[CONTRIBUTION FROM
LABORATORY O F THE TECHNOLOGY]
THEl CATALYSIS
OF
ILLINOIS INSTITUTE
SULFURIC ACID-CATALYZED ALKYLATION OF BENZENE WITH HIGH MOLECULAR WEIGHT 1-ALKENES W. L. LENNEMAN, R. D. HITES,
AND
V. I. KOMAREWSKY
Received October 80, 1968
Recent developments in hydrocarbon synthesis by the Fischer-Tropsch and related processes make available large amounts of straight chain 1-alkenes of high molecular weight (1).Such 1-alkenes might be used to prepare long-chain alkylaromatic hydrocarbons by well-known acid-catalyzed alkylation procedures (2). In order to find out what products would be obtained by alkylation of simple aromatics by high molecular weight 1-alkenes, benzene was alkylated with pure 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene in the presence of sulfuric acid as a catalyst and at a carefully controlled low temperature to minimize rearrangements and other side reactions. EXPERIMENTAL PART
Materials. Eastman Kodak Co. thiophene-free benzene was used. The olefins, obtained in 95% purity from the Humphrey-Wilkinson Co., were further purified by distillation in a Podbielniak column. Only the central cuts were used. The physical properties of the purified olefins are presented in Table I. Procedure. Alkylation was carried out in a 500-ml.three-necked flask provided with a high speed stirrer (Nurnberg Instrument Co.) and held in a cold bath which was kept at an automatically-controlled temperature. A weighed amount of benzene was placed in the flask and cooled t o 4" or below; a weighed amount of sulfuric acid (96%) was then introduced. When the temperature of the acid and benzene was again 3-4", stirring waa started and the olefin was introduced from a dropping-funnel so slowly as t o avoid a temperature rise in the reaction mixture. The total olefin addition time was 45-100 minutes. The cold reaction mixture was then transferred t o a separatory-funnel and the acid was removed. The hydrocarbon layer was washed with cold sulfuric acid and then with a methanol-water solution (2:l) until the washings were neutral to litmus (4-5 washings). This method of washing removed most of the unreacted benzene since methanol, water, and benzene form a ternary mixture in which the alkylaromatics were insoluble. A final washing was done with a methanol-water-sodium carbonate solution (2:0.7:0.3). The washed products were then distilled under a pressure of 5 mm. to a temperature of 60"in order t o remove traces of water, methanol, and benzene. The remaining hydrocarbons were distilled from sodium at a pressure of 1 mm. (For the 1-hexadecene and 1-octadecene alkylates, i t was necessary to repeat the washing procedure after removal of water, methanol, end benzene by preliminary vacuum-distillation .) Examination of the products. Vacuum-distillation at 1mm. pressure separated the alkylates into a monoalkylate fraction and a higher-boiling residue which was not investigated further. The residues were probably dialkylated benzenes. The monoalkylates were tested for unsaturation with permanganate, and their boiling points a t atmospheric pressure were determined by a micro method. In addition, their infrared spectra were obtained with a Perkin-Elmer Model 12B,single beam, double pass infrared spectrometer which was adapted for scanning with a suitable wavelength drive and a Perkin-Elmer Model 81 AC Thermocouple amplifier. 463
464
LENNEMAN, HITES, AND KOMAREWSKY
TABLE I PHYSICAL PROPERTIES OF PURIFIED OLEFINS BOILING BANCE OLEFIN
Temp.,
1-Octene 1-Decene 1-Dodecene 1-Tetradecene 1-Hexadecene 1-Octadecene
"C.
I
121.5-123 170.8-171.6 97.1-97.5 125-125.5 152.O-153 177-178
Pressure, mm.
