Chapter 7

C 44.56 44.29 44.53 44.56 H 6.39 6.31 6.46 6.42

was exposed to the action of pure distilled H_{2}O_{2} at 4-60 p.ct. strength, at ordinary temperatures until disintegrated: a result requiring from nineteen to thirty days. The series of products gave the following analytical results:

C 43.61 43.61 43.46 43.89 44.0 43.87 43.92 43.81 H 6.00 6.29 6.28 6.26 6.13 6.27 6.24 6.27

results lying between the requirements of the formulæ:

5 C_{6}H_{10}O_{5}.H_{2}O and 8 C_{6}H_{10}O_{5}.H_{2}O.

Hydrazones were obtained with 1.7-1.8 p.ct. N. Treated with caustic soda solution the hydrazones were dissolved in part: on reprecipitation a hydrazone of unaltered composition was obtained. The original product shows therefore a uniform distribution of the reactive CO- groups.

The hydralcellulose boiled with Fehling's solution reduced 1/12 of the amount required for an equal weight of glucose.

Digested with caustic soda solution it yielded 33 p.ct. of its weight of the soluble 'acid cellulose.' This product was purified and analysed with the following result: C 43.35 H 6.5. For the direct production of the 'acid' derivative, cellulose was boiled with successive quantities of 30 p.ct. NaOH until _dissolved_. It required eight treatments of one hour's duration. On adding sulphuric acid to the solutions the product was precipitated. Yield 40 p.ct. Analyses:

C 43.8 43.8 43.7 H 6.2 6.2 6.3

The cellulose reprecipitated from solution in Schweizer's reagent gave similar analytical results:

C 43.9 43.8 44.0 H 6.5 6.3 6.4

_Conversion into nitrates._--The original cellulose, hydral- and acid cellulose were each treated with 10 times their weight of HNO_{3} of 1.48 sp.gr. and heated at 85° until the solution lost its initial viscosity.

The products were precipitated by water and purified by solution in acetone from which two fractions were recovered, the one being relatively insoluble in ethyl alcohol. The various nitrates from the several original products proved to be of almost identical composition,

C 32.0 H 4.2 N 8.8

with a molecular weight approximately 1350. The conclusion is that these products are all derivatives of a 'hydralcellulose' 6C_{6}H_{10}O_{5}H_{2}O.

FORMATION OF FURFURALDEHYDE FROM CELLULOSE, OXYCELLULOSE, AND HYDROCELLULOSE.

By LEO VIGNON (Compt. rend., 1898, 126, 1355-1358).

(p. 54) Hydrocellulose, oxycellulose, and 'reduced' cellulose, the last named being apparently identical with hydrocellulose, were obtained by heating carefully purified cotton wool (10 grams) in water (1,000 c.c.), with (1) 65 c.c. of hydrochloric acid (1.2 sp.gr.), (2) 65 c.c. of hydrochloric acid and 80 grams of potassium chlorate, (3) 65 c.c. of hydrochloric acid and 50 grams of stannous chloride. From these and some other substances, the following percentage yields of furfuraldehyde were obtained: Hydrocellulose, 0.854; oxycellulose, 2.113; reduced cellulose, 0.860; starch, 0.800; bleached cotton, 1.800; oxycellulose, prepared by means of chromic acid, 3.500. Two specimens of oxycellulose were prepared by treating cotton wool with hydrochloric acid and potassium chlorate (A), and with sulphuric acid and potassium dichromate (B), and 25 grams of each product digested with aqueous potash. Of the product A, 16.20 grams were insoluble in potash, 2.45 grams were precipitated on neutralisation of the alkaline solution, and 6.35 grams remained in solution, whilst B yielded 11.16 grams of insoluble matter, 1.42 grams were precipitated by acid, and 12.42 grams remained in solution. The percentage yields of furfuraldehyde obtained from these fractions were as follows: A, insoluble, 0.86; precipitated, 4.35; dissolved, 1.10. B, insoluble, 0.76; precipitated, 5.11; dissolved, 1.54. It appears, from the foregoing results, that the cellulose molecule, after oxidation, is easily decomposed by potash, the insoluble and larger portion having all the characters of the original cellulose, whilst the soluble portion is of an aldehydic nature, and contains a substance, precipitable by acids, which yields a relatively large amount of furfuraldehyde.

UNTERSUCHUNGEN ÜBER DIE OXYCELLULOSE.

