PROBLEM OF ITS CONSTITUTION
UEBER CELLULOSE.
G. BUMCKE und R. WOLFFENSTEIN (Berl. Ber., 1899, 2493).
(p. 54) _Theoretical Preface._--The purpose of these investigations is
the closer characterisation of the products known as 'oxycellulose' and
'hydracellulose,' which are empirical aggregates obtained by various
processes of oxidation and hydrolysis; these processes act concurrently
in the production of the oxycelluloses. The action of hydrogen peroxide
was specially investigated. An oxycellulose resulted possessing strongly
marked aldehydic characteristics. The authors commit themselves to an
explanation of this paradoxical result, i.e. the production of a body
of strongly 'reducing' properties by the action of an oxidising agent
upon the inert cellulose molecule (? aggregate) as due to the
_hydrolytic_ action of the peroxide: following Wurster (Ber. 22, 145),
who similarly explained the production of reducing sugars from cane
sugar by the action of the peroxide.
The product in question is accordingly termed _hydralcellulose_. By the
action of alkalis this is resolved into two bodies of alcoholic
(cellulose) and acid ('acid cellulose') characteristics respectively.
The latter in drying passes into a lactone. The acid product is also
obtained from cellulose by the action of alkaline lye (boiling 30 p.ct.
NaOH) and by solution in Schweizer's reagent.
It is considered probable that the cellulose nitrates are hydrocellulose
derivatives, and experimental evidence in favour of this conclusion is
supplied by the results of 'nitrating' the celluloses and their oxy- and
hydro- derivatives. Identical products were obtained.
_Experimental investigations._--The filter paper employed as 'original
cellulose,' giving the following numbers on analysis:
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 formulae:
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 deg. 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 UeBER 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 deg., 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 deg. (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 deg. 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 deg., 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 deg., 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 deg. B.) 4.39
Cotton mercerised (NaOH 40 deg. 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 deg.-40 deg. '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 Schuell).
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 deg.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 deg., 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 deg.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 deg., 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 deg. 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 formulae. 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 formulae 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 deg.-40 deg., 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/
with reference to the highest nitrate, and the decomposition of the
nitrate by alkalis with formation of hydroxypyruvic acid. While these
reactions afford no very sure ground for deductions as to constitutional
relationships, it certainly appears that, if the aldose view of the unit
group is to be retained, this form of the anhydride contains suggestions
of the general tendency of the celluloses on treatment with condensing
acids to split off formic acid in relatively large quantity [Ber. 1895,
1940]; the condensation of the oxycelluloses to furfural; the
non-formation of the normal hydroxy-dicarboxylic acids by nitric acid
oxidations. Indirectly we may point out that any hypothesis which
retains the polyaldose view of cellulose, and so fails to differentiate
its constitution from that of starch, has little promise of progress.
The above formula, moreover, concerns the assumed unit group, with no
suggestion as to the mode of aggregation in the cellulose complex. Also
there is no suggestion as to how far the formula is applicable to the
celluloses considered as a group. In extending this view to the
oxycelluloses, Vignon introduces the derived oxidised group
CHO.(CHOH)_{3}.CH . CO
|_O__|
--of which one is apportioned to three or four groups of the cellulose
previously formulated: these groups in condensed union together
constitute an oxycellulose.
These views are in agreement with the experimental results obtained by
Faber and Tollens (p. 71). They regard the oxycelluloses as compounds of
'celloxin' C_{6}H_8{O}_{6} with 1-4 mols. unaltered cellulose; and the
former they particularly refer to as a lactone of glycuronic acid. But
on boiling with lime they obtain dioxybutyric and isosaccharinic acids;
both of which are not very obviously related to the compounds formulated
by Vignon. We revert with preference to a definitely ketonic formula,
for which, moreover, some farther grounds remain to be mentioned. In the
systematic investigation of the nitric esters of the carbohydrates (p.
