522
Ind. Eng. Chem Res, 1990, 29, 522-526
Kinetic Study of Synthesizing 2,4,6-Tribromophenol Allyl Ether by Phase Transfer Catalytic Reaction Maw-Ling Wang* a n d Hung-Ming Yang Department of Chemical Engineering, National Tsing Hua Uniuersity, Hsinchu, Taiwan, ROC
2,4,6-Tribromophenol and allyl bromide undergo SN2substitution reaction by phase transfer catalysis to produce 2,4,6-tribromophenyl allyl ether. The effects of solvents, reactant concentration, agitation rate, catalysts, and temperature on the conversion are investigated in order to find the optimum operating conditions for this reaction. It is found t h a t no agitation effect is observed when the agitation rate exceeds 600 rpm. T h e order of relative activities of solvents is dichloromethane > chlorobenzene > toluene. A better choice of potassium hydroxide rather than sodium hydroxide enhances the reaction rate. In examining six kinds of phase transfer catalysts, tetra-n-butylammonium bromide (or tetra-n-butylammonium hydroxide) is the best one. T h e apparent reaction rate is first order on the quantity of phase transfer catalyst and allyl bromide, respectively. T h e corresponding activation energy of the apparent rate constant is 13.8 kcal/mol. During the reaction, the concentration of the intermediate product was also measured to observe its behavior in the liquid-liquid system. T h e present study has valuable implications in the synthesis of phenyl allyl ether via the two-phase Williamson reaction.
A necessary condition for a reaction is to cause the collision of two reactant molecules. However, the reaction rate is limited by the contact surface area, mass-transfer rate, and distribution between two immiscible reactants due to their low solubilities. The early conventional method for systhesizing organic chemicals from two immiscible reactants is to employ a protic or aprotic solvent in order to improve their mutual solubilities (Dehmlow and Dehmlow, 1983;Starks and Liotta, 1978; Weber and Gokel, 1977). Nevertheless, this improvement is not so significant. In addition, the reaction was carried out in the extreme operating condition of high temperature to change the reaction path. The disadvantage is that the byproducts are often accompanied by the generation of a desired product. Furthermore, the problems of recovery of the expensive aprotic solvent and of carrying out the reaction in an anhydrous condition make the reaction very difficult in an industrial application. The reaction problem of two immiscible reactants was not solved until 1951. Jarrouse (1951) found that the two-phase reaction is enhanced by adding a small catalytic quantity of quaternary salt. The application of quaternary salt as a phase transfer catalyst in the two-phase reaction to synthesize speciality chemicals is thus extensively studied by many chemists. Today, phase transfer catalysis (PTC) has been considered to be one of the most effective tools in synthesizing organic chemicals from two immiscible reactants (Freedman, 1986; Starks, 1985). The greatest advantages of synthesizing organic chemicals by phase transfer catalysis are acceleration of the reaction rate even at a moderate operating temperature and a high conversion rate of the product as well as high selectivity. Recently, PTC has been extensively applied to reactions by alkylation, arylation, condensation, elimination, and polymerization. Synthesized poly(bromo)phenyl allyl ether can be used as a flame retardant (Jenkner and Buettgens, 1973; Podkoscielny et al., 1980). In the past, the derivatives of bromophenyl ether were synthesized by using alumina chloride as a catalyst in a bromination reaction which was carried out at a very high temperature (Ransford, 1984; Shenbor et al., 1959; Toyo Soda Mfg. Co. Ltd., 1983). However, a low yield of product is obtained even though
* To whom
all correspondence should be addressed.
