Martell, A. E., Calvin, M., “Chemistry of the Metal Chelate Compounds,” I’rentice-Hall, Englewood Cliffs, N. J., 1952. Smithson, G. R., Jr., Shea, J. F., Tewksbury, T. L., J. Metals 1966, 1037. Stary, J., “Solvent Extraction of Metal Chelates,” Macmillan, New York, 1964. Swanson, R. R., Dunning, H. N., House, J. E., Eng. Mining J . 162, No. 10, 110 (1961). Treybal, R. E., “Liquid Extraction,” 2nd ed., McGrawHill, New York, 1963. Vashist, P. N., Beckmann, R. B., Ind. Eng. Chem. 60, 43 (1968).
Weaver, B., Progr. Sci. Technol. Rare Earths 3, 129 (1968). Yerger, E. A., Barrow, G. M., J. A m . Chem. SOC.77, 6206 (1955). Zakarias, M. J., Cahalan, M. J., Trans. Inst. Mining Met. 75, C 245 (1966).
RECEIVED for review February 6, 1969 ACCEPTED May 12, 1969 Research supported by the Office of Saline Water, U. S. Department of the Interior, under Contract 14-01-0001-1134. 98th Annual Meeting, A.I.M.E., Washington, D. C., February 16-20, 1969.
EXPLORATORY PROCESS STUDY Base-Catalyzed Reaction of Organic Chlorides with Sodium Acetate I - D E R
H U A N G ’
A N D
L E O N A R D
D A U E R M A N ’
Department of Chemical Engineering, New York University, New York, N . Y . 10453 The heterophase acetylation reactions of organic chlorides with sodium acetate in the presence of various catalysts were investigated. There is a maximum catalyst concentration beyond which the reaction rate becomes independent of the catalyst concentration, the rate of reaction increases with the dielectric constant of the solvent, the rate of reaction is increased when bromide is added as cocatalyst, and when the chloride is conjugated the isomer ratio in the products is affected by the degree of branching on the carbon atom adjacent to the amine group. Several kinetic models have been analyzed as they relate to the results in this study and the observations of other investigators.
THEcatalytic acetylation of organic chlorides in heterophase reactions with sodium acetate is a class of reactions of considerable industrial importance. T o date, the kinetics is still controversial (Hennis et al., 1968; Merker and Scott, 1961; Ruggeberg et al., 1946; Yamashita and Shimamira, 1957). Work in this area has been reviewed in recent publications (Hennis et al., 1967, 1968). This study reports data which are of importance in process development and are pertinent to the kinetics. Experimental
Material. BENZYLCHLORIDE.Commercial grade benzyl chloride from Velsico was used throughout (except for runs A-70 to A-99, in which reagent grade benzyl chloride was used). Purity, 98.9%, moisture content, less than 0.1%. The reagent grade, from Matheson Coleman & Bell, has a moisture content of less than 0.06%. MYRCENE 85. [(CH&C =CH-(CH&-C(=CH~)C H =CHz]. Commercial grade myrcene was distilled a t 20 mm. of Hg, and Myrcene 85 was collected a t a pot temperature up to 90°C. AMYLCHLORIDE (1-chloropentane), reagent grade from Eastman Kodak, b.p. 105”-07” C., purity 99.9+%. SODIUM ACETATE(anhydrous), commercial grade from Celanese Co., moisture content 1.0%. For runs A-70 to
’ Present address, Givaudan Corp., Clifton, N. J.