41) Will and Lenze have definitely differentiated the ketoses from the
aldoses, as showing an internal condensation accompanying the ester
reaction. Not only are the OH groups taking part in the latter
consequently less by two than in the corresponding aldoses, but the
nitrates show a much increased stability. This would give a simple
explanation of the well-known facts obtaining in the corresponding
esters of the normal cellulose. We may note here that an important item
in the quantitative factors of the cellulose nitric ester reaction has
been overlooked: that is, the yield calculated to the NO_{3} groups
fixed. The theoretical yields for the higher nitrates are
Yield p.ct. N p.ct.
of cellulose of nitrate
Pentanitrate 169 12.7
Hexanitrate 183 14.1
From such statistics as are recorded the yields are not in accordance
with the above. There is a sensible deficiency. Thus Will and Lenze
record a yield of 170 p.ct. for a product with 13.8 p.ct. N, indicating
a deficiency of about 10 p.ct. As the by-products soluble in the acid
mixture are extremely small, the deficiency represents approximately the
water split off by an internal reaction. In this important point the
celluloses behave as ketoses.
In the lignocelluloses the condensed constituents of the complex are of
well-marked ketonic, i.e. quinonic, type. In 'nitrating' the
lignocelluloses this phenomenon of internal condensation is much more
pronounced (see p. 131). As the reaction is mainly confined to the
cellulose of the fibre, we have this additional evidence that the
typical carbonyl is of ketonic function. It is still an open question
whether the cellulose constituents of the lignocelluloses are
progressively condensed--with progress of 'lignification'--to the
unsaturated or lignone groups. There is much in favour of this view,
the evidence being dealt with in the first edition, p. 180. The
transition from a cellulose-ketone to the lignone-ketone involves a
simple condensation without rearrangement; from which we may argue back
to the greater probability of the ketonic structure of the cellulose. We
must note, however, that the celluloses of the lignocelluloses are
obtained as residues of various reactions, and are not homogeneous. They
yield on boiling with condensing acids from 6 to 9 p.ct. furfural. It is
usual to regard furfural as invariably produced from a pentose residue.
But this interpretation ignores a number of other probable sources of
the aldehyde. It must be particularly remembered that laevulose is
readily condensed (a) to a methylhydroxyfurfural
C_{6}H_{1}O_{6} - 3H_{2}O = C_{6}H_{6}O_{3} = C_{5}(OH).H_{2}.(CH_{3})O_{2}
and (b) by HBr, with further loss of OH, as under:
C_{6}H_{12}O_{6} - 4H_{2}O + HBr = C_{5}H_{3}(CH_{2}Br)O
and generally the ketoses are distinguished from the aldoses by their
susceptibility to condensation. Such condensation of laevulose has been
effected by two methods: (a) by heating the concentrated aqueous
solution with a small proportion of oxalic acid at 3 atm. pressure
[Kiermayer, Chem. Ztg. 19, 100]; (b) by the action of hydrobromic acid
(gas) in presence of anhydrous ether; the actual compound obtained being
the omega-brommethyl derivative [Fenton, J. Chem. Soc. 1899, 423].
This latter method is being extended to the investigation of typical
celluloses, and the results appear to confirm the view that cellulose
may be of ketonic constitution.
The evidence which is obtainable from the synthetical side of the
question rests of course mainly upon the physiological basis. There are
two points which may be noted. Since the researches of Brown and Morris
(J. Chem. Soc. 1893, 604) have altered our views of the relationships of
starch and cane sugar to the assimilation process, and have placed the
latter in the position of a primary product with starch as a species of
overflow and reserve product, it appears that laevulose must play an
important part in the elaboration of cellulose. Moreover, A. J. Brown,
in studying the cellulosic cell-collecting envelope produced by the
_Bacterium xylinum_, found that the proportion of this product to the
carbohydrate disappearing under the action of the ferment was highest in
the case of laevulose. These facts being also taken into consideration
there is a concurrence of suggestion that the typical CO group in the
celluloses is of ketonic character. That the typical cotton cellulose
breaks down finally under the action of sulphuric acid to dextrose
cannot be held to prove the aldehydic position of the carbonyls in the
unit groups of the actual cellulose molecule or aggregate.
We again are confronted with the problem of the aggregate and as to how
far it may affect the constitution of the unit groups. That it modifies
the functions or reactivity of the ultimate constituent groups we have
seen from the study of the esters. Thus with the direct ester reactions
the normal fibrous cellulose (C_{6}H_{16}O_{5}) yields a monoacetate,
dibenzoate, and a trinitrate respectively under conditions which
determine, with the simple hexoses and anhydrides, the maximum
esterification, i.e. all the OH groups reacting. If the OH groups are of
variable function, we should expect the CO groups _a fortiori_ to be
susceptible of change of function, i.e. of position within the unit
groups.
