ANALYTICAL CHEMISTRY
898
Levine, H., and Grimaldi, F. S., U. S. Atomic Energy Commission, R e p t . AECD-3186 (1950). Rll Lundell, G. E. F., and Knowles, H. B., J . Am. Chem. Soc., 42, 1439-48 (1920). Patterson, C . , U. S. Atomic Energy Commission, R e p t . AECD3180 (1951). Picciotto, E. E., Bull. SOC. belge d e obol., d e palbontol. et d'hydrol., 59.170-99 (1950). Reynolds, J.,'Phys'. Rev., 79, 789-94 (1950). Stern, T. W., private communication. Stieff, L. R., and Stern, T. W., Bull. Geol. SOC.Amer., 63, 1299 (1952) (abstract). Thomason, P. F., Perry, 11. A , , and Byerly, W. AI,, ANAL. CHEM., 21, 123941 (1949). Tilton, G. R., C. S. Atomic Energy Commission, Rept. AECD3182 (1951). Willard, H. H., and Cake, W. E., J . Am. Chem. SOC.,42, 220812 (1920).
F. S. Grimaldi, also of the U. S. Geological Survey, contributed valuable discussions which aided in the preparation of the carrier from the ore. The technical assistance of J. B. Doak on the maintenance of the Department of Terrestrial Magnetism mass spectrometer contributed materially to the progress of the work. LITERATURE CITED
(1) Banks, C . V., and Byrd, C. H., ASAL. CHEM.,25,416-19 (1953).
(2) Dalton, J. C., Golden, J., Martin, G. R., Mercer, E. R., and Thomson, S. J., Geochim. et Cosmochim. Acta, 3, 272-87 (1953). (3) Davis, G. L., and Aldrich, L. T., Bull. Geol. SOC.Amer., 64, 379-80 (1953). (4) Hageman, F., J . Am. Chem. Sac., 72, 768-71 (1950). ( 5 ) Hayden, R., Reynolds, J., and Inghram, hl. G., Phys. Rev., 75,1500-7 (1949). (6) Inghram, hI. G., Brown, H S. Patterson, C., and Hess, D., Ibid.. 80, 916 (1950).
RECEIVED for review October 1, 1953.
Accepted January 25, 1954.
Dete rmination of 5 4Hy droxymethy I)-2-f u raldehy de and Related Compounds J A M E S H.TURNER, P A U L A. REBERS, P A U L L. BARRICK', and ROBERT
H.COTTONZ
Holly Sugar Corp., Colorado Springs, Colo.
I
N WORKISG with levulose, sucrose, and other products in
this laboratory the authors have had occasion to determine 5-(hydroxymethyl)-2-furaldehyde [5-(hydrosymethyl) furfural]. Hydroxymethylfurfural has been most commonly determined by its ultraviolet absorption (6, 12, 15) in this laboratory because of the sensitivity, speed, simplicity, and comparative selectivity of the method. Interpretation of the results secured is often difficult and unsatisfactory because there are many other compounds having strong absorption bands in the ultraviolet. This study was made to observe the behavior of certain other related compounds with regard to their ultraviolet absorption. Measurements were carried out with the Beckman Model D E quartz spectrophotometer. This study gave an opportunity to make comparisons n i t h other methods of analysis. Melting point of a hydroxymethylfurfural sample made available to the authors was 30-31 "C. (uncorrected); the literature gives 31.5-32.0' C. (uncorrected) ( 1 2 ) . I t s spectrophotometric curve is shown in Figure 1, n.hile in Table I is shown the location of the maxima and minima in Angstrom units with the corresponding values of the molecular absorption coefficients ( E ) . The authors have not discovered as yet any previous mention of the minimum at 2125 A. The hydroxymethylfurfural used in the syntheses reported below was prepared in this laboratory by the method of Middendorp ( 7 ) . The compound 5,5'-(oxydimethylene)di-2-furaldehyde[bis(5-formyl-%furfuryl) ether] x i s obtained as a residue from the distillation of hydroxymethylfurfural a t a pressure of 100 to 200 microns, followed by two successive crystallizations from alcohol ( 7 ) . I t s melting point was 112-112.5' C. (uncorrected); the literature gives 114' C. (corrected) (6). The curve is shown in Figure l. Here, again, the authors have seen no previous mention of the minimum a t ea. 2150 -4. The compound 2,5-furandimethanol [2,5-bis(hydroxymethyl) furan] is made Jvith difficulty by the Cannizzaro reaction ( 7 ) . Newth and Wiggins (8) secured it in 35y0 yield by the partial catalytic reduction of hydroxymethylfurfural. The authors' sample was synthesized according to the directions below using the "crossed" Cannizzaro reaction. 1
Present address, University of Colorado, Boulder, Colo.
