I
PAUL R. STEYERMARK, THOMAS R. STEADMAN, and RICHARD P. GERMANN
W. R. Grace and Co., Research Division, Washington Research Center, Clarksville, Md.
Detergents from Diglucosylurea A new class of nonionic detergents can be built with either phosphates or urea
THE [ 1,3-bis-(~-glucopyranosy1)-urea (diglucosylurea) ] in the
acid (7). The reaction required about 2 hours at 80" to 95" C. and gave diglucosylurea in varying yields not higher than about 30% of crude material. The reacting mixtures were extremely viscous and difficult to stir effectively. Recycling the unchanged starting materials was impractical because part of the glucose formed dark-colored decomposition products.
INTERMEDIATE,
synthesis of diglucosylurea esters has been reported twice (3, 4 ) , but in both cases the compound resulted as a side-product of other reactions. Later, however, diglucosylurea was made directly by condensing two equivalents of D-glucose with one of urea in aqueous isopropyl alcohol in the presence of dilute sulfuric
DIGLUCOSY L U R E A STEARATE
. LEGEND
0 . 2 5 % D E T E R G E N T IN WATER OF 2 GRAIN HARDNESS
SUCROSE STEARATE
I
0 . 3 5 % D E T E R G E N T I N WATER O F I 5 GRAIN HARDNESS
C D
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NRSF
ANI 0 NIC DETERGENT
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I
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NONIONIC DETERGENT
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A
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B
BUILDER ONLY F O R M U L A T I O N II CONTROLCWATER)
2 GRAIN E?I 15 G R A I N
I
HARDNESS HARDNESS
5
0 l
l
l
l
IO l
l
l
l
l
15 l
l
l
l
l
25
20 l
l
l
l
l
l
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I
I N C R E A S E IN R E F L E C T A N C E Figure 1 .
212
1
0 . 3 5 % D E T E R G E N T IN W A T E R OF 2 G R A I N HARDNESS
SUCROSE PALMITATE
NACCONOL
1
0 . 2 5 % D E T E R G E N T I N WATER OF ISGRAIN HARDNESS
-
Dl GLU C 0 S Y L U R E A PALMITATE
STEROX
Another direct synthesis of diglycosylureas has been reported (2) where the corresponding aldoses are heated overnight with urea a t 70" C. in 5% sulfuric acid. A yield of 50% of diglucosylurea was mentioned (70). It has been suggested that both monoand diglucosylurea have the o-glucopyranosyl ring structure (2) because they consumed two and four equivalents of
Cleaning ability of diglucosylurea esters in phosphate formulations compared well with commercial detergents
INDUSTRIAL AND ENGINEERING CHEMISTRY
periodate, respectively. However, on the basis of the infrared spectrum of monoglucosylurea the compound has been recently assigned the open chain (aldehydo) configuration ( 9 ) . T o determine the structures of both mono- and diglucosylurea. oxidations of these compounds with sodium periodate Lvere repeated. If the compounds had the open chain structure, one equivalent of formaldehyde would be expected from each glucose residue. However, only trace amounts of formaldehyde were isolated as the dimedone complex. Even a three-day oxidation liberated only a very small amount of formaldehyde. This result adds to the weight of evidence for the D-glucopyranose structure of the glucosylureas. Isolation of the oxidation product \\'as not attempted.
LEGEND
DIGLUCOSYLUR E A STEAR A T E SUCROSE ST E A R A T E
0.25% D E T E R G E N T I N WATER O F 2 GRAIN HARDNESS 0 . 2 5 % DETERGENT I N WATER O F IS G R A I N H A R D N E S S
D I G L U C OSYLURE A PAL M I T A TE
O . J S % D E T E R O E N T I N WATER OF 2 G R A I N H A R D N E S S
SUCROSE PALMlTATE STEROX
ETZDm
0.35% D E T E R G E N T I N W A T E R OF I S G R A I N H A R D N L S S
CD
N A C C O N O L NRSF BUILDER ONLY FORMULATION I
2 GRAIN HARDNESS 15 G R A I N H A R D N E S S
c 0 N T R O L CWATER2
0
5
15
IO
I N C R E A S E IN R E F L E C T A N C E
Reactions in Nonaqueous Solvents
Formation of diglucosylurea from Dglucose and urea is a reversible reaction in Lvhich water is formed. Therefore, it probably would be best carried out in nonaqueous solvents. Contrary to expectations, all the attempts to improve rhe yield of diglucosy-lurea by using nonaqueous solvents and dispersion media Liere unsuccessful. Either the unchanged starting materials were recovered or glucose polymers were obtained instead. Glacial acetic acid was also tried. but no reaction products were isolated from these experiments. Some time later Wolfrom suggested a "superacidic" system which consists of equal \\.eights of glacial acetic acid and anhydrous zinc chloride ( 7 7). This mixture had been used for acetonation of inositols (7). Large amounts of the mixture were used relative to the amount of the inositols. Several experiments were performed using as solvent a weight of glacial acetic acid about equal to the weight of the starting. D-glucose. T h e zinc chloride employed was only 2 to 5% of this amount. -4lthough D-ghCOSe alone is insoluble in glacial acetic acid, a mixture of two equivalents of D-glucose and one of urea dissolves in acetic acid at 85" to 95" C. in the presence of zinc chloride Ivithin about 1.5 hours. Diglucosylurea precipitates later as it is formed. I t can be isolated either by filtration or by centrifugation, and it can be recrystallized by dissolving it in hot water and diluting thc solution with methanol. Reactions rim for 6 to 8 hours gave the highest yields.
