The process of 4-hydroxybiphenyl synthesis from 4-isopropylbiphenyl

Article abstract of DOI:10.1002/kin.20335

The kinetics of the oxidation of 4-isopropylbiphenyl (1) in the liquid phase by oxygen to 1 -(1,1′-biphenyl-4-yl)-1 -methylethyl hydroperoxide (2) was investigated. The oxidizability of 1 in the temperature range from 60°C to 120°C and the overall energy activation of oxidation were determined. Long-term oxidation of 1 to 2 in the temperature range of 80-120°C was investigated, and the yield and selectivity of the process were determined. Pure 2 was obtained, and its properties were defined. 4-Hydroxybiphenyl was obtained as a result of the acidic decomposition of 2.

Full text of DOI:10.1002/kin.20335

The Process of
4-Hydroxybiphenyl
Synthesis from
4-Isopropylbiphenyl
´
ZBIGNIEW STEC, BEATA ORLINSKA, BARTŁOMIEJ JAKUBOWSKI, JAN ZAWADIAK
Department of Chemical Organic Technology and Petrochemistry, Silesian University of Technology, 4, Krzywoustego Street,
44-100 Gliwice, Poland
Received 15 November 2007; revised 20 February 2008; accepted 28 February 2008
DOI 10.1002/kin.20335
Published online in Wiley InterScience (www.interscience.wiley.com).
ABSTRACT: The kinetics of the oxidation of 4-isopropylbiphenyl (1) in the liquid phase by oxygen
to 1-(1,1ꢀ-biphenyl-4-yl)-1-methylethyl hydroperoxide (2) was investigated. The oxidizability of
1 in the temperature range from 60◦C to 120◦C and the overall energy activation of oxidation
were determined. Long-term oxidation of 1 to 2 in the temperature range of 80–120◦C was
investigated, and the yield and selectivity of the process were determined. Pure 2 was obtained,
and its properties were defined. 4-Hydroxybiphenyl was obtained as a result of the acidic
decomposition of 2. ꢁ 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 527–532, 2008
C
way of producing 3 is characterized by high consump-
tion of energy and environmental pollution due to the
accumulation of wastes. A highly aggressive environ-
ment of reaction causes fast corrosion of apparatus.
The solution suggested in the present paper has
not been quoted so far in the literature. Only a
Japanese patent describes the synthesis of 3- and
4-hydroxybiphenyls, applying a mixture of 3- and
4-isopropylbiphenyls in a ratio of 98.6:1.2 as raw
material. The oxidation was accomplished in a double-
phase system in an alkaline aqueous emulsion in the
presence of Bu4NBr. The resulting product contained
38.9% hydroperoxides and 36.5% alcohols. The reac-
tion product was refluxed with H2SO4 and aq. H2O2
in MeOH, yielding 88.6% 3- and 4-hydroxybiphenyls
[4].
INTRODUCTION
The presented investigations concern a perspective
method of synthesis of 4-hydroxybiphenyl (3) from
4-isopropylbiphenyl (1) (Scheme 1) by means of a pro-
cedure similar to the process of phenol synthesis from
cumene by applying Hock and Lang’s method.
Compound 3 is an important raw material in the
pharmaceutical industry and in the production of plant
pesticides, emulsifiers, and anisotropic polymers with
higher thermal and mechanical resistance [1,2].
The fundamental method for producing 3, ap-
plied on the industrial scale, nowadays is sulfona-
tion. This process is run in two stages: sulfonation of
biphenyl and the fusion of the obtained (1,1ꢀ-biphenyl)-
4-sulfonic acid with sodium hydroxide to 3 [3]. This
In the suggested method, the key stage for pro-
ducing 3 is the oxidation of 1 to 1-(l,1ꢀ-biphenyl-4-
yl)-1-methylethyl hydroperoxide (2). The oxidation
of hydrocarbons in the liquid phase with oxygen to
Correspondence to: Beata Orlin´ska; e-mail: Beata.Orlinska@
polsl.pl
2008 Wiley Periodicals, Inc.
c
ꢀ

528
STEC ET AL.