the reaction is carried out a t such an extreme condition. In the present study, 2,4,6-tribromophenyl allyl ether is synthesized by reacting 2,4,6-tribromophenol with allyl bromide in an organic (chlorobenzene)/KOH alkaline solution when tetra-n-butylammonium bromide is used as the phase transfer catalyst. The main objective of the present study is to investigate the operating conditions that affect the yield of the product. In order to realize the mechanism of the reaction and kinetics, the role of the intermediate product of the phase transfer catalyst, ArOQ (Bu4NO(CGH2)Br,), in the two-phase reaction is investigated in detail. Experimental Section: Two-Phase Reaction Materials. 2,4,6-Tribromophenol (ArOH), allyl bromide (RBr), tetra-n-butylammonium bromide (Bu4N+Br-;QBr), and other reagents are all G.R. grade chemicals, products of Merck & Co., West Germany. Procedures. The reactor is a 300-mL three-neck Pyrex flask, serving the purposes of agitating the solution, inserting the thermometer, taking samples, and feeding feed. The reactor is submerged into a constant-temperature water bath in which the temperature can be controlled to within f O . l "C. To start a kinetic run, a known quantity of potassium hydroxide and 2,4,6-tribromophenol are prepared and dissolved in water. The solution is then introduced into the reactor, which is thermostated a t the desired temperature. A measured quantity of tetra-nbutylammonium bromide ( (n-C,Hg),N+Br-) dissolved in water, allyl bromide (CH2=CHCH2Br), and diphenyl ether (internal standard), which is also a t the desired temperature, is dissolved in the chlorobenzene solvent and is then added to the reactor. During the reaction, an 0.8-mL-aiiquot sample is withdrawn from the reaction solution a t a chosen time. The organic and aqueous phases of the sample are well separated in a few seconds. After separation, 0.1 mL of the organic phase sample is immediately diluted with 4.5 mL of methanol. Usually, it takes less than 20 s to take a sample. In order to make sure that the experimental results are not affected by the sampling procedure, another sampling procedure is also adopted. That is, an excess amount of concentrated HCl solution is poured into the reactor to terminate the reaction by reacting it with KOH in the solution. Then, the agitator is stopped, and the sample
0888-5885/90/ 2629-0522$02.50/0 G 1990 American Chemical Society
Ind. Eng. Chem. Res., Vol. 29, No. 4, 1990 523 is withdrawn from the organic phase for HPLC analysis. It is found that good reproducibility and consistent results are obtained for both procedures. The 2,4,6-tribromophenyl allyl ether obtained from the two-phase reaction is identified. Tetra-n-butylammonium 2,4,6-tribromophenoxide (Bu4NO(C6H2)Br3;ArOQ), which can be synthesized from the reaction of tetra-n-butylammonium bromide with 2,4,6-tribromophenol and NaOH in the aqueous phase, is also identified from the two-phase reaction. The HPLC model is a Tracor 955 & 970A variable-wavelength detecter with a H P 3390A integrator. The column used is Lichrosorb RP-18 (5 pm), Merck & Co., West Germany. The eluent is CH30H/CH3CN/Hz0 = 2.5/2.5/1.1, with a flow rate of 1.0 mL/min at 254 nm (UV detector).
-
Results and Discussion In the organic reactions, two widely accepted mechanisms (SN1and SN2)for nucleophilic substitution reactions were proposed by Hughes et al. (1933). In the SN1 mechanism, the solvolysis of the substrate molecule by the solvent is an important step, and the reaction rate is generally independent of the concentration of the nucleophile. In the SN2mechanism, the substrate and the nucleophile react directly via a transition state to produce products. The rate law of a SN2reaction generally obeys second-order kinetics, and the reaction rate depends on the concentration of both substrate and nucleophile. Some preliminary studies show that the substitution reaction between allyl bromide and potassium tribromophenoxide follows the SN2mechanism. The steps of this two-phase reaction are as follows: Br3(CsH2)0K
A
+ ByNBr A D
Br3(C6H2)0CH2CHCH2+ Bu4NBr
C
Br$6H2)OBu4N B
+ KBr (aqueous) (ocganic)
Br3(C6H2)OBu4N+ CH2CHCH2Br
Step A of the above mechanism proceeds to convert the anion to an active intermediate product, Br3(C6Hz)OBu4N, which is insoluble in water. In general, the reaction rate in step A is faster than that in step C. Steps B and D are the mass transfer of the intermediate product and catalyst between aqueous and organic phases. Step C is the intrinsic reaction in the organic phase and is examined as the rate-determining step from the preliminary studies. The rate expression of step C is given as -d[RBr],/dt
= -k[ArOQ],[RBr],
(1)
where RBr and ArOQ denote the allyl bromide and tetra-n-butylammonium 2,4,6-tribromophenoxide,respectively. If [ArOQ], is kept constant after a short induction period for an aqueous reactant in excess, eq 1 can be expressed as -d[RBr],/dt = -k,,,[RBr], (2) where
kapp = k[ArOQI,
(3)
The conversion of allyl bromide is defined as X , X = 1 - [RBr],/[RBr],O
(4)
Equation 2 can be solved with eq 4 as In (1- X ) = -kappt
(5)
The activation energy of the apparent rate constant (kapp) can be obtained by an Arrhenius plot using the linear
)
I CI
'
12
-
c
9-
-
0
0
X
6-
R g l t o t l o n Speed (rpm)
F i g u r e 1. Effect of agitation speed on the apparent reaction rate constant: 9.072 X 10" mol of tribromophenol, 5.789 X mol of allyl bromide, 6.213 x IO4 mol of Bu4NBr, 50 mL of chlorobenzene, 50 mL of H,O, 50 "C.
