Oxidation of p-cresol with ozone in acetic anhydride

Article abstract of DOI:10.1134/S1070427206010253

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 optimal oxidation conditions were determined. Pleiades Publishing, Inc., 2006.

Full text of DOI:10.1134/S1070427206010253

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.
ORGANIC SYNTHESIS
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.
DOI: 10.1134/S1070427206010253
p-Cresol (p-Cr) oxidation products, p-hydroxyben-
zyl alcohol (p-HBA) and p-hydroxybenzaldehyde
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 5 C.
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)
was 80%.
(
p-HBAd), are used in production of synthetic drugs
and products of fine organic synthesis [1]. These prod-
ucts are prepared by oxidation of p-cresol with sodium
dichromate or chromic anhydride in concentrated sul-
furic acid [2]. 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.
An ozone air mixture with an ozone concentration
of 4 10 4 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 20 C is k = 1.3 l mol 1 s . 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
Ozone is used to oxidize methylbenzenes in acetic
acid to the corresponding benzenecarboxylic acids [3].
The possible intermediates, aromatic alcohols and
aldehydes, are readily oxidized under these conditions
and cannot be isolated.
1
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 [4].
Scheme 1
It is known [5] that p-Cr readily reacts with ozone
in the liquid phase with opening of the aromatic ring
to form peroxides (k = 2 103 l mol 1 s , CCl ,
2
1
4
93 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 [6].
In the first step, ozone attacks the O H 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.
123

124
SEDYKH, GALSTYAN
Under these conditions, virtually no aromatic
c, M
alcohol and aldehyde are formed. In the presence of
acylation catalyst (mineral acid such as sulfuric and
phosphoric acid) in the reaction mixture, p-HBA and
p-HBAd do not decompose and are converted into
p-acetoxybenzyl acetate (p-ABA) and p-acetoxyben-
zylidene diacetate (p-ABDA) having lower reactivity
with respect to ozone. However, under these condi-
tions the total yield of the aromatic products is still as
low as 10% (Fig. 1). It should be noted that the selec-
tivity of the oxidation of the methyl group is indepen-
dent of the type of the mineral acid but the reaction is
accelerated in going from phosphoric to sulfuric acid
(Fig. 2).
,
h
Fig. 1. Kinetic curves of (1) p-CrA consumption and ac-
cumulation of (2) peroxides, (3) p-ABA, and (4) p-ABDA
in oxidation of p-CrA with an ozone air mixture in acetic
The selectivity of oxidation of the side chain in-
creases in the presence of an oxidation catalyst,
variable-valence metal salt [3]. We studied the oxida-
tion of p-CrA catalyzed by manganese(II) acetate
anhydride at 5 C. [p-Cr] = 0.4, [H SO ] = 1.2, [O ] =
0
2
4 0
3 0
4
3
1
4
(
10 M; v = 8.3 10 l s . (c) Concentration and
) time; the same for Fig. 2.
air
(Table 1). This reaction is fast and yields mainly
p-ABA. The oxidation is complete in 1 h at the man-
ganese(II) acetate concentration of 0.18 M and tem-
perature of 5 C. The selectivity of oxidation of
the methyl group is 77%; the yield of p-ABA and
p-ABDA is 56 and 21%, respectively (Table 1).
c, M
After the oxidation completion, the reaction mix-
ture was diluted with a fivefold volume of water and
then was extracted with ether. The organic layer was
distilled under atmospheric pressure to remove the
ether and then in a vacuum (10 mm Hg) to remove
the unchanged p-CrA. Th residue was refluxed in
5% NaOH. The resulting p-HBA was extracted with
ether; the yield based on reacted p-CrA was 51%.
,
h
Fig. 2. Rate and selectivity of p-CrA oxidation with an
ozone air mixture in acetic anhydride at 5 C in the pres-
ence of (1, 2) H SO and (1 , 2 ) H PO . [p-Cr] = 0.4,
The methyl group is selectively oxidized in two
steps with ozone in the presence of manganese(II)
acetate. Under these conditions, ozone reacts mainly
2
4
3
4
0
4
3
1
[
(
acid] = 1.2, [O ] = 4 10 M; v = 8.3 10 l s .
1, 1 ) Consumption of p-CrA and (2, 2 ) total accumulation
0 3 0 air
2+
3
with Mn
{reaction (1), k1 = 4.7 10 [7];
1
k
= 1.3 l mol 1 s , our data} to
of p-ABA and p-ABDA.
AcOC H CH -p+O
6 4 3 3
3+
form reactive Mn species which rapidly and selec-
tively oxidize the methyl group of p-CrA [reac-
tion (2)]:
alkylbenzenes [6], ozone attacks the aromatic ring to
form peroxide monomers by Scheme 2:
Scheme 2
3 O
C
Mn2+ + O3 + H+
Mn3+ + HO + O ,
.
(1)
CH
CH3
CH3
2
O
O
H
O+
O3
.
O
3+
AcOC H CH -p + Mn + H+.
2+
AcOC H CH -p + Mn
6
4
3
6 4 2
C
O
(2)
H
OCOCH3
OCOCH3
OCOCH3
For reaction (1) to occur, ozone should be continu-
ously fed into the system. When the ozone supply is
stopped, the process is decelerated up to its complete
cessation. This fact additionally confirms formation of
reactive catalytic species by reaction (1). Since the
concentration of molecular oxygen under the experi-
CH3
O
Ac O
C
C
H
2
OOH .
OAc
H
OCOCH
3
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 1 2006

