Colloid and nanosized catalysts in organic synthesis: IV. Reduction of nitroarenes with hydrazine hydrate catalyzed with metal nanoparticles

Article abstract of DOI:10.1134/S107036321408012X

Reduction of a series of nitroarenes with hydrazine hydrate catalyzed with colloid iron, cobalt, nickel, and copper particles has been studied. High catalytic activity of nickel and iron nanoparticles has been demonstrated. Special features of nitrobenzene reduction in the presence of cobalt particles have been revealed.

Full text of DOI:10.1134/S107036321408012X

ISSN 1070-3632, Russian Journal of General Chemistry, 2014, Vol. 84, No. 8, pp. 1515–1518. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © V.M. Mokhov, Yu.V. Popov, D.N. Nebykov, 2014, published in Zhurnal Obshchei Khimii, 2014, Vol. 84, No. 8, pp. 1289–1292.
Colloid and Nanosized Catalysts in Organic Synthesis:
1
IV. Reduction of Nitroarenes with Hydrazine Hydrate
Catalyzed with Metal Nanoparticles
V. M. Mokhov, Yu. V. Popov, and D. N. Nebykov
Volgograd State Technical University, ul. Lenina 28, Volgograd, 400131 Russia
e-mail: nervwho@gmail.com
Received January 16, 2014
Abstract—Reduction of a series of nitroarenes with hydrazine hydrate catalyzed with colloid iron, cobalt,
nickel, and copper particles has been studied. High catalytic activity of nickel and iron nanoparticles has been
demonstrated. Special features of nitrobenzene reduction in the presence of cobalt particles have been revealed.
Keywords: catalyst, nanoparticles, nitroarenes, aniline
DOI: 10.1134/S107036321408012X
Reduction of nitrobenzene and its homologs is a
well studied industrial process. However, gas-phase
reduction with heterogeneous catalysts is often too
complicated and unreasonably expensive in view of its
preparative application. The obsolete method of
anilines preparation via reduction of nitrocompounds
with iron filings in highly acidic medium is not
universal.
with sodium borohydride at gold or copper nano-
particles has been studied in [7, 8]. Gold nanoparticles
have been used for nitroarenes hydrogenation with the
amine–borane complex [9]. Application of platinum
nanoparticles has allowed conversion of nitrobenzene
to aniline at 25ºC and hydrogen pressure of 1 bar [10].
However, possibility of aromatic nitrocompounds
reduction using metal nanoparticles as catalyst has not
been systematically studied so far. We successfully
reduced nitrobenzene and its homologs with hydrazine
hydrate in the presence of nickel nanoparticles. The
nickel nanoparticles were prepared as described
elsewhere [11, 12], their average size being of 4–
The nitro group of aromatic compounds is known
to be reduced with hydrazine hydrate under mild
conditions at the Raney nickel [2]. This method suffers
from the drawback of complicated Ni–Al alloy
preparation, not suitable for laboratory practice. Hyd-
rogenation processes utilizing nanodispersed catalysts
have been recently studied in a number of works. For
example, hydrogenation of aromatic compounds,
dienes, and olefins with hydrogen in the presence of
binary noble metal nanoparticles immobilized at the
support has been reported in [3]. Almost quantitative
hydrogenation of arenes in the presence of iridium and
rhodium nanoparticles has been demonstrated in [4].
Reduction of chloronitrobenzene with hydrogen at 1
bar using platinum, palladium, and ruthenium
nanoparticles or their mixtures has been described in
1
6 nm. The so obtained black suspensions were used
as catalysts without isolation of nanoparticles or their
stabilization in suspension. Both the nitrocompound
and the metal precursor were reduced with hydrazine
hydrate; hence, the whole synthesis was carried out as
one-pot process starting from the nitrocompound, the
nickel salt, and hydrazine hydrate.
The reduction was carried out via portionwise
addition of nitrobenzene Ia or its homolog to the
suspension of nickel nanoparticles in a mixture of
hydrazine hydrate and 2-propanol at 20–80ºC. Reduc-
tion was almost immediate at 60–80ºC, accompanied
with the mixture boiling up. The side alkylation of
aniline with the formed 2-propanol was not observed.
Yield of aniline IIa was close to quantitative, the
[
5]. Nitrobenzene has been reduced with hydrogen (1
bar) at nickel nanoparticles coated with palladium [6].
Reduction of 2-, 3-, 4-nitrophenols and 4-nitroaniline
1
For communication III, see [1].
1
515

