ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 10, pp. 1865–1867. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © A.G. Galstyan, A.I. Tarasenko, Yu.A. Shumilova, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 10,
Oxidation of 4-Hydroxytoluene with an Ozone–Oxygen Mixture
in Acetic Acid
A. G. Galstyan, A. I. Tarasenko, and Yu. A. Shumilova
Institute of Chemical Technologies, Dal’ East-Ukrainian National University, Rubezhnoe, Lugansk oblast, Ukraine
Received February 5, 2008
Abstract—Liquid-phase oxidation of 4-hydroxytoluene by ozone to 4-hydroxybenzoic acid in the presence of
cobalt(II) acetate as a catalyst was studied. The optimal oxidation conditions were found.
4-Hydroxybenzoic acic (4-HBA) is widely used in
production of drugs and pharmaceuticals, as conser-
vant for foodstuffs, and for preparation of liquid crys-
tal compounds [1, 2]. In industry, this acid is mainly
produced by carboxylation of potassium phenolate 
and oxidation of 4-hydroxytoluene (4-HT) with Pb,
Mn, and Fe oxides . The drawbacks of these proce-
dures are the process complexity in the first case and
formation of large amounts of toxic wastewater in
the second case.
In this study we examined oxidation of 4-HT by
an ozone–oxygen mixture with the aim to develop a low-
waste process for 4-HBA production.
Published data on ozonation of 4-HT in acetic
acid are lacking. It is only known [5–7] that, in tetra-
chloromethane, ozone rapidly attacks methylphenols at
the lone electron pair of the OH group, which is fol-
lowed by breakdown of the aromatic ring. Products of
methyl group oxidation are not formed under these
The results of preliminary studies of the reaction
of ozone with 4-HT in acetic acid do not differ noticea-
bly from those described in [5–7]: The reaction rate
constant at 20°C is 2.2 × 10
, and only ali-
phatic peroxides are detected in the oxidate after ex-
haustive oxidation of the substrate.
With the aim to protect the OH group of the 4-HT
molecule from the attack by ozone, it was acylated.
The kinetic experiments showed that the reactivity
of acylated 4-HT in reactions with ozone is considera-
bly lower than that of nonacylated 4-HT, as indicated
by the apparent rate constant obtained at 20°C: k
. A drastic decrease in the rate constant
of the reaction of ozone with 4-acetoxytoluene (4-AT),
compared to 4-HT, suggests a change in the oxidation
mechanism. Apparently, in this case, ozone attacks not
the OH group but, in accordance with the classical
concept of the reaction of ozone with alkylbenzenes
[7, 8], predominantly the double bonds of the aromatic
ring (86.8%) and, to a lesser extent, the methyl group
(12.9%) (see figure). At 20°C, 1.15 mol of ozone is
consumed per mole of 4-AT.
Variation of the concentration c of reaction mixture com-
ponents in oxidaiton of 4-AT by an ozone–oxygen mixture
COOH at (1–3) 20 and (1'–3') 95°C in the pres-
ence of cobalt(II) acetate. [4-AT]
= 0.4, [O
] = 0.18 M; v
. (1, 1') 4-AT,
(2) peroxides, (2') 4-ABAl, and (3, 3') 4-ABA. (τ) Time.