But as to how far this is a problem of the constitution or phases of
constitution of the unit groups or of the aggregate under reaction we
have as yet no grounds to determine.
The subjoined communication, appearing after the completion of the MS.
of the book, and belonging to a date subsequent to the period intended
to be covered, is nevertheless included by reason of its exceptional
importance and special bearing on the constitutional problem above
discussed.
~THE ACTION OF HYDROGEN BROMINE ON CARBOHYDRATES.~[4]
H. J. H. FENTON and MILDRED GOSTLING (J. Chem. Soc., 1901, 361).
The authors have shown in a previous communication (Trans., 1898, 73,
554) that certain classes of carbohydrates when acted upon at the
ordinary temperature with dry hydrogen bromide in ethereal solution give
an intense and beautiful purple colour.[5] It was further shown (Trans.,
1899, 75, 423) that this purple substance, when neutralised with sodium
carbonate and extracted with ether, yields golden-yellow prisms of
omega-brommethylfurfural,
CH:C.CH_{2}Br
| |
| O
| |
CH:C.CHO.
This reaction is produced by laevulose, sorbose, cane sugar, and inulin,
an intense colour being given within an hour or two. Dextrose, maltose,
milk sugar, galactose, and the polyhydric alcohols give, if anything,
only insignificant colours, and these only after long standing. The
authors therefore suggested that the reaction might be employed as a
means of distinguishing these classes of carbohydrates, the rapid
production of the purple colour being indicative of _ketohexoses_, or of
substances which produce these by hydrolysis.
By relying only on the production of the purple colour, however, a
mistake might possibly arise, owing to the fact that _xylose_ gives a
somewhat similar colour after standing for a few hours. Hence, the
observations should be confirmed by isolation of the crystals of
brommethylfurfural. No trace of this substance is obtained from the
xylose product.
In order to identify the substance, the ether extract, after
neutralisation, is allowed to evaporate to a syrup, and crystallisation
promoted either by rubbing with a glass rod, or by the more certain and
highly characteristic method of 'sowing' with the most minute trace of
omega-brommethylfurfural, when crystals are almost instantly formed.
These are recrystallised from ether, or a mixture of ether and light
petroleum, and further identified by the melting-point (59.5-60.5 deg.),
and, if considered desirable, by estimation of the bromine.
It is now found, so reactive is the bromine atom in this compound, that
the estimation may be accurately made by titration with silver nitrate
according to Volhard's process, the crystals for this purpose being
dissolved in dilute alcohol:
0.1970 gram required 10.5 c.c. _N_/10 AgNO_{3}. Br = 42.63
p.ct., calculated 42.32 p.ct.
This method of applying hydrogen bromide in ethereal solution is, of
course, unsuitable for investigations where a higher temperature has to
be employed, or where long standing is necessary, since, under such
circumstances, the ether itself is attacked. Wishing to make
investigations under these conditions, the authors have tried several
solvents, and, at present, find that chloroform is best suited to the
purpose. In each of the following experiments, 10 grms. of the
substance were covered with 250 c.c. of chloroform which had been
saturated at 0 deg. with dry hydrogen bromide. The mixture was contained in
an accurately stoppered bottle, firmly secured with an iron clamp, and
heated in a water-bath to about the boiling temperature for two hours.
After standing for several hours, the mixture was treated with sodium
carbonate (first anhydrous solid, and afterwards a few drops of strong
solution), filtered, and the solution dried over calcium chloride. Most
of the chloroform was then distilled off, and the remaining solution
allowed to evaporate to a thick syrup in a weighed dish.
The product was then tested for omega-brommethylfurfural by 'sowing'
with the most minute trace of the substance, as described above. It was
then warmed on a water-oven, kept in a vacuum desiccator over solid
paraffin, and the weight estimated. When necessary, the product was
recrystallised from ether, and further identified by the tests
mentioned. The following results were obtained:
Weight of
crude residue.
Swedish filter paper 3.0 crystallised at once by 'sowing.'
