Synthesis and properties of N-nitro-O-(4-nitrophenyl)hydroxylamine

Article abstract of DOI:10.1007/s11172-009-0281-2

Salts of N-nitro-O-(4-nitrophenyl)hydroxylamine were synthesized by a new method of oxidative nitration, involving the reaction of O-(4-nitrophenyl) hydroxylamine with KNO₂ or NaNO₂ in the presence of PhI(OAc)₂ or PhIO as oxidants. When using Na¹⁵NO ₂, the samples containing the nitro group labeled with the ¹⁵N isotope were obtained. Acidification of the appropriate salt gave N-nitro-O-(4-nitrophenyl)hydroxylamine. It is the first N-nitrohydroxylamine isolated in the H-form. Its thermal stability was investigated and the probable mechanism of decomposition was suggested. From a comparison of the ¹⁴N and ¹⁵N NMR spectra of N-nitro-O-(4-nitrophenyl) hydroxylamine with those of its O- and N-methylated derivatives, its equilibrium with the aci-form (N=NOOH) was inferred.

Full text of DOI:10.1007/s11172-009-0281-2

Russian Chemical Bulletin, International Edition, Vol. 58, No. 10, pp. 2047—2057, October, 2009
2047
Synthesis and properties of NꢀnitroꢀОꢀ(4ꢀnitrophenyl)hydroxylamine
M. S. Klenov, A. M. Churakov, O. V. Anikin, Yu. A. Strelenko, and V. A. Tartakovsky
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: churakov@ioc.ac.ru
Salts of NꢀnitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine were synthesized by a new method of
oxidative nitration, involving the reaction of Oꢀ(4ꢀnitrophenyl)hydroxylamine with KNO2 or
NaNO2 in the presence of PhI(OAc)2 or PhIO as oxidants. When using Na15NO2, the samples
containing the nitro group labeled with the 15N isotope were obtained. Acidification of the
appropriate salt gave NꢀnitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine. It is the first Nꢀnitrohydroxylꢀ
amine isolated in the Нꢀform. Its thermal stability was investigated and the probable mechaꢀ
nism of decomposition was suggested. From a comparison of the 14N and 15N NMR spectra of
NꢀnitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine with those of its Оꢀ and Nꢀmethylated derivatives, its
equilibrium with the aciꢀform (N=NOOH) was inferred.
Key words: hydroxylamines, nitrohydroxylamines, oxidative nitration, oxodiazonium ion,
thermal stability, 1H, 13C, 14N, and 15N NMR spectra.
A method for the synthesis of salts of ОꢀalkylꢀNꢀnitroꢀ
hydroxylamines А (R = Alk) was developed in the 1990s. It
includes nitration of NꢀacetylꢀОꢀalkylhydroxylamines folꢀ
lowed by the treatment of the produced NꢀacetylꢀNꢀnitro
compounds with potassium methoxide.1 Salts А are therꢀ
mally stable. The Nꢀ and Оꢀalkylated derivatives of nitroꢀ
hydroxylamines B and C (R,R´ = Alk) are also relatively
stable.1 At the same time, the Нꢀform of nitrohydroxyꢀ
lamines D is substantially less stable and has not been
isolated in pure state. It was synthesized in situ as exempliꢀ
fied by nitrohydroxylamine with R = 2,4ꢀ(NO2)2C6H3
by nitration of the NꢀMe3Si derivative of Оꢀ(2,4ꢀdinitroꢀ
phenyl)hydroxylamine (reagents and conditions:
(NO2)2SiF6, CH2Cl2, –10 °С) and converted into the
Оꢀmethyl derivative С (R = 2,4ꢀ(NO2)2C6H3, R´ = Me)
in a yield of 31% by the reaction with diazomethane at
0 °С (see Ref. 2).
stability. NꢀNitroꢀОꢀ(4ꢀnitrophenyl)hydroxylamine was
chosen as the model compound.
Results and Discussion
Synthesis. Potassium NꢀnitroꢀОꢀ(4ꢀnitrophenyl)hydrꢀ
oxylaminide 1а was prepared by oxidative nitration of
Оꢀ(4ꢀnitrophenyl)hydroxylamine. This method of Nꢀnitraꢀ
tion developed recently in our laboratory4 makes it possiꢀ
ble to avoid the strongly acidic medium in performing the
reaction (Scheme 1). The nitrating agent is KNO2 in the
presence of PhI(OAc)2 as an oxidant. The reaction was
performed at 0 °С in methanol, the solvent was removed
in vacuo and the product was chromatographically sepaꢀ
rated from the byꢀproduct, viz., pꢀnitrophenol. Salt 1а
prepared according to this procedure in a yield of
38% contains potassium acetate as the admixture
(1Н NMR control).
Scheme 1
ArO—NH2 + PhI(OAc)2 + KNO2
ArO—N–—NO2K+ + PhI + 2 AcOH
1a
Ar = 4ꢀNO2C6H4
Earlier, we have synthesized the Нꢀforms of nitroꢀ
hydrazines.3 In the present work, our aim was to prepare
the Нꢀform of nitrohydroxylamines D and to study its
For the preparation of an analytically pure sample of
salt 1а, we used a solution of PhIO in methanol as the
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1985—1994, October, 2009.
1066ꢀ5285/09/5810ꢀ2047 © 2009 Springer Science+Business Media, Inc.

2048
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Klenov et al.
oxidant instead of PhI(OAc)2. In this case, the yield of salt
1а was 41%.
by 1H, 13C, 14N, 15N NMR spectroscopy. Their elemental
analysis could not be performed because of their tendency
to spontaneously decompose at room temperature. At the
same time, the structures of NHA 2 and 2´ were unambigꢀ
uously confirmed by methylation. The reactions of these
compounds with diazomethane in ether afford Оꢀmethyl
derivatives 3 and 3´, respectively (see Scheme 2), which,
according to the 1H and 13C NMR spectral data, are mixꢀ
tures of the Eꢀ and Zꢀstereoisomers in a ratio of 2.2 : 1
(cf. Ref. 2). By analogy with the Оꢀmethylated nitramines,5
we can ascribe the Eꢀconfiguration to the major isomer.
Methylation with methyl iodide of the silver salts of
NHA prepared by the reactions of salts 1a and 1b with
AgNO3 gives a mixture of Оꢀ and Nꢀmethyl isomers 3, 4
and 3´, 4´, respectively (Scheme 3), in a ratio of 1 : 1
(cf. Ref. 6). The Оꢀmethylated compounds are a mixture
of the Eꢀ and Zꢀstereoisomers in a ratio of 4.4 : 1. The
Nꢀmethyl isomers 4 and 4´ were not isolated in the indiꢀ
vidual state. Their structures were confirmed by specꢀ
tral studies (1H, 13C, 14N, and 15N NMR), including
15N INEPT NMR and twoꢀdimensional 1H—15Nꢀcorreꢀ
lation spectrosopy (1H—15N COSY). The latter experiꢀ
ments allowed us to unambiguously determine the posiꢀ
tion of the signal for the Nꢀnitro group, which coincides
with the signal for the nitro group of the phenyl ring in the
14N NMR spectra.
For the preparation of the compound with the 15N
labeled nitro group, Оꢀ(4ꢀnitrophenyl)hydroxylamine was
nitrated with the system Na15NO2—PhI(OАc)2 using the
commercially available sodium nitrite with 92% enrichꢀ
ment by the 15N isotope. Sodium salt 1b was synthesized
in a yield of 40%.