07014 address, Department of Chemical Engineering and Chemistry, Newark College of Engineering, Newark, N. J. 07102
* Present
A-99 reagent grade anhydrous sodium acetate was used (Matheson, Coleman & Bell). The moisture content was less than 0.1% by the Karl Fischer method. CATALYSTS, all C.P. grades from Eastman Kodak. Solvents. Xylene, b.p. 137-39, from Hess Oil & Chemical. Toluene, b.p. 110-11”, from Hess Oil & Chemical. Chlorobenzene, b.p. 130-2”, from Eastman Organic Chemicals. Nitrobenzene, congealing point 5.8“C., from American Cyanamid. Ethylene glycol, R.I. 1.4309; H 2 0 solubility loo%, from Union Carbide. Procedure. CONVERSIONOF BENZYL CHLORIDETO BENZYLACETATE.I n a 500-ml., round-bottomed, threenecked, jacketed flask equipped with a condenser, stirrer, and thermometer, were charged 1 mole of sodium acetate, 1 mole of benzyl chloride, and 0.01 mole of various types of amines with or without solvent. With stirring, the mixture was heated to the desired temperature in about 10 minutes by circulating hot oil through the jacket. A Lauda Circulator, Model K-2, constant temperature bath (0.1”C. precision) was used to control the oil temperature. The liquid layer of the reaction product was analyzed by gas chromatography (F & M Model 720 dual-column, 6-foot x %-inch i.d. Apiezon columns, column temperature 150”C.) and in some cases was analyzed by chlorine value. The agreement was within 2%. VOL. 8 N O . 3 S E P T E M B E R 1969
227
CONVERSION OF MYRCENE HYDROCHLORIDES TO ESTERS. In a 1-liter three-necked glass flask, 510 grams of distilled Myrcene 85 (80% myrcene) were first converted to myrcene hydrochloride by a procedure described by Webb (1963a). After hydrochlorination, the product, myrcene hydrochlorides, contained 80% of linalyl-geranyl-neryl chlorides (3.0 moles, ratio of tertiary chloride to primary chlorides 70 to 30). The chlorides were then acetylated with 270 grams of sodium acetate (10% excess) a t the desired temperature in the presence of various catalysts with or without solvent. The conversion was determined by chlorine values. The yield was based on gas chromatographic analysis (Apiezon column, 175" C.) on a vacuum-distilled reaction mixture. CONVERSION OF AMYLCHLORIDE TO AMYLACETATE. In a 1-liter Parr-type medium pressure apparatus were placed 1 mole of 1-chloropentane, 1mole of sodium acetate, and 0.01 mole of triethylamine with or without 1 mole of solvent of various types. The mixture was stirred and heated to 155°C. for 4 hours. After reaction, the batch was cooled to room temperature, 200 ml. of cold water were added to dissolve the excess sodium acetate, and the organic and aqueous layers were separated. The reaction product, without further purification, was analyzed by gas chromatography (Apiezon columns, 135" C.). No by-product was found. The conversion was calculated on the basis of the amount of ester formed (using an internal standard). Results
Effect of Catalyst Amount on Rate of Acetylation. The reaction was performed by the general procedure indicated above by varying the amount of the triethylamine or triphenylphosphine. In these runs, both reagent grade benzyl chloride and sodium acetate were used. Results based on the analysis of the liquid phase of the reaction product are given in Tables I and I1 and plotted in Figures 1, 2 , and 3. These data show that the rate is independent of the amount of catalyst when more than 1% (no solvent) or 1.7% (in the presence of solvent) based on benzyl chloride is used. Solvent Effects on Reaction Rate. Results are given in Tables 111, IV, and V. A noticeable parallelism between the rate of formation of ester and the dielectric constant of the solvent was indicated. Effect of KI or KBr on Reaction Rate. Reactions were run according to the general procedure in the presence of small amounts of potassium iodide or potassium bromide (Table VI). Steric Effect of Catalysts on Acetylation of Myrcene HCI. Myrcene hydrochloride reacted with sodium acetate following the general procedure. After reaction, the esters were vacuum-distilled and analyzed by gas chromatography. The yield was calculated on the basis of 100% myrcene charged. The steric effect of the catalyst on the formation of quaternary ammonium intermediates is indicated by the resulting isomer ratios (Table VII). Relationship between Reaction Rate and Basicity of Catalyst. The benzyl chloride reacted with sodium acetate in the presence of various catalysts, as indicated in the general procedure. After 1 hour, the reaction mixture was washed with 1 x 200 ml. of water, and 2 x 100 ml. of water. The crude was analyzed both by gas chromatography and chlorine value (Table VIII). 228
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
Table 1. Acetylation of Benzyl Chloride with Triethylamine Catalyst
Benzyl chloride, 1 mole Sodium acetate, 1 mole
Reaction Temp., C.
Solutwn Reaction ConuerVol., Time, 4CHZC1, swn to Hr. M1. w t . % Ester %
Run No.
