256
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
1701.
13, No. 3
STUDIES ON THE CHEMISTRY OF CELLULOSE I-THE CONSTITUTION OF CELLULOSE1 By Harold Hibbert DEPARTMENT OP CHEMISTRY. YALE UHIVBRSXTY, hrEW HAVZN,CONN,
I n a recent plea for the scientific study of cellulose chemistry2 the writer submitted a new formula for the cellulose nucleus: CHsOH
0
0
I
CH-
CH--0
P
o
ICHOH-CHOH-CH \ I
I
In view of the interesting results recently obtained by Denharn and Woodhouse3 on the methylation of cellulose and of those of Pictet and co-workers4 on the distillation of pure cellulose and starch under reduced pressure, which tend to confirm the writer’s views, a discussion of the constitution OP cellulose in .the light of our previous and present knowledge appears desirable. It has long been known that cellulose is closely related to dextrose, since it yields the latter quantitatively on hydrolysisa fact of fundamental importance. Some of the first work on the subject was carried out by Braconnot6 in 1919, but the identity of the sugar as dextrose was first established by Flechsig.G While the fact of the “quantitative” conversion of cellulose into dextrose has been questioned, the recent work of Willstatter and Zechmeister,? and more especially that of Ost,8 serve to confirm Flechsig’s results and to establish beyond question the fact that dextrose can be obtained in quantitative yield by the hydrolysis of cellulose with acids. Thus the latter author not only succeeded in obtaining a yield, determined polarimetrically, .of 9 5 . 3 per cent of dextrose and in isolating it as a crystalline product, but also converted it into ethyl alcohol of which some SO to 83 per cent of the theoretical quantity was obtained. Furthermore, in his earlier work9 on the acetylation of cellulose he was able to obtain a 90 per cent yield of pentacetylglucose (taking into account the octacetyl cellobiose formed a t the same time). These facts confirm beyond question the quantitative relationship existing between dextrose and cellulose, notwithstanding certain arguments to the contrary.’O PROPOSED FORMULAS FOR CELLULOSE: Of the various formulas proposed for cellulose by different investigators, those of Tollens, 11 Cross and Bevan, Vignon, l 3 Green,” and Barthelemyls may be mentioned. ToLLENS-TollenslB assumes that cellulose possesses the following structure: 1 Presented at the Cellulose Symposium, Division of Industrial and Engineering Chemistry, at the 60th Meeting of the American Chemical Society, Chicago, Ill., September 6 to 10, 1920. 2 Chem. &+ Adel. E n g . , 22 (1920), 838. * J . Chem. Soc., 103 (1913), 1735; 105 (1914), 2537; 111 (1917), 244. 4 Heloetica C h i m . Acta, 1 (1918), 87, 226, 2 (1919), 698; S (1920), 258, -640, 645, 649, See also P. Karrer, Ibid., 3 (19?0), 258; Sarasin, Arch. sci. phys. not., [IV] 46 (1918), 5. 6 Ann. chim. phys., [2] 12 (1819), 172. 6 2. physiol. Chem., 7 (l882), 913. ‘Be?., 46 (1913), 2401. 8 Ibid., 46 (1913), 2995; Ost and Wilkening, Client.-Ztg., 34 (1910), 461. $ A w n . , 398 (1913), 323. 10 M. Cunningham, J . Chem. Soc., 113 (1918), 178; Cross and Bevan, .Ibid., 113 (1918), 182. 11 “Kurzes Handbuch der Kohlenhydrate,” 3rd Ed., 1914. 1 2 J . Chem. Soc., 79 (1901), 366; Rew. gcs. mat. color., 5 (1901), 72; “Researches on Cellulose,” [I], p. 77; [II], p. 131; “Cellulose,” p. 7 5 ; Caoutchouc €9gutta percha, ,1317, 9327. 1 3 Bull. SOC. chim., 131 21 (1899), 599, J . Clsem. Soc., 8 1 (1906), 811; Rev. ges. mol. color., 2 (19071, 130; Z.Forben-Ind., 3 (1904), 97, 309. 16 Caoutchouc & gutta peucha, 1917, 9274, 9325; see criticism by Cross .and Bevan, Ibid.. 9327; Chem. Abs., 11 (1917), 3428. 16 LOC.cit., p. 564.
in which the oxygen of the aldehyde group of one molecule of dextrose is assumed to have condensed with the hydrogen atoms of the two end hydroxyl groups of a second one. I n this way any desired number of molecules may be combined, the -CHO group (A) of the first ultimately combining with the two hydroxyls, B and C of the last, t o form a closed ring. As is indicated below, the formula is quite inadequate to explain the reactions of cellulose. CROSS AND BEvAN’-According to the earlier work of these authors the cellulose nucleus has the constitution indicated by the formula:
CHOH-CHOH This is assumed to be capable of polymerizing to give ring formations such as
in which any desired number of single molecules may be coupled together. On the other hand, instead of such aldol formation, these authors assume that condensation may also take place between the CO group (hydrated) and a secondary alcohol group, as follows: CHOH-CHOH HO CHOH-CHOH )CHz >C< )CHs CHOH-CHOH HO CHOH-CHOH CHOH-CH0 CHOH-CHOH (11)
+ ’
--f
oc
I
cL1CH-~CHz)2-C0-CHs CH3 ----f
Vol. 13, No. 3
CHI \C-CH-CH2-CH2-CO-CH3 CHa'I I OH OH
L
J . Russ. Phys. Chem. Soc., 43, 609; Chem. Zenlr., 1911 (II), 268.