The literature provides neither any kinetic data con-
cerning the oxidation of 1 to 2 nor information about
the properties of 2. The range of investigations com-
prised the kinetics of oxidizing 1 to 2 as well as the
determination of the oxidizability (kp/kt1/2) of 1 and
the overall energy activation of the oxidation of 1
(Ep − 0.5Et). Also the long-term oxidation of 1 with
oxygen in a bubbling reactor to 2 was investigated, and
the yield and selectivity of such a reaction were deter-
mined. The acid decomposition of 2, contained in the
oxidate, gave product 3.
Scheme 1 Method of 4-hydroxybiphenyl synthesis.
hydroperoxides is a free-radical, chain process [5–7]:
Initiation
initiator → radicals
ko
EXPERIMENTAL
R• + O2 −→ RO•2
Propagation
kp
RO•2 + RH −→ ROOH + R•
Compound 1 was supplied by Ru¨tgers Kureha Solvents
GmbH (Duisburg, Germany), with a purity of 99%, b.p.
293–303◦C (lit. 291◦C [10]), n2D0 1.5800 (lit. 1.5831
[11]), d15 = 0.9880.
kt
Termination
2RO•2 −→ stable products
For liquid-phase oxidation, under pO ≈ 0.1–1 atm
2
(then the concentration of dissolved dioxygen in hydro-
carbons is higher than 10−4 mol L−1), the reaction of
alkyl radical with oxygen is very fast and alkyl radicals
are rapidly converted into peroxyl radicals. Because of
this, the concentration of alkyl radicals is much lower
than that of peroxyl radicals, and chains are terminated
only by the reaction between two peroxyl radicals,
while propagation is limited by the reaction of peroxyl
radicals with hydrocarbons [8,9].
The oxidation reactions were carried out in a ga-
sometric apparatus after applying the procedure de-
scribed in the literature [12]. The oxidation was carried
out in a thermostated, 4-cm3 quartz flask, vigorously
mixed by shaking and connected with a thermostated
burette. Oxygen was supplied into the flask from a
burette, in which the pressure was kept constant and
amounted to 1 atm. The reaction was monitored by
measuring the oxygen uptake.
Assuming that the reaction runs in compliance with
the presented diagram and assuming a stationary state
for the rate of oxidation, the following expression will
result:
Long-term oxidations of 1 were carried out in a bub-
bling reactor (oxygen was divided into small bubbles
on entry into the reactor).
Analyses of 2-(1,1ꢀ-biphenyl-4-yl)propane-2-ol (4)
and 1-(biphenyl-4-yl)ethane-1-on (5) were performed
using an Alliance Waters 2690 high-performance liq-
uid chromatograph, equipped with an autosampler and
a UV detector (Waters 996 photodiode array). The
kp
kt1/2
rox = ri1/2
CRH
(1)
˚
where rox is the rate of oxidation, ri is the rate of initia-
tion reaction, kp is the constant rate of the propagation
reaction, kt is the constant rate of the termination reac-
tion, and CRH is hydrocarbon concentration.
The value of kp/kt1/2, called oxidizability, is a mea-
sure of reactivity of hydrocarbons in the free-radical,
chain oxidation. The combination with the Arrhenius
equation allows transformation of Eq. (1) into the fol-
lowing form:
Nova-Pak Silica column 60 A 4 μm (150 mm ×
3.9 mm; Waters) was applied. The mobile phase was a
mixture of n-hexane and 2-propanol (99:1) [13]. The
concentration of 2 in the product was determined by
iodometry [14].