The salts prepared by these methods contain no nitrite
impurities, which was established by the negative color
reaction with the Griess reagent.
Potassium salt 1а is yellow powder melting with deꢀ
composition at 145—155 °С. The structure of the salt was
1
confirmed by the data from IR, H, 13C, and 14N NMR
spectroscopy and elemental analysis. Sodium salt 1b was
spectroscopically characterized, particularly by 15N NMR
spectroscopy, and was not isolated in analytically
pure state.
A suspension of potassium salt 1а in diethyl ether was
carefully acidified with an etheral solution of methaneꢀ
sulfonic acid at 0 °С for the preparation of the Нꢀform of
nitrohydroxylamine (NHA) 2. Nitrohydroxylamine 2´ with
the 15Nꢀlabeled nitro group (Scheme 2) was synthesized
analogously from sodium salt 1b. Acidification is best perꢀ
formed with the preparations of salts 1 that contain a small
amount of КOAc or NaOAc (see Experimental). Pure
samples of NHA 2 and 2´ are white crystals. Upon acidifiꢀ
cation, the excess of methanesulfonic acid should be avoidꢀ
ed, otherwise, the NHA samples obtained after concenꢀ
tration of the ether solution are light yellow in color and
contaminated with 4ꢀnitrophenol and 2,4ꢀdinitrophenol.
Scheme 3
Scheme 2
i. 1) AgNO3, 2) MeI.
The signals for the methyl groups of compounds 3 and
1
4 in the Н and 13С NMR spectra are close to the correꢀ
sponding signals for the previously2 prepared Oꢀ and
Nꢀmethyl derivatives of Оꢀ(2,4ꢀdinitrophenyl)ꢀNꢀnitroꢀ
hydroxylamine.
In the 14N and 15N NMR spectra, the position of the
signal for the Nꢀnitro group of both salt 1а and the Hꢀform
2 significantly depends on the solvent. The maximum difꢀ
ference between the chemical shifts, equal to 12 ppm
(see Table 1), is observed for the Hꢀform 2. The positions
of the signal for the Сꢀnitro group of the phenyl ring,
the signal for the Nꢀnitro group of compound 4 and the
signal for N(O)OCH3 of compound 3 depend little on
the solvent.
Nitrohydroxylamines 2 and 2´ melt with decomposiꢀ
tion at 69—70 °C. These compounds were characterized

NꢀNitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2049
Table 1. 14N NMR spectra data for compounds 1a, 2, 3, 4 and 15N NMR spectral data for compounds 1b,
2', 3', 4' in different solvents
Comꢀ
pound
Fragment
δ(14N), (Δν1/2/Hz), [δ(15N), J/Hz]
CDCl3
CD3OD
Acetoneꢀd6
D2O
1а
N—NO2
—
—
—
–21 (40)
8–8 (200)
888—55
–40 (80)
–11 (340)
[–40.1]
–18 (40)
–11 (240)
—55
–30 (180)
–12 (150)
—55
–28 (60)*
2–9 (720)
[–28.5]
–29 (40)
–11 (460)
[–28.5]
—
C—NO2
N—15NO2
N—NO2
1b
2
–41 (220)**
–12 (380)**
—
–58 (200)
–12 (270)
[–58.6,
C—NO2
2´
3
N—15NO2
N(→O)OMe
C—NO2
–56 (120)
–12 (200)
–56 (110)
–12 (180)
—
3´
4
15N(→O)OMe
3J(H—15N) = 3.9]
–17 (100)
–14 (250)
[–16.3,
888—55
–14 (60)
–12 (200)
—55
–14 (30)
–12 (180)
—
—
—
N—NO2
C—NO2
N—15NO2
4´
3J(H—15N) = 3.4]
888—55
—55
—
* Addition of КОН (2 equiv.) does not change the chemical shift. ** The temperature of spectral registraꢀ
tion is –20 °С.
–
–
In the case of salts 1, the considerable dependence of
the position of the signal for the nitramine group on the
solvent can be explained by different structures of the solꢀ
vated ion pairs. In the case of the Hꢀform 2, one of the
reasons for such dependence may be different degree of
dissociation in different solvents, however, this is obviousꢀ
ly not the only factor (see Table 1).
(δ(N) = 14— 17), it can be seen that the signals for the
Нꢀform 2 are nearly in the middle between the signals for
compounds 3 and 4 (see Table 1). This can be explained
by the fact that, for the Нꢀform 2, the nitramine and
isonitramine forms are in a rapid equilibrium on the NMR
time scale.
Thermal decomposition. The major organic products of
thermal decomposition of NHA 2 are 4ꢀnitrophenol (5)
and 2,4ꢀdinitrophenol (6) (Scheme 4). The ratio of these
products ranges from 10 : 1 to 4 : 1 depending on the deꢀ
composition conditions (Table 3).
Formally, the primary Nꢀnitroamines (—NHNO2)
would exist in the isonitramine form (—N=N(O)OH),
however, it is not generally observed, which is confirmed
by the comparison of the positions of the 14N or 15N sigꢀ
nals for the primary Nꢀnitroamines and their Nꢀ and
Оꢀmethylated or trimethylsilylated derivatives.7 As is seen
from Table 2, the difference between the chemical shifts
of nitramines and isonitramines is ~30 ppm and the sigꢀ
nals for the primary and secondary nitramines differ only
slightly.
Scheme 4
From the comparison of the 14N and 15N signals for
–
NHA 2 (δ(N) = –29— 41) with the signals for Оꢀmethyl
–
compound 3 (δ(N) = –56— 58) and Nꢀmethyl compound 4
Table 2. 15N NMR spectral data (from Na15NO3,
CH2Cl2) for nitramines and the Оꢀsubstituted isoꢀ
nitramines7
The thermal stability of NHA 2 in the solid phase deꢀ
pends significantly on the purity of the sample. The pure
sample (m.p. 69—70 °C with decomp.) weighing 3—5 mg
is completely decomposed at 20 °С in 20 min (see Table 3).
Upon decomposition of larger amounts (~100 mg), brown
vapor of nitric oxides is observed in the flask. If the gases
produced are continuously evacuated (the residual presꢀ
sure in the reaction flask is 1 Torr), the stability of NHA 2
is considerably increased. Only 6% of the compound is
decomposed within 3 h at 20 °С (see Table 3). Apparently,
Compound
δ(15N)
MeNH—15NO2
–20.9
–22.0
–16.4
–49.1
–51.8
Me2N—15NO2
Me(SiMe3)N—15NO2
MeN=15N(→O)OMeꢀ(E)
MeN=15N(→O)OSiMe3ꢀ(E)

2050
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Klenov et al.
