ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 7, pp. 982−985. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © A.L. Plekhov, O.V. Kushch, I.O. Opeida, M.A. Kompanets, 2014, published in Zhurnal Prikladnoi Khimii, 2014, Vol. 87, No. 7, pp. 986−989.
Recently there has been a great deal of interest in
functionalization of organic compounds by oxidation with
molecular oxygen, catalyzed by N-hydroxyphthalimide
(NHPI) [1, 2]. NHPI in combination with cobalt salts
forms an effective catalytic system for autooxidation
of a number of organic substrates such as alkanes and
alkylbenzenes . Ishii et al.  developed a process
for preparing terephthalic acid without using halogen-
containing catalysts. In this process, p-xylene is oxidized
with molecular oxygen in the presence of the catalytic
. To oxidize xylenes to the
corresponding dicarboxylic acids, it is necessary to use
high temperatures (423 K) and a combination of Со(II)
and Mn(II) salts . Ishii and Sakaguchi  suggested a
mechanism of the catalytic action of the NHPI–Со(ОАс)
system, involving participation of the cobalt salt in
the radical generation step. In the process, the cobalt–
oxygen complex formed by Со with О
NHPI to form phthalimide N-oxyl radical (PINO), which
subsequently participates in the catalytic oxidation cycle.
PINO abstracts a hydrogen atom from the RH molecule
to form alkyl radicals with the regeneration of NHPI.
The alkyl radicals react with oxygen to form peroxy
), which subsequently transform into alkyl
hydroperoxide. The catalysis is cyclic and involves return
to the initial oxidation state of the metal, and the PINO
radical transforms into the initial NHPI.
Metal catalysts also actively participate in decompo-
sition of hydroperoxides into radicals, followed by the
formation of carbonyl compounds. However, published
data on the nature and mechanism of catalysis of p-xylene
oxidation with molecular oxygen in the presence of the
system are incomplete.
As we showed previously , the synergistic effect of
the catalytic system NHPI–Co(II) is due to complexation
between the system components, and the magnitude of
the synergistic effect  depends on the structure of the
NHPI molecule. The catalysis efﬁ ciency also depends on
the nature of the cocatalyst.
In this paper we analyze how the catalytic activity
of the NHPI–metal(II) salt system in separate steps
of p-xylene oxidation depends on the nature of the
p-Xylene was puriﬁ ed by the standard procedure .
N-Hydroxyphthalimide (Fluka) was used without pre-
liminary puriﬁ cation. Acetic acid was distilled from Р
(118–120°С at 1 atm). Со(ОАс)
О was of analyti-
cally pure grade; anhydrous cobalt acetate was prepared
according to . Cobalt(II) stearate (analytically pure
grade) was used without preliminary puriﬁ cation. Cobalt
Catalytic Oxidation of p-Xylene with Molecular Oxygen
in the Presence of N-Hydroxyphthalimide
A. L. Plekhov, O. V. Kushch, I. O. Opeida, and M. A. Kompanets
Litvinenko Institute of Physical Organic Chemistry and Coal Chemistry,
National Academy of Sciences of Ukraine, ul. Rozy Luksemburg 70, Donetsk, 830114 Ukraine
Received July 14, 2014
Abstract—Relationships of p-xylene oxidation in the presence of N-hydroxyphthalimide and Co(II) and Mn(II)
salts were studied. The activity of the catalytic system strongly depends on the volume of the ligand incorporated
in the salt. The synergism in combined use of Co(II) and Mn(II) salts is observed only in the step of p-toluic
acid oxidation, whereas replacement of a half of the Co(II) salt by the Mn(II) salt in p-xylene oxidation leads to
additive increase in the reaction rate.