regression method. In order to search out the optimum reaction conditions, several kinds of solvents, the relative amounts of solvent and reactants, the reaction temperature, and the agitation rate are considered. The results are summarized below. (i) Optimum Agitation Rate. The effect of agitation was studied by using the following operating conditions: mol of tribromophenol, 5.789 X mol of 9.072 X allyl bromide, 6.213 X mol of Bu4N+Br-, 50 mL of H20, 50 mL of chlorobenzene, 50 "C. The results are given in Figure 1. As shown in Figure, 1, no improvement in the reaction rate is observed when the agitation rate exceeds 600 rpm. Therefore, the agitation rate was set a t 800 rpm for studying the reaction kinetics from which the resistance of mass transfer between two phases is kept a t a constant value. (ii) Effect of Alkali Hydroxide. In the present study, same moles (1.785 X mol) of sodium hydroxide and potassium hydroxide were separately tested for reactivity by using the following operating conditions: 9.072 X mol of tribromophenol, 5.789 X mol of allyl bromide, 6.213 X mol of Bu,N+Br-, 50 mL of H 2 0 , 50 mL of chlorobenzene, 50 "C. The obtained apparent rate constants for KOH and NaOH are 1.195 X and 9.95 X min-', respectively. These results indicate that a better choice of potassium hydroxide enhances the reaction rate. (iii) Effect of Temperature. T o study the effect of temperature on the conversion of allyl bromide, the following operating conditions were used: 9.072 X mol of tribromophenol, 1.567 mole ratio of tribromophenol to allyl bromide, 14.6 mole ratio of tribromophenol to Bu4N+Br-,1.785 X mol of KOH, 50 mL of H20, 50 mL of chlorobenzene. The results are given in Figures 2 and 3. In Figure 2, the results show that the conversion of allyl bromide increases when the temperature is increased. The corresponding blank experiments without using the catalyst were also carried out to test the effect of the catalyst on the conversion. These results are also given in Figure 2. The addition of Bu4N+Br-greatly enhances the reaction rate. During the experimental run, the intermediate product, Bu4NO(C6H2)Br3,was also detected. The concentration of Bu4NO(C6H2)Br3 in the organic phase versus time is given in Figure 3. Under the set reaction conditions, the concentration of Bu4NO(C6H2)Br3 is almost kept a t a constant value after 5 min of reaction. The reason for one to obtain a constant value of [Bu4NO(C6H2)Br3] from experiment is due to the use of a large excess amount of 2,4,6-tribromophenol relative to allyl bromide (56.7%
Ind. Eng. Chem. Res., Vol. 29, No. 4, 1990
524
0.0
-0.8
-1.2 h
-3.0' 0
m
im
120
Time
21)
300
I 3m
-3.0' 0
m
rm
1M
2 0
Tlme (min)
(min)
Figure 2. Effect of temperature on the conversion: 9.072 X mol of tribromophenol, 1.567 mole ratio of tribromophenol to allyl bromide, 1.785 X mol of KOH, 50 mL, of chlorobenzene, 50 mL of H20, 14.6 mole ratio of tribromophenol to Bu,NBr. Temperature ("C), with PTC, without PTC: 30. 0. -; 40, A , 0 ; 50, 0 ,A; 60, *,
..
