I
R. A. SANFORD, S. M. KOVACH, and
B. S. FRIEDMAN
Sinclair Research Laboratories, Inc., Harvey, Ill.
Alkylation of Benzene and Toluene Low temperature operation gives fair yields of intact alkylate from tri- and tetraisobutylene
INTACT ALKYLATION of benzene and homologs with diisobutylene and its hydrogen chloride addition product has been reported ( 5 ) . Octylation of toluene, for example, was accomplished in good yield with various acid and Friedel-Crafts catalysts, provided the proper operating conditions were chosen. A similar study has been carried out with the higher homologs of diisobutylene (DIB), namely triisobutylene (TIB), tetraisobutylene (TetraIB), and their hydrogen chloride adducts. Ipatieff and Pines ( 2 ) treated benzene and tert-butylbenzene with triisobutylene in the presence of sulfuric acid a t 0' C. and reported only depolyalkylation products-i.e., tert-butylated benzenes. Bruson and Stein (7) alkylated naphthalene with triisobutylene and tetraisobutylene in the presence of sulfuric acid a t 30' C. and claimed the formation of dodecyl- and hexadecylnaphthalenes. However, no proof of structure was offered. Simons and Archer (6) were unable to prepare dodecylphenol by alkylating phenol with triisobutylene in the presence of 70% hydrogen fluoride a t 0' C., but Topchiev and others (7) were more successful using boron fluoride monohydrate as catalyst at 50' C. Proell and Adams (4)employed alkanesulfonic acids as catalysts for the alkylation of toluene with tetraisobutylene. This reaction yielded tert-butyltoluene and triisobutylene. More recently Lee and others (3) reported excellent yields of tert-butyltoluene obtained via the depolyalkylation of toluene with triisobutylene and a boron fluoride monohydrate catalyst. By operating a t the proper conditions of temperature with certain catalysts, fair yields of intact alkylate can be obtained from toluene and triisobutylene and, in the presence of aluminum chloride, a better yield from its hydrogen chloride adduct. These temperatures range from -40' to -60' C. for aluminum chloride, to -20' for sulfuric acid, 0' for ferric chloride, and 25" C. for aluminum chloride-nitromethane.
T H E
'
However, except for a 160/, yield obtained with aluminum chloride at -35' C., only minor amounts of intact alkylate are obtained from tetraisobutylene (none from its hydrogen chloride adduct), the main products being the tert-octyl derivatives. Benzene gives lower yields of intact alkylate and greater amounts of depolyalkylation products. The alkylation procedures and methods of product work-up and identification were the same as previously described (5). Infrared analysis of the dodecyl and hexadecyl derivatives indicated presence of mixtures of tertiary alkylates often containing considerable amounts of secondary alkylates. I t was not possible to establish the location of the aryl group along the branched C12 or CISchain. The physical properties and analytical data of some of the derivatives prepared in this study are given in Table I. All yields are based on weight percentage of olefin converted to a given product. The triisobutylene was Eastman practical grade. Tetraisobutylene was prepared by dimerization of diisobutylene with 96?& sulfuric acid. A 34-gram portion of acid was added to 2040 grams of diisobutylene and stirred without cooling.
Table I.
These New Arenes Were Prepared p-tertp-tertDodecyl- Dodecyl- Hexadecyltoluene toluene benzene
Mol. wt. Calcd. 246.4 Found" 237
B.P., ' C./ mm.
ng Sp. Gr., d90/4 Analysis,
7%
C calcd. Found H calcd. Found a
298/760 164/15 1.4921 1:4921
0.8693 87.7 87.7 12.3 12.4
Cryoscopic,
0.8765 87.6 87.3 12.4 12.5
Because aluminum chloride-catalyzed alkylations of benzene and toluene with diisobutylene often yield considerable dodecyl and hexadecyl derivatives (5),it seemed logical to expect favorable yields of these by direct alkylation of toluene with triisobutylene and tetraisobutylene. However, only moderate amounts of intact alkylate are obtained even a t low temperatures (Table 11). Considerable depolyalkylation occurred.
Table 11. Even at Low Temperatures Depolyalkylation Is the Main Reaction with the Aluminum Chloride Catalyst (Toluene/olefin/AlCla mole ratio, 5/1/0.08) Olefin
260.4 260
277/760
The temperature quick, rose to about 70 O C . and then slowly decreased. After 1 hour of stirring the spent catalyst was drained. This treatment was repeated twice more, after which the washed and dried product was distilled, yielding 4% unreacted diisobutylene, 1570triisobutylene, 7Oy0 tetraisobutylene (boiling point, 235-240 O C. ; ng, 1.4480-1.4498), and 11% higher boiling polymers. A heart cut of the tetraisobutylenes (46% yield; boiling point, 239 '-240' C., ng, 1.4480-2) was used for the alkylation studies. tert-Dodecyl and tert-hexadecyl chlorides were prepared from triisobutylene and tetraisobutylene, respectively, by adding hydrogen chloride gas to the olefin under 100 p.s.i.g. pressure at -20' + 10' C. T o minimize decomposition, the chlorides were stored at -80' C . until used.
326/760 200/30 1:4893 0.8730 87.5 87.8 12.5 12.3
DIB
Temp., O C. -34 Time" 30/60 Toluene derivatives Butyl 7 Octyl 44b Dodecyl 25' Hexadecyl 24.
TIB
- 40 100/10
(1
TetraIB
- 35 60/60
19
5
27 c
6Bd
34f
100 1 6h
a Min. t o add/min. additional stirring. p-tert. G p-/m- ratio, 82/18. p-/m- ratio, 92/8. E p-tert.; used for standards (Table I). f p / m ratio, 60/40. 0 Contains C4tol-Cs. h Cle-to1 isomers plus Crr-tol-Cs. b
VOL. 52, NO. 8
AUGUST 1960
679
Table HI. Triisobutylene Hydrochloride Differs from Tetraisobutylene Hydrochloride in Yielding More Intact Alkylate than Does the Olefin (Arene/alkylating agent/AICla mole ratio, 5/1/0 1) Experiment No.
1
Arene Alkylating agent Promoter Temp., C. Time
TIB
HCI
- 60 170/10
Arene derivatives Butyl Octyl Dodecyl Polyalkyl C d Hexadecyl Polymer
4
5 23 6Ic
5 68 1o c
9 68 12c
d d d
d
d
16
d
d
d
d
d
ptert.
Mixture of isomers.
Triisobutylene yielded both butyl and octyl derivatives as well as a moderate amount of dodecyltoluene (p-/m-, GO/ 40). Tetraisobutylene gave a large amount of octyl derivatives (p-/m- = 92/6) resembling in this respect results reported by Proell and Adams (4) for phenol. I n an attempt to improve yields and selectivity, the hydrogen chloride- addition products of triisobutylene and tetraisobutylene were evaluated (Table 111) as alkylating agents. The hydrochloride of triisobutylene gives better yields of intact alkylate than does the olefin even when hydrogen chloride is bubbled continuously through the reaction mixture during alkylation with the olefin (experiments 2 os. 1).
Table IV.
7
3 97 d
2
