1040
INDUSTRIAL AND ENGINEERING CHEMISTRY
the avcrilgc for thc uppar bulb had hwn iletermined with respect to rz fixed mark on the viscometer. The six water runs at 24.1' C. gave an average (u/OH,,.) of 0.000001502 cm./scc.*, with un average deviation of 0.3% and no curvature error. Ether was run twenty-seven times between 17" and 70' C . The average (v/OtZ.,.) of the runs was 0.000001494 with an average deviation of 0.9%, suggesting slight end and curvature effects. However, the separate ether runs showed consistently increasing values of (v/8Hav.) at decreasing viscosities, up to0.000001512 at 70.7" C., 215.5secondsefflux time, and 0.231 centistoke. This variation is in the opposite direction from that expected. Furthermore, the available viscosity data may be appreciably in error (3). Thus, the more precise weterrun viscometer constant was adopted. With this value the capillary diameter was calculated to be 0.0576 cm. As a further check, using the same value of a as for the styrene viscometer, at the shortest efflux time with butadiene (197 seconds), the correction, &*/g), amounts to less than 0.3% of the total head; thus end effects are probably negligible. The butadiene was shipped February 5, 1944, in ,a 5-gallon cylinder also from the Institute, W. Va., plant and stored out of doors. The analysis was reported as follows: 98.1
Nil
es, p.p.rn. CIIICHO Water, entrained Inhibitor p p.m. p-tert-butylcatechol Nonvolathe'matter, % by wt.
2P
Nil Nil 100 0.03
The remainder of the impurities consisted principally of 1butene and cis- and trans-2-butene. Traces of CI, other C,, and Ca hydrocarbons also may have been present ( 2 ) . The runs on butadiene were made some two months after it was received, in the same way that the ether runs were carried out. After evacuation of the viscometer and connecting tubing, butadiene vapor was admitted from the cylinder which had previously been partially emptied by vaporization; it was then condensed in the viscometer, which was sealed off. In this way only negligible amounts of lighter compounds or polymers should be
Vol. 36, No. 11
present in the viscometer. Four grouph of five runs each nere made at, roughly, O", 12", 25", and 36" C. The average deviations of tho Calculated kinematic viscosities in each group averaged under 0.9%. The runs took less than a day, and no noticeable polymerization occurred. Because of the low viscosity of butadiene, the curvature correction was applied. It was considerable at the higher temperatures, varying from 4% at a Reynolds number of 215 E t 36" down to 0.4% a t 0". The viscometer should have had twice as many turns t o make the curvature correction negligible with butadiene. It was found that the points lay practically on a straight line when log p was plotted against log T. This curve was used for interpolation to give the values in Table I and was also extrapolated 20" C . in each direction. It is estimated that the values of viscosity listed up to 35' are correct within 2%, roughly, and those at the higher temperatures have an increasing possible error up to 5%. NOMENCLATURE
= absolute viseosity, poises = kinematic viscosity, stokes p = density, grams/cc. a = number of viscous flow velocity heads, (u*/g), dissiated in end effects e = ei&x time, sec. D = capillary diameter, cm. L = capillary length, cm. Ha.. = total head, time average, cm. = volume of liquid timed, cc. Q = acceleration of gravity, cm./sec.* g u = average liquid velocity in capillary, cm./sec. p
u
LITERATURE CITED
(1) Dean, M. R.,and Legatski, T. W., IND. ENQ.CHEM., ANAL.ED., 16,8 (1944). (2) Hillenbrand, E. F., Jr., private communication. (3) International Critical Tables, Vol. V, pp. 10-12 (1928). (4) Patnode, W., and Scheiber, W. J., J. Am. Chem. Soc., 61, 3449 (1939); Natl. Bur. Standards, Letter Circ. LC-710 (1942). ( 5 ) White, C. M., Proc. Royal SOC.(London), A123,660, 663 (1929). (6) Willihngttnz, E. A., McCluer, W. R., Fenske, M. R., and McGrew, R. V., IND.ENG.CHEM., ANAL.ED.,6,231 (1934).