0.m 0.018
0.016-
h
-
3i
lL
w
w
2 0.012 CI 0 L
0.-
0.W
0.
0
m
im
im
a00
m
300
0.oOOa 0
m
im
im
I
200
Tlme ( m i n ) Figure 3. Concentration profile of [ArOQ], versus time at different temperatures for using an excess amount of tribromophenol relative mol of tribromophenol, 1.567 mole to allyl bromide: 9.072 X ratio of tribromophenol to allyl bromide, 1.785 X mol of KOH. 50 mL of chlorobenzene, 50 mL of H 2 0 , 14.6 mole ratio of tribromophenol to Bu,NBr, (0) 30 "C, ( A ) 40 "C, (0) 50 "C. (*) 60 "C.
Time ( m i n ) Figure 5. Concentration profile of [ArOQ], versus time at different mol of mole ratios of tribromophenol to allyl bromide: 9.072 X mol of Bu,NBr, 1.785 X mol of tribromophenol, 6.213 X KOH, 14.6 mole ratio of tribromophenol to Bu,NBr, 50 mL of chlorobenzene, 50 mL of H 2 0 , 50 "C, mole ratio of tribromophenol to allyl bromide of ( A ) 1.567, (0)1.045 (*) 0.783, (+) 0.522.
excess amount in stoichiometric quantity). Therefore, the pseudo-first-order kinetics can be applied to the system. The activation energy obtained is 13.8 kcal/mol, which is insensitive to the amount of Bu4N+Br-added. (iv) Effect of Allyl Bromide Reactant. To study the effect of reactant concentration of allyl bromide on the conversion, the following operating conditions were chosen: 9.072 X mol of tribromophenol, 6.213 X mol of Bu4N+Br-,14.6 mole ratio of tribromophenol to Bu4N+Br-, 50 mL of HzO, 50 mL of chlorobenzene, 1.785 X lo-* mol of KOH, 50 "C. The results are shown in Figures 4 and 5 . For the relatively small amount of allyl bromide (or large excess of tribromophenol) shown in Figure 4, the reaction follows a pseudo-first-order reaction in which a straight line is obtained by plotting In (1 - X ) versus time. However, the reaction did not follow a pseudo-first-order reaction for a relatively large amount of allyl bromide being added to the reactor. The corresponding concentrations of the intermediate product, Bu4NO(C6H2)Br3, changing with time during the reaction are given in Figure 5 . The intermediate product, Bu,NO(C6H2)Br3,was consumed more quickly a t a relatively large concentration of allyl bromide. From the results shown in Figures 2-5, it is obvious that a pseudo-steady-state approximation can be applied for the case of molar ratio of ArOH/RBr greater
than 1. For this, the concentration of ArOQ was kept at a constant value by using a large excess amount of ArOH. The results given in Figures 4 and 5 indicate that [ArOQ] was not kept at a constant value for a ArOH/RBr molar ratio of less than 0.783, from which the pseudo-steady-state approximation cannot be applied. A constant concentration of ArOQ leads to a straight line of In (1 - X )versus time. This result is feasible for one to apply the pseudofirst-order reaction kinetics. (v) Effect of Water. In general, a higher concentration of the intermediate product, Bu4NO(C6H,)Br3,or reactants in the aqueous phase will enhance the reaction rate. This is due to a large concentration gradient across the interface to make the mass transfer of intemediate product from the aqueous phase to the organic phase. The effect of water on the conversion was studied by choosing the following mol of tribromophenol, operating conditions: 9.072 X 5.789 x mol of allyl bromide, 6.213 X mol of mol of KOH, 50 mL of chloroBu,N+Br-, 1.785 x benzene, 50 "C. The results, shown in Table I (runs 2 and 10-13), were obtained as one would expect. (vi) Effect of Potassium Hydroxide. The effect of the concentration of potassium hydroxide on the conversion was studied by using the following operating condimol of tribromophenol, 5.789 X tions: 9.072 X
Ind. Eng. Chem. Res., Vol. 29, No. 4, 1990 525 Table I. Effects of Potassium Hydroxide, 2,4,6-Tribromophenol, and Water on the Apparent Pseudo-First-Order Rate Constantsd mole ratio vol ratio KOH/ bromophenol/ water/chloro- 103K,,,, no. bromophenola allyl bromideb benzene' min-' 1.567 1.0 11.30 1 1.379 1.567 1.0 11.95 2 1.970 1.567 1.0 12.20 3 3.940 1.567 1.0 7.65 4 5.911 1.0 5.40 5 7.881 1.567 1.044 1.0 10.20 6 1.970 1.305 1.0 11.00 7 1.970 1.828 1.0 12.25 8 1.970 2.089 1.o 12.25 9 1.970 1.567 0.6 12.40 10 1.970 1.5 11.55 11 1.970 1.567 1.567 2.0 11.25 12 1.970 2.5 10.80 13 1.970 1.567 mol. *Allyl bromide: 5.789 X "2,4,6-Tribromophenol: 9.072 X mol. Chlorobenzene: 50 mL. dTetra-n-butylammonium bromide: 6.213 X lo-' mol.