* Present address, T h e Huron Milling Co., Harbor Beach, Mich.
Eighty-seven grams of hydroxymethylfurfural were dissolved in 250 ml. of formalin. One hundred and twenty grams of sodium hydroxide were dissolved in 175 ml. of mater, and the solution was chilled to 10" C. by an ice bath. The formalin-hydroxymethylfurfural solution was added slowly to the sodium hydroxide solution. During the addition the reaction mixture was stirred continuously while the temperature was kept below 30" C. by cooling. Following the addition of the sodium hy, droxide solution it was held a t 40" C. for 30 minutes, then at 60 to 65" C. for 6 hours on a steam bath. Carbon dioxide was bubbled in until the p H was 9.0. Following a dilution to 8iO ml., the mixture was extracted with three portions of ethyl acetate. The extract was concentrated to one-fourth volume (250 ml.) a n d chilled in ice. The crystals !+-ere collected, washed v,ith 45 ml. of ethyl acetate, and dried a t 65" C. to give 68 grams of 2,5bis(hydroxymethy1)furan in 76.9% yield. Its melting point n as 74.5-75' C. (uncorrected); the literature gives 75.5-77" C. (8). Its spectrophotometric curve is shown in Figure 1. The compound tetrahpdro-2,5-furandimethanol[2,5-bis(hydroxymethyl)tetrahydrofuran] was prepared in a manner similar to that used by Haworth, Jones, and Wiggins ( 3 ) and Sewth and Wiggins (8). Forty grams of hydroxymethylfurfural were dissolved in 400 ml. of absolute methanol, to T? hich were added 5 grams of Raney nickel. Hydrogen was added until the initial
BIS5-FORMYL-2-FURFURYLlETHER +~UEOUS SOL 1, 4 57 r m
7 1 Y/ML W20
1900 2000
2200
2600 2800 3000 WAVE LENGTH IN ANGSTROMS
2400
3200
3400
Figure 1. Absorption Curves for Certain Furan Derivatives, 20' C.
3600
V O L U M E 26, NO. 5, M A Y 1 9 5 4
899
pressure was 1500 pounds per square inch, and the mixture was heated to 160" C. After 18 hours a t 160" C. the pressure read 2000 pounds per square inch, and the reaction was judged complete. Following the removal of the Raney nickel by filtration, the methanol was evaporated. A flash distillation of the residue a t 160" C., 30 mm. was carried out. The distillate consisted of 40 grams of a slightly colored liquid; na;.6 1.4652; literature, n12 1.4760 (S).
for the blank of the paper gave a relatively lower absorption peak a t 2240 A. as compared to the mixture before purification, which indicates that an impurity, probably 2,5-bis( hydroxymethy1)furan, has been at least partially removed. A qualitative separation using pure compounds and 1-butanol-ethyl alcoholwater as developing solvent and ammoniacal silver nitrate as a spray reagent showed that hydroxymethyl-furfural and 2,5bis(hydroxymethy1)tetrahydrofuran could be separated and detected. This procedure indicated the absence of hydroxymethylfurfural in the preparation of 2,5-bis(hydroxymethyl) tetrahydrofuran. The compound 5-(hydroxymethyl)-2-furoic acid (Figure 1) was prepared according to the method of Reichstein (11). The curve and data for furfural (Figure 1 and Table I ) are taken from the literature (6, 16). The curve and data for levulinic acid (Figure 2 and Table I ) are also taken from the literature (6, fa).
1
Figure 2.