Ordinary cotton 3.3 " "
Mercerised cotton 2.1 " "
Straw cellulose[6] 2.3 " "
Laevulose 2.2 " "
Inulin 1.3 " "
Potato starch 0.37 " "
Cane sugar 0.85 " "
Dextrose 0.33 uncrystallisable.
Milk sugar 0.37 "
Glycogen 0.34 "
Galactose 0.34 "
The products from _dextrose_, _milk sugar_, and _galactose_ absolutely
refused to crystallise even when extracted with ether and again
evaporated, or by 'sowing,' stirring, &c.
The _glycogen_ product deposited a very small amount of crystalline
matter on standing, but the quantity was too minute for examination;
moreover, it refused altogether to crystallise in contact with the
aldehyde. It may fairly be stated, therefore, that these last four
substances give absolutely negative results as regards the formation of
omega-brommethylfurfural; if any is formed, its quantity is altogether
too small to be detected.
The specimen of _starch_ examined was freshly prepared from potato, and
purified by digestion for twenty-four hours each with _N_/10 KOH, _N_/4
HCl, and strong alcohol; it was then washed with water and allowed to
dry in the air. It will be seen that this substance gave a positive
result, but that the yield was extremely small, and might yet be due to
impurity. Considering the importance of the behaviour of starch, for the
purpose of drawing general conclusions from these observations, it was
thought advisable to make further experiments with specimens which could
be relied upon, and also to investigate the behaviour of dextrin. This
the authors have been enabled to do upon a series of specimens specially
prepared by C. O'Sullivan, and thus described by him:
1. Rice starch, specially purified by the permanganate method.
2. Wheat starch " " "
3. Oat starch, contains traces of oil, washed with dilute KOH
and dilute HCl.
4. Pea starch, first crop, washed with alkali, acid (HCl), and
strong alcohol.
5. Natural dextrin, D = 3.87, alpha_{D} = 194.7; K = 0.95, (c
2.628).
6. alpha-Dextrin, C equation purified without fermentation, 30
precipitations with alcohol (Trans., 1879, 35, 772).
The examination of these specimens was conducted on a smaller scale, but
under the same conditions as before, _one gram_ of the substance being
treated with 12.5 c.c. of the saturated chloroform solution and heated
in sealed tubes for two hours as above. The results were as follows:
Weight of
crude residue.
1. Rice starch 0.046 crystallised at once by 'sowing.'
2. Wheat starch 0.044 " "
3. Oat starch 0.049 " "
4. Pea starch 0.064 " "
5. Natural dextrin 0.088 " "
6. alpha-Dextrin 0.055 " "
The results may therefore be summarised as follows:--Treated under these
particular conditions all forms of cellulose give large yields of
omega-brommethylfurfural, some varieties giving as much as 33 per cent.
Laevulose, inulin, and cane sugar give yields varying from 22 to 8.5 per
cent.; various starches give small yields (average about 4.5 per cent.);
and dextrins 5 to 8 per cent., whereas dextrose, milk sugar, and
galactose give, apparently, none at all.
The yields represent the solid crystalline residue; this when purified
by recrystallisation gives, probably, about three-quarters of its weight
of pure crystals. (In the case of dextrose, &c., the yields represent
the weight of syrup.)
These numbers, however, by no means represent the maximum yields
obtainable, owing to the comparatively slight solubility of hydrogen
bromide in chloroform. The process was conducted in the above manner
only for the sake of uniform comparison. The ether method previously
described gives much larger yields; for example, 12 grms. of inulin
treated with only 60 c.c. of the saturated ether gave 2.5 grms. of
substance. For the purpose of obtaining larger yields, other methods are
being investigated.
The facts recorded above, taken in conjunction with those given in our
previous communications, appear to point definitely to the following
general conclusions. First, that the various forms of _cellulose_
contain one or more groups or nuclei identical with that contained in
_laevulose_, and that such groups constitute the main or essential part
of the molecule. Secondly, that similar groupings are contained in
_starches_ and _dextrins_, but that the proportion of such groupings
represents a relatively small part of the whole structure.
The nature of this grouping is, according to the generally accepted
constitution of _laevulose_, the six-carbon chain with a ketonic group:
C.C.C.C.C.C
|| .