Preparation of Triacetyllevoglucosan J
U
GEORGE H. COLEMAN, CHESTER M. McCLOSKEY, AND ROBERT KIRBY State University of Iowa, Iowa City, Ioroa
T
EVOGLUCOSAN (l,&anhydro-D-glucose), which is readily prepared from its triacetate (2B), has found extensive use as a synthetic agent in the field of carbohydrates. A recent patent (9) describes a pharmaceutical application in which compounds of the sulfanilamide type are combined with levoglucosan. The ready availability of levoglucosan should now make possible investigation of other industrial applications utilizing especially its unusual stability to heat and alkali. The preparation of levoglucosan by the pyrolysis of various carboyhydrates (8, 6, 14, 17) has been described. Although the yields are good on a small scale, they fall off rapidly as the amount is increased (4)so that the preparation of large quantities by this method has not been feasible. The use of glucosyltrimethyl ammonium halide (7) and an alkali involves the expensive tetraacetylglucosyl halide as an intermediate and is thus not practical.
In 1894 Tanret (16) observed that, when several natural glucosides are heated with an alkali, an anhydroglucose results now known as levoglucosan. Recently Montgomery, Richtmyer, and Hudson (11, 12) showed that this reaction is characteristic of phenyl and several substituted phenyl &D-glucosides. The same authors (IO)had previously modified the procedure of Helferich and Schmitz-Hillebrecht (3) for the preparation of phenyl tetraacetyl-p-D-glucoside by the exchange of phenyl for acetyl as catalyzed by p-toluenesulfonic acid. Levoglucosan is a trihydroxy inner acetal. I t possesses both a 1,3-dioxolane and a pyranose ring. Water and warm alcohol dissolve it readily. Acids hydrolyze it slowly to glucose, but alkalies have no effect. The unsubstituted compound or its derivatives are split readily to glucose derivatives by reagents such as a mixture of sulfuric acid and acetic anhydride (I), phosphorus pentsbro-
November, 1944
INDUSTRIAL AND ENGINEERING CHEMISTRY
mide, liquid hydrobromic acid (8),and titanium tetrachloride (20). It polymeriees to dimers, tetramers, hexamers, etc., under the influence of heat and zinc chloride, platinum black ( I S ) , or zinc dust (5). It forms crystalline trimethyl ether (4) and tribenzyl ether (21)as well as a crystalline triacetate (18)and a crystalline tribenzoate (18). The trimethyl ether has been reported to give phenol under the influence of sodium in liquid ammonia a t room temperature (15). Levoglucosan has been identified as a constituent of tobacco smoke (19). The present synthesis involves the preparation of phenyl tetraacetyl-&&glucoside from phenol and fl-D-glUCOSe pentaacetate. This glucoside is simultaneously deacetylated and converted to levoglucosan by heating with alkali. The isolation of crystalline levoglucosan was not found practical since impurities prevented complete crystallization. Isolation was therefore accomplished through the triacetate which crystallizes readily:
n
CeH60H
AcOLH
catalyst, heat
H+OAC
r 4 H
c:
AcO H HIOAC
dilute alkali
H~OH
I
HObH
--c
heat
YbOAc H
H
H
@+Glucose pentaacetate
Phenyl tetraacetylp-D-glucoside
Levoglucosan
This method of preparing phenyl tetraacetyl-8-D-glucoside and triacetyllevoglucosan can be used for relatively I'arge-scale preparation of these compounds with little further modification. The runs were varied from 0.3 to 3 moles of starting materials. There waa no change in yield with variation in the sire of runs. PHENYL TETRAACETYL-8-D-GLUCOSIDE
To a solution of 15 grams of p-toluenesulfonic acid monohydrate in 1000 grams of warm phenol were added 1170 grams of &Dglucose pentaacetate. The flmk was fitted with a capillary tube and arranged for distillation. The mixture was heated strongly on a steam bath under a reduced pressure of 20 mm. for 30 minutes after the liquid began to distill, then under 10-12 nun. for 15 minutes. At this point distillation was interrupted and a solution of 5 grams of sodium hydroxide in 300 ml. of warm phenol waa added. The distillation was continued at 10-12 mm. until distillation nearly ceased. The pressure ww then reduced to about 1 mm. and distillation continued as long as phenol came over. The thick residue was stirred with 2 liters of hot water and the mixture allowed to cool. The water was decanted, the residue dissolved in 1 liter of hot 95% alcohol, and the solution allowed to stand a t room temperature for 15-20 hours. During this time crystallization occurred. The crystals were filtered off, washed with 300 ml. of 70% alcohol, and air-dried. The yield was 825965 grams (65-76oJo) of phenyl tetraacetyl-@-D-glucosidehaving 8 melting point of 120-122' C. The product was sufficiently pure for the preparation of levoglucosan. TRIACETY LLEVOGLUCOSAN
To a solution of 858 grams of sodium hydroxide in 6.7 liters of water were added 1100 grams of phenyl tetraacetyl-@-D-glucoside. The mixture was heated in a n oil bath at gentle reflux for 20 hours. At the end of this period the solution waa cooled to
1041
The practical preparation of triacetyllevoglucosan from 8-D-glucose pentaacetate is described. The scale of laboratory operation was limited only by the size of equipment available. An interesting property of levoglucosan, which may add to its commercial value, is its unusually high stability to heat and alkali.
