Kinetic Study of Carbonylation of α-Bromo-p-xylene with Iron Pentacarbonyl by Phase-Transfer Catalysis

Article abstract of DOI:10.1006/jcat.1998.2185

The reaction kinetics of the carbonylation of α-bromo-p-xylene (BrCH₂C₆H₄CH₃, BX) with iron pentacarbonyl (Fe(CO)₅) by phase-transfer catalysis was studied in an organic solvent/alkaline solution. The concentration of tetra-n-butylammonium bromide ((n-C₄H₉)₄NBr, TBAB), NaOH, NaBr, aqueous volume and temperature were evaluated to achieve the optimum reaction condition. The reaction behavior was discussed by the apparent reaction-rate constants for BX and bis(p-methylbenzyl) ketone ((p-CH₃C₆H₄CH₂)₂CO, BMBK), respectively, and the relationship of consumption of BX and Fe(CO)₅. The product distributions of BX with Fe(CO)₅ on various reactions conditions were measured. The activation energies was obtained at TBAB = 1.24 and 0 mmol as Well.

Full text of DOI:10.1006/jcat.1998.2185

JOURNAL OF CATALYSIS 178, 604–610 (1998)
ARTICLE NO. CA982185
Kinetic Study of Carbonylation of �-Bromo-p-xylene with Iron
Pentacarbonyl by Phase-Transfer Catalysis
1
Ho-Shing Wu and Wen-Han Tan
Department of Chemical Engineering, Yuan-Ze University, 135, Far-East Road, ChungLi, Taoyuan, 32026, Taiwan, Republic of China
Received October 1, 1997; revised June 8, 1998; accepted June 22, 1998
tions could be applied to organometallic chemistry. The re-
The reaction kinetics of the carbonylation of �-bromo-p-xylene action mechanism was corrected and clarified in our pre-
BrCH2C6H4CH3, BX) with iron pentacarbonyl (Fe(CO)5) by phase- vious work (13). However, the nature of phase-transfer
(
transfer catalysis was studied in an organic solvent/alkaline
organometallic reaction is complicated, the reaction kinet-
ics is rarely investigated so far. Here, we report the kinetic
study of the stoichiometric carbonylation of �-bromo-p-
xylene with iron pentacarbonyl by phase-transfer catalysis
under nitrogen atmosphere.
solution. The concentration of tetra-n-butylammonium bromide
((n-C4H9)4NBr, TBAB), NaOH, NaBr, aqueous volume and temper-
ature were evaluated to achieve the optimum reaction condition.
The reaction behavior was discussed by the apparent reaction-
rate constants for BX and bis( p-methylbenzyl) ketone (( p-
CH3C6H4CH2)2CO, BMBK), respectively, and the relationship of
consumption of BX and Fe(CO)5. The product distributions of BX
with Fe(CO)5 on various reactions conditions were measured. The
EXPERIMENTAL
activation energies was obtained at TBAB = 1.24 and 0 mmol as Materials
well.
�c 1998 Academic Press
Tetra-n-butylammonium
bromide
((n-C4H9)4NBr,
TBAB), �-bromo-p-xylene (BrCH2C6H4CH3) (Janssen),
iron pentacarbonyl (Fe(CO)5) (Strem), and other reagents
were all reagent grade chemicals.
INTRODUCTION
Many chemists (1–3) have studied the phase-transfer
catalyzed reaction system. Advantages arising from the
syntheses of organic chemicals with phase-transfer cata-
lysis (PTC) are rapid rate of reaction, high selectivity of
product, moderate operating temperature, and suitability
for industrial-scale production. Moreover, phase-transfer
catalysisisa valuable synthetictechnique in transition metal
organometallic chemistry. Transition metals are active cata-
lysts for a variety of organic reactions. They are useful in
conjunction with phase-transfer catalysts, particularly when
hydroxide anions and other inorganic species are required
to complete the reaction sequence. Use of phase-transfer
catalysts as cocatalysts with transition metal compounds of-
fers some additional options and advantages compared to
the conventional reaction (4, 5).
