Liquid-phase catalytic oxidation of 2,5-dimethylbiphenyl

Article abstract of DOI:10.1023/A:1012461631396

Liquid-phase catalytic oxidation of 2,5-dimethylbiphenyl provided 2,5-biphenyldicarboxylic acid. The effect on reaction of temperature, catalyst type, and reagents concentration was investigated.

Full text of DOI:10.1023/A:1012461631396

Russian Journal of Organic Chemistry, Vol. 37, No. 6, 2001, pp. 830 833. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 6, 2001,
pp. 877 880.
,
,
Original Russian Text Copyright
2001 G. Koshel , Magagnini, S. Koshel , Lebedeva, Postnova, Kulichikhin, Bilibin.
Liquid-phase Catalytic Oxidation of 2,5-Dimethylbiphenyl
G. N. Koshel,1, P. Magagnini2, S. G. Koshel,1, N. V. Lebedeva1,
M. V. Postnova1, V. G. Kulichikhin3, and A. Yu. Bilibin4
1Yaroslavl State Technical University, Yaroslavl, 150023 Russia
2University of Pisa, Pisa, Italy
3Institute of Petrochemical Synthesis, Russian Academy of Sciences, Moscow, Russia
4Institute of Macromolecular Compounds, Russian Academy of Sciences, St. Petersburg, Russia
Received May 25, 2000
Abstract Liquid-phase catalytic oxidation of 2,5-dimethylbiphenyl provided 2,5-biphenyldicarboxylic acid.
The effect on reaction of temperature, catalyst type, and reagents concentration was investigated.
Biphenylcarboxylic acids are promising monomers
for preparation of composite and mesomorphic
thermotropic materials. For instance, mesomorphic
polymers based on 2,5-biphenyldicarboxylic acid (I)
possess extremely high strength and heat resistance.
At the same time they have lower (by about 100 C)
melting point that is favorable for processing [1].
However acid I is not produced in Russia or abroad,
and all the known methods of its synthesis are
multistage and reagents-consuming and afford the
target product in low yield [2].
We developed a procedure for acid I preparation
by oxidation of 2,5-dimethylbiphenyl (II). The latter
is synthesized by alkylation of p-xylene with cyclo-
hexanol followed by dehydrogenation of the arising
1,4-dimethyl-2-cyclohexylbenzene (III) [3].
1070-4280/01/3706-0830$25.00 2001 MAIK Nauka/Interperiodica