+24
96 X SUCROSE SOLUTION
Absorption Curves for Levulinic Acid and Tetrahydro-2,5-furandimethanol
Its curve is shown in Figure 2 . Absorption data in Table I suggest the possible presence of 1.0% of 2,5-bis(hydroxyrnethyl)furan because of the minor peak a t 2240 A. An attempt was made to purify the tetrahydro compound using paper chromatographic development followed by elution of the various sections of paper. The section containing the 2,5-bis(hydroxyrnethyl) tetrahydrofuran was eluted. Its absorption spectrum corrected
Figure 3.
Absorption Curves for Sugar Solutions
Table I. Molecular Absorption Coefficients (e) Compounda 3- (Hydroxymethy1)-2-furaldehyde [5- (hydroxymethy1)furfurall
Literature Reference (12) (6)
This paper 5,5'-(Oxydimethylene) di-2-furaldehyde (bis(5-formyl-2-furfurylether) ] alcoholic solution aqueous solution !2,5-Furandimethanol [2,5-bis(hydroxymethyl)furan] Tetrahydro-2,5-furandimethanol [2,5-bis(hydroxymethyl)tetrahydrofuran] 5- (Hydroxymethyl)-2-furoic acid
(6)
This paper This paper
Not reported previously N o t reported previously N o t reported previously
2-Furaldehyde [furfural]
(6)
Levulinic acid
(6)
D-Glucose [dextrose] Sucrose D-Fructose [levulose]
(10)
This paper
(9)
This paper
(4)
t,
max. '2840
"2mgi
16,900
rnax. ' 2840 max. 2825 max. e 2810 max. E 2820 max. 2235-40 max. ' 2880 max. ' 2495
16,830
'
ty7yi
28,600 29,180 28,350
min. 2450 max. 2420 min. 2435
167 12,050 14,800
min. 2450 min. ' c a . 2130 min. 2400 min. ' 2400 2780 2780
'2600 min. '2400-40
nnn. e 2345 min max. 0.381 ' 2790 2400 a T h e preferred Chemical Abstracts name is given first, followed by t h e trivial name in brackets. b Subscript of t refers t o wave length in Angstroms. Superscript of L designates maxima or minima. is a maximum a t 2500 A. with a molecular absorption coefficient of 7900. (6)
This paper
5230 4208 5207
max.
6000
rnax. 2300
6357
' 2300 max. ' 2265
5746 min.
' 2150
4260
9900
max. 25.1 '2700 No crest No crest Qualitative description S o crest max. 0.490 281 5 t 0.380
g&
Liters Mole-1 Cm.-'b
16,700
24.1
3371 1470
max. 2240 rnax. ca. 2025 max. '2300
100.9 3470 2305
14.3 0.055 0.0069 0.014 0.063 0.126 0.100 Thus, t h e expression
c
Fgi 7900 means t h a t there
ANALYTICAL CHEMISTRY
900 The above compounds are associated with the degradation products of sugars, but in order to interpret the curves of partly degraded sugar solutions it is necessary t o know the type and amount of absorption of pure sugar solutions. The curve for dextrose (Figure 3) was determined, using a sample of Eastman anhydrous dextrose purified with activated carbon. The curve for sucrose (Figure 3) was obtained on a sample supplied by the National Bureau of Standards. Commercial sucrose contains a small amount of impurity that absorbs in the ultraviolet region. The crest of the curve for this impurity is a t 2600 to 2630 A , , the location of that for levulinic acid, although it is doubtful if enough levulinic acid would be present to account for the absorption. The same type of curve was found in canned orange juice and in beet molasses. The curve for levulose presented a problem because this compound is not stable a t the temperatures ordinarily used in its crystallization (40" to 30' C.). Previous workers ( 5 ) suggested that purified levulose solutions possessed a n ultraviolet absorption band at 2800 A,, but indicated that their results were inconclusive because crystallization a t ordinary temperatures appeared insufficient for purification Latex work ( 4 ) also showed the presence of an absorption band a t 2800 A. However, levulose dihydrate ( 17 , 18) can readily be recrystallized a t low temperatures (0' t o -15' C J , at which temperatures little, if any, decomposition t:ikes place
Table 11. Absorbance of Le%uloseSolutions Sample Original sample First recrystallization Second Third Fourth
7
Yield orig aaniy
4bsorbance IO'%, 25' C , 2780 -4
...
