Vol. 16, No. 12 -
INDUSTRIAL A N D ENGINEERING' C H E M I S T R Y
1274
The Constitution of Cellulose' By A. W. Schorger C. F.
BURQESS
LABORATORIES,MADISON, Wrs.
UR knowledge of the constitution of cellulose is based almost entirely on the preparation of two derivatives. It has been shown that cellulose on acetolysis yields
0
cellobiose octaacetate and on methylation, followed by hydrolysis, 2, 3, 6-trimethyIgluco~e.~In 1919, Haworth and Leitch3 showed that cellobiose probably had the following constitution:
All the numerous cellulose formulas previously proposed become untenable through their inability to give practically quantitative yields of 2, 3, 6-trimethylgluoose, and it is unnecessary to discuss them in detail. Karrer' thought that the following formula best explained the constitution of cellulose:
CHzOH
I I
C H --0-0/ q : Z e
H OJ ' /
y H ,,,,
0
\ZOM I e
1
CHOH
\dH
cM::"z
I CHOH CHzOH I
2, 3,6-Trimethyl~lucose
I
CH
"\i
I
CHOH
HO\
CHz.CH(OH) .CH.CH(OH) .CH(OH).CH a
--
b
CH.CH2OH
Cellulose (Karrer) I1
CHOH
I
CHOH
-
\dH 0 -X Cellulose (Hibbert)
It remained for Irvine and his associates6 to show that cellulose could be converted into 2, 3,6-trimethylglucose with a yield of 89 per cent, and that no isomeric trimethylglucose was formed; hence all the glucose residues are identical. I n view of the fact that it has so far beenimpossible to account for more than 50 to 60 per cent of cellobiose in the acetolysis of cellulose, Irvine, as a precaution, formulated cellulose as a tri-1, 5-anhydroglucose. CHzOH .CH(OH). C H
II
CHOH
I
I I
O
------lo/.--
I I
~H-O-CH.CH(OH)
I 0 I
CH.CH(OH) .CH(OH).CH
CH-0-X
/O\
Cellulose (Karrer) I
Cellulose was looked upon as a dimeride of anhydrocellobiose (cellosan), polymerization taking place through subsidiary valencies leaving the oxygen bridges intact. The strong cohesion in the polymerized cellulose molecule is due to valency forces of unusual strength. Later,s owing to the formation of aceto-1, 6-dibromoglucose from cellulose, the formula for cellulosan was changed to :
CHzOH
I
-----lo-------
CHOH
Cellobiose
CH-0-CH.CH.CH(OH)
~ H . C H ( O H.CH(OH, ) .CH.C!H.CH~OH
L
CHOH
Further work4 has rendered it quite certain that cellobiose is a glucose-&glucoside of the constitution given above. To fulfil the requirements that cellulose gives cellobiose and 2,3,6-trimethylglucose, Hibbert proposed the formula given below, in which X represents additional glucose anhydride groups. This is identical with the grouping proposed by Haworth and H i r ~ t . ~
G \
9
P
.CH(OH) .CH.&H.CH~OH
CHzOH Cellulose (Irvine) 1 Presented before the Division of Cellulose Chemistry a t the 67th Meeting of the American Chemical Society, Washington, D. C., April 21 t o 26, 1924. 2 Denham and Woodhouse, J . Chem. SOC.(London), 105, 2357 (1914); 111, 244 (1917); Haworth and Leitch, I b i d . , 113, 188 (1918); Irvine and Hirst, Ibid., 121, 1213 (1922). * Ibid., 115,813 (1919). 4 Haworth and Hirst, Ibid., 119,193 (1921). 1 THISJOURNAL, 13,256,334(1921). 6 J . Chem. SOC. (London), 123,518 (1923); J . SOC.Chcm. Ind., 41, 362R (1922).
