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Vol. 40, No. 8
INDUSTRIAL AND ENGINEERING CHEMISTRY
it was desirable to know to what extent methylcyclopentadiene would interfere in the fulvene analytical procedures with acetone a n d benzaldehyde. The extinction coefficients were determined for methylcyclopentadiene and cyclopentadiene fulvene color, formed with both acetone and benzaldehvde. Figure 1 shows the extinction coefficients obtained as a function of reaction time at a constant temperature of 32” C. The reaction rate with benzaldehyde is more rapid than with acetone for both methylcyclopentadiene and cyclopentadiene fulvene formation. Cyclopentadiene reacts with both benzaldehyde and acetone at a greater rate than does methylcyclopentadiene. The fulvene color formed with cyclopentadiene is more intense than with methylcyclopentadiene. This apparent greater color intensity may be because of the presence of nonreactive 5-methyl-l,3-~yclopentadieneisomer in the methylcyclopentadiene used. These observations indicate that methylcyclopentadiene will interfere in the determination of cvcloDentadiene bv fulvene formation; the error is greater for the benzaldehyde fulvene
method than for the acetone method. However, the difference in the reaction rates of methylcyclopentadiene and cyclopentadiene in forming the fulvene color with benzaldehyde and acetone suggests a n analytical method of analyzing for methylcyclopentadiene and cyclopentadiene in the presence of each other.
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LITERATURE CITED
Doss, M. P., “Physical Constants of the Principal Hydrocarbons,” Nemr York, The Texas Co., 1943. Harkness, J. B., Kistiakowsky, G. B., and Mears, W. H., J. Chem. Phys., 5, 682-94 (1937). Kaufmann, H., and Wasserman, A., J . Chem. SOC.(London), 1939, 870-1.
Soday, F. J., U. S. Patent 2,352,9’79 (July 4, 1944). Stern, G., and Hoess, W.. U. S. Patent 2,067,511 (Jan. 12, 1937). Stobbe, H., and Ruess, F., Ann., 391, 151-68 (1912). Terent’ev, A. P., and Soloklin, L. A., Sintet. Kauchuk, 5, 9-12 (1933).
Uhrig, X., Lynch, E., and Becker, H. C., IND.ENG.CHEM., APTAL. ED.,18, 550-3 (1946).
Wilson, P. J., and Wells, J. H., Chem.Reu., 34, 1 (1944). Zelinsky, N. D., and Lewina, R. J., Ber., 66,477-8 (1933). RECEIVED JUIY i o , 1947.
es from
ellaxlose YIELD AND COMPOSITION R. L. MITCHELL, S. C. ROGERS, AND CEO. J. RITTER Forest Products Laboratory, U . S . D e p a r t m e n t of Agriculture, Madisan, Wis.
Hemicelluloses equivalent to 26.1% of the wood were extracted stepwise from maple holocellulose (a-cellulose plus hemicelluloses in wood). These were subjected to chemical analyses that characterize hemicelluloses which are composed principally of pentosans, associated with uronic acids, and the chemical side groups-acetyl and methoxyl. Concurrently, the residues resulting from the extraction of the holocellulose during isolation of the hemicelluloses were analyzed to characterize them as hemicelluloses and or-cellulose. By integrating the data from the isolated hemicelluloses with those of the corresponding holocellulose residues, it was possible to follow the degradative effect of the extractions on the hemicelluloses and the or-cellulose.
ESEARCH has been conducted by several workers on hemicelluloses from wood holocellulose (6-9). On the other hand, data are meager on the composition of the residues resulting from the extraction of hemicelluloses from the holocellulose ( 6 ) . This paper presents data on the composition of isolated maple hemicelluloses and also of the corresponding residues resulting from the extraction of holocellulose with hemicellulose solvents of increasing intensity. PREPARATION O F HEMICELLULOSES
Hemicelluloses were prepared from maple holocellulose isolated in 1-pound batches by the method of Van Beckum and Ritter (9). The holocellulose was light cream in color‘and was equivalent t o 74.0% of the extractive-free ovendry wood. The hemicelluloses were removed from the air-dried maple holocellulose of known moisture content by consecutive treatments
with the following solvents used at a 15 to 1 solvent-holocellulose ratio: (A) water at 95’ C. for 1 hour; (U) sodium carbonate solution of 2.0% concentration a t 20” C. for 24 hours; (C) sodium hydroxide solution of 4.0y0 concentration a t 20” C. for 24 hours; and (D) boiling 10.0% sodium hydroxide solution for 1 hour ( 5 ) . The solvents containing the dissolved hemicelluloses were filtered from the residues and the hemicelluloses were precipitated from each of the solutions by the addition of methyl alcohol, then filtered, washed with methyl alcohol and with acetone, and dried. The holocellulose residue remaining after tiltratiou of the hemicellulose solutions was made acid to litmus with hydrochloric acid, washed with water, air-dried, and weighed to ohtain the loss in weight due to the extraction. Approximately 20 grains of each holocellulose residue were reserved for analysis; the remainder was treated with the next consecutive hemicellulose solvent. Yields of the hemicelluloses dissolved and of the Corresponding holocellulose residue are shown in Table I.