747 745 15 15 15 15
1.4098 1.4218 1.4302 1.4362 1.4414 1.4452
RESULTS
Data pertaining to the alkylation experiments are presented in Table 11. Absence of material boiling below the monoalkylates and absence of unsaturation in the monoalkylates by the permanganate test indicated that the olefins reacted completely. The yields of monoalkylates were 70-90 %, based on the olefin. Infrared spectra of the monoalkylates are presented in Figures 1-6. The spectrum of the alkylate from 1-octeneis identical with the spectrum of 2-phenyloctane published by the American Petroleum Institute's Research Project 44. The spectra of the other monoalkylates indicate they are all 2-phenyl alkanes. For one thing, the absence of an absorption band at 12.81 microns, shown by 3-phenylpentane (Figure 7), and attributable to a single methylene group between a terminal methyl and a carbon bonded to a benzene ring (3), rules against a 3-phenyl alkane structure for these monoalkylates. Furthermore, 4-,5-, 6-, or 7-phenyl alkanes would be expected to produce two absorption bands in the TABLE I1 SULFURIC ACID-CATALYZED ALKYLATION OF BENEENEWITH HIQH MOLECULAR WEIGHT ALKENES Alkene. . . . . . . . L-CaHia 42.1 Weight, g.. . . Benzene, g.. . . . 117.1 77.0 Acid, g.. . . . . . . Monoalkyla t e, g.. . . . . . . . . Yield, %. . . . B.p. at 746 mm., "C.. . B.p. a t 1mm., "C * . . . . . . . 69-71 3 . . . . . . . . . , 1.4849 2.0 Residue, g.. . . ,
1-CioHno 63.1 117.2 77.0
94-96 1.4828 3.1
1-CuHzt 63.1 117.2 77.0
1-ClcH28 84.6 202.2 200.0
l-C16H82 56.1 a02 * 2s 103.0
1-ClaHl4 88.6 219 .Oa 200.0
74.4 80.5
84.4 70.4
56.0 75.1
80.7 70.4
296-298
326-328
353-355
-
119-122 1.4814 9.1
137-142 1.4809 9.6
159-163 1.4799 11.5
175-180 1.4793 9.5
An additional 200-300 g. of benzene was added during the run as a solvent for the alkylate. 4
465
HzSO4-CATALYZED ALKYLATION OF BENZENE
Z 3 4
5
6
7
8
9
IO
I1
I2
1 3
14
15
M IC R O N 5
FIG. 1. INFRARED SPECTRUM OF MONOAL~YLATE FROM SULFURIC ACID-CATALYZED ALKYLBENZENE WITH 1-OCTENE(0.025-mm. cell).
ATION OF
Z 3 4
5
6
7
8
9
IO
I1
I.?
1 3
I4
I5
MICRONS
FIG. 2. INFRARBD SPECTRUM OF MONOALKYLATE FROM SULFURIC ACID-CATALYZED ALHYLBENEZNE WITH ~-DECENE (0.025-mm. cell).
ATION OF
466
LENNEMIIN, HITES, AND KOMAREWSKY
u
u 2
4
m
a
51 m 4
2 3 4 5
6
7
a
Q
IO
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17
I3
10
IS
MICRONS
FIG. 3. INFRARED SPEICTRUM OR MONOALICYLATEI FROM 8ULB.OaIC ACID-cATALYS5D ALKYLATION OF BBINZENB WITH ~-DODECENEI (0.0258 mm. cell).
8 3 4
5
6
7
8
Q
IO
II
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I3
14
15
MICRONS
FIG.4. INFRARED SPECTRUM OF MONOALKYLATE FROM SULFURIC ACID-CATALYZ~D ALKYLATION OF BENZENE WITH ~-TETRADECENE (0.025-mm. c e l l ) .
467
H2SOa-CATALYZED ALKYLATION OF BENZENE
8 3 4
5
6
8
7
IO
9
II
I2
14
I3
15
MICRONS
FIQ. 5. INFRARED SPECTRUM OF MONOALKYLATE FROM SULFURIC ACID-CATALYZED ALKYLBENZENE WITH ~-HEXADECENE (0.025-mm. c e l l ) .
ATION OF
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1
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-
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OB 0.0 I
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1.5 2 3 4
5
6
7
8
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15
MICRONS
FIQ,6. INFBARED SPECTRUM OF MONOALKYLATE FROM SULFURICACID-CATALYZED ALKYLBENZENE WITH 1-OCTADECENE (0.025-mm. c e l l ) .
ATION OF
468
LENXEMAN, HITES, AND KOMAREWSKY l
2 3 4
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MICRONS
FIG.
7.
INFRARED
SPECTRUM O F 3-PHENYLPENTANE (0.025-mm. Cell).
13.40 to 13.90 micron region caused by two methylene chains of different length. Such absorption is absent in the spectra of the monoalkylates. Acknowledgments. The infrared spectra were obtained by Mrs. Lorna Patterson. The sample of 3-phenylpentane was supplied by the Universal Oil Products Company. SUMMARY AND CONCLUSIONS
Benzene was alkylated with 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene in the presence of sulfuric acid acid at 34". Monoalkylates were obtained in 70-90 % yield. Their infrared spectra indicate they are 2-phenyl alkanes. Physical properties of the monoalkylates are presented. CHICAGO, ILLINOIS REFERENCES
(1) (a) STORCH,GOLUYBIC, AND ANDERSON, The Fischer-Tropsch and Related Syntheses, John Wiley and Sons, New York, 1952; (b) WEIL AND LANE,Synthetic Petroleum from the Synthine Process, Chemical Publishing Go., New York, 1948. (2) PRICE,Org. Reactions, 3, 1 (1946); FRANCIS, Chem. Revs., 42, 107 (1948). (3) MCMURRAY AND THORNTON, Anal. Chem., 24, 318 (1952).
