ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 1, pp. 123!126. + Pleiades Publishing, Inc., 2006.
Original Russian Text + A.A. Sedykh, A.G. Galstyan, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 1, pp. 125!128.
AND INDUSTRIAL ORGANIC CHEMISTRY
Oxidation of p-Cresol with Ozone in Acetic Anhydride
A. A. Sedykh and A. G. Galstyan
Dal’ East-Ukrainian National University, Rubezhnoe Branch, Rubezhnoe, Lugansk oblast, Ukraine
Received July 26, 2005
Abstract-Preparation of aromatic alcohols and aldehydes by oxidation of p-cresol with ozone in acetic
anhydride in the presence of sulfuric acid, manganese acetate, and potassium bromide was studied. The op-
timal oxidation conditions were determined.
p-Cresol (p-Cr) oxidation products, p-hydroxyben-
zyl alcohol (p-HBA) and p-hydroxybenzaldehyde
(p-HBAd), are used in production of synthetic drugs
and products of fine organic synthesis . These prod-
ucts are prepared by oxidation of p-cresol with sodium
dichromate or chromic anhydride in concentrated sul-
furic acid . The disadvantages of this procedure are
formation of large amounts of difficult to utilize toxic
waste and relatively low selectivity. To overcome
these disadvantages, environmentally clean oxidizing
agent, ozone, can be used.
Ozone is used to oxidize methylbenzenes in acetic
acid to the corresponding benzenecarboxylic acids .
The possible intermediates, aromatic alcohols and
aldehydes, are readily oxidized under these conditions
and cannot be isolated.
To decelerate the oxidation at the step of formation
of p-HBA and p-HBAd and to develop a low-waste
technology of their production, we studied the reac-
tion of p-Cr with ozone in acetic anhydride in the
presence of a strong mineral acid. Under these condi-
tions, acetic anhydride is a strong acylating agent and
reacts with the intermediate reaction products to form
the acetate and acylal derivatives which are more
resistant to oxidation .
It is known  that p-Cr readily reacts with ozone
in the liquid phase with opening of the aromatic ring
to form peroxides (k =2010
293 K). In acetic acid, one p-Cr molecule is consumed
per three ozone molecules, which suggests that this
process occurs in two steps by Scheme 1 .
In the first step, ozone attacks the O3H bond to
form the phenoxy radical. Then hydroxy radical is
added to phenoxy radical with opening of the aromatic
ring. The product reacts with two ozone molecules to
form the aliphatic peroxide.
To stabilize the aromatic ring of p-cresol, its OH
group was acylated. Weighed portions of p-Cr and
acetic anhydride were loaded in a flask. A mixture of
acetic anhydride and phosphoric acid taken in a 10 : 1
weight ratio was added in small portions at 5oC.
The reaction mixture was poured into water after
20 min. The oil was separated, washed with a 5%
solution of sodium hydroxide and water, and distilled
in a vacuum. The yield of p-cresyl acetate (p-CrA)
An ozone3air mixture with an ozone concentration
of 4 010
M was bubbled through a p-CrA solution
in acetic anhydride. The kinetic experiments showed
that the reactivity of p-CrA with respect to ozone sub-
stantially decreases: the rate constant of this reaction
at 20oCisk = 1.3 l mol
. This fact and the stoi-
chiometric coefficient of ozone in this reaction (one
ozone molecule per substrate molecule) confirm the
change in the oxidation mechanism. In this case, in
accordance with the classical concept on ozonolysis of