O
But the results might, on the other hand, be considered indicative of
the anhydride or 'lacton' grouping, which Tollens suggested for
laevulose:
C.C.C.C.C.C
\ /
\ / .
O
The latter very simply represents the formation of
omega-brommethylfurfural from laevulose,[7]
------O-----
| H H |
| | | |
OH.C-----C---C---C--C-----CH_{2}.OH
H_{2} OH OH OH H
giving
H H
HC.C:C.C:C.CH_{2}Br
|| \ / ,
O \ /
O
although by a little further 'manipulation' of the symbols the change
could, of course, be represented by reference to the ketonic formula.
~The Ketonic Constitution of Cellulose.~
C. F. CROSS and E. J. BEVAN (J. Chem. Soc., 1901, 366).
In this paper the authors discuss more fully the theoretical bearings of
the observations of Fenton and Gostling, the two papers being
simultaneously communicated. The paper is mainly devoted to a review of
the antecedent evidence, chemical and physiological, and to a general
summing up in favour of the view that cellulose is a polyketose
(anhydride).
* * * * *
(p. 79) ~Composition of the Seed Hair of Eriodendron~ (~Anf.~)--Some
interest attaches to the results of an analytical investigation which we
have made of this silky floss. There is little doubt that cotton is
entirely exceptional in its characteristics: both in structure and
chemical composition it fails to show any adaptation to what we may
regard as the _more obvious_ functions of a seed hair--which certainly
do not demand either structural strength or chemical resistance. The
following numbers determined for the kapok differentiate it widely from
the cottons:
Ash, 1.3; moisture, 9.3; alkaline hydrolysis (loss) (a) 16.7,
(b) 21.8. Cellulose, by chlorination, &c., 71.1.
In reacting with chloride it shows the presence of unsaturated groups,
similar to the lignone of the woods. This was confirmed by a
well-marked reaction with ferric ferricyanide with increase of weight
due to the fixation of the blue cyanide.
But the most characteristic feature is the high yield of furfural on
boiling with condensing acids. The following numbers were determined:
Total furfural from original fibre 14.84
In residue from alkali hydrolysis 11.5
In cellulose isolated by Cl method 10.4
Treated with sulphuric acids of concentration, (a) 92.1 grs.
H_{2}SO_{4} per 100 c.c., (b) 105.8 grs. per 100 c.c., the fibres
dissolve, and diluted immediately after complete solution it was
resolved into
(a) (b)
Reprecipitated fraction 68.7 43.7
Soluble fraction yielding furfural 13.2 14.3
By these observations it is established that the furfuroids are of the
cellulose type and behave very much as the furfuroids of the cereal
celluloses.
This group of seed hairs invites exhaustive investigation. The furfuroid
constituents are easily isolated, and as they constitute at least
one-third of the fibre substance it is especially from this point of
view that they invite study.
RECHERCHES SUR L'OXYCELLULOSE.
L. VIGNON.
~Resume of investigations (1898-1900) of Oxycellulose, published as a
brochure~ (Rey, Lyon, 1900).
(a) A typical oxycellulose prepared from cotton cellulose by the
action of HClO_{3} (HCl + KClO_{3}) in dilute solution at 100 deg. for one
hour gave the following numbers:
C H O
Elementary composition 43.55 6.03 50.42
Oxycellulose Original cellulose
Analysis by Lange's method
Soluble in KOH (at 180 deg.) 87.6 12.0
Insoluble in KOH (at 180 deg.) 12.4 88.0
Oxycellulose Original cellulose
Heat of combustion 4124-4133 4190-4224
Heat evolved in contact with 50 times wt.}
normal KOH per 100 grms. } 1.3 cal. 0.74 cal.
Oxycellulose Cellulose
Absorption of colouring } Saffranine 0.7 0.0
matters at 100 deg. per 100 grms. } Methylene blue 0.6 0.2
(b) _Yield of furfural from cellulose, oxy- and
hydro-cellulose._--From the hydrocelluloses variously prepared the
author obtains 0.8 p.ct. furfural; from bleached cotton 1.8 p.ct.; and
from the oxycelluloses variously prepared 2.0-3.5 p.ct. The 'furfuroid'
is relatively more soluble in alkaline solutions (KOH) in the cold. The
insoluble residue is a normal cellulose.
