solvent, a crude material
+
+
+
150 (3)[M ], 119 (7)[M - OCH3], 118 (100)[M
-
+
+
OCH3 - H], 92 (27)[C H8 ], 91 (50)[C H7 ], 45 (32)
7
7
[C2H5O+].
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