EhN, Mole 70
A-70
0.0
110
235
A-79
0.84
118-21
236
A-77
1.03
118-21
236
A-80
1.52
118-9
237
A-83
2.23
116-9
238
A-78
3.45
116-20
240
A-82
5.02
118-20
242
A-75
5.53
118-9
243
A-76
10.04
117-8
249
A-96
16.2
117-23
257
A-96R
16.2
118-21
257
In Xylene, 1.0 Mole 2.0 22.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.0 2.0 0.5 1.o 0.5 2.0 0.5 1.o 2.0 0.5 1.0 2.0
100 100 80.8 67.3 51.3 76.0 62.0 46.5 51.5 29.1 23.4 45.4 24.5 17.3 45.3 21.7 9.4 45.8 18.0 44.3 6.6 47.5 24.5 6.2 47.3 24.3 6.3
0 0 16.7 29.0 44.5 21.0 34.0 49.2 38.6 62.7 73.4 50.3 72.2 80.1 50.4 75.3 89.0 49.9 79.3 51.4 92.3 48.2 72.2 92.7 48.6 72.4 92.6
94.0 90.3 84.7 37.8 24.6 18.0 11.2 11.1 6.6 12.1 5.6 12.5 11.2
5.1 8.3 13.2 58.1 72.1 79.3 86.9 87.1 92.3 85.9 93.4 85.5 86.9
No Solvent A-88
0.10
119
115
A-72
0.31
120-8
115
A-71
0.56
120-30
116
A-73
1.0
110-20
116
A-74
1.0
105-20
116
A-85 A-81
6.1 10.0
115-20 117-20
123 129
0.6 1.0 1.5 0.6 1.2 0.6 1.3 0.6 1.4 0.6 1.5 0.6 0.6
Table II. Acetylation of Benzyl Chloride with Triphenylphosphine Catalyst
Benzyl chloride, Sodium acetate, Xylene, Solution volume,
$$P, Mole
Reaction Temp.,
Run No. A-93
0.222
117-20
A-91
0.512
119-20
A-92
1.0
119-20
A-95
2.44
119-22
A-94
4.92
119-20
CT /O
c.
1 mole 1 mole 1 mole 235 ml.
Reaction Time, Hr. 0.6 1.1 0.6 1.1 0.6 1.1 0.6 1.1 0.6 1.1
Conuer+CHzCl, sion to Ester, % Wt. % 91.6 90.8 85.6 76.0 87.3 79.2 85.3 74.4 84.2 73.5
7.1 7.9 12.4 21.0 10.9 18.1 12.7 22.5 13.7 23.3
.z
I I B
I
I, I
0 0.5Hrs.h xylene(116-20°C)
Q 1.0 Hrs. in xylene(1I6-2O0C)
OB Hrs.no solvent (115-20°C)
IT/, 0
, , , , , , , , , , , 2 4 6 8 IO 12 14 Molar Ratio of Catalyst to Benzyl Chloride ,
,
,
16
Figure 1. Acetylation of benzyl chloride with anhydrous sodium acetate in presence of triethylamine catalyst
-
0 +
Q
"1
Reaction Time,Hours Figure 3. Decomposition of benzyl chloride in concentrated solution
0 01.6Hrs.in xylene(117-20°C) A 1 - 1 Hrs. in xylene (117-20°C)
Table 111". Solvent Effect on Acetylation Rate of Benzyl Chloride
Benzyl chloride, Sodium acetate, Triethylamine, Solvent,
1 mole 1 mole 0.01 mole 1 mole
Reaction Run No. A-23 A-33 A-36 A-46 A-51
0
I
2 3 4 5 Molar Ratio ot Catalyst to Benzyl Chloride
A-34 A-40
Figure 2. Acetylation of benzyl chloride with anhytridrous sodium acetate i n presence of phenylphosphine catalyst
Order of Acetylation Reaction at High Dilution. The benzyl chloride reacted with sodium acetate according to the general proced.ure in the presence of 10 moles of xylene and 0.0508 mole of triethylamine catalyst. The reactions were observed to be first-order with respect to benzyl chloride (Figure 4 ) . Data are given in Table IX. Discussion
The rate of benzyl chloride conversion reaches a limit with increasing catalyst concentration. This effect, which
Solwni None Xylene Xylene Chlorobenzene Cyclohexanone Nitrobenzene Ethylene glycol
Const'b Temp., Time, 2 P C . 12PC. o C . hr. (7.0 a t 13" C.) 120 1 2.37 2.17 113-16 1 113-16 1 5.94
4.4
Conwrsion to Ester, % 92.1 11.0 13.4
115
1
24.7
18.2
...