0 430
61.;
0.310
35.1;
0 243 0.227 0 218
19 lj
11.0
the anhydrous basis as the percentage of the original starting weight. Thus it is seen that the absorbance approaches a constant value as the compound is recrystallized, indicating that a pure levulose solution possesses an ultraviolet absorption band as shown in Figure 3. It was found that the absorbance of levulose solutions varied with the concentration according to Beer's law up to a concentration of a t least 20%. The effect of temperature on the absorption of levulose solutions, unlike its effect on the absorption of most compounds, is marked (Figure 4). The variation is linear, reversible, and dependent upon the concentration. The temperature coefficients for the absorbance between 15' and 30" C. for 10.39 and 20% by weight levuloee solutions are, respectively, 0,000761 and 0 000760 per degree Centigrade per per cent levulose. Since the ultraviolet absorption of hydroxymeth?lfurfural does not vary app!rcsiably with temperature (Figure 4 ) whereas that ot a purified levulose solution does, the absorption observed for the levulose solution cannot be attributed to the presence of hydroxymethylfurfural. Since the specific rotation of levulose ( I S ) also varies linearly with the temperature, it follows that, fqr any given concentration, the specific rotation varies linearly with the absorbance. Lin increase in absorbance resulting from an increase in tempei ature is accompanied by a decrease in the negative value of the specific rotation. This suggests that the complex equilibrium affecting the specific rotation of levulose is related to the ultraviolet absorption of its solutions. Others have pointed out ( 2 )that a free keto group will absorb in the range of 2600 to 3000 A, so perhaps the increase in absorption of levulose solutions with increase of temperature is an indication of a larger amount of free keto groups. I
'
_
-
CRYSTALLIZ 41'10N PROCEDURE
(SI7 679. LEVULOSE SOLJTION. AT 5.c FOR 12 m v s
Two hundred grams of crystalline Holly levulose were dissolved in 108 grams of water at 25" C., cooled to -10" C., seeded, stirred occasionally, and allolyed to stand a t least 5 hours. The crystals were isolated a t 0" C., using a small basket-type centrifuge. The data as to yield and absorbance of 10% solutions a t 25' C. and 2780 A. for four successive recrystallizations ns the dihydrate are listed in Table 11. A fifth recrystallization was carried out, but the yield was small, and, owing t o difficulties of manipulation, a somewh:tt higher value (0.235) was secuied. The yields were reported on
go+ x
w 03 &67%
0
1
Figure 5 .
"
l
28
'
"
23
4
30
31
Figure 4. Variation in Absorption of Levulose Solutions with Temperature
LEVULOSE SOLUTION,O
01
21502200
F ' i ' l ' I ' l ' l ' " ' 1 , l ' l ' l " ' ~ ' 1 4 15 16 17 18 13 2 0 21 22 2 3 24 25 2 6 27 TEMPERATURE-DEGREES CENTIGRADE
-
'
2300
2400 2500 2690 2700 WAVE LENGTH IN AYGSTROMS
2800
2900
3000
Change in 4bsorption of a Levulose Solution 011 C. for 12 Days Storing at
Levulose stored as the solid dihydrate in the refrigerator for a week or two showed no significant change in absorption. Pure levulose solutions standing at 5' C. for 12 days gave an increased absorption. Differences from initial values are those of n hydroxymethylfurfural curve (Figure 5 j. Solutions of hydrosymethylfurfural allowed t o stand a t room temperature for several days produced a hybrid curve consisting of itself and its corresponding wid (Figure 6 ) with an isobestic point a t 2610 to 2650 A. The fractional part oxidized in a unit time appears to be constant up to 90% conversion a t a concentration of 7.1 y per ml., but at higher concentrations (71 y per ml.) the rate of conversion falls off with time. The amount of oxygen dissolved in the liquid a t any one time probably affects the rate of reaction. A commercial sterilized levulose solution containing hydroxymethylfurfural showed a hybrid curve of levulose-hydroxymethylfurfural-hydroxymethylfuroic acid on standing a t room
V O L U M E 26, NO. 5, M A Y 1 9 5 4
901
temperature for 8 days; aftei 21 daj-s very little hydrosymethylfurfural was left. The rate of oxidation was roughly the same as if levulose were absent. Thus, it appears that spectrophotometric evaluations of sugar solutions should include a search for hydrosymethylfuroic acid. The behavior of the lower crest of hydroxymethylfurfural at 2300 A., mentioned by Mackinney and Temmer ( 6 ) , in which they described an increase in c on standing, was not substantiated in the authors' experiments. Values of E remained close to 3208 up to 48 hours at 20" C. and for 34 da? s or more at 5' C. The value of the 2840 A. crest remained at top value for 24 days a t 5' C.