O. V. FABER und B. TOLLENS (Berl. Ber., 1899, 2589).

~Investigations of Oxycellulose.~

(p. 61) The author's results are tersely summed up in the following conclusions set forth at the end of the paper: The oxycelluloses are mixtures of cellulose and a derivative oxidised compound which contains one more atom O than cellulose (cellulose = C_{6}H_{10}O_{5}), and for which the special designation _Celloxin_ is proposed.

Celloxin may be formulated C_{8}H_{6}O_{6} or C_{6}H_{10}O_{6}, of which the former is the more probable.

The various oxycelluloses may be regarded as containing one celloxin group to 1-4 cellulose groups, according to the nature of the original cellulose, and the degree of oxidation to which subjected. These groups are in chemical union.

Celloxin has not been isolated. On boiling the oxycelluloses with lime-milk it is converted into isosaccharinic and dioxybutyric acids. The insoluble residue from the treatment is cellulose.

The following oxycelluloses were investigated:

A. _Product of action of nitric acid upon pine wood_ (Lindsey and Tollens, Ann. 267, 366).--The oxycelluloses contained

1 mol celloxin: {2 mol. cellulose on 6 hours' heating {3 mol. cellulose on 3 hours' heating

with a ratio H : O = 1 : 9 and 1 : 8.7 respectively: they yielded 7 p.ct. furfural.

B. _By action of bromine in presence of water and_ CaCO_{3} _upon cotton_.--Yield, (air-dry) 85 p.ct. Empirical composition C_{12}H_{20}O_{11} = C_{6}H_{10}O_{5}.C_{6}H_{10}O_{6}: yielded furfural 1.7 p.ct.

C. _Cotton and nitric acid at_ 100°, two and a half hours (Cross and Bevan).--Yield, 70 p.ct. Composition

4 C_{6}H_{10}O_{5}.C_{6}H_{8}O_{6}

yielded furfural 2.3 p.ct.

D. _Cotton and nitric acid at_ 100° (four hours).--A more highly oxidised product resulted, viz. 3 C_{6}H_{10}O_{5}.C_{6}H_{8}O_{6}: yielded furfural 3.2 p.ct.

_By-products of oxidation._--The liquors from B were found to contain saccharic acid: the acid from C and B contained a dibasic acid which appeared to be tartaric acid.

The isolation of (1) isosaccharinic and (2) dioxybutyric acid from the products of digestion of the oxycelluloses with lime-milk at 100° was effected by the separation of their respective calcium salts, (1) by direct crystallisation, (2) by precipitation alcohol after separation of the former.

CELLULOSES, HYDRO- AND OXYCELLULOSES, AND CELLULOSE ESTERS.

L. VIGNON (Bull. Soc. Chim., 1901 [3], 25, 130).

(a) _Oxycelluloses from cotton, hemp, flax, and ramie._--The comparative oxidation of these celluloses, by treatment with HClO_{3} at 100°, gave remarkably uniform results, as shown by the following numbers, showing extreme variations: yields, 68-70 p.ct.; hydrazine reaction, N fixed 1.58-1.69; fixation of basic colouring matters (relative numbers), saffranine, 100-200, methylene blue, 100-106. The only points of difference noted were (1) hemp is somewhat more resistant to the acid oxidation; (2) the cotton oxycellulose shows a somewhat higher (25 p.ct.) cupric reduction.

(b) _'Saccharification' of cellulose, cellulose hydrates, and hydrocellulose._--The products were digested with dilute hydrochloric acid six hours at 100°, and the cupric reduction of the soluble products determined and calculated to dextrose.

100 grms. of gave reducing products equal to Dextrose

Purified cotton 3.29 " Hydrocellulose 9.70 Cotton mercerised (NaOH 30° B.) 4.39 Cotton mercerised (NaOH 40° B.) 3.51 Cellulose reprecipitated from cuprammonium 4.39 Oxycellulose 14.70 Starch 98.6

These numbers show that cellulose may be hydrated both by mercerisation and solution, without affecting the constitutional relationships of the CO groups. The results also differentiate the cellulose series from starch in regard to hydrolysis.

(c) _Cellulose and oxycellulose nitrates._--The nitric esters of cellulose have a strong reducting action on alkaline copper solutions. The author has studied this reaction quantitatively for the esters both of cellulose and oxycellulose, at two stages of 'nitration,' represented by 8.2-8.6 p.ct. and 13.5-13.9 p.ct. total nitrogen in the ester-products, respectively. The results are expressed in terms (c.c.) of the cupric reagent (Pasteur) reduced per 100 grs. compared with dextrose (=17767).