121
1
79.9
36.1
21.9
118-20
1
92.6
41.2
30.0
120
1
83.3
1.1 1.1 1.0 1.0
26.9 56.1 90.4 92.9
Xitrobenzene-Toluene Mixture
A-42 A-43 A-44 A-45
Fraction Nitrobenzene 0.206 0.409 0.609 0.806
6.72d 11.99 18.45 25.81
109-14 113-15 117-20 115-20
"Solution volumes in ml.: A-23:115, A-33, 36:235, A-46:216, A-51:218, A-34:217, A-40:171, A-42 to 45:106, 105, 104, 103. International Critical Tables (1928). Dielectric constant of solution is approximately % dielectric constant of solvent plus dielectric constant of benzyl chloride, which is 7.0 ut 13" C. By interpolation. Miller and Maass, 1960.
VOL. 8 N O . 3 S E P T E M B E R 1 9 6 9
229
Table IV". Solvent Effect on Acetylation Rate of Myrcene Hydrochloride
Table VII". Influence of Steric Effects of Catalysts on Isomer Distribution
Myrcene hydrochloride, Sodium (acetate), Catalyst (acetate), Reaction temperature, Reaction time,
Myrcene hydrochloride, 1.5 moles Sodium acetate, 1.65 moles Solvent, 1.0 mole Run No.
Dielectric Const. at 20" C.
Solvent
Reaction ConverTemp., Time, sion to C. hr. Ester, R
'
Catalyst: n-Butylamine', 0.11 mole B-1 B-4 B-6 B-2 B-5 B-8
None Cyclohexanone Nitrobenzene None Cyclohexanone Nitrobenzene
B-11 B-13 B-14
None Cyclohexanone Nitrobenzene
2.7 18.2 36.1
70-1 66-70 68-70 70-3 66-70 68-72
1.2 1.2 1.2 3.2 3.2 3.2
11.4 24.5 59.3 19.2 37.8 89.8
2.2 2.2 2.2
6.4 17.9 56.1
Catalyst: Triethylamine, 0.01 mole 67-69 66-9 65-9
"Solution w1ume.s in ml.: B-1,2: 303; B-4,5,6,8: 406; B-11: 284; B-13,14: 387. 'Mixture of desired isomers: linalyl, gerunyl, and neryl acetates. I n 0.22 mole HOAc.
Run No.
Catalyst (in HOAc)
Weight Yield Esters, % '
% Tertiary Ester in Total Esters
B- 15 B-16 B-19 B-20 B-17 B-18
Trimethylamine Triethylamine Tri-n-butylamine Tri-n-amylamine n-Butylamine n-Propylamine
97.3 97.2 90.0 94.7 97.9 90.5
4.2 11.6 8.2 12.0 70.2 57.2
"Solution volumes in ml.: B-l5:198, B-16:202, B-19:209, B-20:213, B-l7:198, B-18:197. ' Mixture of three desired acetates: tertiary acetate (linulyl acetate) and two primary acetates (geranyl and neryl). Table VIII. Influence of Basicity of Catalyst on Reaction Rate
Benzyl chloride, 1 mole Sodium acetate, 1 mole Catalyst, 0.01 mole
Table V". Solvent Effect on Acetylation Rate of Amyl Chloride
Amyl chloride, Sodium acetate, Triethylamine, Solvent,
Reaction
1 mole 1 mole 0.01 mole 1 mole
Run
No.
ConuerReaction sion to Temp., Time, Ester, "C. hr. 70
No.
Solvent
Dielectric Const. at 20" C.
C-1 C-2 C-3 C-4
None Xylene Cyclohexanone Nitrobenzene
(6.6 at 11.C.) 2.37 18.2 36.1
Run
155 155 155 155
4.0 4.0 4.0 4.0
4.6 4.5 38.8 45.9
"Solution volumes in ml.: C-1:121; C-2:241; C-3:224; C-4:223. Table VI". Effect of KI or KBr on Acetylation Rate
Organic chloride, 1 mole Sodium acetate, 1 mole Triethylamine, 0.01 mole (except for myrcene HCI) Reaction Run No.
K I or KBr
Weight,
G.
Temp., O
c.
1 mole 1.1 mole 0.078 mole 85-90" C. 16 hours
Time, hr.