LIQUID-PHASE CATALYTIC OXIDATION
The oxidation of hydrocarbon II was carried out
831
at the atmospheric pressure in acetic acid in the
presence of a catalytic system cobalt(II) acetate
manganese(II) acetate sodium bromide. We establish-
ed that at a high initial concentration of compound II
1
(c0>1.5 mol l ) and at a high relative concentration
in the catalytic system of promotor (NaBr) only one
methyl group underwent oxidation. We isolated from
the reaction mixtures compounds that by their
1
elemental analysis, GLC, and H NMR spectra cor-
responded to monocarboxylic acids of methylbi-
phenyls IV and V.
Further oxidation of separated compounds IV and
V at 95 C and the following concentrations of the
1
catalyst components: cobalt(II) acetate 0.1 mol l ,
1
sodium bromide 0.1 mol l , manganese(II) acetate
1
0.005 mol l resulted in formation of acid I that was
isolated from the reaction mixture and identified.
Similar result was obtained at the liquid-phase oxida-
tion of hydrocarbon II at its initial concentration
Fig. 1. Kinetic curves of compound II consumption and
accumulation of oxidation products. (1) 2,5-dimethylbi-
phenyl (II); (2) 2,5-biphenyldicarboxylic acid (I); (3)
5-methyl-2-biphenylcarboxylic acid (V); (4) 9-fluorenone-
3-carboxylic acid (VII); (5) 3-methyl-9-fluorenone (VI);
(6) 2-methyl-5-biphenylcarboxylic acid (IV).
1
0.75 mol l . Under these conditions the reaction
occurs as successive oxidation of the methyl groups
into carboxyls first with formation of monocarboxylic
acids IV, V and then of dicarboxylic acid I through
the corresponding intermediate methylformylbi-
phenyls. The presence of the latter in the reaction
mixture was proved by polarographic method.
The most reactive bonds in molecule II are
presumably C H bonds of the methyl group in the
ortho-position to the benzene ring caused by its
I-effect { + (C5H5) according to Taft is equal to
+0.60 [4]}. This assumption is in agreement with
the accumulation of the monocarboxylic acids IV and
V in the process of hydrocarbon II oxidation (Fig. 1).
During the investigation of hydrocarbon II oxida-
tion into acid I we separated from the reaction mix-
ture side oxidation products identified as 3-methyl-9-
fluorenone (VI) and 9-fluorenone-3-carboxylic acid
(VII), and therewith the concentration of compound
VI in the course of the process went through a
maximum. It is presumable that ketone VI forms
from acid V: It is known that biphenylcarboxylic
acids with a carboxy group in the ortho-position with
respect to the second benzene ring are capable to
yield fluorenones in acidic media [5]. During the
reaction ketone VI is apparently oxidized into
9-fluorenone-3-carboxylic acid (VII).
Fig. 2.Temperature effect on accumulation of 2,5-biphenyl-
dicarboxylic acid (I) during the liquid-phase oxidation of
2,5-dimethylbiphenyl (II) (cI0I 1, cC0o(OAc) 0.05, cNaBr 0.05,
2
1
c0Mn(OAc)2 0.005 mol l ). (1) 105, (2) 95, (3) 80 C.
lytic system components in the following intervals,
1
mol l : cobalt(II) acetate, 0.005 0.5; manganese(II)
acetate, 0 0.1; sodium bromide, 0.01 0.1. The reac-
tion rate was measured by oxygen consumption. The
kinetic curves of hydrocarbon (II) oxidation in the
temperature range 80 105 C are presented in Fig. 2.
It was established that within this temperature interval
the reaction rate grew fivefold. From the experi-
mental data on the initial reaction rates we determined
We carried out a series of one-factor experiments
in order to elucidate the effect on the oxidation rate
of compound II of temperature within 80 105 C
range, concentration of the substrate II in 0.1
1
1 mol l range, and the concentrations of the cata-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 6 2001