Procedure
3
An aqueous solution (50 cm ) of sodium hydroxide and
tetra-n-butylammonium bromide (phase-transfer catalyst)
was prepared and introduced into the reactor (250 cm ,
three-necked flask) which was thermostated at the desired
3
�
temperature (25 � 0.02 C). Measured quantities of �-
bromo-p-xylene, diphenyl methane ((C6H5)2CH2) (internal
3
standard for HPLC) and organic solvents (50 cm ), which
were also maintained at the desired temperature, were
then added to the reactor. The solution was agitated at
7
00 rpm for 15 min and the reactor was purged with inert
3
nitrogen gas (40 cm /min). After reaction, the flow rate
of nitrogen and the agitated rate were set at 40 cm /min,
3
1
000 rpm, respectively. A known quantity of iron pentacar-
The stoichiometric carbonylation of �-bromo-p-xylene
bonyl was then added to the reactor. An aliquot sample
was withdrawn from the reaction solution at a selected
(
BrCH2C6H4CH3, BX) with Fe(CO)5 under phase-transfer
condition has been studied (6–10). The mechanistic fea-
tures and the selectivity of this reaction have been reported
3
time interval. The sample (0.5 cm ) was immediately added
3
3
to 2 cm dichloromethane (CH2Cl2)/2 cm of water to
quench the reaction. The organic phase contents (bis( p-
methylbenzyl) ketone (( p-CH3C6H4CH2)2CO) and p-
xylene ( p-CH3C6H4CH3, PX)) were then analyzed quan-
titatively by HPLC using the method of internal standard.
The p-methylphenylacetic acid ( p-CH3C6H4COOH,
(
11–13). The results of their reports demonstrated that the
syntheses of metal carbonyls under phase-transfer condi-
1
To whom all correspondence should be addressed. E-mail: cehswu@
ce.yzu.edu.tw.
604
0021-9517/98 $25.00
Copyright �c 1998 by Academic Press
All rights of reproduction in any form reserved.

CARBONYLATION OF �-BROMO-p-XYLENE
605
MPAA) was extracted from the aqueous layer after of �-bromo-p-xylene with iron pentacarbonyl is written as
acidification. The accuracy of these analytical techniques shown in Scheme 1. The seven reaction paths (i)–(vii) exist
was within 2–3% and most of the data could be correctly in this carbonylation reaction. Hence, the reaction expres-
reproduced within 5% of the values reported in this work. sions are listed as
The yield of BMBK was calculated from the quotient of
k1
�
�
[
BMBK] and n. [limiting reactant]. The n values for BX 2Q OH + Fe(CO)5 → Q Fe(CO)4 + CO2 + H2O
[1]
[2]
2
and Fe(CO)5 were 0.5 and 1, respectively.
k2
�
�
�
Q Fe(CO)4 + BX → Q BFe(CO)4 + Q X
Liquid chromatography was carried out on a Shimadzu
LC-10AD instrument, using a column packed with Chem-
coPak 5-ODS-H. The eluent was CH3OH/H2O = 3/1 (flow
2
k
3
�
�
Q BFe(CO)4 *ꢀ Q BCOFe(CO)3
[3]
k� 3
3
rate 1.0 cm /min) and was monitored at 266 nm (UV
k4
�
�
Q BCOFe(CO)3 + BX → BMBK + Q X + Fe(CO)3 [4]
detector). The bis( p-methylbenzyl) ketone, p-xylene, and
p-methylphenylacetic acid were analyzed by means of
elemental analysis on a Perkin-Elmer 2400-CHN, mass
k5
�
�
Q BFe(CO)4 + CO → Q BCOFe(CO)
[5]
4
k6
�
�
spectrometry on a JEOL SX-102A mass spectrometer, Q BCOFe(CO) + BX → B COFe(CO) + Q X
[6]