I n this formula, depending upon whether the oxygen linkage a or b was broken, either cellobiose or maltose would be obtained. This formula is untenable, however, since half of the glucose would be obtained as 2, 3, 5--trimethylglucose. I n the writer's opinion the earlier formula of Karrer was far more nearly correct and the change unfortunate. It is still to be determined in what way the orthoglucosanQ (anhgdroglucose) groups are held together in the cellulose molecule, and the size of the latter. HesslO holds the extreme view that cellulose consists of the units CsHloOs,held together by "association" and not by condensation or polymerization. From our present knowledge of hydrocellulose we must assume the opening up of an anhydride position with the formation of an aldehyde group and yet without depolymerization of the cellulose molecule.ll Without calling in the aid of crystal valencies none of the formulas proposed explain the resistance of cellulose (to hydrolysis and other chemical reactions. The Irvine formula should hydrolyze with comparative ease; the ring having been broken, the resulting straight-chain compound would be expected to break down rapidly and completely to gIucose. I-Iibbert** has recently proposed a spiral ring structure to represent the polymerization of cellulose. I n this arrangement there is lack of symmetry and the bridge linkage would appear to be particuIarly susceptible t o strain. No satisfactory chemical method is available for determining the size of the cellulose molecule. Rontgen ray Cellulosechemze, 2 , 127 (1921). Karrer and Smirnov, Heloetica Chim. Acta, 5, 187 (1922). @ Schorger, THIS JOURNAL, 16, 141 (1924). 1 0 A n n . , 436, 1 (1923). 11 Heuser and Neuenstein, Cellulosechemie, 3, 88 (1922). 12 J . A m . Chem. Soc., 45, 3124 (1923). 1
8
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1924
1275
spectrographsl3 indicate that the cellulose in plant fibers is composed of crystals symmetrically arranged with respect to the axis of the fiber, forming a parallelepiped. The group ( C ~ H I O Ois~regularly )~ repeated, indicating that cellulose is built up of anhydrocellobiose units. IrvineI4 in a recent pa.per has remarked that [‘speculation in the absence of experiment is best avoided in the carbohydrates.” The writer has hesitated for nearly two years to advance a formula for cellulose unsupported by laboratory proof. It seems, however, that the structure given below might clarify the question of the mode of polymerization, since it offers a tangible line of attack.
4-Hydrolysis a t (2) or (3) would result in a slight degradation of the molecule but not in the formation of an active carbonyl group; at both (2) and (3) a n aldehyde group would be formed, giving a hydrocellulose. The molecule would still be largely intact, but more readily hydrolyzable than normal cellulose. 5-Hydrolysis a t (2), (3), and (4)wouldrupture thecorresponding rings t o give a dextrin with reducing properties. It would be possible to obtain a dextrin without reducing properties by fission a t (3) and (4),or a t ( 5 ) and (6). The dextrins would be more or less readily hydrolyzed, since i t is improbable t h a t there is much stability t o the facial 10 and 12-membered rings in themselves.
........................................................................................................................................
Toxicity of Nicotine as a n Insecticide and Parasiticide’
1!
CHzOH I 0-CH
SH20H
(3) O---CH
CH
I
I
(7) H + O J> ’H
I
CHOH
CHOH
J H o H o/FH
,...... j
C!H/(l)
i
CHOH
CHOH 1
{HOH
CHOH CH----O---C!H~(5)
(4)
dHzOH
o/--
i
CH.................>.
CH/
I
I
(6)
By E. R. deOng (8)
o/C;H
CH
I
UNIVERSITY OF CALIFORNIA, BERKELEY, CALIF.