Table 3. Thermal decomposition of NHA 2 in the solid
state and in solutiona
Table 4. Solventꢀdependence of the decomposition rate
of NHA
b
c
Solvent Т/°Сb
t/hc
Conversion
Yield (%)
Solvent
Т/°Ca
t1
t2
of NHA 2 (%)
5
6
CH2Cl2
CH2Cl2
Benzene
CHCl3
CHCl3
CHCl3
MeCN
Acetone
EtOAc
0
20
20
–20
4
20
20
20
20
20
20
20
20
20
20
20
0d
0d
1 day
5 h
5 h
—
1 day
6 h
1 day
3 days
3 days
—
—
—
d
0d
—
—
—
20
0
0.3
24
3
100
100
6
76
73
83
71
70
14
16
15
20
19
2—3 dayse
75 min
5 min
25 min
30 min
40 min
1 day
d
e
20
20
CHCl3
5
100
100
CH2Cl2 20
5
PhH
H2O
20
40
6
100
53
72
74
19
11
Et2O
14
Dioxane
MeOH
EtOH
THF
H2O
1 day
a The conversion and the yields of the products were deꢀ
1—2 days
2 days
2 days
6 days
10 days
1
termined according to the Н NMR spectra. b The reacꢀ
—
—
—
—
tion temperature. c The reaction time. d Decomposition
in the solid state. e Decomposition in the solid state under
evacuation (the residual pressure is 1 Torr).
H2O/MeOH (1 : 1)
a The temperature at which the decomposition was carried out.
b The time period from the point of mixing of NHA with the
solvent to the point of appearance of the first traces of 5 and
6 (TLC).
the nitric oxides evolved upon decomposition of NHA
considerably accelerate decomposition.
The reduction of the temperature to 0 °С increases the
time of total decomposition of NHA 2 up to 24 h (see
Table 3). NHA 2 can be stored at –20 °С without any
change for more than two months.
c The time of complete decomposition of NHA 2 (TLC).
d The decomposition products appear immediately after mixꢀ
ing of NHA with the solvent.
e During the reaction, a portion of NHA 2 is precipitated as
colorless crystals.
The stability of NHA 2 in solutions strongly depends
on the solvents, which can be divided into several groups.
The first group includes the nonpolar solvents (CH2Cl2,
CHCl3, benzene), wherein NHA is unstable. In these solꢀ
vents, decomposition at 20 °С starts almost immediately
after dissolution and is completed in 5—6 h. NHA is someꢀ
what more stable in these solutions at low temperatures
(Table 4). The second group includes the polar aprotic
solvents (EtOAc, MeCN, acetone). The first traces of the
decomposition products of NHA in these solvents at
20 °С, viz., compounds 5 and 6, appear after 25—40 min.
The strongest stabilizing effect was shown by the aprotic
basic solvents (THF, dioxane, Et2O) and polar protic solꢀ
vents (H2O, H2O : MeOH = 1 : 1, MeOH, EtOH), whereꢀ
in the first traces of the decomposition products of NHA
appear after 1—10 days (see Table 4).
Scheme 5
Putative decomposition pathways. Since the Оꢀ and
Nꢀalkyl derivatives of NHA are comparatively stable comꢀ
pounds1,2 and decomposition of NHA 2 starts even at
room temperature, one can assume that the first step of
decomposition is autoprotolysis (Schemes 5 and 6). A seꢀ
ries of structures can be produced upon protonation of
NHA, but only two of them, viz., E and F, can dissociate,
at least formally, to form the stabilized cations, viz., nitroꢀ
nium cation and oxodiazonium cation G, respectively
(Scheme 5), which, in turn, can be involved in further
reactions.
dissociation to yield compounds I and J, respectively
(Scheme 6).
In turn, compounds I and J can dissociate to form
cation G and the corresponding anions (Scheme 7), which
can reattack the ambident cation G at the αꢀnitrogen atom
to produce compounds K and L, respectively. These comꢀ
pounds can be irreversibly decomposed: compound K is
decomposed to form Oꢀnitrosophenol M and N2O3 and
compound L is decomposed according to the concerted
mechanism of fragmentation to form Oꢀnitrosophenol M,
N2O, the nitrosonium cation, and the 4ꢀnitrophenolate
anion. In such case, the key step of decomposition of
Probably, cations E and F, being the members of ion
pairs E + H and F + H, can react with anion Н without

NꢀNitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2051
Scheme 6
Note. Hereinafter, displayed in bold type are 15N labeled atoms.
Scheme 7
Scheme 8
compounds I and J is migration of the anionic groups
from the βꢀnitrogen atom to the αꢀnitrogen atom to form
a new N—O bond.
This migration is analogous to the processes occured
in the furazan and tetrazole series upon transformation of
the nitramine group into the nitroso group under the acꢀ
tion of nitrating agents (Scheme 8).8
The nitrosation species formed according to Scheme
7, including N2O3, would, in turn, react with the starting
NHA 2. Nitrosation most likely occurs at the N atom to
afford N2O and nitroether O (Scheme 9). The latter can
be a precursor of HNO3, which, upon the reaction with
N2O3, can result in the formation of N2O4.
The nitrating agents (nitro ester O or HNO3) can also
react with the starting NHA 2 according to a scheme analꢀ
ogous to Scheme 8 (Scheme 10). Nitroso ester М and
N2O3 may be the products of this reaction.
In order to verify the proposed mechanisms, we estiꢀ
mated the approximate rates of decomposition of NHA 2
(CHCl3, 0 °С) in the presence of HNO3, as well as in the
presence of N2O4 (see Scheme 4 and Table 5). When neiꢀ
ther of these reagents was added, the decomposition reacꢀ
tion proceeds with the induction period. The reaction starts
only after 75 min that is easy to control by the appearance
of the yellow coloration of the solution caused by comꢀ

2052
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Klenov et al.
Scheme 9
Table 5. Decompositiona of NHA 2 in CHCl3 in the presence of
HNO3 and N2O4
c
Reagent 2 : Reagent
t1/minb
t2
Yield (%)
(mol/mol)
5
6
d
d
—
—
75
65
60
10
0
24 h
24 h
24 h
24 h
24 h
24 h
73
71
68
67
70
23
18
16
16
17
21
19
75
77
HNO3
HNO3
HNO3
N2O4
N2O4
N2O4
1 : 0.1
1 : 1
1 : 2
1 : 0.1
1 : 1
1 : 2
0
0
2 min
a The reaction temperature is 0 °С and the concentration of
NHA 2 is 0.05 mol L–1; the product yields were determined
according to the 1Н NMR spectra.
b The time period from the point of mixing of NHA with the
reagent to the point of appearance of the first traces of 5 and 6
(TLC).
c The time of complete transformation of NHA 2.
d Decomposition of NHA 2 without addition of the reagents.
Scheme 10
with NHA 2 is faster than the reaction with compound 5:
the conversion of 5 at the twoꢀfold excess of N2O4 was
only 16% in 10 min (Table 6), whereas the reaction with
NHA 2 was completed already in 2 min (see Table 5).
Scheme 11
pounds 5 and 6 and by observing the first traces of these
products using TLC. The reaction rate is then sharply
increased (the degree of conversion is ~50% in 50 min
according to the data from the 1Н NMR spectrum), howꢀ
ever, NHA completely disappears only after ~24 h. The
addition of 0.1 equiv. of HNO3 does not virtually influꢀ
ence the induction period, the total reaction time, and the
ratio of the reaction products 5 and 6 (see Scheme 4 and
Table 5). The considerable amount of HNO3 (2 equiv.)
decreases the induction period, however, this does not
eliminate this period completely. At the same time, upon
addition of 0.1 equiv. of N2O4, the reaction proceeds withꢀ
out the induction period. Although the addition of 1 equiv.
of N2O4 does not influence the total conversion time of
NHA, it causes the considerable increase in the fraction of
6 among the reaction products and, upon addition of
2 equiv. of N2O4, the total conversion time of NHA is
reduced to 2 min.