1 It seems probable that such a change could be induced by the use of a suitable condensing agent, such as iodine, phosphoric acid, etc., and these experiments are to be carried out.
RESEARCH PROBLEMS IN COLLOID CHEMISTRY
I
By Wilder D.Bancroft C O R N ~ LUNIVERSITY, L ITHACA,N. Y . Received November 5 , 1920
(Continued)
wonder whether iodine perhaps forms a colloidal solution in glycerol. (94) WILL ANY LIQUID PEPTIZE A WETTED-SOLID AT A SUFFI(98) THEORY O F PEPTIZATION BY MIXED soLvENTs-There CIENTLY HIGH TEMPERATURE?-we believe that when a liquid are a number of cases where mixed solvents will peptize a solid is adsorbed by a solid, it tends to peptize the solid. We know much better than either one alone-cellulose nitrates in ether that a t higher temperatures the action increases and we get and alcohol, casein in pyridine and water,' and probably cingelatin peptized by water, glass' by water, and vulcanized rubber2 chonine in chloroform and alcohol,2 as well as phloretine in ether by various organic liquids; but there are no experiments to show and water.a The theory of this has not been worked out. Celluwhether this is absolutely general and whether any solid will lose nitrate swells in alcohol and not in ether;4 but it is not be peptized a t a sufficiently high-temperature by any liquid known whether this is universal. We do not know whether which wets it. alcohol peptizes cellulose nitrate at higher temperatures. Zein (9j ) PEPTIZATION OF PRECIPITATES BY GLYCEROL, SUGAR, is also peptized in mixed solvents.6 Larguier des Bancels6 ~TC.-A concentrated solution of sugar in water will prevent the claims that gelatin is peptized more readily by aqueous alcohol precipitation of lime, calcium silicate,s silver chromate, silver or aqueous acetone than by water alone. chloride,4 and the hydrous oxides of copper: uranium, and iron.6 (99) IS IODIDE ADSORBED WHEN GELATIN IS PEPTIZED BY Invert sugar is about seven times as effective as cane sugar in POTASSIUM IomDE?-The experiments of Briggs and Hieber7 holding up hydrous ferric oxide. Grimaux' showed that glycerol furnish conclusive proof that the liquefaction of gelatin by poprevents the precipitation of hydrous ferric oxide by caustic tassium iodide solutions is a case of reversible peptization. As potash. We ought to get peptization of the precipitates in all yet, however, nobody has shown that there is marked adsorption these cases under favorable conditions, but this has never been of potassium iodide by gelatin. proved experimentally. Some preliminary work has shown that ( 100) COLLOIDAL CALCIUN CARBONATE-springs considers that, the time factor may be very important and that one may get in natural waters, calcium and magnesium carbonates, silica peptization a t the end of a week or more, in cases where there and alumina are in solution, while, in green waters, they are was no apparent immediate action. partly suspended through a deficiency in the carbon dioxide. (96) STUDY OF PEPTIZATION BY, AND ADSORPTION OF, UNDISSOCIIfl the blue Rhone we have 785 CaCOs and 7 9 . 5 CO2, while in ATED SALTS-There is no work a t all on peptization by salts in the green Rhine we have 1056 CaC03 and 7 6 COZ. This raises practically nonionizing solvents, and yet cases of this sort must the question whether we know that calcium bicarbonate is really occur and will undoubtedly be found if looked for. dissolved in water and is not calcium carbonate peptized by ( 9 7 ) DOES GLYCEROL PEPTIZE IoDINE?+--Contrary to the usual carbon dioxide. Ultrafiltration would probably settle this opinion, iodine is abundantly soluble in glycerol.* First dis- point. It would also be of interest to know exactly what the solve the iodine in alcohol or acetone, then add glycerol and suspended material is which occasionally makes the water in drive off the first solvent by evaporation a t a low temperature. porcelain-lined swimming tanks look green d solution can also be obtained by heating iodine and glycerol (101) cocoa-Cocoa is a colloidal solution and the making in a closed vessel to 120' to 150'. These elaborate directions of cocoa should be discussed from the viewpoint of the colloid do not sound like an ordinary case of solution and make one chemist. PEPTIZATION
1 Barus, A m . J . Sci., [3] 38 (1899), 408; 41 (1891), 110; [41 6 (1898), 270; 7 (1899), 1; Phil. Mag., [5] 47 (1899), 104, 461. * Barus, A m . J. S c i , [3] 42 (1891), 359. * Weisberg, Bull. soc. chim., [3] 16 (1896), 1097. 4 Lobry de Bruyn, Ber., 36 (1902), 3079. i Graham, J . Chem. Soc., 16 (1862), 253. 6 Riffard, Comgl. rend., 77 (1873), 1103. * I b i d . , 98 (1884), 1485, 1540. I Catillon, J . Soc. Chcm. Ind., 22 (1903), 377.
Levites, 2. Kolloidchem., 8 (1911), 4. (1873), 533. 3 Schiff, 2. physik. Chem., 23 (1897). 355. 4 Private communication from Professor Chamot. 5 Galeotto and Giampdlmo, 2. Kolloidchem., 3 (1908), 118. 6 Compt. rend., 146 (1911), 290. 7 J . Phys. Chem., 24 (1920), 74. 8 J . Chem. Soc., 46 (1884), 260. 1
* Oudemanns, J. Chem. Soc., 26