mol of allyl bromide, 6.213 X mol of Bu4N+Br-,50 mL of H20,50 mL of chlorobenzene, 50 "C. The results, shown in Table I (runs 1-5), indicate that an optimum conversion of allyl bromide appears by using a 1.97-3.94 molar ratio of KOH to tribromophenol. A further increase of KOH will decrease the reaction rate. This phenomenon may be explained by the competitive reaction of the nucleophile and the anion in the aqueous phase. More anions existing in the aqueous phase will retard the formation of the intermediate product more significantly. If the quantity of KOH used is just at the stoichiometric level or less to the 2,4,6-tribromophenol, the reaction rate will decrease due to the decrease in formation of 2,4,6-tribromophenoxide ion initially. (vii) Effect of the Quantity of Tribromophenol Reactant. The following operation conditions were chosen for studying the effect of the quantity of tribromophenol reactant on the conversion: 5.789 X mol of allyl bromide, 6.213 x lo-, mol of Bu4N+Br-,50 mL of H 2 0 , 1.785 X mol of KOH, 50 mL of chlorobenzene, 50 "C. The results, shown in Table I (runs 2 and 6-9), indicate that an increase of tribromophenol reactant leads to an increase in the conversion up to 9.072 X mol of tribromophenol. Further increasing the quantity of tribromophenol does not change the conversion significantly. (viii) Effect of Solvents. In the phase transfer catalytic reaction, the solvent will dramatically influence the conversion. To study the solvent effects on the conversion, the reaction was carried out under the following reaction conditions: 9.072 X mol of tribromophenol, 1.567 mole ratio of tribromophenol to allyl bromide, 6.213 X lo-, mol of Bu4N+Br-,1.785 X mol of KOH, 50 mL of H,O, 50 mL of organic solvent, 30 "C. Chlorobenzene, dichloromethane, and toluene are used as the solvents. The obtained apparent rate constants are 6.875 X lo-,, 2.725 X min-' for toluene, chlorobenzene, and and 3.638 X dichloromethane, respectively. It is obvious that a higher conversion is obtained in dichloromethane because of the high polarity. The order of relative activities of solvents is dichloromethane > chlorobenzene > toluene. As expected, the reaction shows better reactivity in protic or polar solvent. (ix) Effect of Catalyst, Bu4N+Br-. The following operating conditions are specified for studying the effect of the catalyst, Bu,N+Br-, on the conversion of allyl mol of tribromophenol, 0.783 mole bromide: 9.072 X ratio of tribromophenol to allyl bromide, 1.785 X lo-, mol
t
-'*I3
-2.0
0
a,
1M
io0
200
T ime ( m i n )
F i g u r e 6. Effect of the amount of BulNBr on the conversion for using an excess amount of allyl bromide relative to tribromophenol: 9.072 X mol of tribromophenol, 0.788 mole ratio of tribromophenol to allyl bromide, 1.785 X mol of KOH, 50 mL of chlorobenzene, 50 mL of HzO 50 "C, mole ratio of tribromo phenol to Bu,NBr of (0) 29.2 (A)14.6 (0)9.73, (*) 7.3, (+) 5.84.