4
2
4
and NMR spectra in deuteriated chloroform on a JEOL
00 MHz FT-NMR spectrometer.
k7
3
B2COFe(CO)4 → BMBK + Fe(CO)4
B2COFe(CO)4 + CO + Q OH
[7]
[8]
�
RESULTS AND DISCUSSION
k8
�
→
Q BCOFe(CO)4 + MPAA
Many reactions happened simultaneously in the stoi-
�
chiometric carbonylation of �-bromo-p-xylene (BX) with 2Q OH + Fe(CO)
5
iron pentacarbonyl under phase-transfer condition. The re-
k9
→
�
Q HFe(CO)4 + CO2 (or Na2CO3 + H2O)
[9]
action mechanism is quite complex. The main products
included bis( p-methylbenzyl) ketone (BMBK), p-xylene
k10
�
�
Q HFe(CO)4 + BX → PX + Fe(CO)4 + Q X.
[10]
(
PX), and p-methylphenylacetic acid (MPAA). In this
study, the product distributions of carbonylation of BX with The rate expressions of BX, BMBK and Fe(CO)5 are obtai-
Fe(CO)5 on various reaction conditions by phase-transfer ned and written as
catalysiswere listed in Table 1. The major product isBMBK.
d[BX]
The amount of PX is slight. The total yield of stoichiometric
carbonylation of BX with Fe(CO)5 for BMBK, MPAA, and
PX ranged between 70 to 80% . When the amount of BX
was excess to that of Fe(CO)5, the yield approach 100% .
Our previous work (13) has reported that BX and Fe(CO)5
were self-decomposed in the alkaline solution during the
course of the reaction.
�
�
=
� (k2[Q Fe(CO)4] + k4[Q BCOFe(CO)3]
+
2
dt
�
�
k6[Q BCOFe(CO)4]+k10[Q HFe(CO)4])[BX]
[11]
d[BMBK]
�
=
(k4[Q BCOFe(CO)3]
dt
�
On the basis of various literature sources (14–22) and
the result in our previous study (13), the carbonylation
+ k6[Q BCOFe(CO)4])[BX]
[12]
[13]
d[Fe(CO)5]
�
2
=
� (k1 + k9)[Q OH] [Fe(CO)5].
dt
TABLE 1
Product Distributions of Carbonylation of BX with Fe(CO)5
on Various Reaction Conditions
A generalized approach describing the phase-transfer cata-
lyzed reaction system is to use a pseudo-first-order reaction
(
1, 2). Hence, Eqs. [11]–[13] can be rewritten as
BX (mmol)
TBAB (mmol)
BMBK (% )
MPAA (% )
PX (% )
d[BX]
1
1
1
1
1
2
3
5
0.6
0.6
0.6
0.6
0.6
6.5
7.1
3.0
1.24
1.55
1.86
2.32
3.1
1.24
1.24
1.24
62.4
70.9
68.1
67.1
65.5
80
0.51
3.75
3.80
12.9
19.6
18.9
11.9
0.5
� 1
� 1
� 1
0
0
2
=
� kapp,1[BX]
dt
�
�
kapp,1 = k2[Q Fe(CO)4] + k4[Q BCOFe(CO)3]
2
�
�
+ k [Q BCOFe(CO) ] + k [Q HFe(CO) ] [14]
6
4
10
4
89
98.5
0
1
d[BMBK]
=
kapp,2[BX]
dt
Note. Reaction conditions: Fe(CO)5 = 5.3 mmol, NaOH = 0.125 mol,
reaction time = 240 min, C6H6 = 50 cm , aqueous phase = 50 cm , N2 =
0 cm /min, 25 C.
�
�
kapp,2 = k4[Q BCOFe(CO)3] + k6[Q BCOFe(CO)4]
3
3
3
�
[15]
4

6
06
WU AND TAN
SCHEME 1
The stoichiometric consumed moles of BX and Fe(CO)5
d[Fe(CO)5]
are 2 and 1, respectively when 1 mole of BMBK produces
and RC-value equal to 2. We discuss the reaction behavior
of the carbonylation by Eqs. [14]–[17] in the following.
