Efficiency of phase-transfer catalysis in cyclopentene epoxidation with hydrogen peroxide

Article abstract of DOI:10.1134/S1070427212040210

The effect of the structure and amount of the phase-transfer catalyst (quaternary ammonium salts) and the solvent effect on cyclopentene oxidation with an aqueous hydrogen peroxide solution in the liquid-liquid two-phase system was studied. The phase-tran

Full text of DOI:10.1134/S1070427212040210

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2012, Vol. 85, No. 4, pp. 661−665. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © A.E. Meshechkina, L.V. Mel’nik, G.V. Rybina, S.S. Srednev, A.S. Shevchuk, 2012, published in Zhurnal Prikladnoi Khimii, 2012,
Vol. 85, No. 4, pp. 646−650.
ORGANIC SYNTHESIS
AND INDUSTRIAL ORGANIC CHEMISTRY
Efficiency of Phase-Transfer Catalysis in Cyclopentene
Epoxidation with Hydrogen Peroxide
A. E. Meshechkina, L. V. Mel’nik, G. V. Rybina, S. S. Srednev, and A. S. Shevchuk
Yaroslavl State Technical University, Yaroslavl, Russia
e-mail: kluevatv@ystu.ru
Received October 4, 2011
Abstract—The effect of the structure and amount of the phase-transfer catalyst (quaternary ammonium salts) and
the solvent effect on cyclopentene oxidation with an aqueous hydrogen peroxide solution in the liquid–liquid two-
phase system was studied. The phase-transfer catalyst and solvent ensuring high reaction rate and high selectivity
with respect to target products were chosen.
DOI: 10.1134/S1070427212040210
Today there is increasing interest in use of aque-
ous solutions of hydrogen peroxide instead of organic
hydroperoxides and per acids as agents for oxidation of
unsaturated compounds [1, 2], because 30% hydrogen
peroxide solution is readily available, cheap, stable in
transportation, and environmentally safe; furthermore,
hydrogen peroxide has high relative content of available
oxygen. These advantages make hydorgen peroxide
promising as agent for various processes.
hydrogen peroxide, and phase-transfer catalyst (PTC).
Depending on the reaction temperature and pH of the
aqueous phase, the process can be directed to synthesis
of either 1,2-epoxycyclopentane (1,2-ECP) or 1,2-cyclo-
pentanediol (1,2-CD) [6].
In this study we examined how the structure and
amount of PTC and the nature of the solvent affect the
efficiency of oxygen (peroxy group) transfer from the
aqueous phase to the organic phase in which cyclopentene
is oxidized.
Analysis of procedures for preparing 1,2-epoxy-
cyclopentane by oxidation of cyclopentene (CP) with
isopropylbenzene hydroperoxide and aqueous solution of
hydrogen peroxide (HP), made in [3], revealed technical
and economical advantages of hydrogen peroxide.
EXPERIMENTAL
Cyclopentene isolated from the С5 fraction of pyroly-
sis was purified by fractional distillation to 98% purity.
The solvents (chemically or analytically pure grade) were
additionally purified by fractional distillation. Hydrogen
peroxide (35% aqueous solution), sodium tungstate dihy-
drate, phosphoric acid (80%), and phase-transfer catalysts
(Table 1) of chemically or analytically pure grade were
used without any pretreatment.
Processes used for oxidation of unsaturated substrates
with aqueous hydrogen peroxide solutions can be con-
ventionally classed with respect to implementation, in ac-
cordance with the catalysts used. The first group includes
oxidation processes performed on heterogeneous catalysts
(titanium silicalite, zeolites), with alcohols, mainly meth-
anol, used as solvent [3, 4]. The second group includes
oxidation processes performed with soluble catalysts,
compounds of Group V and VI metals (W, Mo, V) [5].
Among them, particular place is occupied by reactions
performed in two-phase water–organic solvent systems.
A temperature-controlled glass reactor equipped
with a reflux condenser, a thermometer, and a sampling
neck was charged with the aqueous (sodium tungstate,
phosphoric acid, hydrogen peroxide, water) and organic
(phase-transfer catalyst, solvent, cyclopentene) phases,
prepared in advance separately. The mixture was vigor-
The catalytic complex is formed directly in the reac-
tion medium from sodium tungstate, phosphoric acid,
661

662
MESHECHKINA et al.