Qualitatively, the oxidate was analyzed by TLC
(Kieselgel 60 F254 plates, gel layer 0.2 mm thick;
CH2Cl2:(CH3)2CO (9:1 v/v) as the developing liquid
for products). Spots of the products were observed in
254 nm light. Elementary analyses were carried out
1
−0.5E
eE
t CRH
(2)
p
kp∞
kt∞
on a Perkin-Elmer 2400 series II instrument. The H
rox = ri0.5
√
RT
NMR and 13C NMR analyses of 2 were run on a Varian
Unity Inowa 300 spectrometer.
where kp∞, kt∞ are preexponential factors and Ep is
energy of activation of the propagation reaction, Et
is energy of activation of the termination reaction,
and Ep − 0.5Et is the overall energy of activation of
oxidation.
1-(l,1ꢀ-Biphenyl-4-yl)-1-methylethyl hydroperoxide
(2) was separated from the oxidate by its sodium salt.
Thirty grams of the oxidate containing 34.5% of 2
(10.35 g, 45.3 mmol 2) was dissolved in 120 cm3 of
toluene. The mixture was cooled to 5◦C. Then 11.1 cm3
International Journal of Chemical Kinetics DOI 10.1002/kin

4-HYDROXYBIPHENYL SYNTHESIS FROM 4-ISOPROPYLBIPHENYL
529
traction with 2% aqueous solution of NaOH (60 cm3,
30.6 mmmol) (to separate fractions a centrifuge was
used). Then, the aqueous phase (at the bottom) was
neutralized by adding 5% aq. HCl (23 cm3) and the
precipitate of 3 was filtered off. 2.93 g (17.22 mmol,
yield = 84%) of chromatographic pure 3 was obtained,
m.p. 165–167◦C (lit. 166–167◦C [15]).
of 20% aqueous solution of NaOH (67.7 mmol NaOH)
was dropped into the stirred mixture for 0.5 h. The
precipitate of sodium salt of 2 was filtered off and was
washed with water (5 × 5 cm3) and hexane (5 × 5 cm3).
Next, the precipitate of sodium salt of 2 was stirred in
60 cm3 of water and neutralized with 5% aqueous HCl
solution (until pH 7). Afterward, 2 was filtered and
washed with water (3 × 5 cm3) to give 7.18 g of 2 (yield
66%), 94% pure (as determined by iodometry). The 2
was purified twice by precipitation of the sodium salt
and then neutralization. 2 was obtained with a purity
exceeding 97%, m.p. 83.5–85◦C. Elemental analysis:
calculated for C15H16O2, 78.92%C, 7.06%H; found,
78.93%C, 6.95%H; Oactive: calculated 7.01; found,
RESULTS AND DISCUSSION
To determine the oxidizability of 1, the initial rates
of oxidation of 1 (rox) were measured in the presence
of azo-initiators, the initiating properties of which (ri)
were known. The amount of initiator was adjusted to
get similar initiation rate at different temperatures. By
using Eq. (1), the oxidizability of 1 was calculated.
The kinetic data concerning the oxidation of 1
within a temperature range of 60–110◦C are shown in
Table I. For comparison, the kinetic data of the oxida-
tion of cumene are quoted too. This table indicates that
the susceptibility to oxidation of 1 is about 20%–30%
lower that that of cumene.
1
6.80%. H NMR (CDCl3/TMS) δ = 7.26–7.65 (m,
9Harom, and 1HOOH), 1.67 (s, 6H, C(CH3)2OOH). 13
C
ꢀ
NMR 143.6, 140.7, 140.4 (C-ar 1 ,1,4), 128.8, 127.3,
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
127.1, 125.9 (C-ar 2 ,2,3 ,3,5 ,5,6 ,6), 127.3 (C-ar 4 ), 83.9
(C(CH3)2OOH), 26.1 (C(CH3)2OOH).
The hydroperoxide 2 was relatively unstable and
partially decomposed to 3 in the presence of traces of
impurities.