The data of Table 5 (see Scheme 4) suggest that N2O4
reacts with NHA 2 considerably faster than HNO3 and it
is nitrosating rather than nitrating species that are responꢀ
sible for the formation of 6. This fact was confirmed by the
independent experiments. It was shown that compound 5
was not nitrated by HNO3 in CHCl3 for 1 day at 0 °С,
while the reaction with N2O4 was completed in 4 h
(Scheme 11, Table 6). Note that the reaction of N2O4
The data presented confirm the following scheme of
decomposition of NHA 2. At first, the reaction of two
molecules proceeds according to one of the mechanisms
Table 6. Reaction of 5 with the nitrating and nitrosation
a
agents in CHCl3
Reagent tb
5 : Reagent Conversion Yield
(mol/mol)
of 5 (%)
6 (%)
HNO3
HNO3
N2O4
1 day
1 day
4 h
1 : 1
1 : 2
1 : 1
1 : 2
0
2
96
16
0
50
98
88
N2O4 10 min
a The reaction temperature is 0 °С, the concentration of
5 is 0.07 mol L–1; the conversion and the yields of the
products were determined according to the 1Н NMR
spectra.
b The reaction time.

NꢀNitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2053
shown in Schemes 6 and 7. These reactions are slow (the
initiation step). As a result of these reactions, the nitrosatꢀ
ing species are produced, which rapidly react with NHA
to form N2O and the nitrating species. To explain the
sharp acceleration of the reaction, one should suppose
that the nitration step proceeds at the rate comparable
with that of nitrosation. It is obvious that, in this case, the
nitrating agent is not HNO3, but more reactive species, for
example, nitronitroso derivative N or 4ꢀnitrophenyl niꢀ
trate O. Upon its reaction with NHA 2, some new nitrosaꢀ
tion species are produced (see Scheme 10) and the deꢀ
composition process is accelerated.
can be formed according to the analogous scheme upon
the reaction of the labeled NHA 2´ with the unlabeled
nitrosation species. The ~2 : 1 ratio of the labeled and
unlabeled nitrous oxides indicates that the labeled and
unlabeled nitrosation species are also in the ratio 2 : 1.
This is in agreement with Scheme 10 where the molecule
of N2O3 corresponds to two nitrosation species.
Summing the presented equations describing decomꢀ
position of the labeled compound 2´ and adding the water
molecule to the left side of an equation, one can derive the
chemical equation (Scheme 12), which demonstrates the
ratio of the labeled and unlabeled nitrous oxides.
For the refinement of the reaction mechanism, deꢀ
composition of the labeled NHA 2´ was studied. Decomꢀ
position was performed in a sealed NMR tube in CDCl3 at
Scheme 12
20 °С for 5 h. The reaction products were identified by 14
N
and 15N NMR spectroscopy. In the spectra, besides the
signals for the nitro groups of compounds 5 and 6, the
signals for HNO3 were observed. The 14N NMR spectra
also contained the signals for the unlabeled nitrous oxide
NNO corresponding to the central and terminal N atoms
(cf. Ref.9) and the signals for the labeled nitrous oxide
N15NO corresponding to the terminal N atom. The
15N NMR spectra displayed the signal for the labeled niꢀ
trous oxide N15NO corresponding to the central N atom
(cf. Ref. 10). Nitrous oxide labeled in the terminal N
atom is not formed. No molecular nitrogen, neither laꢀ
beled nor unlabeled, is also produced upon decomposiꢀ
tion. According to the 14N NMR spectra, the ratio of the
labeled and unlabeled nitrous oxides in view of the degree
of enrichment is 2 : 1. The intergration of the signals in the
14N spectra was performed by taking into account the
ratio of the signal intensities in the spectra of certain samꢀ
ples of N2O in the corresponding solvent, which were deꢀ
termined in the same mode of signal accumulation.
After recording the spectra, compound 5 and comꢀ
pound 6 were isolated from the reaction mixture in yields
of 70% and 19%, respectively (Scheme 4). The mass specꢀ
tral data allow us to determine that, in view of the degree
of enrichment, the molar ratio of compounds 6 with the
unlabeled nitro groups, one labeled nitro group and two
labeled nitro groups is 1 : 2.0 : 0.2.
The suggested mechanism of decomposition conforms
with the experimental data, however, the real mechanism
is probably more complex. For example, some steps can
proceed involving the radical species.
In view of the data obtained for the decomposition
reactions, we can explain some features of the solvent
effect on the stability of 2. In the nonꢀpolar solvents
(CH2Cl2, CHCl3), the molecules of NHA 2 can be associꢀ
ated into dimers (cf. data in Ref. 13 for the primary nitrꢀ
amines), which increases the rate of autoprotolysis. The
increase in stability in the polar solvents is caused by the
fact that the concentration of the dimers in these solvents
is significantly lower due to solvation. The ion pairs formed
as a result of autoprotolysis are in solvateꢀdivided state,
which retards their interaction with each other. One of the
factors influencing the increase in the stability of the NHA
2 in H2О is, apparently, dissociation to form the stable
anion. The considerable degree of dissociation is evidenced
by the chemical shift of the Nꢀnitro group of NHA 2 in the
14N NMR spectrum at δ –29, which is close to the chemꢀ
ical shift of potassium salt of NHA 1а at δ(14N) –28
(see Table 1).
Since the nitrosation species account for the formaꢀ
tion of 6, the ratio of compounds 6 with the labeled and
unlabeled nitro groups, equal to ~2 : 1, evidences that
the labeled and unlabeled nitrosation species were in the
same ratio.
The formation of a small amount of the doubleꢀlabeled
6 upon nitration of 5 with labeled nitric acid in the presꢀ
ence of nitric oxides was also observed by other auꢀ
thors.11,12 It was assumed that this process involves the
radical species.
ОꢀMethyl derivative of nitrohydroxylamine 3 is conꢀ
siderably more stable than the Hꢀform 2. When heated in
CHCl3 at 61 °С for 1.3 h, its conversion is merely 8%. The
decomposition products are compounds 5 (the yield based on
the converted substance is 75%) and 6 (13%). Heating in
octane at 70 °С for 14 h leads to 57% conversion, the
yields of 5 and 6 are 89% and 7%, respectively (Scheme 13).
Thus, decomposition of the Нꢀform of nitrohydroxyꢀ
lamine 2 is a multistep process. Within the present work,
we are intrested not so much in the features of the total
decomposition reaction of NHA, as in the possibility to
establish the first reaction step, which eventually deterꢀ
mines the stability of the compound. As it follows from
The formation of labeled nitrous oxide upon nitrosaꢀ
tion of labeled NHA 2´ with the labeled nitrosation speꢀ
cies conforms with Scheme 9. The unlabeled nitrous oxide

2054
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Klenov et al.
Scheme 13
MeOH (100 mL) at 0 °C, finely ground KNO2 (1.2 g, 14.1 mmol)
was carefully added at once and the mixture was stirred until
the solid completely dissolved. A solution of PhI(OAc)2 (4.54 g,
14.1 mmol) in MeOH (50 mL) was then added dropwise with
stirring to the resulting mixture over 15 min. The reaction mixꢀ
ture was kept for 5 min at 0 °C and the solvent was removed
in vacuo. The solid residue was carefully ground in a mortar and
washed with СH2Cl2 (2×50 mL) with vigorous mixing for 30 min.