--- 0
CW20H
j
The foregoing formula represents in plane surface a polycyclic compound containing in horizontal section two 10-membered rings, and with two 10-membered and two 12-membered rings in the faces. The orthoglucosan groups are symmetrically arranged, forming a parallelepiped. So little is known of the higher membered cyclic compounds containing oxygen in the ring that it is useless to speculate on their stability. It would seem, however, that a polycylic compound as above would be far more stable than an 18-membered ring of the Irvine type from the standpoint of structure alone as well as crystal valencies. It will be noted that the butylene oxide ring common to the sugars is absent. The indirect evidence on which the assumption of the presence of this ring in cellulose is based does not affect the validity of the proposed formula. The salient features of the chemistry of the cellulose molecule as represented by the foregoing formula may be summarized as follows:
ICOTINE as a commercial insecticide is usually marketed as a nicotine sulfate, although the alkaloid itself is sometimes sold in the free or uncombined state (I-nicotine). Levorotatory nicotine is readily volatilized, and has been found to be much more toxic than when combined with acids to form nonvolatile salts. Hence, the commercial form of nicotine sulfate is much less toxic than when the alkaloid is freed from the combining acid. Nicotine sulfate is nonvolatile but becomes so in proportion as it is changed to the free base nicotine by the addition of alkali to neutralize the combining acid. Toxicity as an insecticide is due to a fumigating action (except where ingested by mouth), the curve of which is very similar to that from spraying. This is in accord with the work of McIndoo.2 A comparison was made of the rates of volatilization and the toxicity to aphids both by spraying and fumigating with free nicotine and nicotine sulfate. The volatilization rate from a film on leaf surfaces and from solutions was determineda by assays of the residual nicotine after exposure for definite periods. Bio-assays were made to determine the toxicity to aphids by spraying and by fumigation.
1-It is capable of giving only 2, 3, 6-trimethylglucose. 2-It is possible to obtain the theoretical yield of cellobiose octaacetate on acetolysis, but this is highly improbable, since: 3-It is also capable of yielding an isomeride of cellobiose, though it would not be maltose. Fission a t (l), ( 2 ) , (4), ( 5 ) ,and VOLATILIZATION TESTS (6) would give cellobiose, and at (7), ( 8 ) , (l), (3),and (4),the isomeride, isocellobiose. There are equal chances for the formaThe solutions used in all these tests (except No. 8) were of tion of crllobiose and isocellobiose. Failure to isolate the latter may be due to the greater ease of hydrolysis or acetolysis a t (l), nicotine sulfate which had been made from the pure alkaloid (2),. (6), and ( 5 ) due to the valency angles. Isolation of isocel- combined with sulfuric acid to neutrality with phenol red lobiose even in small quantity would be satisfactory proof of the and then by the addition of varying amounts of alkali changed CHzOH
I
CHOH
I
CHO
I I I I CH-0-CH I CHOH I
/CH
/ dHOH
CHOH
CHzOH “Isocellobiose”
existence of this linkage in cellulose. The celloisobiose of Ost,’6 according to Bertrand, is a mixture of cellobiose and procellose. Procellose is apparently a trisaccharide and has been assigned a chain formula obtainable by hydrolysis at one of the glucoside linkages in the Irvine formula. Herzog, CeZZuZosechemie, 2, 101 (1921); Umschau, 26, 53 (1921). 14 THIS JOURNAL, 15, 1163 (1923). 16 2. angew. Chem., 38, 100 (1920); Cellulosechemie, 8, 25 (1922). 16 Comfit. rend., 176, 1583 (1923); 177, 85 (1923).
18
in part to free base nicotine. Distilled water was used in all solutions except in two instances, where tap water was used alone and in another case where alkaline soap was added. The alkalinity of 100 cc. of the tap water used was equivalent to 1.3 cc. 0.02 N sulfuric acid. The difference in volatility between free nicotine and nicotine sulfate is very marked. The former after 24 hours shows only a trace of nicotine, while the latter has a range of recovery from 29.9 to 46.1 per cent, as shown in Table I. This proves that free nicotine may be entirely released in 24 hours and that from 85 to 90 per cent is available in the first 3 hours during clear weather, while from 13 to 19 per cent of the nicotine sulfate may be present after 48 hours of cloudy weather. Such long periods required for activation necessarily reduced 1 Abstract of a paper presented under the title “Comparison of Levoand Dextro-Rotatory Nicotine as an Insecticide and Parasiticide” before the Division of Agricultural and Food Chemistry at the 67th Meeting of the American Chemical Society, Washington, D. C., April 21 to 26,1924. 2 J . A g r . Research, 7, 89 (1916). a Chapin, Bur. Animal Industry, Bull. 133.