OXIDATION OF p-CRESOL WITH OZONE IN ACETIC ANHYDRIDE
125
mental conditions is higher by one and half orders
of magnitude than that of ozone, the benzyl radical
formed by reaction (2) reacts mainly with molecular
oxygen by reaction (3) to form the peroxy radical
which is converted into p-ABA by reactions (4) (6):
Table 1. Yield of the products of oxidation of the methyl
group in p-CrA at 5 C and various concentration of
Mn(OAc)2. [p-Cr]0 = 0.4, [H2SO4]0 = 1.2, [O3]0 = 4
4
1
0
M;
= 1 h
Yield, %
[
Mn(OAc)2]0,
.
.
AcOC H CH -p + O
AcOC H CH O -p, (3)
6 4 2 2
6
4
2
2
M
p-ABA
p-ABDA
.
.
AcOC H CH O -p + O
AcOC H CH O -p + 2O ,
6
4
2
2
3
6
4
2
2
0
0
0.14
0
0
.05
.10
30.1
42.4
51.3
56.1
54.2
8.7
12.5
17.2
21.3
20.1
(
4)
.
2+
3+
AcOC H CH O -p + Mn
AcOC H CH O -p + Mn ,
6 4 2
6
4
2
.18
.20
(
5)
+
AcOC H CH O -p + Ac O + H
AcOC H CH OAc-p
6
4
2
2
6
4
2
Table 2. Yield of the oxidation products of the methyl
group in p-CrA at 5 C and various KBr concentrations.
+
AcOH.
(6)
[
[
p-Cr]0 = 0.4, [Mn(OAc) ] = 0.18, [H SO ] = 1.2,
2 0 2 4 0
Introduction of potassium bromide in the system
increases the conversion and selectivity of catalytic
oxidation of the methyl group of p-CrA to 84%.
The major reaction product is p-ABDA. Its yield
reaches 67% (Table 2).
4
O ] = 4 10 M;
= 50 min
3
0
Yield, %
[
KBr] , M
0
p-ABA
p-ABDA
After the reaction completion, the reaction mixture
was poured into a glass beaker filled by two thirds
with finely divided ice and then was diluted to 100 ml
with cold water. The mixture was vigorously stirred
until the oil solidified. The solid product was filtered
off, washed with cold water, and dried. Concentrated
HCl (20 ml), water (20 ml) and alcohol (4 ml) were
added to crude p-ABDA. The mixture was refluxed
with stirring for 1 h. The reaction mixture was cooled,
and p-HBAd precipitate was filtered off. The yield
based on p-CrA was 62%.
0
0
0
0
0
.02
.06
.08
.10
.12
40.2
24.2
19.3
17.2
17.1
39.8
51.9
60.3
67.1
66.3
.
2+
AcOC H C(O )HOAc-p + Mn Br
6
4
2+
.
AcOC H C(O )HOAc-p + Mn Br ,
(12)
(13)
6
4
+
AcOC H C(O )HOAc-p + Ac O + H
Potassium bromide reacts with manganese(II) ace-
6
4
2
.
2+
tate catalyst to form Mn Br which is more reactive
AcOC H CH(OAc) -p + AcOH.
3
+
6
4
2
than Mn :
The increase in the oxidative conversion of p-CrA
in the presence of potassium bromide is due to ac-
cumulation of reactive complex Mn Br in the sys-
Mn2+ + Br
Mn Br + O3
Mn Br ,
2+
(7)
(8)
.
2+
2
+
2+
.
.
Mn Br + HO + O .
2
tem. Oxidation of p-ABA in the presence of this com-
.
3+
2
+
plex is faster than that in the presence of Mn [9].
Mn Br oxidizes the methyl group of p-ABA by the
following scheme:
2
+
.
EXPERIMENTAL
AcOC H CH OAc-p + Mn Br
AcOC H C HOAc-p
6 4
6
4
2
Mn2+ + Br + H+,
AcOC H C HOAc-p + O AcOC H C(OO )HOAc-p,
Analytically pure grade acetic anhydride and man-
ganese(II) acetate were used as received. Crystalline
p-Cr was recrystallized repeatedly from water.
+
(9)
.
.
6
4
2
6 4
(
10)
The experiments were performed in a glass column
with a porous partition. Acetic anhydride (10 ml),
p-Cr (0.4 M), appropriate mineral acid (1.2 M), and
a weighed portion of the catalyst were placed in the
.
.
AcOC H C(OO )HOAc-p + O
AcOC H C(O )HOAc-p
6
4
3
6 4
+
2O2,
(11)
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 1 2006