Table 1. Effect of the structure of the phase-transfer catalyst on the reaction of cyclopentene with an aqueous solution of hydro-
gen peroxide. Solvent 1,2-dichloroethane; initial concentration, M: CP in organic phase 5.0, Н2О2 in aqueous phase 4.0, sodium
tungstate in aqueous phase 0.06; molar ratios: Н2О2 : CP = 1.3 : 1, Na2WO4·2H2O : H3PO4 : PTC = 1 : 2 : 0.36; aqueous to
organic phase volume ratio 1.6 : 1; 60°С; pH of aqueous phase 1.6
Yield based on CP
Conversion, %
Number of C
atoms in PTC
cation
loaded, %
PTC
τ, min
CP
Н2О2
1,2
ECP
41.3
Tetraethylammonium bromide (TEAB)
Tetraethylammonium iodide (TEAI)
Tetrabutylammonium bromide (TBAB)
8
8
180
200
180
48.0
35.1
94.5
95.4
6.7
7.6
8.8
96.7
93.5
27.5
85.7
16
[C14H29N(CH3)2C6H5CH2]Cl
(Katamin AB)
23
28
140
140
99.7
99.8
92.3
95.3
4.8
7.6
94.9
92.2
[CH3(C9H19)3N]Cl (Adogen 464)
results of the CP epoxidation without PTC in dimethyl-
formamide. In this case, the reaction mixture does not
become fully homogeneous, probably because of the
presence of salts, and is an emulsion. Despite the fact that
the reaction was performed with vigorous stirring, the CP
conversion in 3 h was as low as 6%, with the degree of
nonselective HP decomposition reaching 50%.
ously stirred (600 rpm) with a single-blade power-driven
stirrer. The reaction time was counted from the start of
stirring. The reaction progress was monitored by hy-
drogen peroxide conversion, which was determined by
iodometric titration. The products obtained were analyzed
by chemical methods and gas–liquid chromatography.
Two consecutive reactions were shown to occur under
the experimental conditions: CP epoxidation to 1,2-ECP
[reaction (1)] and subsequent hydrolysis of the epoxide
formed to 1,2-CD [reaction (2)]:
Experiments were performed under the conditions
ensuring the 1,2-CD formation. As seen from Table 1,
with an increase in the total amount of carbon atoms in
the PTC cation, the reaction rate, CP conversion, and
1,2-CD yield increase. TEAB and TEAI are ineffective
PTCs, because they do not ensure sufficient transfer of the
catalytic complex to the organic phase; the CPconversion
is insignificant, whereas nonproductive HP decomposi-
tion is enhanced.At the same time, in the presence of such
PTCs as KataminAB andAdogen 464, the CPconversion
is fast and selective.
keff 1
O + H2O,
(1)
1,2-ECP
+ H2O2
CP
keff 2
.
+ H2O
HO
OH
O
(2)
Analytical studies of the transfer of ammonium salts
from aqueous solutions into chloroform revealed correla-
tion between the cation size and extraction constant [7].
For quaternary ammonium salts, the following equation
was obtained:
1,2-CD
The CP epoxidation occurs in the organic phase, and
the 1,2-ECPhydrolysis, in the aqueous phase. The forma-
tion of both 1,2-ECP and 1,2-CD is strongly influenced
by the efficiency of the first limiting step, cyclopentene
epoxidation.
log KQ = –2.00 + 0.54n,
(3)
Without PTC, the reaction of CP with an aqueous HP
solution is slow and inefficient. This is illustrated by the
where n is the number of C atoms in ammonium ions.
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EFFICIENCY OF PHASE-TRANSFER CATALYSIS
663
The anion on PTC affects the CP epoxidation effi-
ciency to a lesser extent. The use of iodides in this reac-
tion is not appropriate. It is known [7] that the I– anion is
considerably more lipophilic than the Cl– and Br– anions
and can inhibit the main reaction owing to competition
with the catalytic complex ion in its transfer to the organic
phase. Furthermore, iodide ion is oxidized with hydrogen
peroxide to molecular iodine.