The effects of the amount of tetra-n-butylammonium
bromide (phase-transfer catalyst, TBAB) on the consump-
tion mole ratio of BX to Fe(CO)5 and apparent reaction-
rate constant are displayed in Fig. 1. The apparent reaction-
rate constants are proportional linearly to the amount of
TBAB when the amount of TBAB exceeded 0.3 mmol.
The turnover number based on the concentration of TBAB
=
� kapp,3[Fe(CO)5]
dt
�
2
kapp,3 = (k1 + k9)[Q OH] .
[16]
The fixed value of kapp is called the apparent first-order
reaction-rate constant which is obtained so that the con-
sumption of BX is restricted below 15% .
As mentioned above, the BX and Fe(CO)5 can be self-
decomposed. A definition is employed to describe the re-
lationship of consumption (abbreviated RC) of BX and
Fe(CO)5 (Eq. [17]):
-1
was 132 min . Because the turnover number kept con-
stant for various [TBAB] and no improvement in the re-
action rate was observed when the agitation rate exceeded
[BX]|240 min � [BX]|0 min
RC = [
.
[17]
Fe(CO)5]|240 min � [Fe(CO)5]|0 min

CARBONYLATION OF �-BROMO-p-XYLENE
607
FIG. 2. Effects of NaOH on kapp: (᭺) kapp,1; (ᮀ) kapp,2 (a) TBAB =
3
1
.24 mmol, (b) TBAB = 0 mmol. C6H6 = 50 cm , BX = 10.6 mmol,
3
3
�
FIG. 1. Effects of the amount of tetra-n-butylammonium bromide
Fe(CO)5 = 5.3 mmol, aqueous phase = 50 cm , N2 = 40 cm /min, 25 C.
3
(
TBAB) on (a) RC and (b) kapp: (᭺) kapp,1; (ᮀ) kapp,2. C6H6 = 50 cm ,
3
BX = 10.6 mmol, Fe(CO)5 = 5.3 mmol, aqueous phase = 50 cm , NaOH =
distributed itself in the aqueous phase rather than in the or-
ganic phase. Therefore, the onium hydroxide can exist in
the organic phase, even in nonpolar media. The reaction
3
�
0
.125 mol, N2 = 40 cm /min, 25 C.
1
000 rpm, the mass-transfer effect can be neglected in the mechanism of phase-transfer catalyst between two phases
present study. The RC-value increases and is less than 2 was clarified to be the extraction mechanism in the previous
when the amount of TBAB increases up to 0.5 mmol. The work (13). Figures 2 and 3 display the effects of the NaOH
increment of phase-transfer catalyst in the reaction sys-
tem cannot obtain the larger amount of product BMBK,
whereas the product of MPAA increased when the amount
of TBAB increased (Table 1). The sum of yields of BMBK,
MPAA, and PX was increased with an increasing amount of
TBAB. When the mole ratio of TBAB to Fe(CO)5 increases,
the concentration of free QOH increases. Adding more
catalyst enhanced the yield of MPAA. The phenomenon is
similar to the result of Abbayes and Alper (22) and Collman
et al. (17). Hence, if the product of BMBK is favored, the
concentration of QOH must be low and the production of
carbon monoxide must be eliminated (reaction path (ii)).
The mechanism of phase-transfer catalytic carbonyla-
tion was described by an interfacial mechanism (10–12).
The evidence was that, since the onium hydroxide was
not extractable into the organic phase and the reaction
rate depended on the agitation rate, the reaction involv-
ing the hydroxide ion should occur at the interface. From
the results of the previous work (24, 25), a small amount of
onium hydroxide (QOH) was observed in the organic phase
when alkaline solutions were used. The distribution ratios
of QOH between two phases (= [QOH]org/[QOH]aq) were
increased when the concentration of base was increased
FIG. 3. Effects of NaOH on (a) yield of BMBK, (b) RC, (᭺) TBAB =
and also it increased when the concentration of onium hy-
droxide was increased. Tetra-n-butylammonium hydroxide Fig. 2.