Conversionto Ester, 70
A-8 A-27 A-10" A-23 A-4" A-53 A-6 A-13 A-22 A-24 A-14 A-52 A-7 A-16 A-12 A-21 A-30
Catalyst Pyridine
PK 8.85
Triethylamine
3.35
Triphenylphosphine Diethylethanolamine Tri-n-butylamine Triamylamine Diethylamine Dimethylbenzylamine Choline base Triethanolamine tert-Butylamine 1-Naphthylamine Water (14 moles)'
3.11 3.02 5.07 6.2 3.6 10.0
Conuersion to
Temp., Time, Ester, hr. 70 O C .
113-20 115-20 118-22 120 117-20 118-20 120-24 120-23 121 120-22 112 118-22 119-22 117-20 120-23 100
1 1 1 1 1 1.2 1 1 1 1 1 1.2 1 1 1 1 3.0
93.4 92.3 88.1 92.1 90.0 89.3 81.9 67.9 59.6 43.3 31.5 26.0 15.2 16.4 0.4 (0.5 1.0
"Catalyst 0.10 mole. '1 mole of triethylbenzyl chloride with 1 mole
of sodium acetate.
Benzyl Chloride (in 1 Mole of Xylene) A-36 A-35 A-38 A-41 A-39
None KI KI KBr
KI'
... 10 5 10 10
110-14 115 112-17 116 120-25
1 1 1 1 1
13.4 70.0 46.7 60.8 87.8
Myrcene Hydrochloride (Use n-Butylamine', 0.08 Mole) B-3 None .. . 69-72 1.2 11.4 B-22 70-73 3.2 19.2 B-21 KBr 6.8 66-72 1.2 31.1 3.2 51.0 B-24 KI 6.8 70-73 1.2 40.1 3.2 88.7
c-1 C-6
None KI
Amyl Chloride 155 8.3 155
...
4.0 4.0
4.6 29.9
"Solution wlumes in ml.: A-runs (except A-39:175):235; B-runs: 203; C-runs:121. ' I n 0.5 mole xylene. e I n 0.16 mole HOAc.
230
l & E C PRODUCT RESEARCH A N D DEVELOPMENT
we refer to as the "leveling-off' effect, has been observed for both nitrogen- and phosphorus-containing catalysts (Tables I and 11). I t is observed a t approximately the 1.5% level (Figure l ) ,within the range that the catalyst is used in practice. Furthermore, it occurs abruptly. Yamashita and Shimamura (1957) concluded that the rate increased with the initial catalyst concentration. (Pyridine was the catalyst used in this phase of their study.) However, they studied the effect with only two different catalyst concentrations. The upper catalyst concentration, above 0.02 mole, is in the range of concentrations that we could predict that the rate has "leveled off." If a line is constructed through this point parallel to the concentration axis, and another line is constructed through the first point and the origin, the relative molar concentration of catalyst and benzyl chloride is 1.5 to 100, the value found in this study.
2.00
become rate-limiting. Although Yamashita and Shimamura stated that the first step is the slow step, they depicted the reaction schematically in the following way:
1.95
RC1+ RSN Z RN’RjC1
W
-0 .6 1.90
RN’R;
5
-F E
$
2 1.80 W
-
0,
0
I .75
d
IO
20
4
I
30
40
Reaction Time Hours Figure 4. First-orcler plot for acetylation of benzyl chloride at high dilution
~~
~
Table IX. Kinetic Order of Acetylation Reaction Elenzyl chloride, 1 mole Sodium acetate, 1 mole 10 moles Xylene, Triethylamine, 0.0508 mole Solution volume, 1321 ml.
