I
HOWARD F. DREW and JOHN R. SCHAEFFER The Procter & Gamble Co., Miami Valley Laboratories, Cincinnati 31, Ohio
Ethylene Oxide Addition to Long-chain Alcohols Use of alkaline catalysts and exclusion of moisture are essential for good results with this reaction
MANY
contained moisture 50.05%. Catalysts were reagent-grade sodium, sodium hydroxide, and boron trifluoride etherate. Either of the latter two was added directly to the alcohol; metallic sodium was dissolved in excess methanol, the long-chain alcohol was added, and the mixture was heated until all of the original methanol was distilled over. Procedure. Alcohol and catalyst (1% by weight of sodium or sodium hydroxide and 2% by weight of boron trifluoride etherate) were combined, and ethylene oxide was added up to the desired gain in weight. Air was exeluded and the usual safety precautions (bubble counters, safety traps) were taken. For the basic catalysts, a temperature of 150' to 160' C. was needed. Boron trifluoride gave a much faster rate, even as low as 70' to 80' C. I n this work, however, a temperature of 125' C. was used. Separation of Reaction Products. The products are waxy solids and could not be satisfactorily crystallized or distilled. Simple solvent extraction procedures also failed, but a 50-tube allglass countercurrent distribution apparatus was successful. Two different sol-
examples of the addition reaction of alcohols and epoxides are known; the reaction has been very useful for introducing progressive changes in properties of the alcohols. Yet little attention has been paid to the course or products of the reaction. Published studies are limited chiefly to reactions between lower aliphatic alcohols and unsymmetrical alkylene oxides. Industrially, an alkaline catalyst seems to be preferred, although the reaction may also be acid-catalyzed, or uncatalyzed ( 2 ) . However, sometimes an acid catalyst may be preferred, as for example to carry out the reaction a t a lower temperature and a faster rate. The reaction of long-chain alcohols with ethylene oxide using the two types of catalysts has not been described in detail. In this work the influence of several catalysts on the yield and products of the reaction has been studied.
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Experimental Starting Materials. The alcohol, after distillation, was a mixture of Cle and CIS saturated normal alcohols (molecular weight 257, moisture 10.05%). Commercial ethylene oxide 'Oor E
O
2
h
3
4
5
6
7
8
9
1
0
1
1
1
2
1
3
1
4
1
5
Wave length in Microns 1001
vent systems were used: methanol 50, and heptane 50 volumes, and hexane 35, chloroform 15, ethanol 40, and water 10 volumes. The organic solvents were dried and distilled before use; they left no measurable residue upon evaporation. Fractions were evaporated at room temperature under nitrogen and residues from even-numbered tubes were weighed. Analysis. The major fraction from each reaction was presumed to be polyglycol ethers (the apparatus could not separate the isologous ethers from one another). The secondary fraction was presumed to be polyethylene glycol, arising from small amounts of water in the reaction mixture. The infrared absorption of the monoether fraction was compared with 2-dodecoxyethanol and triethylene glycol monododecyl ether, both of which were synthesized independently and purified by vacuum distillation. The spectra of the polyethylene glycols were compared with Polyethylene Glycol 300 (Union Carbide Chemicals Co.). Figure 1 shows how closely the curves compared. A and B are typical for material recovered from peak tubes a t left end and center, respectively, of Figure 2. The distribution ratios of the reference samples also were determined, and from these the expected locations of the peaks were calculated. These corresponded to the observed peaks for the unknown samples. 2-Dodecoxyethanol. This compound was prepared according to Cooper and Partridge (3). Product was distilled through a six-foot spiral rod column. Earlier, this compound was reported by Palfray (7) as a solid melting a t 51 O C. The authors' data support Cooper's claim that Palfray's compound was not 2-dodecoxyethanol. Triethylene Glycol Monododecyl Ether. This previously unreported compoundtwas prepared in the same way.
Discussion
REFERENCE : C12He@(C2H,O), 2
3
4
5
6
7
E
9
1 0 1 1
H
1 2 1 3 1 4 1 5
Wave l e n g t h in Microns
Figure 1. Infrared absorption shows close comparison of principal reaction products with Polyethylene Glycol 300 and ( 6 ) C I ~ H ~ ~ O ( C ~ H * O ) ~ H
Figure 2 is typical countercurrent distribution kurves for the reaction of alcohol with 5 moles of ethylene oxide, catalyzed by boron trifluoride etherate and by sodium hydroxide, respectively, The former (Figure 2, A ) yielded 68% glycol monoethers and 19% glycols. Average molecular weights (determined by analysis for hydroxyl groups) were VOL. 50, NO. 9
SEPTEMBER 1958
1253
Literature Background
F i g u r e 2. T y p i c a l countercurrent distribution curves for the addition of five moles of ethylene oxide to a long-chain alcohol shows greater yield of des i r e d p r o d u c t with sodium hydroxide catalyst
TUBE NUMBER
loor
A.
Catalyst Boron trifluoride
Solvent System Methanol to heptane, 1 to 1
E.
Sodium hydroxide
Hexane, 35; chloroform, 15; ethanol, 40; water, 10
VOI.