Upon washing, PhI and the major part of pꢀnitrophenol passed
into the СH2Cl2 solution. The residue was dissolved in MeOH
(80 mL), silica gel (5 g) was added to the solution, the solvent
was removed in vacuo and the residue was transfered onto
a column with silica gel (d = 50 mm, h = 20 mm) and eluted with
a 4 : 1 mixture of CHCl3 and AcOEt (200 mL). The eluate conꢀ
tained the last portion of pꢀnitrophenol; the total yield of
pꢀnitrophenol according to the 1H NMR spectral data was 50%.
AcOEt (200 mL) and a 1 : 1 mixture of MeOH and AcOEt
(200 mL) were then used as eluents. The combined eluates were
concentrated. A yellowish powder (1.5 g) was obtained, which
contained according to the 1H NMR spectral data (Et4NBr as
the quantitative internal standard) potassium salt 1a (1.28 g,
38%) and AcOK (220 mg). This preparation containing 15% (w/w)
AcOK was then used for the preparation of the Нꢀform of
NꢀnitroꢀОꢀ(4ꢀnitrophenyl)hydroxylamine.
Procedure B. Synthesis with the use of PhIO. To a solution
of Oꢀ(4ꢀnitrophenyl)hydroxylamine (1.08 g, 7.01 mmmol) in
MeOH (50 mL) at 0 °C, finely ground KNO2 (0.6 g, 7.05 mmol)
was added at once and the mixture was stirred until the solid
completely dissolved. A solution of PhIO (1.54 g, 7.01 mmol) in
MeOH (50 mL) was then added dropwise with stirring over 5 min.
The reaction mixture was kept for 5 min at 0 °C, silica gel (3 g)
was added and the mixture was concentrated to dryness. The
solid residue was transfered onto a column filled with silica gel
(d = 50 mm, h = 20 mm). The elution was performed first with
a 4 : 1 mixture CHCl3 — AcOEt (200 mL) and then with AcOEt
(150 ml) to afford a mixture (910 mg) of pꢀnitrophenol (500 mg,
52%) and PhI. Subsequent elution with a 1 : 1 mixture
MeOH—AcOEt (100 mL) gave potassium salt 1a (685 mg, 41%)
as a yellow powder, m.p. 145—155 °C (decomp.). Found (%):
С, 30.31; H, 1.66; N, 17.83; K, 16.59. C6H4KN3O5. Calculatꢀ
ed (%): С, 30.38; H, 1.68; N, 17.61; K, 16.48. IR (КBr), ν/cm–1
(region of 1200—1550 cm–1): 1260, 1308, 1340, 1348, 1384, 1456,
1508. 1H NMR (D2O), δ: 7.10 (d, 2 H, Н(2), Н(6), J = 9.3 Hz);
8.10 (d, 2 H, Н(3), Н(5), J = 9.3 Hz). 13C NMR (D2O), δ: 113.7
(C(2), С(6)); 125.5 (С(3), С(5)); 141.6 (С(4)); 160.9 (С(1)).
Sodium Nꢀ[nitroꢀ15N]ꢀОꢀ(4ꢀnitrophenyl)hydroxylaminide
(1b). Sodium salt 1b was synthesized from Oꢀ(4ꢀnitrophenyl)ꢀ
hydroxylamine (330 mg, 2.14 mmol), Na15NO2 (150 mg,
2.14 mmol, the degree of enrichment is 92%), and PhI(OAc)2
(690 mg, 2.14 mmol) according to the procedure analogous to
the procedure A for the preparation of 1a. According to the
1H NMR spectral data, the specimen obtained contained sodiꢀ
um salt 1b (191 mg, 40%) and AcONa (29 mg). This mixture
containing 13% (w/w) AcONa was then used for the preparation of
the Нꢀform 2´. 1H NMR (D2O), δ: 7.27 (d, 2 H, Н(2), Н(6), J =
= 9.3 Hz); 8.27 (d, 2 H, Н(3), Н(5), J = 9.3 Hz). 14N NMR (D2O),
δ: –10 (CNO2, Δν1/2 = 380 Hz); –29 (NNO2, Δν1/2 = 40 Hz).
NꢀNitroꢀОꢀ(4ꢀnitrophenyl)hydroxylamine (2). Warning! Comꢀ
pound 2 can spontaneously decompose at room temperature.
It is recommended to store it at –20 °C in solid state or as
an etheral solution (10 mg mL–1).
the foregoing, the reason for the low stability of the Нꢀform
2 in the nonꢀpolar solvents (benzene, CH2Cl2, CHCl3)
and in solid state is relatively fast formation of the nitrosaꢀ
tion species to be involved in subsequent reactions. The
key step responsible for the formation of the nitrosation
species is the reaction of the nucleophiles with oxodiazoꢀ
nium ion G at the αꢀnitrogen atom (see Scheme 7). Forꢀ
mally, oxodiazonium ion G can be also formed due to the
initial denitration reaction of NHA (see Scheme 5) or the
equivalent reaction (see Scheme 6, reaction (1)) and due
to the initial elimination of the water molecule from NHA
(Scheme 5) or the equivalent reaction (see Scheme 6, reꢀ
action (2)). The same reactions would also occur upon
decomposition of the primary nitramines, however, they
are more stable in actual practice than NHA 2. The deniꢀ
tration processes of the primary nitramines and NHA most
likely proceeds at the comparable rates and the process of
water elimination would proceed faster in the case of NHA
2, since this compound apparently exists as an equilibrium
mixture of the nitramine and isonitramine forms. It is
possible that this feature is the reason for the lower therꢀ
mal stability of NHA. Hereafter, we are planning to study
the formation of the oxodiazonium ion from NHA 2 in the
strongly acidic medium.
Experimental
1
Н, 13С, and 14N NMR spectra were recorded on a Bruker
AMꢀ300 spectrometer with working frequencies 300.13, 75.5,
and 21.5 MHz, respectively. The 15N NMR spectra were reꢀ
corded on a Bruker DRXꢀ500 (50.70 MHz) spectrometer. The
chemical shifts are given relative to SiMe4 (1H, 13C) or MeNO2
(
14N, 15N, external standard, the upfield chemical shifts are negꢀ
ative). IR spectra were recorded on a Specord Mꢀ80 spectromeꢀ
ter. Mass spectra were obtained on a Kratos MSꢀ300 (EI, 70 eV)
instrument. The course of the reaction was monitored by TLC
using Silufol UVꢀ254 and Merck 60 F254 plates. Silica gel was
used for column chromatography. Oꢀ(4ꢀNitrophenyl)hydrꢀ
oxylamine14 and an etheral solution of diazomethane15 were
prepared according to known procedures. Quantitation of the
products using 1Н NMR spectroscopy was carried out with tetraꢀ
chloroethane as the internal standard.
Potassium NꢀnitroꢀОꢀ(4ꢀnitrophenyl)hydroxylaminide (1a).
Procedure A. Synthesis with the use of PhI(OAc)2. To a solution
of Oꢀ(4ꢀnitrophenyl)hydroxylamine (2.17 g, 14.1 mmol) in

NꢀNitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2055
Procedure A. To a suspension of a sample of K salt 1a (238 mg,
1.0 mmol) and AcOK (42 mg, 0.43 mmol), which was prepared
according to procedure A, in Et2O (7 mL), a solution of MsOH
(0.083 mL, 1.29 mmol) in Et2O (1 mL) was added dropwise at
0 °C over 1 min with vigorous stirring. The reaction mixture was
vigorously stirred for 1 h at 0 °C. The precipitate that formed was
filtered off, washed with Et2O (5×5 mL) and the solvent was
removed in vacuo. The residue was dried in vacuo (1 Torr) for
15 min at 0 °C to obtain NHA 2 (180 mg, 90%) as white crystals,
m.p. 69—70 °C (decomp.).