The best results were obtained with Katamin AB and
Adogen 464. Katamin AB used in production of disin-
fectants and synthetic detergents is readily available and
cheap, which makes attractive its use in the process.
It was shown that, up to a certain limit, the PTC
amount does not affect the rate of the reaction of CP
with HP. This is due to the fact that the reaction rate is
determined by the PTC concentration, which, in turn, is
determined by the concentration of the component taken
in deficiency. Figure 1 shows how the effective constant
of the CP epoxidation with hydrogen peroxide in the
1,2-CD synthesis depends on the PTC : sodium tungstate
molar ratio.
PTC : Na2WO4
Fig. 1. Rate constant keff of cyclopentene conversion in its reac-
tion with aqueous solution of hydrogen peroxide as a function
of the PTC : Na2WO4 molar ratio.
In accordance with this estimate, the PTCs used in this
study can be ranked in the following performance order:
TEAB : TEAI : TBAB : Katamin AB : Adogen 464 =
0.001 : 0.001 : 1 : 500 : 1000000. The CP conversion rate
increases in the same order.
With an increase in the PTC : sodium tungstate molar
ratio from 0.2 : 1 to 1.2 : 1, the reaction rate does not in-
crease noticeably, because in this case the concentration of
the active complex is determined by the sodium tungstate
content. The CP conversion in the process remains on
the level of 98–99%, and the HP conversion is 94–98%,
with >98% selectivity with respect to 1,2-CD. As the
PTC : sodium tungstate ratio is decreased to 0.05 : 1, the
reaction rate drastically decreases, because the catalytic
Unsymmetrical PTCs (KataminAB andAdogen 464)
are extracted more efficiently than the symmetrical PTCs.
The extraction constant of Adogen 464, determined [8]
from the experimentally found content of peroxy groups
in the organic phase for the reaction under consideration,
is (6.7 ± 0.3) × 104, which confirms high performance
of this PTC.
Table 2. Solvent effect on the synthesis of 1,2-cyclopentanediol from cyclopentene and aqueous hydrogen peroxide solution.
Phase-transfer catalystAdogen 464; initial concentration, M: CPin organic phase 5.0, Н2О2 in aqueous phase 4.0, sodium tungstate
in aqueous phase 0.06; molar ratio Н2О2 : CP = 1.3 : 1, Na2WO4·2H2O : H3PO4 : PTC = 1 : 2 : 0.36; aqueous to organic phase
volume ratio 1.6 : 1; 60°С; pH of the aqueous phase 1.6
Yield based on CP
Conversion, %
Relative dielectric
permittivity ε
loaded, %
Solvent
τ, min
CP
Н2О2
96.8
95.6
1,2-ECP
1,2-CD
76.6
N,N-Dimethylformamide
n-Butanol
36.71
17.49
180
150
98.0
98.2
21.4
10.4
87.8
Dichloroethane
10.27
3.42
140
140
99.8
99.6
95.3
94.4
7.6
7.2
92.2
92.4
Trichloroethylene
Tetrachloroethylene
Xylene
2.30
2.27
120
120
98.0
99.3
92.4
92.9
5.4
5.9
92.6
93.4
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664
MESHECHKINA et al.
the low correlation coefficient of the CP oxidation rate
with ε (R2 = 0.75) shows that, in our case, this parameter
is not decisive. Strong effect on the rate of the reaction
of CP with HP in the two-phase system is exerted by the
capability of the solvent to extract the catalytic complex,
the degree of phase transfer of the ions, and the degree
of their solvation.
As seen from Fig. 2, polar solvents such as n-butanol
and dimethylformamide are unsuitable for this reaction.
They are miscible with water to different extents, with
partial homogenization of the system.As a result, the ole-
fin concentration in the organic phase and the reaction rate
decrease. These solvents are basic, which also decreases
the rate of epoxidation, which is an electrophilic reaction.