Other Catalysts
Other Lewis acids, such as aluminum chloride and boron trifluoride, also catalyzed the reaction. Sulfur dioxide gave a practically colorless material.
Figure 2.
Diglucosylurea esters as well as sucrose esters can be built with urea
Contrary to the findings of the first experiments with acetic acid, the reaction also proceeds in the absence of catalysts. Ho\vever, the induction period during Lvhich a complete solubilization of the starting materials takes place is longer, and the yield of diglucosylurea is slightl) lolver. In the earlier experiments Dglucose and urea were heated with a large amount of glacial acetic acid both a t the boiling temperature of the mixture and a t 85" to 95" C . The mixtures Lvhen heated to boiling for 1 hour underwent extensive decomposition. O n the other hand, when the reaction was run a t 85" to 95' C., the starting materials remained in suspension for about 2 hours. and then dissolved to form a brown solution. Since no diglucosylurea \vas obtained from that solution, we concluded that other reactions had taken place. I n all probability, the reaction had not been continued long enough to observe precipitation of diglucosylurea. The consistent results in preparing diglucosylurea (Table I) suggested that the reaction was reversible even in glacial acetic acid, and that an equilibrium \vas reached a t a level of about 40y0 of diglucosylurea. Therefore. it would be expected that a n excess of the starting Dglucose would improve the yield. This indeed was the case. .A large excess of D-glucose was unnecessary since most of it remained in suspension in acetic acid. Two-step Reaction
Diglucosylurea could also be prepared in a two-step reaction. When acetone was added to the solution of D-glucose and urea in glacial acetic acid, a crystalline, very hygroscopic intermediate separated out. I t had a positive specific optical rotation [a]? f 44". When this material was redissolved in glacial acetic acid, and the mixture heated for
4.5 hours a t 90" to 95" C., diglucosylurea was obtained in a yield of 31.3%. Reactions at Reduced Pressure
hluch better yields of diglucosylurea lvere obtained by carrying out the reaction a t a reduced pressure in the presence of boric acid A well stirred mixture of D-glucose, urea, acetic acid, and about 1.3% of boric acid per weight of glucose was heated a t 85" to 95" C . until a clear solution was formed. The system pressure !vas then lowered to about 300 mm. to allow the solvent to distill a t the rate of about 1 ml. per minute. Fresh acetic acid was added from time to time to maintain a constant volume of solvent. Titration of the distillate with Karl Fischer reagent showed that a t least 80% of the calculated amount of water formed in the reaction had been removed
Table I. Consistent Yields of Diglucosylurea Were Obtained in Glacial Acetic Acid. Catalyst Type %* YieldC [.]ye
Starting with Stoichiometric Aniounts of Glucose and Urea ZnCL AlCla BF3.EtzO (Et0)3PO None
3.3 0.16 0.14 0.67
...
37.6 42.0 39.6 35.6 38.6
-33.3 -32.9 -35.4 -35.9 -35.3
Starting with Excess D-Glucose Excess, % SO2
50
-34.8 51 47.9 -37.0 so2 50 -36.1 so2 51 -36.5 a Reactions run for 6 to 8 hours at 8 5 O to 95' C. As % of D-glucose. After one AlC13
+ SO1
50 100 10
recrystallization.
VOL. 53, NO. 3
MARCH 1961
2 13
H
OH
swatches (Foster D. Snell Laboratories, Xew York) washed in a 1.aunder-OMeter with different detergent formulations. Diglucosylurea esters have been found to be good nonionic detergents in phosphate formulations (6). A surprising discovery has also been made that both diglucosylurea esters ( 8 )and sucrose esters could be “built” with urea. Detergent formulations shown in Table I1 bvere used:
H
0
H
OH CH30H
+
H
-
OH
H Table II. Diglucosylurea Esters Were Formulated Either with Phosphate Builders or with Urea
Transesterification of methyl esters of fatty acids gave diglucosylurea
Formulation, % I I1 within 3 to 4 hours. Pure diglucosylurea was thus obtained in yields of the order of 60 to 66%. Boric acid proved to be a n outstanding cataiyst for this reaction. Its high activity may be due to its ability to form positively charged complexes with polyhydroxy compounds. The complex of boric acid with D-glucose behaves then like a conventional strong acid but without its destructive properties.