(107 mg, 99%) was obtained as white crystals, m.p. 93—96 °C
(a mixture of the E/Zꢀisomers in a ratio of 2.2 : 1). After recrysꢀ
tallization from МеОН, the ratio of the E/Zꢀisomers was 9 : 1,
m.p. 102—106 °С (decomp.). Found (%): С, 39.57; H, 3.34;
N, 19.63. C7H7N3O5. Calculated (%): С, 39.44; H, 3.31; N, 19.71.
MS, m/z: 213 [M]+, 183 [M – CH2O]+. IR (КBr), ν/cm–1
:
1344, 1492, 1520, 1540, 1568.
1
Major isomer (E). H NMR (СDCl3), δ: 4.11 (s, 3 Н, Me);
7.34 (d, 2 H, Н(2), Н(6), J = 9.2 Hz); 8.27 (d, 2 H, Н(3), Н(5),
J = 9.2 Hz). 13C NMR (СDCl3), δ: 57.5 (Me); 115.1 (C(2), С(6));
125.8 (С(3), С(5)); 144.0 (С(4)); 160.3 (С(1)).
Procedure B. Potassium salt 1a (100 mg, 0.42 mmol) preꢀ
pared according to procedure B was dissolved in MeOH (15 mL).
A freshly calcined AcOK (30 mg, 0.31 mmol) was added to the
solution and the mixture was stirred until the solids completely
dissolved. The solvent was evaporated in vacuo. The solid resiꢀ
due was vigorously ground in a mortar, suspended in Et2O
(10 mL) and cooled to 0 °C. A solution of MsOH (0.042 mL,
0.66 mmol) in Et2O (1 mL) was added dropwise to the suspenꢀ
sion over 1 min with vigorous stirring. The reaction mixture was
vigorously stirred for 1 h at 0 °C. The workꢀup of the reaction
mass was performed as described in the previous experiment,
NHA 2 (60 mg, 72%) was obtained as white crystals, m.p. 63—65 °C
(decomp.). The attempts to prepare NHA 2 without use of AcOK
resulted in the yellowish preparations containing the impurity of
pꢀnitrophenol. IR (КBr), ν/cm–1 (region of 1300—1600 cm–1):
1336, 1488, 1504, 1588. 1H NMR (dioxaneꢀd8), δ: 7.36 (d, 2 H,
Н(2), Н(6), J = 9.2 Hz); 8.30 (d, 2 H, Н(3), Н(5), J = 9.2 Hz).
1H NMR (CD3OD), δ: 7.44 (d, 2 H, Н(2), Н(6), J = 9.3 Hz);
8.37 (d, 2 H, Н(3), Н(5), J = 9.3 Hz). 13C NMR (dioxaneꢀd8), δ:
114.7 (C(2), С(6)); 125.5 (С(3), С(5)); 144.6 (С(4)); 162.2 (С(1)).
14N NMR (dioxaneꢀd8), δ: –14 (C—NO2, Δν1/2 = 610 Hz); –37
Minor isomer (Z). 1H NMR (СDCl3), δ: 4.13 (s, 3 Н, Me);
7.34 (d, 2 H, Н(2), Н(6), J = 9.2 Hz); 8.27 (d, 2 H, Н(3), Н(5),
J = 9.2 Hz). 13C NMR (СDCl3), δ: 57.1 (Me); 114.8 (C(2), С(6));
125.9 (С(3), С(5)); 144.0 (С(4)); 160.3 (С(1)).
1ꢀMethoxyꢀ2ꢀ(4ꢀnitrophenyl)diazene[1ꢀ15N] 1ꢀoxide (3´).
To a solution of NHA 2' (30 mg, 0.15 mmol) in Et2O (2 mL), an
excess of a solution of diazomethane prepared from Nꢀmethylꢀ
Nꢀnitrosourea (0.1 g) in Et2O (5 mL) was added dropwise at
0 °C. The solvent was removed in vacuo. Product 3´ (32 mg,
99%) was obtained as white crystals, m.p. 93—96 °C. The prodꢀ
uct is a mixture of the E/Zꢀisomers in a ratio of 2.2 : 1.
1
Major isomer (E). H NMR (СDCl3), δ: 4.10 (d, 3 Н, Me,
J(1H—15N) = 4.0 Hz); 7.33 (d, 2 H, Н(2), Н(6), J = 9.2 Hz);
8.26 (d, 2 H, Н(3), Н(5), J = 9.2 Hz).
1
Minor isomer (Z). H NMR (СDCl3), δ: 4.12 (d, 3 Н, Me,
J(1H—15N) = 4.0 Hz); 7.34 (d, 2 H, Н(2), Н(6), J = 9.2 Hz);
8.27 (d, 2 H, Н(3), Н(5), J = 9.2 Hz).
NꢀMethylꢀNꢀnitroꢀОꢀ(4ꢀnitrophenyl)hydroxylamine (4) and
E(Z)ꢀ1ꢀmethoxyꢀ2ꢀ(4ꢀnitrophenyl)diazene 1ꢀoxide (3). A soluꢀ
tion of AgNO3 (0.36 g, 2.1 mmol) in distilled water (1 mL) was
added dropwise to a solution of К salt 1a (0.5 g, 2.1 mmol) in
distilled water (6 mL). The voluminous beigeꢀcolored precipiꢀ
tate was filtered off, washed with EtOH (5 mL) and dried in
a vacuum desiccator over P2O5 for 12 h. The Ag salt (615 mg,
95%) was obtained as white crystals, m.p. 162—168 °C (decomp.).
The Ag salt obtained was then used in the synthesis without
additional purification. To a suspension of the Ag salt (165 mg,
0.54 mmol), MeI (0.05 mL, 0.8 mmol) in dry MeCN (5 mL) was
added at once at 20 °C in an argon atmosphere. The reaction
mixture was stirred for 12 h at 20 °C. The precipitate that formed was
filtered off and washed with CH2Cl2 (5 mL). The filtrates were
combined and the solvent was removed in vacuo. A mixture of comꢀ
pounds 3 and 4 (100 mg, 87%) was obtained in a ratio of 1 : 1
according to the 1H NMR spectral data. Compound 3 is a mixture
of the E/Zꢀisomers in a ratio of 4.4 : 1; according to the 1H NMR
spectral data, it is identical to the compound 3 prepared above.
(N—NO2, Δν
= 670 Hz). 14N NMR (CD3COOD), δ: –9
1/2
(C—NO2, Δν1/2 = 380 Hz); –30 (N—NO2, Δν1/2 = 120 Hz).