126
SEDYKH, GALSTYAN
column. The column was thermostated and an ozone
(yield 56%). Introduction of potassium bromide into
the catalytic system allows preparation of p-hydroxy-
benzaldehyde in the form of triacetate in a 67% yield.
4
air mixture (ozone concentration 4 10 M) was
1
passed through at a flow rate of 30 l h under the
steady operation conditions of the ozonizer. The ozone
concentration in the gas phase was determined spec-
trophotometrically by the absorption in the range
REFERENCES
2
54 290 nm.
1
. JPN Patent 2172940.
The oxidation products were identified and their
2. Weygand Hilgetag, Organisch-chemische Experimen-
tierkunst, Leipzig: Johann Ambrosius Barth, 1964,
3th ed.
concentration in the solution was determined by
gas liquid chromatography on an LKhM-80 chroma-
tograph with a flame ionization detector using a
3
4
5
6
. Galstyan, G.A., Galstyan, T.M., and Mikulenko, L.I.,
Kinet. Katal., 1994, vol. 35, no. 2, p. 255.
. Potapenko, E.V. and Galstyan, G.A., Ukr. Khim. Zh.,
2
m 4 mm column packed with Chromaton N-AW.
The stationary phase was SE-30 in the 5% amount of
the support weight. The analysis was performed under
the following conditions: vaporizer temperature
2
000, vol. 66, no. 1, p. 34.
. Razumovskii, S.D., Globenko, G.M., et al., Neftekhi-
miya, 1972, vol. 12, p. 65.
2
50 C; thermostat temperature 180 C; flow rate of
the carrier gas (nitrogen) 1.8, hydrogen 1.8, and air
. Galstyan, G.A., Tyupalo, N.F. and Razumovskii, S.D.,
Ozon i ego reaktsii s aromaticheskimi soedineniyami v
zhidkoi faze (Ozone and Its Reactions with Aromatic
Compounds in the Liquid Phase), Lugansk: Vostochno-
Ukr. Nats. Univ., 2004.
1
1
8 l h . p-Nitrochlorobenzene was used as the in-
ternal reference.
CONCLUSION
7
. Perepletchikov, M.L., Tarunina, V.N., Tarunin, B.I.,
and Aleksandrov, Yu.A., Zh. Obshch. Khim., 1985,
vol. 55, no. 3, p. 487.
p-Cresol was oxidized with ozone in acetic an-
hydride in the presence of mineral acid, manganese(II)
acetate, and potassium bromide as catalysts. In the
presence of manganese(II) acetate, the reaction can be
stopped at the step of formation of p-hydroxybenzyl
alcohol in the form of the corresponding diacetate
8. Zakharov, I.V. and Galetii, Yu.V., Neftekhimiya, 1978,
vol. 18, no. 4, p. 615.
9. Potapenko, E.V. and Galstyan, G.A., Zh. Prikl. Khim.,
2000, vol. 73, no. 7, p. 1218.
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 79 No. 1 2006