Run A-98, Temp. 11 7” C. Run A-99, Temp. 102” C. Reaction @CH2C1“, Reaction @CH2C1“, time, mole Log time, mole Log hr. % (@CHzC1) hr. 5% (GCHZCl) 3.0 94.5 1.9754 3.0 94.5 1.9754 6.27 88.1 11.9495 6.8 91.2 1.9604 7.23 87.0 1.9395 12.8 84.6 1.9274 9.02 83.1 11.9196 15.2 80.9 1.9080 81.0 1.9085 19.3 77.9 1.8915 10.02 78.8 11.8965 24.6 73.0 1.8633 12.23 13.23 76.9 1.8859 30.4 67.8 1.8312 16.60 69.0 1.3388 35.2 63.8 1.8048 18.0 69.4 1.3413 37.15 61.9 1.7917 23.2 63.0 l.7993 39.1 59.0 1.7708 27.2 57.8 1..7619
Apparent rate constant, k’, hr.-’. 0.0204 0.013 Apparent activation ene:rgy. 8.8 kcal. a
+ RjN
This would imply that the salt is formed by rapid equilibrium, followed by a slow step in which the salt and the acetate combine to yield the ester. This mechanism cannot explain the leveling-off effect, either. The increasing amine concentration should increase the concentration of quaternary ammonium chloride by mass action. The solubility of sodium acetate might be expected to be unchanged, because the addition of the amine does not change the dielectric constant significantly. Hennis et al. (1968) have proposed a mechanism of the following type:
1.85
1.7c
+ R”C0;-ROCOR”
Free solvent basis (percentage calculated on basis o f benzyl chloride
and benzyl acetate only).
This leveling off effect is not readily deducible from the mechanisms proposed for this reaction. According to Yamashita and Shimamura, the slow step is the formation of the quaternary ammonium chloride salt from the alkyl halide and amine catalyst. This may be the slow step when the catalyst concentration is low, and we discuss experimental evidence that this is the case in dilute solutions, but as the catalyst concentration increases and the conversion of benzyl chloride levels off, another step must
+ R’CO;Na+ 2 R,N+O-OCR’ + Na+X R,N+-OOCR’ + R”X-+R’COOR” + RIN’X-
R,N-X-
I n this mechanism it is not possible to predict a levelingoff effect. One would expect the increased amine concentration to increase the quaternary ammonium salt concentration. On the other hand, the abrupt onset of the effect (Figures 1 and 2) suggests a phase transformation. We suggest that the reaction rate levels off because the quaternary ammonium halide solubility limit is reached. This type of salt is known to have limited solubility in organic solvents (Davies and Cox, 1937; Davies and Lewis, 1934), although the actual solubilities of these salts in the experimental conditions in this study are not known. Moreover, we would like to raise a question about Hennis et al.’s mechanism. In contrast to Ruggeberg et al.’s (1946) proposal that the quaternary ammonium acetate thermally decomposes to the ester, Hennis et al. suggest that the quaternary ammonium acetate reacts with the alkyl halide via a nucleophilic substitution reaction to form the ester and regenerate the quaternary ammonium halide catalyst. Their mechanism does not explain why there is a minimum temperature below which the acetylation reaction will not proceed. For example, in the acetylation of myrcene hydrochlorides, 60” C. is the lower limit for the nitrogen-based catalysts (Webb, 1962, 1963a,b). In the acetylation of benzyl chloride, 5WC. was shown as the lowest temperature for reaction with pyridine as catalyst (Yamashita and Shimamura, 1957). Fierce and Weichman (1967) report “threshold temperatures” for the acetylation of various halides. They give 70“C. for 1,3-dichloropropane, and about 100”C. for “normal” alkyl chlorides having up to 20 carbon atoms. The minimum temperature and its variation with the starting material can be explained by Ruggeberg et al.’s mechanism, which postulates that the quaternary ammonium acetate thermally decomposes to amine and ester. These decomposition reactions are known to exist and have been widely reported (Eliel and Anderson, 1952; Fuson et al., 1939; Lawson and Collie, 1888; Snyder and Brewster, 1949). The quaternary ammonium acetates decompose over temperature ranges and the minimum temperature for such decomposition to occur would be expected to vary with the particular compound. VOL. 8 NO. 3 S E P T E M B E R 1 9 6 9
231