4-Hydroxybiphenyl (3) was obtained from the acid
decomposition of 2. 13.62 g of the oxidate containing
34.5% of 2 (20.58 mmol 2) with 2.5 cm3 of acetone
was dropped into a solution of 0.06 g of concentrated
H2SO4 (0.58 mmol H2SO4) in 12 cm3 of acetone at
56◦C for 5 min. The heat of the decomposition reaction
was removed by partial vaporization of the acetone.
Since oxidate was added, the whole 2 decomposed to
3 during 5 min (the reaction was controlled by TLC
analysis). Then the mixture was neutralized by adding
0.45 g of Na2CO3 (4.24 mmol). Next the precipitate of
Na2CO3–Na2SO4 was filtered and acetone was evap-
orated. The remaining solid was diluted in 13 cm3 of
t-BuPh. Product 3 was isolated from the mixture by ex-
Figure 1 illustrates the dependence of −ln(kp/kt1/2
)
on the reciprocal of temperature. Based on the pre-
sented data and employing Eq. (2), the overall energy
of activation (Ep– Et/2) could be calculated.
The overall energy of activation (Ez = Ep – Et/2)
of the free-radical chain process of the oxidation of
1 amounts to 25.8
0.8 kJ/mol, and in the case of
cumene amounts to 29.1 0.8 kJ/mol.
To check the progress of the process at higher
conversion of 1, it was tested in the bubble reactor.
As initiator 1,1ꢀ-azobis(cyanocyclohexane) was used.
The oxidation was run within the temperature range
of 80–120◦C. The concentration of 2 in the reaction
Table I Kinetic Data of the Oxidation of 1 with Molecular Oxygen, p = 1 atm
Concentration
k /k1/2 × 102e
p
t
of Initiator × 103
r × 107c
Concentration of
1 (mol/dm3)
r
× 105
k /k1/2 × 102
for Cumene
i
ox
p
t
T (◦C)
(mol/dm3)
(mol/dm3·s)c
(mol/dm3·s) λd
(dm3/(mol·s)1/2
)
(dm3/(mol·s)1/2
)
60
70
80
90
100
110
120
15.09a
3.89a
1.08a
5.80b
1.60b
0.40b
0.10b
1.72
1.76
1.76
1.76
1.81
1.57
1.29
4.91
4.87
4.83
4.79
4.76
4.72
4.68
0.69
1.07
1.12
1.43
1.81
2.04
2.55
39
60
63
81
99
0.34
0.48
0.55
0.71
0.94
1.17
1.47
0.42
0.57
0.77
0.98
1.36
1.72
2.08
130
198
a 2,2-Azo-bis-isobutyronitrile as initiator (kd = 1.6 × 1015e−30800/RT [16]).
b 1,1ꢀ-Azobis(cyanocyclohexane) as initiator (kd = 5.24 × 1016e−35400/RT [17]).
c ri is calculated from the following equation: ri = 2ekdCi, where e is efficiency of initiation (with 0.6 taken for oxidation in the presence of
azo-initiators); kd is the constant rate of the initiator decomposition; Ci is the initiator concentration [18].
d λ = rox/ri is the length of the kinetic chain.
e Data for cumene [19].
International Journal of Chemical Kinetics DOI 10.1002/kin

530
STEC ET AL.
Figure 1 −ln(k /k1/2) of 1 (I) and cumene (II) versus reciprocal absolute temperature.
p
t
mixture was determined iodometrically. The kinetic
curves indicating the accumulation of 2 are shown in
Fig. 2.
reaction rate was slower (after 7 h the reaction product
contained 19.5% of 2).
The by-products of the oxidation of 1 to 2 are alco-
hol 4 and ketone 5, which are formed in small amounts
as a result of the transformation of the respective alkoxy
radical (Scheme 2).
The concentrations of 2, 4, and 5 in the mixture
after the oxidation of 1 at 90◦C, 100◦C, and 110◦C are
presented in Table II.
The amount of 4 in the mixture after the oxidation
is about 15 to 20 times less than 2. A considerable
increase in the content of 4 was observed when the
oxidation took place at 110◦C and the concentration of
2 decreased. The content of 5 was about three to four
times less that the content of 4.
