Reduction of Nitrophenols in an Electrocatalytic System
N. M. Ivanova, E. A. Soboleva, E. V. Kulakova, V. P. Malyshev, and I. V. Kirilyus
Kazakh Republic Institute of Organic Synthesis and Coal Chemistry, Joint-Stock Company,
Karaganda, Kazakh Republic
Abishev Chemicometallurgical Institute, Daughter State Enterprise, Karaganda, Kazakh Republic
Received December 28, 2007
Abstract―Results of research into hydrogenation of o- and p-nitrophenols in an electrocatalytic system on a
cathode activated with d- and s-metal catalysts are presented. The optimal conditions for o-aminophenol
formation on Raney nickel were identified by the probability-determined method for the experimental design.
ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 3, pp. 421–428. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © N.M. Ivanova, E.A. Soboleva, E.V. Kulakova, V.P. Malyshev, I.V. Kirilyus, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol.
82, No. 3, pp. 428–435.
Nitrophenols belong to aromatic nitro compounds
that are the subject of much investigation in connection
with their conversion to anilines. This process ranks
among the most important reactions in organic
chemistry and yields amines that find extensive
industrial, agricultural, and pharmaceutical applica-
tions. Probably, this is specifically responsible for large
developmental efforts dedicated to reduction of
nitroaromatic compounds, in particular, nitrophenols.
They range from the earliest developments in which
reduction was effected with pig-iron chips  to the
modern ones applying nanostructured activated iron,
silver, and palladium powders [2–4].
As known, electrochemical reduction of nitroaromatic
compounds is complicated by various side chemical
transformations which are strongly dependent on рН of
the medium . For example, reduction of o-
nitrophenol (o-NP) on porous copper hydrophobized
electrodes in 15% aqueous NaОН at 50–70°С yields o-
azoxyphenol, o-azophenol, and o-aminophenol (o-AP),
and in an acid electrolyte (10% H
) o-NP is
reduced to o-AP in a virtually quantitative yield .
Reduction of p-NP in an electrolytic cell on an
amalgamated copper cathode yields a mixture of p-AP
and aniline (in approximately 22:1 molar ratio) .
Electrochemical reduction of o-, m-, and p-nitro-
phenols on glassy carbon and copper cathodes against
1 M NaOH background yields aminophenols in high
An example of chemical methods for reduction of
nitrophenols is that utilizing FeS–NH
O system in which o-NP is reduced within 8 h with
56% yield of the product, and p-NP, within 5 h with
74% yield . In a similar system with iron sulfide
replaced by aluminum metal and under ultrasonic
irradiation the reduction of o-NP proceeds, by contrast,
more vigorously (within 2.5 h, with o-AP in 90%
yield), than in the case of p-NP (within 3 h, 86% yield)
. Also, o-NP is reduced under the action of Na
NaSH with 90% yield of the amine product . In the
O/indium powder system in a methanol
solution under ultrasonic irradiation the reduction of p-
NP within 2 h gives p-AP in 86% yield .
Also, the catalytic reduction of nitroaromatic
compounds can be accompanied by interaction and
isomerization of intermediates. At the same time,
numerous methods of their successful catalytic
reduction to corresponding amines in high yields are
also known. For example, o-, m-, and p-nitrophenols
react with formic acid (or ammonium formiate) in the
presence of Raney nickel in methanol at Т~20°С and
form the corresponding aminophenols in 85–90% yield
within 10–20 min . With 5% Pt/C and the same
reactants, the reduction of p-NP takes 45 and 60 min,
respectively, for 91% yield of the product, and that of
o-NP, 60 and 100 min, respectively, for 89% yield [14,
15]. The maximal yields for p-AP are observed in
hydrogenation of p-NP with molecular hydrogen in the
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