1
516
MOKHOV et al.
product losses taking place during its isolation. Aniline
content in the distilled product was of 100% (GLPC).
Yield of aniline was of 94%.
In contrast to Ni and Fe particles, reduction of
nitrobenzene in the presence of cobalt nanoparticles
led to formation of the side product, N-phenylhyd-
roxylamine, along with aniline. Due to the low
solubility in aqueous 2-propanol, it could be easily
isolated in the form of white crystalline solid quickly
NO2
NH2
o
Ni , N H H O
2
4
2
−
2H O
2
R
R
Iа−Ie
R = H (а), o-CH (b), n-OC
IIа−IIe
(d), n-NH (e).
NH2
3
2
H
5
(c), o-NH
2
2
o
.
Fe , N H H O
2
4
2
Reduction of 2-nitrotoluene, 4-ethoxynitrobenzene,
-nitroaniline, and 4-nitroaniline proceeded similarly,
−
2H O
2
2
but the heat evolution was somewhat lower. The yields
of the reduction products were of 78–83%, and their
properties were in agreement with the reference data
NO
NH
2
2
o
.
Cu , N H H O
2
4
2
[13].
−
2H O
2
The mass ratio of nitrobenzene and the catalyst
used in this work was of 100 : 1 compared to 10 : 1 in
the typical procedure involving the Raney nickel.
Reduction of nitrobenzene in the presence of nickel
nanoparticles was successfully carried out in the
aqueous heterogeneous system upon vigorous stirring
as well.
NH2
NHOH
o
.
Co , N H H O
2
4
2
+
−2H O
2
The nanoparticles dispersion was unstable towards
coagulation and precipitation; therefore, the catalyst
could be separated off the reaction mixture via careful
filtration. Isolated from air, the catalyst could be used
repeatedly without significant loss of activity. In
contrast to the Raney nickel, the nanoparticles were
not pyrophoric and were rapidly oxidized into the
oxide without ignition in contact with air.
becoming yellow in air. Its physical properties were in
agreement with the reference data [15].
Selective reduction of nitroarenes to arylhydroxyl-
amines catalyzed with platinum nanoparticles applied
on carbon at 20ºC and hydrogen pressure of 1 bar was
reported [16].
Apparently, colloid dispersions of all nanoparticles
of the VIIIB group elements can act as catalysts of
nitroarenes reduction. However, elements of other
groups can catalyze such reduction reactions as well.
For example, we carried out reduction of nitrobenzene
with hydrazine hydrate in the presence of copper
colloid dispersion, resulting in formation of aniline
with 92% yield.
Colloid dispersion of the nickel nanoparticles was
successfully used for reduction of 8-nitroquinoline III
to 8-aminoquinoline IV with yield of 72%.
o
Ni , N H
.
H O
4 2
2
−
2H O
2
N
N
NO2
NH2
III
IV
To summarize, the results reported in this work reveals
promising potential of developing the nitroarenes
reduction methods involving metal nanoparticles.
Creation of ferromagnetic colloid catalysts that can
be easily removed and recycled has been among
topical issues in the field of catalysis [14]. Keeping
this in mind, we attempted reduction of nitrobenzene
into aniline in the presence of iron nanoparticles
prepared similarly to the nickel ones. The reduction
was accompanied with significant heat evolution,
being complete within several minutes at 40–80ºC.
EXPERIMENTAL
GLPC analysis was carried out with the Crystal-
lolux 4000M chromatograph (helium as carrier gas,
HP-5 column, flame ionization detector, hexane as
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 84 No. 8 2014