Cellulose maximum nitration (13.5 p.ct. N) 3640 Oxycellulose maximum nitration (13.9 p.ct. N) 3600 Cellulose minimum nitration (8.19 p.ct. N) 3700 Oxycellulose minimum nitration (8.56 p.ct. N) 3620

The author concludes that, since the reducing action is independent of the degree of nitration, and is the same for cellulose and the oxycelluloses, the ester reaction in the case of the normal cellulose is accompanied by oxidation, the product being an oxycellulose ester.

_Products of 'denitration'._--The esters were treated with ferrous chloride in boiling aqueous solution. The products were oxycelluloses, with a cupric reduction equal to that of an oxycellulose directly prepared by the action of HClO_{3}. On the other hand, by treatment with ammonium sulphide at 35°-40° 'denitrated' products were obtained without action on alkaline copper solutions.

OXYCELLULOSES AND THE MOLECULAR WEIGHT OF CELLULOSE.

H. NASTUKOFF (Berl. Ber. 33 [13] 2237).

(p. 61) The author continues his investigations of the oxidation of cellulose. [Compare Bull. Mulhouse, 1892.] The products described were obtained by the action of hypochlorites and permanganates upon Swedish filter paper (Schleicher and Schüll).

4. _Oxidation by hypochlorites._--(1) The cellulose was digested 24 hrs. with 35 times its weight of a filtered solution of bleaching power of 4°B.; afterwards drained and exposed for 24 hrs. to the atmosphere. These treatments were then repeated. After washing, treatment with dilute acetic acid and again washing, the product was treated with a 10 p.ct. NaOH solution. The oxycellulose was precipitated from the filtered solution: yield 45 p.ct. The residue when purified amounted to 30 p.ct. of the original cellulose, with which it was identical in all essential properties.

The oxycellulose, after purification, dried at 110°, gave the following analytical numbers:

C 43.64 43.78 43.32 43.13 H 6.17 6.21 5.98 6.08

Its compound with phenylhydrazine (_loc. cit._) gave the following analytical numbers:

N 0.78 0.96 0.84

(2) The reagents were as in (1), but the conditions varied by passing a stream of carbonic acid gas through the solution contained in a flask, until Cl compounds ceased to be given off. The analysis of the purified oxycellulose gave C 43.53, H 6.13.

(3) The conditions were as in (2), but a much stronger hypochlorite solution--viz. 12°B.--was employed. The yield of oxycellulose precipitated from solution in soda lye (10 p.ct. NaOH) was 45 p.ct. There was only a slight residue of unattacked cellulose. The analytical numbers obtained were:

Oxycellulose C 43.31 43.74 43.69 " H 6.47 6.42 6.51 ________________________

Phenylhydrazine compound N 0.62 0.81

B. _Oxidation by permanganate_ (KMnO_{4}). (1) The cellulose 16 grms. was treated with 1100 c.c. of a 1 p.ct. solution of KMnO_{4} in successive portions. The MnO_{2} was removed from time to time by digesting the product with a dilute sulphuric acid (10 p.ct. H_{2}SO_{4}). The oxycellulose was purified as before, yield 40 p.ct. Analytical numbers:

Oxycellulose C 42.12 42.9 " H 6.20 6.11 ________________________

Phenylhydrazine compound N 1.35 1.08 1.21

(2) The cellulose (16 grms.) was digested 14 days with 2500 c.c. of 1 p.ct. KMnO_{4} solution. The purified oxycellulose was identical in all respects with the above: yield 40 p.ct. C 42.66, H 6.19.

(3) The cellulose (16 grms.) was heated in the water-bath with 1600 c.c. of 15 p.ct. H_{2}SO_{4} to which were added 18 grms. KMnO_{4}. The yield and composition of the oxycellulose was identical with the above. It appears from these results that the oxidation with hypochlorites acids 1 atom of O to 4-6 of the unit groups C_{6}H_{10}O_{5}; and the oxidation with permanganate 2 atoms O per 4-6 units of C_{6}H_{10}O_{5}. The molecular proportion of N in the phenylhydrazine residue combining is fractional, representing 1 atom O, i.e. 1 CO group reacting per 4 C_{36}H_{60}O_{31} and 6 C_{24}H_{49}O_{21} respectively, assuming the reaction to be a hydrazone reaction.