1
.24 mmol, (ᮀ) TBAB = 0 mmol. The reaction conditions are the same as

6
08
WU AND TAN
concentrations on the apparent rate constant, RC, and the
yield of BMBK. Apparent rate constants were low and
remain nearly constant in the absence of TBAB because
the concentration of NaOH in the organic phase was sat-
urated. The kapp,1 value was larger than the kapp,2 value.
The reaction path (v) is not the favorite reaction. How-
ever, the apparent reaction rate constant was increased
with an increasing amount of NaOH when the amount of
TBAB = 1.24mmol. The relationship between the apparent
reaction rate constant and the amount of NaOH follows
the second-order polynomial approximation. This finding
corresponding to Eq. [16]. The consumption rate of BX
and the yield of BMBK increased when the concentration
of NaOH increased (Fig. 3). The yield and RC remain al-
most constant (62% and 2) as the NaOH concentration
was larger than 0.125 mol. The increment of the concen-
tration of NaOH cannot increase the maximum yield of
BMBK.
While the amount of BX or Fe(CO)5 was excess, the
BMBK had a high yield (Table 1). When the molar ratio of
BX to Fe(CO)5 was more than 10, the yield of RCOR raised
to 100% . This situation can inhibit the decay of Fe(CO)5 0.0125 mol, N2 = 40 cm /min.
and produce the single product of BMBK. Figure 4 shows
FIG. 5. Effects of temperature on kapp: (᭺) kapp,1; (ᮀ) kapp,2
3
(
1
a) TBAB = 1.24 mmol, (b) TBAB = 0 mmol. C6H6 = 50 cm , BX =
3
0.6 mmol, Fe(CO)5 = 5.3 mmol, aqueous phase = 50 cm , NaOH =
3
a plot of RC and kapp against the concentration ratio of
of RX to Fe(CO)5. For conventional kinetics, the chang-
BX to Fe(CO)5. When the amount of Fe(CO)5 remained at
.3 mmol, the amount of BX varied and the molar ratio of
ing amount of RX cannot vary the apparent reaction rate
constant. However, this behavior may happen in the liquid–
liquid phase-transfer catalyzed reaction (26–28). When the
rate of organic reaction competes with the rate of mass
transfer between the catalyst, the concentration of imme-
diate catalyst QOH in the organic phase can not maintain
constant. The rate of the side reaction and the decaying rate
of Fe (CO)5 increased when the concentration of QOH in
the organic phase decreased.
5
RX to Fe(CO)5 varied from 0.5 to 10. The RC value was
increased still to 3 with an increasing concentration ratio
Figure 5 depicts the temperature effect on the apparent
reactant rate constant. The apparent rate constant increases
when the temperature is increased. The reaction rate con-
stant is sensible for high temperature in the blank reac-
tion. The corresponding blank experiments without using
the catalyst were also carried out in order to test the effect
of the catalyst. The ratio of apparent reaction-rate constant
of the catalyzed reaction to the uncatalyzed reaction ex-
ceeds by 100 times in Fig. 5. The activation energy was cal-
culated by Arrhenius law. The activation energies of the
blank reaction for kapp,1 and kapp,2 were 56.1 kJ/mol and
5
7.3 kJ/mol, respectively. Upon addition of TBAB, a much
faster reaction rate was observed, and the activation energy
kapp,1 and kapp,2 decreased to 53.7 kJ/mol and 52.2 kJ/mol, re-
spectively, corresponding to 1.24 mmol of TBAB. This find-
ing indicates that the contribution of TBAB for extracting
the hydroxide ion is larger than that for increasing reactiv-
ity of hydroxide ion. In general, the catalyzing capability
of phase-transfer catalyst results from the increasing the
distance between anion and cation. NaOH and QOH are
hydrophilic compound, and distributes itself in the aqueous
FIG. 4. Effects of [BX]/[Fe(CO)5] on (a) RC and (b) kapp: (᭺) kapp,1;
3
(
ᮀ) kapp,2. C6H6 = 50 cm , Fe(CO)5 = 53 mmol, TBAB = 1.24 mmol, aque-
3
3
�
ous phase = 50 cm , NaOH = 0.125 mol, N2 = 40 cm /min, 25 C.