COLLOID AND NANOSIZED CATALYSTS IN ORGANIC SYNTHESIS: IV.
1517
solvent, evaporator temperature 250ºC, programmed
heating of the column at 12 deg/min from 100 to
o-Phenylenediamine (IIc). Prepared similarly from
0.5 g of NaOH, 1 mL of water, 30 mL of 2-propanol,
25 g of hydrazine hydrate, 0.8 g (0.0028 mol) of
Ni(NO ) ·6H O, and 13.8 g (0.1 mol) of 2-nitroaniline.
2
10ºC).
3
2
2
Aniline Ia. a. A mixture of 0.6 g of NaOH, 1 mL of
Yield 8.4 g (0.078 mol, 77.5%), mp 99–100ºC (mp
water, 50 mL of 2-propanol, and 61 g (1.22 mol) of
hydrazine hydrate was heated to 60–80ºC. Then, a
solution of 1 g (0.0054 mol) of NiCl ·6H O or 1.55 g
1
00–102ºC [13, p. 1039]).
2
2
p-Phenylenediamine (IId). Prepared similarly
(
0.0054 mol) of Ni(NO ) ·6H O in aqueous 2-propanol
3
2
2
from 0.5 g of NaOH, 1 mL of water, 30 mL of 2-
propanol, 25 g of hydrazine hydrate, 0.8 g (0.0028 mol)
of Ni(NO ) ·6H O, and 13.8 g (0.1 mol) of 4-nitro-
was added portionwise upon vigorous stirring. The so
obtained black solution was refluxed during 30 min,
and then 30 g (0.244 mol) of nitrobenzene was added
dropwise avoiding violent boiling and foaming of the
mixture. After addition of nitrobenzene, reaction
mixture was refluxed during 10–15 min and filtered; 2-
propanol was then distilled off. Water layer was
separated off, and the organic layer was distilled to
give 22.2 g on aniline (0.24 mol, 98%), bp 183–184ºC,
3
2
2
aniline. Yield 8.8 g (0.082 mol, 82%), mp 138–140ºC
(
mp 139–141ºC [13, p. 1041]).
4
-Ethoxyaniline (IIe). Prepared similarly from
0
2
.5 g of NaOH, 1 mL of water, 30 mL of 2-propanol,
5 g of hydrazine hydrate, 0.8 g (0.0028 mol) of
Ni(NO ) ·6H O, and 16.7 g (0.1 mol) of 4-nitro-
2
0
20
3 2
2
n
1.5860 (bp 184ºC, n 1.5863 [13, p. 425]).
D
D
phenetol. Yield 10.3 g (0.075 mol, 75%), bp 248–
2
49ºC (bp 248.6ºC [13, p. 1037]).
b. Iron nanoparticles prepared similarly from 0.5 g
of NaOH, 1 mL of water, 50 mL of 2-propanol, 41 g
0.81 mol) of hydrazine hydrate, and 2.7 g (0.01 mol)
of FeCl ·6H O. Reduction of 20 g (0.163 mol) of
8
-Aminoquinoline (IV). Prepared similarly from
(
0
1
.25 g of NaOH, 1 mL of water, 15 mL of 2-propanol,
5 g of hydrazine hydrate, 0.4 g (0.0014 mol) of
3
2
nitrobenzene was performed similarly to yield 14.5 g
Ni(NO ) 6H O, and 8.7 g (0.05 mol) of 8-nitro-
20
3 2·
2
(
0.155 mol, 94%) of aniline, bp 182–184ºC, nD 1.5862.
quinoline. Yield 5.2 g (0.036 mol, 72%), mp 63–66ºC
o
(
mp 64–65 C [17]).
c. Cobalt nanoparticles were prepared similarly
from 0.5 g of NaOH, 1 mL of water, 40 mL of 2-
propanol, 25 g of hydrazine hydrate, and 2.4 g
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