Further investigations of the oxycelluloses by treatment with (a) sodium amalgam, (b) bromine (water), and (c) dilute nitric acid at 110°, led to no positive results.

By treatment with alcoholic soda (NaOH) the products were resolved into a soluble and insoluble portion, the properties of the latter being those of a cellulose (hydrate).

_Molecular weight of cellulose and oxycellulose._--The author endeavours to arrive at numbers expressing these relations by converting the substances into acetates by Schutzenberger's method, and observing the boiling-points of their solution in nitrobenzene.

FERMENTATION OF CELLULOSE

V. OMELIANSKI (Compt. Rend., 1897, 125, 1131-1133).

Pure paper was allowed to ferment in the presence of calcium carbonate at a temperature of 35° for 13 months. The products obtained from 3.4743 grams of paper were: acids of the acetic series, 2.2402 grams; carbonic anhydride, 0.9722 grams; and hydrogen, 0.0138 gram. The acids were chiefly acetic and butyric acid, the ratio of the former to the latter being 1.7 : 1. Small quantities of valeric acid, higher alcohols, and odorous products were formed.

The absence of methane from the products of fermentation is remarkable, but the formation of this gas seems to be due to a special organism readily distinguishable from the ferment that produces the fatty acids. This organism is at present under investigation.

* * * * *

(p. 75) ~Constitution of Cellulose.~--It may be fairly premised that the problem of the constitution of cellulose cannot be solved independently of that of molecular aggregation. We find in effect that the structural properties of cellulose and its derivatives are directly connected with their constitution. So far we have only a superficial perception of this correlation. We know that a fibrous cellulose treated with acids or alkalis in such a way that only hydrolytic changes can take place is converted into a variety of forms of very different structural characteristics, and these products, while still preserving the main chemical characteristics of the original, show when converted into derivatives by simple synthesis, _e.g._ esters and sulphocarbonates, a corresponding differentiation of the physical properties of these derivatives, from the normal standard, and therefore that the new reacting unit determines a new physical aggregate. Thus the sulphocarbonate of a 'hydrocellulose' is formed with lower proportions of alkaline hydrate and carbon disulphide, gives solutions of relatively low viscosity, and, when decomposed to give a film or thread of the regenerated cellulose, these are found to be deficient in strength and elasticity. Similarly with the acetate. The normal acetate gives solutions of high viscosity, films of considerable tenacity, and when those are saponified the cellulose is regenerated as an unbroken film. The acetates of hydrolysed celluloses manifest a retrogradation in structural and physical properties, proportioned to the degree of hydrolysis of the original.

We may take this opportunity of pointing out that the celluloses not only suggest with some definiteness the connection of the structural properties of visible aggregates--that is, of matter in the mass--with the configuration of the chemical molecule or reacting unit, but supply unique material for the actual experimental investigation of the problems involved. Of all the 'organic' colloids cellulose is the only one which can be converted into a variety of derivative forms, from each of which a regular solid can be produced in continuous length and of any prescribed dimensions. Thus we can compare the structural properties of cellulose with those of its hydrates, nitrates, acetates, and benzoates, in terms of measurements of breaking strain, extensibility, elasticity. Investigations in this field are being prosecuted, but the results are not as yet sufficiently elaborated for reduction to formulæ. One striking general conclusion is, however, established, and that is that the structural properties of cellulose are but little affected by esterification and appear therefore to be a function of the special arrangement of the carbon atoms, i.e. of the molecular constitution. Also it is established that the molecular aggregate which constitutes a cellulose is of a resistant type, and undoubtedly persists in the solutions of the compounds.

It may be urged that it is superfluous to import these questions of mass-aggregation into the problem of the chemical constitution of cellulose. But we shall find that the point again arises in attempting to define the reacting unit, which is another term for the molecule. In the majority of cases we rely for this upon physical measurements; and in fact the purely chemical determination of such quantities is inferential. Attempts have been made to determine the molecular weights of the cellulose esters in solution, by observations of depression of solidifying and boiling-points. But the numbers have little value. The only other well-defined compound is the sulphocarbonate. It has been pointed out that, by successive precipitations of this compound, there occurs a continual aggregation of the cellulose with dissociation of the alkali and CS residues and it has been found impossible to assign a limit to the dissociation, i.e. to fix a point at which the transition from soluble sulphocarbonate to insoluble cellulose takes place.