CARBONYLATION OF �-BROMO-p-XYLENE
609
FIG. 6. Effects of temperature on (a) yield of BMBK, (b) RC, (᭺)
TBAB = 1.24 mmol, (ᮀ) TBAB = 0 mmol. The reaction conditions are
the same as Fig. 5.
FIG. 7. Effects of NaBr on kapp: (᭺) kapp,1; (ᮀ) kapp,2 (a) TBAB =
3
1.24 mmol, (b) TBAB = 0 mmol. C6H6 = 50 cm , BX = 10.6 mmol,
3
Fe(CO)5 = 5.3 mmol, aqueous phase = 50 cm , NaOH = 0.0125 mol, N2 =
3
�
0 cm /min, 25 C.
4
phase rather than in the organic phase. The reaction type of
NaOH is similar to that of QOH. The tetra-n-butyl ammo-
nium cation allows ion-pair to have a long distance. Hence,
the activation energy is slightly decreased. In addition, the
tetra-n-butyl ammonium cation is a lipophilic group so
that the concentration of QOH in the organic phase is
larger than that of NaOH. According to Fig. 5, the fac-
tor plays a crucial role in promoting the reaction rate.
Figure 6 displays the effect of temperature on RC and yield
of BMBK. When the temperature is high, the reactivity in
the blank reaction approaches to that in PTC (1.24 mmol)
reaction. The concentration of NaOH in the organic phase
was increased with a temperature raise. Hence, the blank
reaction can also obtain the higher yield of BMBK by using
the higher temperature.
both phases. The effect of the aqueous volume ratio on
the apparent reaction rate constant is shown in Fig. 9. The
apparent reaction-rate constants have an optimum value
when the aqueous volume is around 30 mL.
In general, bromide ions are generated during the reac-
tion. The increase of sodium bromide salt will retard the
reaction rate. In order to find the salt effect on the reaction,
extra sodium bromide was added to the reactor. Figures 7
and 8 display the effect of NaBr in the reaction. When a
larger amount of NaBr is added, the reaction rate is signif-
icantly reduced. Hence, the amount of by-product NaBr in
the aqueous solution would directly influence the reaction
rate. The reducing effect in the absence of TBAB makes
more sense than that in the presence of TBAB.
For a constant quantityoforganicsolvent (50mL), chang-
ing the aqueous volume in the reaction system not only af-
fects the concentration of reactants in the aqueous phase
but it also variesthe equilibrium coefficientsand masstrans-
FIG. 8. Effects of NaBr on (a) yield of BMBK, (b) RC, (᭺) TBAB =
1
.24 mmol, (ᮀ) TBAB = 0 mmol. The reaction conditions are the same as
fer coefficients of the catalyst and interfacial areas between Fig. 7.

6
10
WU AND TAN
REFERENCES
1
2
. Dehmlow, E. V., and Dehmlow, S. S., Phase Transfer Catalysis. Verlag
Chemie, Weinheim, 1993.
. Starks, C. M., Liotta, C., and Halpern, M., Phase Transfer Catalysis,
Fundamental, Application and Industrial Perspectives. Chapman &
Hall, London, 1994.
3. Weber, W. P., and Gokel, G. W., Phase Transfer Catalysis in Organic
Syntheses. Springer-Verlag, New York, 1977.
4
5
6
. Alper, H., Advances in Organometallic Chemistry 19, 183 (1981).
. Vancheesan, S., J. Sci. Ind. Res. 44, 75 (1985).
. Kimura, Y., Tomita, Y., Nakanishi, S., and Otsuji, Y., Chem. Lett., 321
(
1979).