Nꢀ[Nitroꢀ15N]ꢀОꢀ(4ꢀnitrophenyl)hydroxylamine (2´). To
a suspension of the preparation containing sodium salt 1b (87 mg,
0.39 mmol) and AcONa (13 mg, 0.16 mmol) in Et2O (7 mL),
a solution of MsOH (0.033 mL, 0.5 mmol) in Et2O (1 mL) was
added dropwise at 0 °C over 1 min with vigorous stirring. The
reaction mixture was vigorously stirred for 1 h at 0 °C. The workꢀ
up of the reaction mixture as described in the previous experiꢀ
ment (procedure A) afforded NHA 2´ (65 mg, 84%) as white
crystals, m.p. 69—70 °C (decomp.). Product 2´ was dissolved in
1
Et2O (13 mL) and the solution was stored at –20 °C. H NMR
(dioxaneꢀd8), δ: 7.35 (d, 2 H, Н(2), Н(6), J = 9.2 Hz); 8.31
(d, 2 H, Н(3), Н(5), J = 9.2 Hz). 15N NMR (dioxaneꢀd8), δ:
–36.2 (N—NO2).
1ꢀMethoxyꢀ2ꢀ(4ꢀnitrophenyl)diazene 1ꢀoxide (3). Procedure
A. To a suspension of a sample containing potassium salt 1a
(238 mg, 1.0 mmol) and AcOK (42 mg, 0.43 mmol) in Et2O
(5 mL), a solution of MsOH (0.083 mL, 1.29 mmol) in Et2O (1 mL)
was added dropwise at 0 °C over 1 min with vigorous stirring.
The reaction mixture was vigorously stirred for 1 h at 0 °C and an
excess of a solution of diazomethane prepared from Nꢀmethylꢀ
Nꢀnitrosourea (0.2 g) in Et2O (5 mL) was added dropwise. The
residue was filtered off and washed with Et2O (5×5 mL). The
solvent was removed in vacuo. Product 3 (170 mg, 80%) was
obtained as white crystals, m.p. 93—96 °C.
1
Compound 4. H NMR (СDCl3), δ: 3.68 (s, 3 Н, Me); 7.22
(d, 2 H, Н(2), Н(6), J = 9.2 Hz); 8.27 (d, 2 H, Н(3), Н(5),
J = 9.2 Hz). 13C NMR (СDCl3), δ: 45.5 (Me); 114.0 (C(2),
С(6)); 125.9 (С(3), С(5)); 143.9 (С(4)); 162.5 (С(1)).
NꢀMethylꢀNꢀ[nitroꢀ15N]ꢀОꢀ(4ꢀnitrophenyl)hydroxylamine
(4´) and E(Z)ꢀ1ꢀmethoxyꢀ2ꢀ(4ꢀnitrophenyl)diazene[1ꢀ15N] 1ꢀoxꢀ
ide (3´). A mixture of compounds 3´ and 4´ (in a ratio of 1 : 1)
was prepared from sodium salt 1b according to the procedure
analogous to that for the preparation of the unlabeled products 3
and 4. 1H NMR (СDCl3), δ: 3.68 (d, 3 Н, Me, J(1H—15N) =
= 3.4 Hz); 7.22 (d, 2 H, Н(2), Н(6), J = 9.2 Hz); 8.27 (d, 2 H,
Н(3), Н(5), J = 9.2 Hz).
Procedure B. To a solution of NHA 2 (100 mg, 0.5 mmol) in
Et2O (10 mL), an excess of a solution of diazomethane prepared
from NꢀmethylꢀNꢀnitrosourea (0.2 g) in Et2O (5 mL) was added
dropwise at 0 °C. The solvent was removed in vacuo. Product 3
Decomposition of NHA 2 in the solid state. For the preparaꢀ
tion of the solid sample of NHA 2, we used a standard procedure

2056
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
Klenov et al.
that included vacuum concentration (1 Torr) to dryness of
a solution of NHA 2 (10 mg, 0.05 mmol) in Et2O (1 mL) in
a oneꢀnecked flask at 0 °C in 5 min. The subsequent operations
were performed in the same flask. Air was let in the flask, the
sample was heated to 20 °C and kept for 20 min. The reaction
products were dissolved in CD3OD (0.55 mL). The product yields
were determined by 1H NMR spectroscopy (see Table 3).
Decomposition of NHA 2 in the solid state under evacuation.
A sample of NHA 2 prepared according to the standard proceꢀ
dure as described in the previous experiment was heated to 20 °C
and kept for 2 h at the residual pressure of 1 Torr. The flask was
then cooled to 0 °С, air was let in and the reaction products were
immediately dissolved in CD3OD (0.55 mL). The yields of the
products were determined by 1H NMR spectroscopy (see Table 3).
Decomposition of NHA 2 in solutions. To a sample of NHA 2
prepared according to the standard procedure, the solvent
(CHCl3, CH2Cl2, or benzene) (1 mL) was added. The decomꢀ
position conditions (reaction temperature and time) are given in
Table 3. After completion of the reaction, the solvent was reꢀ
moved in vacuo. The product yields were determined by 1H NMR
spectroscopy (see Table 3).
Decomposition of NHA 2 in H2O. To a sample of NHA 2
prepared according to the standard procedure, H2O was added.
The reaction mixture was heated at 40 °C for 14 h, then cooled
to 20 °C and extracted with AcOEt (4×1 mL). Et2O (2 mL) was
added to the extract in order to stabilize the unconsumed NHA 2.
The combined organic layer was washed with a brine (0.5 mL),
dried with MgSO4 and concentrated in vacuo at 0 °C. The reacꢀ
tion products were immediately dissolved in CD3OD (0.55 mL).
The product yields were determined by 1H NMR spectroscopy
(see Table 3).
a precooled to 0 °C solution of HNO3 (the amount is given in
Table 6) in CHCl3 (0.02 mL) was added with stirring at 0 °C at
once. The reaction mixture was kept for 1 day at 0 °С. After
completion of the reaction (TLC), the solvent was removed
in vacuo. The conversion of 4ꢀnitrophenol and the yield of
2,4ꢀdinitrophenol were determined by 1H NMR spectroscopy
(see Table 6).
Reaction of 4ꢀnitrophenol with N2O4 in СHCl3. To a soluꢀ
tion of 4ꢀnitrophenol (10 mg, 0.07 mmol) in CHCl3 (0.8 mL),
a precooled to 0 °C solution of N2O4 (the amount is given in
Table 6) in CHCl3 (0.2 mL) was added with stirring at 0 °C
at once. The reaction mixture was kept with vigorous stirring
at 0 °С for the period indicated in Table 6. After compleꢀ
tion of the reaction (TLC), the solvent was removed in vacuo.
The conversion of 4ꢀnitrophenol and the yield of 2,4ꢀdinitꢀ
rophenol were determined by 1H NMR spectroscopy (see
Table 6).
Decomposition of NHA 2´ in CDCl3. NHA 2´ (20 mg,
0.10 mmol) ground at 0 °C was placed under argon into an NMR
tube cooled to –30 °C. CDCl3 (0.6 mL) precooled to –20 °C was
then added at once. The cooled tube was sealed, then heated to
20 °C and kept for 5 h. The 1H, 14N, and 15N NMR spectra were
recorded. In the 1H NMR spectrum, the signals for 4ꢀnitropheꢀ
nol and 2,4ꢀdinitrophenol coinciding with those for the authenꢀ
tic samples were observed. 14N NMR (CDCl3), δ: –13 (NO2
groups of 5 and 6, Δν1/2 = 240 Hz), –47 (HNO3, Δν1/2 = 30 Hz;
the signal coincided with that for the knowing sample of HNO3
in CDCl3), –148 (br.s, the central N atom in NNO, Δν
=
1/2
= 15 Hz, 1J(14N—14N) = 4.2 Hz, cf. Ref. 9), –231 (the terminal
N atom in NNO and N15NO, Δν = 20 Hz). The molar ratio
1/2
NNO : N15NO, equal to 0.3 : 0.7, was determined from the ratio
of the signal intensities for the central and terminal N atoms
taking into account the integral intensities of the corresponding
signals in the solution of the authentic sample of N2O in СDCl3.