roosh temperature and neutralized by the addition of 908 grams of concentrated sulfuric acid previously diluted with an equal weight of ice. The solution was Concentrated to dryness under reduced pressure, the residue was thoroughly extracted with 5 liters of boiling alcohol, and the undissolved salts were washed with additional solvent. Considerable bumping was experienced during the concentration when the salts started to separate if the flask was heated only on a steam bath. This difficulty was overcome by the use of a? internal steam coil. Coils made of both block tin and of copper were used satisfactorily. The alcohol solution was concentrated to dryness under reduced pressure and the residue acetylated by the cautious addition of 3 liters of acetic anhydride. Warming was sometimes necessary to start the re action. The acetylation mixture was heated for one hour on the steam bath. Sufficient water (250 ml.) was then continuously added to hydrolyze the excess acetic anhydride, and the acetic acid was removed under reduced pressure. The solid residue was extracted with 4 liters of chloroform in order to' dissolve the triacetyllevoglucosan, and the resulting solution was washed twice with 1liter of water to remove suspended salts. The chloroform was removed by distillation on a steam bath, reduced pressure being used near the end. The sirupy residue was mixed with 300 ml. of 95% alcohol and allowed t o crystallize. The crystals were filtered off and the filtrate concentrated to a sirup. It was then diluted with 100 ml. of ether and placed in the ice box to crystallize. The combined crystalline products were triturated with 400 ml. of ice cold ether and filtered. The yield of product was 550-600 grams, melting a t 108-109° c. ('73-80%). ACKNOWLEDGMENT
The authors wish to express their appreciation to the Corn Products Refining Company for financial assistance. LITERATURE CITED
Freudenberg and Soff, Ber., 69,1249 (1936). Hann and Hudson, J . Am. Chem. SOC.,63, 1484 (1941). Helferich and Schmitz-Hillebrecht, Be?., 66,378 (1933). Irvine and Oldham, J. C h . SOC.,1921, 1744. Ibid.. 1925,2903. Karrer, Natunvissenschaften, 9, 399 (1921). Karrer and Smirnoff, Helv. Chdm. Acta, 4,817 (1921) Ibid., 5, 124 (1922).
Meyer, Brit. Patent 519,661 (April 2, 1940). Montgomery, Richtmyer, and Hudson, J. Am. Chem. Soc., 61, 692 (1942).
Ibid.,65, 6 (1943). Ibid., 65, 1848 (1943). Pictet, Hdv. Chim. A d a , 1, 226 (1918). Pictet and Sarasin, Cmpt. rend., 166, 38 (1918). Shorygin and Makarova-Zemlyanskaya, Cuinpt. rend. dcod. aci. U.R.S.S., 23,915 (1939). Tawet, Bull. 800. chim., [SI 11, 949 (1894). Venn, J . TeztileInet., 15,414 (1924). Vongeriohten and Muller, Ber., 39,244 (1906). Wenuaoh, Fa&. Mitt. (Iaterr. Tabakregie., June, 1938, 4-5; Chem. Zentr., 1939,II,1403. Zemplh and Csthras, Ber., 62,993 (1929). ZemplBn, Csb6sle,and Angyal, Ibid., 70, 1854 (1937). Zempl6n and Paosu,Ibid.. 62, 1613 (1929).