832
KOSHEL, et al.
Effect of catalyst composition and of its amount on the yield of 2,5-biphenyldicarboxylic acid (I) (95 C)
Yield, %
acids IV, V
Molar ratio
Molar ratio
Reaction
time, min
hydrocarbon II: catalyst
cobalt(II)acetate: sodium bromide
acid I
7.14
0.95
9.50
3.66
6.52
2.94
0.88
3.61
6.82
4.84
2.11
1
1
1
160
60
48
18
51
78
9
46
51
52
9
10
48
33
20
32
9
18
43
88
25
11
160
160
200
180
185
150
135
180
130
1
10
0.67
0.13
1
1.05
2
68
74
6
graphically the apparent activation energy of oxida-
tion equal to 50 5 kJ mol.
from the solvent DMSO-d6 (99% 2H enriched);
internal reference TMS.
Note that at increased temperature the selectivity of
compound I formation is reduced, and the reaction
product contains up to 5% of acid VII. The latter
spoils the consumers, quality of acid I. The best
temperature for attaining relatively high reaction rate
and the good quality of the target acid I is 95 C. The
treatment of the kinetic curves obtained was carried
out along the method of initial rates.
GLC analysis was carried out on a chromatograph
LKhM-8 MD equipped with a flame-ionization
detector, a steel column 1000 3 mm, stationary phase
4.8% of methylvinylsilicone on Chromosorb G-AW;
1
carrier gas nitrogen, flow rate 30 ml min ,
programmed heating from 100 to 240 C at a rate
1
8 deg min .
Analysis of the oxidation product for methylformyl-
biphenyl content was performed with the use of
polarograph LP-7 with a dropping mercury electrode
relative to saturated calomel electrode. Aldehyde
concentration was determined from a calibration plot
measured with benzaldehyde as standard.
The experiments show that the conversion of
hydrocarbon II in oxidation process reaches 100%,
the selectivity depends on the ratio of the hydrocarbon
and catalyst and on the ratio of the components of the
catalytic system (see table).
The results of experiments evidence that the best
yield of acid I ( 80%) is obtained at oxidation of
compound II in acetic acid in the presence of cobalt-
manganese-bromide catalyst at the molar ratio cobalt
and manganese acetates to sodium bromide equal to
1: 1, and the molar ratio hydrocarbon to catalyst
3 4: 1.
p-Xylene alkylation with cyclohexanol. To a
mixture of 234 g of p-xylene and 217.12 g of sulfuric
acid at 5 8 C was added within 1 h 74.61 g of cyclo-
hexanol. The reaction mixture was kept for 3 h at the
same temperature. Then the hydrocarbon layer was
separated and washed in succession with water,
concn. aqueous alkali, and again water till pH 7.
Then the solution was dried with calcium chloride,
and the excess p-xylene was distilled off in a vacuum.
We obtained 86.6 g (62%) of 1,4-dimethyl-2-cyclo-
hexylbenzene (III) as a clear colorless liquid, bp
135 C (16 mm Hg), d240 0.9375, nD20 1.5267.
EXPERIMENTAL
IR spectra were recorded on Specord 75IR instru-
ment from mulls in mineral oil. 13C NMR spectra
were registered from 10% solutions in DMSO-d6 on
spectrometer Tesla BS-567A (25.142 MHz) in
Fourier-transform mode at wide-band decoupling
from protons (band width 900 Hz); pulse width 8 s,
response collection time 1.069s, pulse interval 100 s,
Dehydrogenation of 1,4-dimethyl-2-cyclohexyl-
benzene (III). The dehydrogenation of 86.8 g of
hydrocarbon III was performed in the presence of
43 g of palladium catalyst (Production standard TU
0-02-974-74) at 300 C for 5 6 h. On completion of
2
scan number 160 2200; stabilization on H nuclei
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 6 2001