The mechanism of the thermal decomposition of quaternary ammonium acetate to produce amine and acetate has been discussed by Hughes and Ingold (1933). Quaternary phosphonium acetate and tertiary sulfine acetate salts are reported (Lawson and Collie, 1888) to resemble the quaternary ammonium acetate salts in their behavior when heated, and would therefore be expected to be useful catalysts for this reaction. This has been found to be the case (Webb, 1966; Yamashita and Shimamura, 1957). We believe that a t low catalyst concentration the formation of the quaternary ammonium salt is the slow step. From Table IX, the acetylation of benzyl chloride to benzyl acetate in the presence of triethylamine as catalyst is seen to be a first-order reaction with respect to benzyl chloride. The apparent activation energy of this reaction is calculated to be 8.8 kcal. This is evidence that the formation of the quaternary ammonium salt is the ratecontrolling step because of the similarity between the values for the activation energy of the over-all reaction, found in this study, and the activation energies previously found for the formation of a quaternary ammonium salt. Muchin et al. (1926) have reported the apparent activation energies for the formation of triethyl benzyl ammonium chloride from benzyl chloride and triethylamine to be 9.2 and 10.8, respectively, in nitrobenzene and benzene solvents. Further confirmation of the formation of the quaternary ammonium salt follows from the data in Table VII, which summarizes the effects of tertiary and primary amine catalysts in the acetylation of myrcene hydrochlorides, containing 70% tertiary chloride and 30% primary chloride (hydrocarbon-free basis). The data reveal that the primary amine catalyst produces approximately the same proportion of tertiary acetate as in the starting material; however, the amount of tertiary acetate produced from tertiary amine catalyst is disproportionately low. This can be attributed to steric hindrance between the chloride and amine in the formation of quaternary ammonium salt. One of the most interesting findings of this study concerning the solvent effect contradicts the conclusions of previous investigators (Mills et al., 1962) that ". . .the reaction of simple alkyl halides with alkali metal salts of carboxylic acids in suitable solvents to produce ester is of little preparative value, owing to poor yields and conversion.. ." Our data reveal (Tables IV and V) that the reaction proceeds satisfactorily in a solvent of high dielectric constant-for example, the conversions of amyl
232
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
acetate from amyl chloride after 4 hours are 45.9 and 4.6%, respectively, for the systems with and without nitrobenzene solvent. Acknowledgment
Thanks are due L. Polinski, G. Kitchens, and M. Sonn for helpful discussions. Literature Cited
Davies, W. C., Cox, R. G., J . Chem. SOC. 1937, 614. Davies, W. C., Lewis, W. J., J . Chem. SOC.1934, 1600. Eliel, E., Anderson, R., J. A m . Chem. SOC.71, 291 (1949). Fierce, W. L., Weichman, R. L. (to Union Oil Co.), U. S. Patent 3,341,575 (Sept. 12, 1967). Fuson, R. C., Corse, J., Horning, E. C., J. A m . Chem. SOC.61, 1290 (1939). Hennis, H. E., Easterly, J. P., Collins, L. R., Thompson, R. L., IND.ENG. CHEM.PROD.RES. DEVELOP.6, 193 (1967). Hennis, H. E., Thompson, L. R., Long, J. P., IND.ENG. CHEM.PROD. RES. DEVELOP. 7, 96 (1968). Hughes, E. D., Ingold, C. K., J . Chem. SOC.1933, 526. International Critical Tables, Vol. III, p. 83, McGrawHill,New York, 1928. Lawson, A. T., Collie, N., J . Chem. SOC.53, 624 (1888). Merker, R. L., Scott, M. J., J . Org. Chem. 26, 5180 (1961). Miller, C. G., Maass, O., Can. J . Chem. 38, 1606 (1960). Mills, R. H.,Farrar, M. W., Weinkauff, 0. J., Chem. I d . (London) 1962, 2144. Muchin, G. E., Ginzburg, R. B., Moiseeva, K. M., Ukraine Chem. J . 2, 136 (1926). Ruggeberg, W. H. C., Ginsberg, A., Frantz, R. K., Id. Eng. Chem. 38, 207 (1946). Snyder, H. R., Brewster, J. H., J . A m . Chem. SOC.71, 291 (1949). Webb, R. (to Glidden Co.), U.S. Patent 3,031,442 (April 24, 1962). Webb, R. (to Glidden Co.), U.S. Patent 3,016,408 (Jan. 9, 1963a). Webb, R. (to Glidden Co.), U.S. Patent 3,067,839 (Feb. 5, 1963b). Webb, R. (to Union Camp Corp.), U.S. Patent 3,293,286 (Dec. 20, 1966). Yamashita, Y., Shimamura, T., Kogyo Kagaku Zasshi 60, 423 (1957). RECEIVED for review May 1, 1968 ACCEPTED May 9, 1969 Condensation of part of the research carried out by one of the authors (IH)at New York University in partial fulfillment of the requirements for the degree of doctor of philosophy.