Fig. 2. Rate constant keff cyclopentene conversion in its reaction
with aqueous solution of hydrogen peroxide as a function of the
relative dielectric permittivity ε of the solvent used.
Nonpolar solvents such as alkyl halides and xylene do
not differ significantly in the activity. All these solvents
do not hinder the reaction sterically, readily dissolve the
catalytic complex, and allow the reaction of CP with an
aqueous HP solution to be performed in a short time with
high selectivity.
complex concentration starts to be determined by the PTC
concentration and decreases. Therefore, we suggested
to use the PTC amounts with which the PTC : sodium
tungstate ratio is no less than 0.3 : 1 to ensure high reac-
tion rate and no more than 0.5 : 1 to avoid nonproductive
PTC consumption.
Thus, in choosing a solvent for the reaction of CPwith
HP, the main criteria should be feasibility parameters such
as the solvent availability and cost, and also the procedure
for isolating reaction products.
The phase-transfer efficiency in the step of the 1,2-
ECP formation is also affected by the solvent. It should
be hydrophobic and inert under the reaction conditions; it
should readily dissolve the catalytic complex and exhibit
high extraction power [7]. Under the reaction conditions,
all the solvents used (Table 2) are resistant to the effect
of hydrogen peroxide.
The PTC after the reaction was found to remain in the
organic phase, which opens possibilities for its reuse. In
this case, the best solvents for the reaction of CP with
aqueous HP solution are tetrachloroethylene and xylene.
Their boiling points are higher than that of 1,2-ECP.
Therefore, in isolation of the reaction product from their
organic phase, 1,2-ECP can be separated from PTC by
fractional distillation and the catalyst can be recycled as
solution in the solvent chosen. 1,2-CD does not affect
the organic phase separation, because it practically fully
passes to the aqueous phase.
For different solvents, the constants of PTC extraction
from aqueous solutions differ by factors of tens and thou-
sands. For example, the constant of TBAB extraction from
aqueous solutions varies as follows: n-butanol (6.9) >
1,2-dichloroethane (6.1) > trichloroethylene (0.2) [7].
However, in this study we have not noticed so dramatic
differences in the time of CP conversion and selectivity
of final product formation (Table 2). We believe that the
use of such an active PTC asAdogen 464 or KataminAB
levels off possible differences in the extraction ability of
the solvents.
CONCLUSIONS
(1) The rate of cyclopentene epoxidation with an
aqueous solution of hydrogen peroxide increases with
an increase in the length of the hydrocarbon chain of the
phase-transfer catalyst. The nature of the anion affects
the process to a considerably lesser extent. Katamin AB
can be used as effective phase-transfer catalyst in cyclo-
pentene epoxidation.
The solvents miscible with water (dimethylfor-
mamide, n-butanol) decrease the PTC activity owing to
its solvation [7]. At the same time, the reaction rates in
these solvents somewhat differ. The CP oxidation rate
correlates with the dielectric permittivity of the solvent
(Fig. 2).
The results presented in Table 2 and in Fig. 2 are con-
sistent with the known data on the solvent effect on the
rate of olefin epoxidation with per acids [9]. However,
(2) For the reaction of cyclopentene with hydrogen
peroxide to be performed at a high rate with high selectiv-
ity, it is necessary to use inert hydrophobic solvents with
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EFFICIENCY OF PHASE-TRANSFER CATALYSIS
pp. 4–8.
665
low dielectric permittivity.
4. Danov, S.M., Sulimov, A.V., and Sulimova, A.V., Zh. Prikl.
Khim., 2008, vol. 81, no. 11, pp. 1847–1850.
(3) The use of tetrachloroethylene and xylene allows
isolation of 1,2-epoxycyclopentane from the organic
phase by fractional distillation and simultaneous recy-
cling of the catalytic complex for its reuse in the form of
a solution in the solvent chosen.
5. Mizuno, N., Yamaguchi, K., and Kamata, K., Coord. Chem.
Rev., 2005, vol. 249, pp. 1944–1956.
6. RF Patent 2369594.
7. Dehmlow, E.V. and Dehmlow, S.S., Phase Transfer
Catalysis, Weinheim: Chemie, 1983, 2nd ed.
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