LIQUID-PHASE CATALYTIC OXIDATION
833
the process the catalyst was filtered off, and the
filtrate distilled in a vacuum. We obtained 82.3 g
(95%) of 2,5-dimethylbiphenyl (II) as a colorless
liquid, bp 123 C (9 mm Hg), nD20 1.5790. 13C NMR
spectrum (DMSO-d6), C, ppm: 19.0 (C13), 19.9
number 262. C14H12O2. Calculated, %: C 79.20;
H 5.70. Acid number 264.
5-Methyl-2-biphenylcarboxylic acid (V), color-
less crystalline compound, mp 156 157 C. 13C NMR
spectrum (DMSO-d6), C, ppm: 22.2 (C14), 124.0
128.2 (C3,4,6,8 12), 130.0 (C2), 130.2 (C5), 138.6
(C1), 139.4 (C7), 171.2 (C13). Found, %: C 79.03; H
5.81. Acid number 266. C14H12O2. Calculated, %: C
79.20; H 5.70. Acid number 264.
(C14), 125.0 128.9 (C3,4,6,8 12), 130.3 (C5), 133.2
(C2), 138.7 (C1), 139.2 (C7). Found, %: C 92.47,
92.66; H 8.35, 8.10. C14H14. Calculated, %: C 92.26;
H 7.74.
Oxidation of 2,5-dimethylbiphenyl (II). Through
a solution of 1.092 g of compound II in 6.93 ml of
acetic acid in the presence of 199.3 mg of cobalt(II)
acetate, 82.4 mg of sodium bromide, and 9.8 mg of
manganese(II) acetate at 95 C was passed an oxygen
3-Methyl-9-fluorenone (VI). In 50 ml of concn.
sulfuric acid 5 g of compound V was heated to 55 C
at stirring for 10 min. The reaction mixture was
poured on ice, the separated precipitate was filtered
off, washed with water, and dried in air at room
temperature. We obtained 4.65 g of compound VI.
Yellow crystalline substance, mp 163 165 C. 165 C.
IR spectrum ( , cm ): 860 (1,2,4-substituted benzene
ring), 1376 and 1465 (CH3), 1735 (>Cæ in a five-
membered ketone).
1
flow at a rate 1.5 l h for 1 2 h. The reaction was
monitored by an amount of oxygen consumed. The
content in the reaction mixture of the initial hydro-
carbon II, intermediate compounds IV, V, and the
final reaction product I was determined by GLC. The
duration of the process was 1 3 h. On completion of
the reaction the mixture was cooled, the separated
precipitate of acid I was filtered off, washed with
water, and dried in air at room temperature. The
yield of acid I was 1.089 g (75%), colorless crystals,
mp 277 C. 13C NMR spectrum (DMSO-d6), C, ppm:
125.4 129.1 (C3,4,6,8 12), 131.1 (C5), 135.6 (C2),
138.9 (C1), 139.9 (C7), 165.7 (C14), 168.1 (C13).
Found, %: C 69.42; H 4.16. Acid number 469.
C14H10O4. Calculated, %: C 69.30; H 4.21. Acid
number 463.
1
9-Fluorenone-3-carboxylic acid (VII). From 5 g
of compound I along procedure similar to that of
compound VI preparation we obtained 4.23 g of
compound VII. Yellow crystalline substance, mp
1
283 284 C. IR spectrum, , cm : 835 (C H of a
monosubstituted benzene ring), 860 (1,2,4-substituted
benzene ring), 1590 1610 (COO in the spectrum of
acid VII potassium salt), 1720 (>CO in a five-
membered ketone). Found, %: C 74.89; H 3.62.
C14H9O3. Calculated, %: C 75.00; H 3.57.
Monocarboxylic methylbiphenyl acids IV, V.
Through a solution of 40.95 g of compound II in
110 ml of acetic acid in the presence of 3.74 g of
cobalt(II) acetate, 2.32 g of sodium bromide, and
18.4 mg of manganese(II) acetate at 95 C was passed
REFERENCES
1. Koshel, G.N., Koshel, S.G., Rudkovsky, E.K.,
Poli, G., Vitolo, S., and Magagnini, P., Chimica
Industria, 1998, vol. 80, no. 2, pp. 183 189.
2. Alder, K., Heimbach, K., and Neufang, K., Lieb.
Ann., 1954, no. 586, p. 138.
3. Koshel, G.N., Lebedeva, N.V., Krestinina, T.B.,
Koshel, S.G., and Postnova, M.V., Russian Patent
2078100, 1997; Byull. Izobr., 1997, no. 12.
4. Mathieu, J. and Panico, R., Foundation Theory in
Organic Chemistry, New York: Harper & Row, 1981.
5. Mikhalenko, S.A., Zh. Org. Khim., 1962, vol. 32,
no. 5, pp. 1610 1613.
1
an oxygen flow at a rate 1.5 l h for 4 h. On
completion of the reaction the mixture was cooled,
the separated precipitate of the monocarboxylic acids
IV, V was filtered off, washed with water, and dried.
2-Methyl-5-biphenylcarboxylic acid (IV), color-
less crystalline compound, mp 206 207 C. 13C NMR
spectrum (DMSO-d6), C, ppm: 19.7 (C13), 124.6
131.5 (C3,4,6,8 12), 139.8 (C2), 149.2 (C1), 141.1
(C7), 167.0 (C14). Found, %: C 79.03; H 5.81. Acid
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 6 2001