. Tanguy, G., Weinberger, B., and Abbayes, H. D., Tetrahedron Lett.
4(37), 4005 (1983).
. Tanguy, G., Weinberger, B., and Abbayes, H. D., Tetrahedron Lett.
5(48), 5529 (1984).
. Tustin, G., and Hembre, R. T., J. Org. Chem. 49, 1761 (1984).
7
8
9
2
2
1
1
0. Ou, C. B., and Liu, L. K., J. Chin. Chem. Soc. 32, 23 (1985).
1. Abbayes, H., Clement, J. C., Laurent, P., Tanguy, G., and Thilmont, N.,
Organometallics 7, 2293 (1988).
1
1
2. Laurent, P., Tanguy, G., and Abbayes, H., J. Chem. Soc. Chem. Com-
mun., 1754 (1986).
3. Wu, H. S., and Tan, W. H., J. Chem. Tech. Biotechnol. 67, 381
(
1996).
FIG. 9. Effects of aqueous volume on kapp: (᭺) kapp,1; (ᮀ) kapp,2.
3
14. Krusic, P. J., and Cote, W. J., J. Am. Chem. Soc. 106, 4042 (1984).
15. Collman, J. P., Winter, S. R., and Clark, D. R., J. Am. Chem. Soc. 94(5),
C6H6 = 50 cm , BX = 10.6 mmol, Fe(CO)5 = 5.3 mmol, PTC = 1.24 mmol,
3
�
NaOH = 0.125 mol, N2 = 40 cm /min, 25 C.
1
788 (1972).
6. Siegl, W. O., and Collman, J. P., J. Am. Chem. Soc. 94(7), 2516
1972).
1
1
CONCLUSION
(
7. Collman, J. P., Finke, R. G., Cawse, J. N., and Brauman, J. I., J. Am.
Chem. Soc. 99(8), 2515 (1977).
The kinetics of carbonylation of �-bromo-p-xylene with
iron pentacarbonyl in an organic/alkaline solution by 18. Peake, B. M., Symons, M. C. R., and Wyatt, J. L., J. Chem. Soc. Dalton
Trans., 1171 (1983).
phase-transfer catalysis was investigated. Apparent-rate
constants were low and remain nearly constant in the ab-
sence of TBAB because the concentration of NaOH in the
1
9. Norwood, K., Ali, A., Flesch, G. D., and Ng, C. Y., J. Am. Chem. Soc.
12(21), 7502 (1990).
0. Cooke, M. P., Jr., J. Am. Chem. Soc. 92(20), 6080 (1970).
1
2
organic phase was saturated. The relationship between the 21. Abbayes, H. D., and Buloup, A., Tetrahedron Lett. 21, 4343
apparent reaction rate constant and the amount of NaOH
follows the second-order polynomial approximation when
the amount of TBAB = 1.24 mmol. The contribution of
TBAB for extracting the hydroxide ion is larger than that
for increasing the reactivity of the hydroxide ion.
(1980).
2
2. Abbayes, H. D., and Alper, H., J. Am. Chem. Soc. 99(1), 98
(
1977).
2
2
3. Wu, H. S., and Lin, Y. K., J. Chem. Eng. Japan 27(6), 818 (1994).
4. Wang, M. L., and Wu, H. S., J. Org. Chem. 55(8), 2344 (1990).
25. Wu, H. S., Fang, T. R., Meng, S. S., and Hu, K. H., J. Mol. Catal. 136(2),
35 (1998).
26. Wu, H. S., and Lai, J. J., Ind. Eng. Chem. Res. 34(5), 1536
1995).
1
ACKNOWLEDGMENT
(
The authors thank the National Science Council, Taiwan, Republic of 27. Wang, M. L., and Wu, H. S., Chem. Eng. Sci. 46(2), 509 (1991).
China for financial support under Grant NSC 84-2214-E-155-004.
28. Wu, H. S., and S. S. Meng, AIChE, J. 43(5), 1309 (1997).