On these grounds it will be seen we are reduced to a somewhat speculative treatment of the hypothetical ultimate unit group, which is taken as of C_{6} dimensions.

As there has been no addition of experimental facts directly contributing to the solution of the problem, the material available for a discussion of the probabilities remains very much as stated in the first edition, pp. 75-77. It is now generally admitted that the tetracetate _n_ [C_{6}H_{6}O.(OAc)_{4}] is a normal cellulose ester; therefore that four of the five O atoms are hydroxylic. The fifth is undoubtedly carbonyl oxygen. The reactions of cellulose certainly indicate that the CO- group is ketonic rather than aldehydic. Even when attacked by strong sulphuric acid the resolution proceeds some considerable way before products are obtained reducing Fehling's solution. This is not easily reconcilable with any polyaldose formula. Nor is the resistance of cellulose to very severe alkaline treatments. The probability may be noted here that under the action of the alkaline hydrates there occurs a change of configuration. Lobry de Bruyn's researches on the change of position of the typical CO- group of the simple hexoses, in presence of alkalis, point very definitely in this direction. It is probable that in the formation of alkali cellulose there is a constitutional change of the cellulose, which may in effect be due to a migration of a CO- position within the unit group. Again also we have the interesting fact that structural changes accompany the chemical reaction. It is surprising that there should have been no investigation of these changes of external form and structure, otherwise than as mass effects. We cannot, therefore, say what may be the molecular interpretation of these effects. It has not yet been determined whether there are any intrinsic volume changes in the cellulose substance itself: and as regards what changes are determined in the reacting unit or molecule, we can only note a fruitful subject for future investigation. _A priori_ our views of the probable changes depend upon the assumed constitution of the unit group. If of the ordinary carbohydrate type, formulated with an open chain, there is little to surmise beyond the change of position of a CO- group. But alternative formulæ have been proposed. Thus the tetracetate is a derivative to be reckoned with in the problem. It is formed under conditions which preclude constitutional changes within the unit groups. The temperature of the main reaction is 30°-40°, the reagents are used but little in excess of the quantitative proportions, and the yields are approximately quantitative. If now the derivative is formed entirely without the hydrolysis the empirical formula C_{6}H_{6}O.(OAc)_{4} justifies a closed-ring formula for the original viz. CO<[CHOH]_{4}>CH_{2}; and the preference for this formula depends upon the explanation it affords of the aggregation of the groups by way of CO-CH_{2} synthesis.

The exact relationship of the tetracetate to the original cellulose is somewhat difficult to determine. The starting-point is a cellulose hydrate, since it is the product obtained by decomposition of the sulphocarbonate. The degree of _hydrolysis_ attending the cycle of reactions is indicated by the formula 4 C_{6}H_{10}O_{5}.H_{2}O. It has been already shown that this degree of hydrolysis does not produce molecular disaggregation. If this hydrate survived the acetylation it would of course affect the empirical composition, i.e. chiefly the carbon percentage, of the product. It may be here pointed out that the extreme variation of the carbon in this group of carbohydrate esters is as between C_{14}H_{20}O_{10} (C = 48.3 p.ct.) and C_{14}H_{18}O_{9} (C = 50.8 p.ct.) i.e. a tetracetate of C_{6}H_{12}O_{6} and C_{6}H_{10}O_{5} respectively. In the fractional intermediate terms it is clear that we come within the range of ordinary experimental errors, and to solve this critical point by way of ultimate analysis must involve an extended series of analyses with precautions for specially minimising and quantifying the error. The determination of the acetyl by saponification is also subject to an error sufficiently large to preclude the results being applied to solve the point. While, therefore, we must defer the final statement as to whether the tetracetate is produced from or contains a partly hydrolysed cellulose molecule, it is clear that at least a large proportion of the unit groups must be acetylated in the proportion C_{6}H_{6}O.(OAc)_{4}.

It has been shown that by the method of Franchimont a higher proportion of acetyl groups can be introduced; but this result involves a destructive hydrolysis of the cellulose: the acetates are not derivatives of cellulose, but of products of hydrolytic decomposition.

It appears, therefore, that with the normal limit of acetylation at the tetracetate the aggregation of the unit groups must depend upon the CO- groups and a ring formula of the general form CO<[CHOH]_{4}>CH_{2} is consistent with the facts.

Vignon has proposed for cellulose the constitutional formula

O------CH | | \ | O \[CHOH]_{3} | | / CH_{2}-CH/