0.E
0.01
0.d
0
,
El
\
io0
, 180
m
Tlme (min)
Figure 7. Concentration profile of [ArOQ], versus time a t different amounts of Bu,NBr for using excess amounts of allyl bromide relative to tribromophenol: 9.072 X mol of tribromophenol, 0.788 mole ratio of tribromophenol to allyl bromide, 1.785 X mol of KOH, 50 mL of chlorobenzene, 50 mL of H20, 50 "C, mole ratio of 29.2, (A)14.6, (0) 9.73, (*) 7.3, (+) tribromophenol to Bu,NBr of (0) 5.84.
of KOH, 50 mL of H 2 0 , 50 mL of chlorobenzene, 50 "C. As shown in Figure 6, the reaction rate increases with increasing the mass of the catalyst. The corresponding concentrations of the intermediate product, Bu4N(OC6H2)Br3,in the organic phase changing with time are given in Figure 7. For a relatively small amount of catalyst used in the reaction, the intermediate product always stays at a constant concentration. However, Bu,NO(C6H2)Br3 is consumed more quickly when a relatively large amount of catalyst is used. This is due to a fast reaction in a high concentration of catalyst. For use of a large excess amount of Br3(C6H2)OKin the aqueous phase, the concentrations of the intermediate product in the organic phase for different quantities of Bu4N+Br-used are time-invariant after a short induction period. The obtained values of [Bu,NO(C6H2)Br3]are 4.80 x 1V3,1.04 x 1.53 x 2.02 X and 2.61 x M, corresponding to 29.2, 14.6, 9.73, 7.3, and 5.84 molar ratios of tribromophenol to Bu4N+Br-. The results show that the concentrations of ArOQ are approximately proportional to the amounts of added Bu,N+Br- catalyst. This indicates that the effect of catalyst on the reaction is first-order for the conversion of allyl bromide, as shown in Figure 8.
526
Ind. E n g . Chem. Res., Vol. 29, No. 4, 1990 approach 100%. The reaction obeys second-order kinetics. The use of potassium h y d r o x i d e , dichloromethane, and tetra-n-butylammonium bromide will make the conversion f a s t in the phase transfer catalytic reaction. The effects of the other operating conditions, such as reactant concentration, agitation rate, and temperature, on the conversion are also investigated in detail. The measured concentrations of the intermediate product, Bu,NO(C,H,)Br,, d u r i n g the reaction will make it possible for one to make a dynamic simulation in a further study.
o.041 I
0.m -
n 0.E n
-
Y
0.01
0.
-
0.00
Acknowledgment 0.06
0.10
0.16
0.20
Mole R o t l o (Bu4NBr/Trlbromophenol)
F i g u r e 8. Pseudo-first-order reaction rate constant versus mole ratio of Bu,NBr to tribromophenol for using an excess amount of tribromophenol relative to allyl bromide: 1.567 mole ratio of tribromophenol to allyl bromide, 50 mL of chlorobenzene, 50 mL of mol of triHzO, 1.785 X mol of KOH, 50 "C, 9.072 X bromophenol. Table 11. Dependence of t h e Apparent Pseudo-First-Order Rate Constants o n T e m p e r a t u r e a n d Catalysts4 i03K,,,, min-' PTC at 30 "C at 40 "C at 50 "C a t 60 "C Bu,NBr 2.725 21.4 5.725 11.95 Bu,NBrb* 4.55 9.40 18.85 34.95 12.39 24.61 44.98 Bu,NBrb** 6.055 6.60 12.90 22.3 Bu,NOHc 2.60 20.5 5.90 10.30 Bu,NHSO,~ 2.60 BzEt3NCl' 0.226 0.903 1.96 3.71 22.7 BzBu,NBrf 2.35 5.38 12.95 PEG-IOOV 0.226 0.839 1.75 2.97 Operating conditions: 1.567 mole ratio of tribromophenol to allyl bromide, 14.6 mole ratio of KOH to tribromophenol. bTetran-butylammonium bromide: (*) mole ratio of KOH to tribromophenol = 9.73, ( * * ) mole ratio of KOH to tribromophenol = 7.3. CTetra-n-butylammonium hydroxide. dTetra-n-butylammonium hydrogen sulfate. e Benzyltriethylammonium chloride. f Benzyltributylammonium bromide. gPoly(ethy1ene glycol 1000).