(c) _Nitrates of cellulose, oxy- and hydro-cellulose._--Treated with
the usual acid mixture (H_{2}SO_{4} 3 p., HNO_{3} 1 p.) under conditions
for maximum action, the resulting esters showed uniformly a fixation of
11.0 NO_{2} groups per unit mol. of C_{24}. The oxycellulose nitrate
was treated directly with dilute solution of potassium hydrate in the
cold. From the products of decomposition the author obtained the osazone
of hydroxypyruvic acid [Will, Ber. 24, 400].
(d) _Osazones of the oxycelluloses._--Oxycelluloses prepared by
various methods are found to fix varying proportions of phenylhydrazine
(residue), viz. from 3.4-8.5 p.ct. of the cellulose derivative reacting,
corresponding with, i.e. calculated from, the nitrogen determined in the
products (0.87-2.2 p.ct.). The reaction is assumed to be that of osazone
formation.
The author has also established a relation between the phenylhydrazine
fixed and the furfural which the substance yields on boiling with
condensing acids. This is illustrated by the subjoined series of
numbers:
Phenylhydrazine Furfural
Fixed p.ct. formed p.ct.
Cotton (bleached) 1.73 1.60
Oxycellulose (HClO_{3}) 7.94 2.09
" (HClO) 3.37 1.79
" (CrO_{3}) (1) 7.03 3.00
" (CrO_{3}) (2) 7.71 3.09
" (CrO_{3}) (3) 8.48 3.50
(e) _Constitution of cellulose and oxycellulose._--The results of
these investigations are generalised as regards cellulose (C_6) by the
constitutional formula
CH--CH_{2}
/ | |
(CHOH)_{3} O |
\ | |
CH--O .
The oxycelluloses contain the characteristic group
COH
/
(CHOH)_{3}
\
CH--CO
\ /
O
in union with varying proportions of residual cellulose.
QUANTITATIVE SEPARATION OF CELLULOSE-LIKE CARBOHYDRATES IN VEGETABLE
SUBSTANCES.
WILHELM HOFFMEISTER (Landw. Versuchs-Stat., 1897, 48, 401-411).
To separate the hemicelluloses, celluloses, and the constituents of
lignin without essential change, the substance, after being freed from
fat, is extracted with dilute hydrochloric acid and ammonia, and the
residue frequently agitated for a day or two with 5-6 p.ct. caustic soda
solution. It is then diluted, the extract poured off, neutralised with
hydrochloric acid, treated with sufficient alcohol, and the
hemicellulose filtered, dried, and weighed. The residue from the soda
extract is washed on a filter with hot water, and extracted with
Schweizer's reagent.
When the final residue (lignin) is subjected to prolonged extraction
with boiling dilute ammonia (a suitable apparatus is described, with
sketch) until the ammonia is no longer coloured, a residue is obtained
which mostly dissolves in Schweizer's reagent, and on repeating the
process the residue is found to consist largely of mineral matter. The
dissolved cellulose-like substances often contain considerable amounts
of pentosanes.
According to the nature of the substance, the extraction with ammonia
may take weeks, or months, or even longer; the ammonia extracts of hard
woods (as lignum vitae) and of cork are dark brown, and give an odour of
vanilla when evaporated down. The residues, which are insoluble in
water, but redissolve in ammonia, have the properties of humic acids.
Other vegetable substances, when extracted, yielded, besides humic
acids, a compound, C_{6}H_{7}O_{2}, soluble in alcohol and chloroform,
but insoluble in water, ether, and benzene; preparations from different
sources melted between 200 deg. and 210 deg..
FOOTNOTES:
[4] The original paper is reproduced with slight alterations.
[5] This purple colour would appear to be due to a highly dissociable
compound of omega-brommethylfurfural with hydrogen bromide. The aldehyde
gives yellow or colourless solutions in various solvents, which are
turned purple by a sufficient excess of hydrogen bromide. Dilution, or
addition of water, at once discharges the colour.
[6] Other forms of cellulose were also examined--for example, pinewood
cellulose--and the substances separated from solution as thiocarbonate
(powder and film). All of these gave good yields of
omega-brommethylfurfural.
[7] The change is empirically represented as
C_{6}H_{12}O_{6} + HBr - 4H_{2}O = C_{6}H_{5}O_{2}Br.