15N NMR (CDCl3), δ: –14.04 (dd, 2ꢀ15NO2 group of the 2,4ꢀdiꢀ
nitrophenyl fragment, 3J(1H—15N) = 2.5 Hz, 4J(1H—15N) =
= 1.0 Hz), –46.8 (H15NO3), –147.2 (t, the central N atom in
Solventꢀdependence of the decomposition rate of NHA 2. To
a sample of NHA 2 prepared according to the standard procedure,
the solvent (0.5 mL) was added at the temperature indicated in
Table 4. The time period from the point of mixing of NHA 2
with the solvent to the time of appearance of the first traces of
compounds 5 and 6 was determined by TLC (CHCl3—AcOEt,
4 : 1). The total decomposition time of NHA 2 was determined
in the same manner.
N
15NO, 1J(14N—15N) = 6.2 Hz, cf. Ref. 10).
After recording of the spectra, the NMR tube was opened
Reaction of NHA 2 with HNO3 in СHCl3. To a sample of
NHA 2 prepared according to the standard procedure, СHCl3
(1 mL) precooled to 0 °C was added and the mixture was stirred
at 0 °С until dissolution of 2. A solution of HNO3 (the amount is
given in Table 5) in CHCl3 (0.02 mL) was added at the same
time. The time period from the point of mixing of NHA 2 with
the reagent to the point of appearance of the first traces of 5 and
6 was determined by TLC. After completion of the reaction
(TLC), the solvent was removed in vacuo. The product yields
were determined by 1H NMR spectroscopy (see Table 5).
Reaction of NHA 2 with N2O4 in СHCl3. To the sample of
NHA 2 prepared according to the standard procedure, СHCl3
(0.8 mL) precooled to 0 °C was added and the mixture was
stirred at 0 °С until dissolution of 2. A solution of N2O4 (the
amount is given in Table 5) in CHCl3 (0.2 mL) was added at the
same time, the solution immediately becoming yellow. The reꢀ
action mixture was kept at 0 °С for the period indicated in Table 5.
After completion of the reaction (TLC), the solvent was reꢀ
moved in vacuo. The product yields were determined by 1H NMR
spectroscopy (see Table 5).
and the reaction mixture was concentrated in vacuo. The reacꢀ
tion products were separated by preparative TLC on silica gel
(CHCl3) to obtain 2,4ꢀdinitrophenol (3 mg) and 4ꢀnitrophenol
(9 mg). 2,4ꢀDinitrophenol obtained was analyzed by mass specꢀ
trometry. MS, m/z (ratio of the signal intensities): 287, 288,
289 [M]+ (1 : 1.9 : 0.19). In veiw of the degree of enrichment,
the molar ratio of 6 with the unlabeled nitro groups, 6 with one
and two labeled nitro groups is 1 : 2.0 : 0.2.
Thermal decomposition of 1ꢀmethoxyꢀ2ꢀ(4ꢀnitrophenyl)ꢀ
diazene 1ꢀoxide (3) in СHCl3. A solution of compound 3 (10 mg,
0.047 mmol) in СHCl3 (7.5 mL) was refluxed (61 °C) for 1.3 h,
then cooled and the solvent was removed in vacuo. According to
the 1H NMR spectral data, the conversion of compound 3 is 8%,
the yields of 5 and 6 based on the consumed material are 75%
and 13%, respectively.
Thermal decomposition of 1ꢀmethoxyꢀ2ꢀ(4ꢀnitrophenyl)ꢀ
diazene 1ꢀoxide (3) in octane. A solution of compound 3 (10 mg,
0.047 mmol) in octane (1 mL) was kept at 70 °C for 14 h, then
cooled and the solvent was removed in vacuo. According to the
1H NMR spectral data, the conversion of compound 3 is 57%,
the yields of 5 and 6 based on the consumed material are 89%
and 7%, respectively.
Reaction of 4ꢀnitrophenol with HNO3 in СHCl3. To a soluꢀ
tion of 4ꢀnitrophenol (10 mg, 0.07 mmol) in CHCl3 (1 mL),

NꢀNitroꢀOꢀ(4ꢀnitrophenyl)hydroxylamine
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 10, October, 2009
2057
7. S. L. Ioffe, A. L. Blyumenfeld, A. S. Shashkov, Izv. Akad.
Nauk SSSR, Ser. Khim., 1978, 246 [Bull. Acad. Sci. USSR.
Div. Chem. Sci. (Engl. Transl.), 1978, 27, 218].
8. A. M. Churakov, S. E. Semenov, S. L. Ioffe, Y. A. Strelenko,
V. A. Tartakovsky, Mendeleev Commun., 1995, 102.
9. Yu. A. Strelenko, N. M. Sergeyev, J. Mol. Struct., 1996,
378, 61.
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 07ꢀ03ꢀ00409).
References
1. E. N. Khodot, I. E. Chlenov, V. A. Tartakovsky, Izv. Akad.
Nauk, Ser. Khim., 1994, 178 [Russ. Chem. Bull., Int. Ed.,
1994, 43, 174].
10. P. K. Bhattacharyya, B. P. Dailey, J. Chem. Phys., 1973,
59, 5852.
11. A. H. Clemens, J. H. Ridd, J. P. B. Sandall, J. Chem. Soc.
Perkin Trans. 2, 1984, 1667.
2. E. N. Khodot, I. M. Petrova, O. V. Anikin, I. E. Chlenov,
Izv. Akad. Nauk, Ser. Khim., 1995, 2276 [Russ. Chem. Bull.,
Int. Ed., 1995, 44, 2183].
12. M. Ali, J. H. Ridd, J. Chem. Soc. Perkin Trans. 2, 1986, 327.
13. V. A. Shlyapochnikov, Kolebatel'nye spektry alifaticheskih niꢀ
trosoedinenii [Vibrational Spectra of Aliphatic Nitro Comꢀ
pounds], 2nd Ed., Yoshkar Ola, Mari State University, 2007,
p. 157 (in Russian).
14. A. J. Castellino, H. Rapoport, J. Org. Chem., 1984, 49, 1348.
15. F. Arndt, in Organic Syntheses, 15, Wiley, New York,
1935, p. 3.
3. M. S. Klenov, A. M. Churakov, O. V. Anikin, Yu. A. Streꢀ
lenko, V. A. Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2008,
625 [Russ. Chem. Bull., Int. Ed., 2008, 57, 638].
4. O. A. Anikin, G. V. Pokhvisneva, D. L. Lipilin, A. V. Mezheꢀ
nin, V. A. Tartakovsky, Izv. Akad. Nauk, Ser. Khim., 2009,
1981 [Russ. Chem. Bull., Int. Ed., 2009, 58, 2043].
5. V. N. Yandovich, B. V. Gidaspov, I. V. Tselinskii, Usp.
Khim., 1980, 49, 461 [Russ. Chem. Rev. (Engl. Transl.), 1980,
49, 237].
6. E. N. Khodot, O. V. Anikin, I. E. Chlenov, Izv. Akad. Nauk,
Ser. Khim., 1996, 1740 [Russ. Chem. Bull., Int. Ed., 1996,
45, 1649].
Received April 1, 2009