The investigations have proved that 1 was oxidized
quickly to 2, and the reaction of oxidation did not need
to be carried out in a double-phase system in an al-
kaline aqueous emulsion. Oxidation of 1 for 4 h at a
temperature of 100◦C and 110◦C gave a product con-
taining 37.4% and 32.0% of 2, respectively. Later, the
rate of oxidation was decreased due to the formation of
by-products inhibiting the free-radical chain process.
When the reaction was run at 90◦C, no inhibition
was observed (after 7 h the reaction product contained
39.6% of 2). Probably, the hydroperoxide did not de-
compose to inhibitors at this temperature. At 80◦C the
Figure 2 Oxidation of 1 (10 cm3) with oxygen at 80◦C (I), 90◦C (II), 100◦C (III), 105◦C (IV), 110◦C (V), and 120◦C (VI).
Initiator: 1,1ꢀ-azobis(cyanocyclohexane) 0.1706 g (I), 0.915 g (II), 0.0470 g (III), 0.0470 g (IV), 0.0224 g (V), and 0.0104 g
(VI).
International Journal of Chemical Kinetics DOI 10.1002/kin

4-HYDROXYBIPHENYL SYNTHESIS FROM 4-ISOPROPYLBIPHENYL
531
Scheme 2 Products of the thermal decomposition of 2.
Table II Oxidation of 1 with Oxygen in the Bubble Reactor
Temperature (◦C) Time (h) Concentration of 2 (%) Concentration of 4 (%) Concentration of 5 (%) α(%) S (%)
2
3
4
5
6
7
11.4
18.2
24.9
30.2
35.3
39.6
0.50
0.86
1.22
1.51
1.67
2.06
0.23
0.29
0.31
0.45
0.47
0.44
10.7
16.8
23.7
29.1
34.1
38.9
94
94
94
94
94
94
90◦C
2
3
4
5
6
7
21.2
32.0
37.4
41.7
43.8
44.2
1.11
1.64
2.12
2.46
2.68
2.97
0.37
0.43
0.44
0.55
0.70
0.69
20.2
30.9
37.2
41.2
43.6
44.3
93
93
93
93
92
92
100◦C
2
3
4
5
6
7
24.9
30.8
33.8
33.9
32.2
30.9
1.13
1.58
2.10
2.70
4.00
4.97
0.43
0.48
0.64
0.83
1.24
1.54
23.7
29.7
33.3
34.2
34.3
34.3
94
93
92
90
85
81
110◦C
The selectivity of the oxidation of 1 to 2 at 90◦C was
high and amounted to 94%. At 110◦C it amounted, in
the initial phase, to 94%–92%, after which it dropped
to 81% due to the decrease in the concentration of 2.
The product of oxidation run at 100◦C, containing
34.5% of 2 was subjected to acid decomposition in
the presence of H2SO4. Because of the high selectivity
of oxidation (the low content of alcohol), H2O2 did
not have to be applied, as stated in the patent [4]. The
product 3 was selected by extraction with an aqueous
NaOH solution. In result pure 3 was obtained with a
yield of 84%.
Compound 1 oxidizes quickly with a high selectiv-
ity to 2 in a single-phase system (without adding alka-
line aqueous emulsion) and without any catalyst. The
oxidizability of 1 is comparable with that of cumene.
In the course of the oxidation of 1 with oxygen at 90–
100◦C after 5–7 h, a product, containing about 40% of
2, was obtained. In these conditions 2 was formed with
a selectivity of about 93%–94%.
Compound 2, which was contained in the oxidate,
can be immediately subjected to acid decomposition to
3 in the presence of H2SO4. Because of the low content
of 4, H2O2 need not be applied, so that the safety of
work as well as the economical indices of the process
is improved.
CONCLUSIONS
The investigations showed that 3 can be obtained from
1 by applying a process similar to Hock-Lang’s method
of phenol production from cumene.
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