TABLE I. YIELD AXD PERCENTAGE COMPOSITIONa OF MATERIALS Yield on Basis of Extrac- Uronic tiveAcid Free AnhyWood, dride,
Pentosan,
Methoxyl,
Naterial 70 % % ’% Maple holocellulose 74.0 4.58 25.2 0.94 Hemicellulose A 3.0 16.4 52.7 2.5 Holocellulose residue A 71.0 4.32 24.0 0.75 Hemicellulose B 5.1 28.9 63.1 2.6 Holocellulose residue B 65.9 2.97 22.5 0.57 Hemicellulose C 9.6 12.2 82.7 2.1 Holocellulose residue C 56.3 1.92 11.7 0.44 Hemicellulose D 8.4 6.5 58.3 1.4 Holccellulose residue D 47.9 1.06 2.6 0.23 a Baaed on weight of ash-free, ovendry materials.
(I-
Acetyl,
% 2.95 9.3 2.06
Cellulose, % ’ 70.3
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72.3
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94.5
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77.1
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89.3
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August 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
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alcohol. Their loss was taken into account in the conversion of the analytical Summation of data (Table I) to the weight of the wood Components, 7% shown in Table 11. I n Table I1 t h e Difference value of acetyl lost during the extraction between of hemicellulose B was 1.46%. ThereHemi- consecuUronic tive celluYield Acid fore, the yield of hemicellulose B, Table holocellose Pento- MethA?of Materials and a-Cellu11, column 2, should be 3.64% (5.1 lulose Acetyl, analysan, Material, hydride, Extraction OXYL residues lose, % ses % Procedure % % % % 1.46 = 3.64). This is the value used Maple holocellulose 74.0 3.50 18.60 0.69 2.18 51.8 for converting the analytical values for 3.0 0.49 1.58 0.08 0.27 2:42 2:82 Hemicellulose A 5i:3 Holocellulose residue A 71.0 3.06 17.1 0.53 1.46 .. hemicellulose B in Table I to the correHemicellulose B 5.1 3.64b 1.05 2.29 0.09 3.43 8.02 sponding values on the basis of the wood 3.56b in Table 11. Holocellulose residue B 65.9 1.95 14.8 0.38 50.8 1.17 7.93 0.20 .. 9:iO 9:25 Hemicellulose C 9.6 a-Cellulose values in column 7 show 5012 Holocellulose residue C 56.3 1.08 6.55 0.25 .. 8.4 0.46 4.9 0.13 .. 5:49 6:08 Hemicellulose D a gradual increase from 70.3% in t h e 45:3 Holocellulose residue D 47.9 0.51 1.22 0.07 .. .. holocellulose to 94.5% in holocellulose a ValueR based on weight of extractive-free, ovendry wood. residue D. b Corrected value for loss of acetyl. The recalculated data as given in columns 3 to 6 in Table I1 can be used as a quantitative check on the yield data in ANALYSlS AND DISCUSSION OF ANALYTICAL RESULTS column 2. For example, the summation of the analytical data OB The hemicelluloses and the holocellulose residues were anathe composition of hemicellulose A is 2.42% in column 7, as comlyzed according to the following methods: Uronic acids were pared with 3.0% in column 2, the yield value for hemicellulose determined according to the 12.0% hydrochloric method (4); A. If the analytical values of holocellulose residue A (columna pentosans, according t o Bray ( 1 ) ; methoxyl, according t o Clark 3 to 6) are subtracted from the corresponding values of the holo(8); acetyl, according to Clark (92) ; and a-cellulose, according to cellulose, the differences so obtained total 2.82% (column 8). Bray (1). These analyses famished valuable information on the The total of the analytical values for hemicellulose B is 3.43y0 composition and the chemical characteristics of the hemicellu(column 7) as compared with 3.64% (column 2) after the yield loses and the residues resulting from extraction of the hemicelluwas corrected for loss of acetyl. The total compares favorably loses from the holocellulose. with 3.56% (5.02 1.46 = 3.56) which is the summation of t h e The data so obtained made it possible to follow the changes differences between the analytical values of holockllulose residues that occurred in the nature of the hemicelluloses during their A and B, corrected for acetyl, becauee it was not included in the stepwise removal from the holocellulose. The a-cellulose deteranalysis of hemicellulose B. mination on the holocellulose and its residues showed the effect Analytical data on hemicellulose C totals 9.3% (column 7) of the hemice~luloseextraction procedures on the a-cellulose. as compared with 9.6% yield (column 2), and with 9.25% (column Yield and the analytical results are shown in Table 11. 