Instead of diluting the solution with concentrated saline and extracting the ester with butanol, as recommended in Osipow and York’s patent ( 5 ) ,dimethyl sulfoxide was removed at a reduced pressure. The reaction product was extracted from the residue with methanol, and unaltered diglucosylurea was recrystallized from aqueous methanol and recycled. Diglucosylurea esters could be recrystallized from methanol without methanolysis. Their purity was determined by the saponification \Talue under mild conditions. Approximately 1 mmo!e of the ester \vas heated for 3 hours a t 60’ C. with 20 ml. of 0.25 ,Vpotassium hydroxide in 95% aqueous ethanol. If the ester was refluxed with aqueous alkali, part of the alkali was used in sidereactions and inaccurate results were obtained. Diglucosylurea monostearate was obtained in a yield of 71%,. The pure materia! was dextrorotatory in solutions in dimethyl sulfoxide, [a]’,” 19.9’. Diglucosylurea monopalmitate, obtained in a 38.7% yield, had a specific optical rotation in dimethyl sulfoxide [a12 20.2’. Neither compound had a sharp nielting point.
Other Diglycosylureas
Preparation of diglycosylureas b) condensation of hexoses Lvith urea in glacial acetic acid seems to be a general reaction. Thus 1,3-digalactosylurea and 1,3-dimannosylurea were made by heating the corresponding aldoses with urea in glacial acetic acid at normal pressure and without a catalyst. Digalactosylurea was obtained in a yield of 19.7% and dimannosylurea in a yield of 74.2%.
Monoesters of diglucosylurea were prepared according to the technique of Osipow and York ( 5 ) by heating for several hours a solution of one equivalent of diglucosllurea Lvith 0.33 equivalcnt of methyl ester of a fatty acid in dimethyl sulfoxide a t 90’ to 95’ C. at 15 mm. The reaction was catalyzed by anhydrous potassium carbonate. ?\lethano1 formed in the reaction was continuously removed (above).
+
Detergency Evaluation
The detergency evaluation of diglucosylurea esters consists in comparing the reflectancv of standard soiled cloth
C M.P., O C. > 360 190to 195 >300
In water.
2 14
At 24’ C.
[ a ] ~ ~ Calcd. - 37b
+
9.6c -49.6b
40.61
25 40
100
100
25
10
10 15
75 ... -
Results with Formulation I are presented in Figure 1, and those with Formulation I1 are shown in Figure 2. Acknowledgment
The authors are greatly indebted to Melville L. Wolfrom of The Ohio State University for suggesting the use of acetic acid-zinc chloride mixtures to catalyze the condensation of glucose with urea. literature Cited
(1) Angyal, S. J., MacDonald, C. G . J . Chem. SOC. 1952, p. 686. (2) Benn, M. H., Jones, A. S., Chem. 3 Ind. (London) 1959, p. 997. (3) Johnson. T. B., Bergmann, W., J . A m . Chem. SOC. 54, 3360 (1932). (4) Helferich, B., Kosche, W., Ber. 59, 69 119251. \----/.
Physical Constants and Analyses of Diglycosylureas Analysis Hexose Glucose Galactose Mannose
. .. ... ... ...
+
Esterification of Diglucosylurea
Starting
Active ingredient Sodium tripolyphosphate Tetrasodium pyrophosphate Sodium metasilicate pentahydrate Sodium sulfate Urea Total
H
Found 40.31 39.75 41.56
At 23’ C.
INDUSTRIAL AND ENGINEERING CHEMISTRY
N
Calcd.
Found
Calcd.
Found
6.30
5.96 6.93 6.81
7.29
7.18 6.70 7.24
(5) Osipow, L. L., York, LV. C (to LV. R. Grace & Co.), C . S.Patent No. 2,903,445 (September 8, 1959). f6\ Ibid.. 2.919.248 (December 29, 1959). (7) Ibid.; 2;967;859 (January 10, 1961). (8) Osipow, L. L., York, L$’. C. (to W. R. Grace 8: C o . ) , U. S. Patent .4pplication 769,571 (October 27 1958). (9) Segal. L., O’Connor, R. T.. Eggerton, F. V., J . Am. Chem. SOC. 82, 2807 (1960). (10) Stacey,M., T e University of Birmingham (England), private communication (1959). (11) Wolfrom, Melville L., The Ohio State University, Columbus, Ohio, private communication (1959). RECEIVED for review September 15, 1960 ACCEPTED November 10. 1960 Presented at meeting-in-miniature of Washington and Maryland Sections, ACS, May 6, 1960.