The directions followed were the same as for furfural, while the sensitivity &-asabout one fifth as great. Beer's law was closely obeyed up to 6.2 y per ml., and somewhat less closely up to 25 y per ml. The determination of the ultraviolet absorption spectra is more sensitive than the polarographic method and simpler than the Schiff base method. Furthermore, the shape of the ultraviolet absorption curve is an aid to the qualitative identification of t,hc compounds present, as well as the most sensitive basis for the quantitative determination of these compounds. ACKNOWLEDGMENT
Appreciation ip extended to H. S. Isbell of the National Bureau of Standards, Washington, D. C., for the sample of pure sucrose, and to Frank E. Young of the TVestern Regional Research Laboratory, U. S. Department of ;Igricult,ure, Albany, Calif., for the seed crystals of levulose dihydrate. The sample of hydroxymethylfurfural was secured through the kindness of SidneS- h l . Cantor anti the .kmerican Sugar Refining Co., Philadelphia, Pa.
-I
I.lC
1.0-
-
7.1 Y/ML WDROXYMETWLFURF
0.9 -
080.7
-
7.1 Y/ML WDROXYMETHYFURFURAL-43 DAYS, 2O'C P'
d
$0.60
LITERATURE CITED
-
f0.5 x 0.4
-
I'
7 I Y/ML HYOROXYMETHYFURFURAL-I5 DAYS, 2O'C
(1) Cantor. 3. 11.. and
P-
0.3 0.2-
d
01-
b..
0 1
1900
2000
1
1
~
2lW
Figure 6.
2200
1
~
~
1
1
1
1
1
1
2300 2 4 0 0 2500 2 6 0 0 2700 WAVE LENGTH IN ANGSTROMS
--*.----*
,
2800
~
,
1
2900 3000
.4utoxidation of 5-(Hydrox>-methyl)-2furaldehyde
5,5'-(Osydimet hylene idi-2-furaldehyde [biv-(5-formyl-2-furfury]) ether] in aqueous solution at 20" c'. for 3 weeks shelved a complete change in its absorption curve analogous to the osidaThe new crest was at, 2500 to tion of h!.drosymeth?-lfurfural. 2550 .4. \Then the alcoholic solution of bis-(forniylfurfuryl) ether was allowed to stand at 20" C. for 6 v-eeks, no change in absorption spectrum xvas noted. Polarographic methods have also been used in this laboratory for the dekrmination of hydrosymethylfurfural ( 1). Concentration of the sample used varied from 100 to 200 -1 per nil., although more dilute solutions could probably be analyzed. The Schiff base with m-phenylenediamine dihydrochloride was successfully used here employing a photoelectric colorimeter ( 1 4 ) .
,
1
Peniston, Q. P.. J . Am. C h o n . Soc., 62,2113 (1940). ( 2 ) Gilman, H.. editor-in-chief, "Organic Chemistry, an Advanced Treatise," Vol. 11, 2nd ed., p. 1788, New York, John Wiley bSons, 1043. (3) Ham-orth, IT. K . , .Jones. W.G . AI., and Wiggins, L. F., J . Chmn. SOC., 1945,1-4. (4) Heidt, L. J.. J . F r a 7 ~ k l i ~Inat., i 234,473-85 (1942). (5) Iiwierinski, L.. and Alarchlewski, L., Bull. intern. acad. polon. sci., 1927A,379-94: 1929A,317-30. (6) llarkinney, G.. and Tenimer, O., .I. A m . Chem. Soc.. 70,358690 (1948). (7) lliddendorp. J. A,. Rrc. t m r . c h i m . , 38, 1-71 (1919). (8) Sewth. F. W., and Wiggins. L. F., Research ( L o n d o n ) , 3, Suppl. 50-1 (1950). (9) Siederhoff, P.. Z . p/zu.s