8) for summation of differences between holocellulose residues Table I, column 2, shows that the holocellulose used as a B and C. source for the hemicelluloses was equivalent to 74.0% of the The sum of the analytical values for hemicellulose D is 5.49oj, wood on a n ovendry basis. Four consecutive extractions of the (column 7); this compares well with 6.08%, the summation of material removed four batches of hemicelluloses totaling 26.1% differences between holocellulose residues C and D. These values, (3.0 5.1 9.6 8.4 = 26.1) of the wood. After corrections however, are 2.9 and 2.3% less than 8.4%, the yield of hemicelluwere made for materials other than hemicelluloses in the four lose D. The discrepancy can be explained on the basis t h a t extractions, the yield became 22.1%. 47.9 = 2.3) of a-cellulose was approximately 2.3% (50.2 Uronic acids, as shown in column 3 were concentrated in the degraded to the extent of becoming soluble in the 10% sodium hemicelluloses. Hemicellulose was extracted from the holohydroxide solution used for extracting hemicellulose D. cellulose by means of hot water at 95' C. (method A). Uronic The total analytical value for hemicelluloses A, B, C, and D acid content of 16.4 compares favorably with 17.1% for the shown in Table 11, column 7, plus the 1.46 acetyl that was reuronic acid content of the hot water-soluble aspen hemicellulose moved from holocellulose residue A by the sodium carbonate reported by Thomas (8). Hemicellulose extracted with 4.0% extraction (column 6), is 22.10%. sodium hydroxide solution (method C) with 12.2% uronic acid Values in column 9 show the degradation effects of the hot is in close agreement with 12,1y0uronic acid for an aspen hemiwater, 2.0% sodium carbonate, 4.0y0sodium hydroxide, and cellulose fraction extracted from aspen holocellulose with 5.070 10.0% sodium hydroxide extractions on the a-cellulose. They potassium hydroxide as reported by Thomas (8),and 14.6% show that the last treatment was too severe. for uronic acid in spruce hemicelluloses as reported by Kurth and Ritter (6). These results indicate that hemicellulose fractions LITERATURE CITED prepared from different woods may have uronic acid percentages in close agreement. (1) Bray, M. W., Forest Products Laboratory, Madison, JVk, Rept. Further, the uronic acid content gradually decreased from 4.3 R19 (revised 1939). (2) Clark, E. P., IND. ENG.CHEM.,ANAL.ED.,8 , 4 8 7 (1932). in holocellulose residue (method A) to 1.0% in holocellulose (3) Clark, E. P., J.Assoc. Ofic.Agr. Chemists, 15, 136 (1932). residue (method D). (4) Dickson, A., Otterson, H., and Link, K. P., J . Am. Chem. SOC., Pentosans, like uronic acids, were concentrated more in the 52, 775 (1930). hemicelluloses than in the corresponding holocellulose residues (5) Irvine, J. C., and Hirst, E. L., J . Chem. SOC.,125, 1 5 (1924). (6) Kurth, E. F., and Ritter, G. J., J . Am. Chem. SOC.,56, 2720 as shown in column 4. (1934). Methoxyl values were fairly constant throughout the four (7) Mitchell, R. L., and Ritter, G. J., Ibid., 62, 1958 (1940). hemicelluloses, whereas those of the horocellulose residues de(8) Thomas, B. B.,Paper Ind. and Paper World, 27, 274 (1945). crease gradually from 0.75 to 0.23%. (9) Van Beckum, W. G., and Ritter, G . J., Paper Trade J., 105, 127 (1937). The acetyl groups were removed entirely and lost during the isolation of hemicellulose by the sodium carbonate extraction RECEIVED August 1, 1947. (method B) as they are not precipitated by the addition of methyl AND FRACTIONS" TABLE 11. YIELD AND COMPOSITION O F HOLOCELLULOSE
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