In this study, several kinds of phase transfer c a t a l y s t s , such as C7H7(C2HJ3N+C1-, PEG-1000, B u 4 N + B r - , C7H7(C,H&N+Br-, Bu4N+OH-,and Bu4N+HS04-were examined to test their reactivities. The experimental results are given in Table 11. Tetra-n-butylammonium bromide or tetra-n-butylammonium hydroxide will be an excellent phase transfer catalyst in the allylation of tribromophenol. Conclusion The synthesis of 2,4,6-tribromophenyl allyl ether, which is the o n l y reaction product, is easily carried out b y phase transfer catalysis. The reaction rate is enhanced by a d d i n g a small quantity of phase transfer catalyst to the reaction s y s t e m . Under appropriate conditions, the conversion can
We acknowledge the financial support from the National Science Council, Taiwan, Republic of China (Grant NSC 77-0402-E007-16). R e g i s t r y No. 2,4,6-Tribromophenyl allyl ether, 3278-89-5; 2,4,6-tribromophenol, 118-79-6; allyl bromide, 106-95-6; sodium hydroxide, 1310-73-2; potassium hydroxide, 1310-58-3; chlorobenzene, 108-90-7; dichlorobenzene, 75-09-2; toluene, 108-88-3; water, 7732-18-5; tetra-n-butylammonium bromide, 1643-19-2; tetra-n-butylammonium hydroxide, 2052-49-5; tetra-n-butyla m m o n i u m hydrogen sulfate, 32503-27-8; benzyltriethylammonium chloride, 56-37-1; benzyltributylammonium bromide, 25316-59-0; poly(ethy1ene glycol lOOO), 25322-68-3.
Literature Cited Dehmlow, E. V.; Dehmlow, S. S. Phase Transfer Catalysis; Verlag Chimie: Weinheim, 1983. Freedman, H. H. Industrial Application of Phase Transfer Catalysis (PTC): Past, Present and Future. Pure Appl. Chem. 1986, 58, 857--868. Hughes, E. D., Ingold, C. K. Patel, C. S. Mechanism of the Thermal Decomposition of Quaternary Ammonium Compounds. J . Chem. SOC. 1933, 526-530. Jarrouse, J. The Influence of Quaternary Ammonium Chloride on the Reaction of Labile Hydrogen Compounds and Chlorine-Substituted Chlorine Derivatives. C. R. Hebd. Seances Acad. Sci., Ser. C 1951, 232, 142441434, Jenkner, H.; Buettgens, W., (Chemische Fabrik Kalk G.m.b.H.), Halophenyl Dihalopropyl Ethers. Ger. 2150241 (C1. C O ~ C )April , 12, 1973. Podkoscielny, W.; Tarasiuk, B.; Palka, Z.; Zaluski, S.; Kiszczak, W.; Gawecki, J.; Lebedowicz, B. 2,4,6-Tribromophenyl Allyl Ether. Pol. 106632 (CI. C07 C43/28), Jan 31, 1980. Ransford, G. H. (Ethyl Corp.) Octabromobiphenyl Oxide. Eur. Pat. Appl. Ep. 107978, 1984. Shenbor, M. I.; Burmistrov, S. I.; Lepskaya, N. M. Chloro-Substituted Diphenoxyethane. Izv. Vyssh. C'chebn. Zaued. Khim. Khim. Tekhnol. 1959,2, 215-218. Starks, C. M. Phase Transfer Catalysis: An Overview. Am. Chem. Soc., Symp. Ser. 1985, 326, 1-7. Starks, C. M.; Liotta, C. Phase Transfer Catalysis, Principles and Techniques; Academic Press: New York, 1978. Toyo Soda Mfg. Co., Ltd. Decabromodiphenyl Ether. Japan Patent 58-222043, 1983. Weber, W. P.; Gokel, G. W. Phase Transfer Catalysis in Organic Synthesis; Springer Verlag: New York, 1977. Received for review May 1, 1989 Revised manuscript received December 4, 1989 Accepted January 4, 1990