7 0
430 and 700, respectively. Two other fractions were isolated. The one shown at the right-hand end of the curve represented 8% of the total; its identity is unknown. I t contains no hydroxyl group, and has an average of two oxyethylene units to each long-chain group. Attempts to identify it either as an acetal or as a diether were unsuccessful. The remaining 5% of the mixture was volatile and was isolated by distilling the reaction mixture a t 100’ C., above which no further distillation occurred. Redistillation through a 5-foot Podbielniak column gave two fractions. Boiling point, specific gravity, and index of refraction suggested that these are pdioxane and 2-methyldioxolane, the former constituting about 70% of the total. The dry-ice traps contained traces having the characteristic acrid odor of acetaldehyde. The base-catalyzed reaction (Figure 2, B ) differs from the acid-catalyzed reaction in several respects. The yield of glycol monoethers is greatly increased,
and only small amounts of polyethylene glycol are obtained. None of the nonvolatile by-product is present, and quantitative recovery of the original sample suggests no volatile fraction. The main peak was shifted to the right, suggesting the possibility of a different distribution of isologs. Additional curves, not reproduced, were obtained for reactions involving u p to 20 moles of ethylene oxide, and also for a sodium-catalyzed reaction (Table I). With increasing ethylene oxide, the yield of the desired product diminishes and that of by-products increases, particularly with boron trifluoride. Here side reactions eventually account for more than half of the total product. Can by-product formation be accounted for by the water in the reaction mixture? There are traces in the alcohol, ethylene oxide, and sodium hydroxide, and when the latter reacts with alcohol it forms more water. Water from all sources accounted exactly for the amount of polyethylene glycol
Physical Properties Anal. Found H, OH % % value % % value 73.0 13.15 246 72.79 12.98 247 67.87 12.03 177 67.39 12.01 173 C,
B.P.,
O C .
C12Hs60CHsCHzOH 119/0.9mm. C I ~ H ~ ~ O ( C H ~ C H ~ O 164/0.4 )~H mm.
Table 1. CzH40 Added,
Catalyst
5
BFs BFa BFa NaOH NaOH Na
1 254
C,
Composition of Alcohol-Ethylene Oxide Reaction Products
Moles 6.7 20 5 20 20
n3$
1.4412 1.4469
Anal. Calcd. H, OH
% By-products % % RO(CzHaO),H H O ( C Z H ~ O ) ~Nonvolatile H Volatile 68 19 8 5 60 23 11 6 41 32 14 13 96 4 0 0 0 0 88 12 0 0 95 5
INDUSTRIAL AND ENGINEERING CHEMISTRY
Subject Examples of uncatalyzed reactions Manufacture and use of monoethers of polyalkene glycols Catalyst influence on type and amount of isomers formed Dimerization of alkene oxide to dioxane or its alkyl derivatives promoted by boron trifluoride Kinetics and mechanism of basecatalyzed reactions Various products prepared by basecatalyzed reactions By-product formation in adding fatty acids and epoxides
actually observed. The use of metallic sodium, thus eliminating one source of water, should decrease the yield of polyethylene glycol. This was confirmed, as shown in Table I. I n the boron trifluoride reactions, on the other hand, water accounted for only 7% of the polyethylene glycol. Acid-catalyzed, water-producing side reactions are evidently responsible for the large amount actually found. To conclude, side reactions occur to a substantial degree when boron trifluoride catalyzes as little as 5 moles of ethylene oxide to an alcohol. Hence this reaction should find little general utility as a commercial process. The use of an alkaline catalyst and the exclusion of water from the reaction mixture does, however, accomplish the desired result. Acknowledgment
The assistance of E. S. Lutton and C. B. Stewart for the countercurrent distribution work is acknowledged, also that of E. R. Wilson for the preparation of 2-dodecoxyethanol and triethylene glycol monododecyl ether. Literature Cited (1) Bartlett, P. D., Ross, S. D., J . Am. 70, 926 (1948). Chem. SOC. (2) Chitwood, H. C., Freure, B. T., Zbid., 68,680 (1946). (3) Cooper, F. C., Partridge, hl. Mi., J . Chem. SOG. 1950, p. 459. (4) Fife, H. R., Roberts, F. H. (to Union Carbide Chemicals Co.), U. S. Patent 2,448,664 (Sept. 7, 1948). (5) Kadesch, R. G., J . Am. Chem. SOG. 68, 41 (1946). (6) Malkemus, J. D., J . Am. Oil Chemists’ SOC.33, 571 (1956). (7) Palfray, L., Sabetay, S., Halasz, A,, Comfit. rend. 208, 289 (1939). (8) Reeve, W., Sadle, A., J. Am. Chem. SOC.72, 1251 (1950). (9) Satkowski, W. B., Hsu, C . G., IND. END.CHEM.49, 1875 (1957). (IO) Stevens, C . E., J. Am. Oil Chemists’ SOC.34, 181 (1957). (11) Wrigley, A. N.. Smith F. D., Stirton, A. J., Ibid., 34,39 (1957). RECEIVED for review December 20, 1957
ACCEPTED April 7 , 1958
Division of Petroleum Chemistry, 129th Meeting, ACS, Dallas, Tex., April 1956.
