CONSTITUENTS GENERALLY
(1) ~Reactions of the Carbohydrates with Hydrogen Peroxide.~
C. F. CROSS, E. J. BEVAN, and CLAUD SMITH (J. Chem. Soc., 1898, 463).
(2) ~Action of Hydrogen Peroxide on Carbohydrates in the Presence of
Ferrous Salts.~
R. S. MORRELL and J. M. CROFTS (J. Chem. Soc., 1899, 786).
(3) ~Oxidation of Furfuraldehyde by Hydrogen Peroxide.~
C. F. CROSS, E. J. BEVAN, and T. HEIBERG (J. Ch. Soc., 1899, 747).
(4) EINWIRKUNG VON WASSERSTOFFHYPEROXID AUF UNGESAeTTIGTE
KOHLENWASSERSTOFFE.
C. F. CROSS, E. J. BEVAN, and T. HEIBERG (Berl. Ber., 1900, 2015).
~ACTION OF HYDROGEN PEROXIDE ON UNSATURATED HYDROCARBONS.~
The above series of researches grew out of the observations incidental
to the use of the peroxide on an oxidising agent in investigating the
hydrolysed furfuroids (102). Certain remarkable observations had
previously been made by H. J. H. Fenton (Ch. Soc. J., 1894, 899; 1895,
774; 1896, 546) on the oxidation of tartaric acid by the peroxide,
acting in presence of ferrous salts, the --CHOH--CHOH-- residue losing
H_{2} with production of the unsaturated group, --OH.C=C.OH--. These
investigations have subsequently been considerably developed and
generalised by Fenton, but as the results have no immediate bearing on
our main subject we must refer readers to the J. Chem. Soc., 1896-1900.
From the mode of action diagnosed by Fenton it was to be expected that
the CHOH groups of the carbohydrates would be oxidised to CO groups, and
it has been established by the above investigations (1) and (2) that the
particular group to be so affected in the hexoses is that contiguous to
the typical
|
--CO
group. There results, therefore, a dicarbonyl derivative ('osone'),
which reacts directly with 2 mol. phenyl hydrazine in the cold to form
an osazone. This was directly established for glucose, laevulose,
galactose, and arabinose (2). While this is the main result, the general
study of the product shows that the oxidation is not simple nor in
direct quantitative relationship to the H_{2}O_{2} employed. The
molecular proportion of the aldoses affected appears to be in
considerable excess, and the reaction is probably complicated by
interior rearrangement.
In the main, the original aldehydic group resists the oxidation. But a
certain proportion of acid products are formed, probably tartronic acid.
On distillation with condensing acids a large proportion of volatile
monobasic acids (chiefly formic) are obtained. The proportion of
furfural obtained amounts to 3-4 per cent. of the weight of the original
carbohydrate.
Since the general result of these oxidations is the substitution of an
OH group for an H atom, it was of interest to determine the behaviour of
furfural with the peroxide. The oxidation was carried out in dilute
aqueous solution of the aldehyde at 20 deg.-40 deg., using 2-3 mols. H_{2}O_{2}
per 1 mol. C_{5}H_{4}O_{2}. The main product is a hydroxyfurfural, which
was separated as a hydrazone. A small quantity of a monobasic acid was
formed, which was identified as a hydroxypyromucic acid. Both aldehyde
and acid appear to be the alpha beta derivatives. The aldehyde gives
very characteristic colour reactions with phloroglucinol and resorcinol
in presence of hydrochloric acid, which so closely resemble those of the
lignocelluloses that there is little doubt that these particular
reactions must be referred to the presence of the hydroxyfurfural as a
normal constituent.
The study of these oxidations was then extended to typical unsaturated
hydrocarbons--viz. acetylene and benzene. (4) From the former the main
product was acetic acid, but the attendant formation of traces of ethyl
alcohol indicates that the hydrogen of the peroxide may take a direct
part in this and other reactions. This view receives some support from
the fact that the interaction of the H_{2}O_{2} with permanganates has
now been established to be an oxidation of the H_{2} of the peroxide by
the permanganate oxidation, with liberation, therefore, of the O_{2} of
the peroxide as an unresolved molecule [Baeyer].
Benzene itself is also powerfully attacked by the peroxide when shaken
with a dilute solution in presence of iron salts. The products are
phenol and pyrocatechol, with some quantity of an amorphous product
probably formed by condensation of a quinone with the phenolic products
of reaction.
* * * * *
These types of oxidation effects now established give a definite
significance to the physiological functions of the peroxide, which is a
form of 'active oxygen' of extremely wide distribution. It would have
been difficult _a priori_ to devise an oxidant without sensible action
on aldehydic groups, yet delivering a powerful attack on hydrocarbon
rings; or to have suggested a synthesis of the sugars from tartaric acid
with a powerful oxidising treatment as the first and essential stage in
the transformation.
Our present knowledge of such actions and effects suggests a number of
new clues to genetic relationships of carbon compounds within the plant.
The conclusion is certainly justified that the origin of the pentoses is
referable to oxidations of the hexoses, in which this form of 'active
oxygen' plays an important part.
We must note here the researches of O. Ruff, who has applied these
oxidations with important results in the systematic investigation of the
carbohydrates.
UEBER DIE VERWANDLUNG DER _D_-GLUCONSAeURE IN _D_-ARABINOSE (Berl. Ber.,
1898, 1573).
~CONVERSION OF _D_-GLUCONIC ACID INTO _D_-ARABINOSE.~
* * * * *
_D_ UND _L_ ARABINOSE (_Ibid._ 1899, 550).
* * * * *
ZUR KENNTNISS DER OXYGLUCONSAeURE (_Ibid._ 1899, 2269).
~ON OXYGLUCONIC ACID.~
Ruff in these researches has realised a simple and direct transition
from the hexoses to the pentoses. By oxidising gluconic acid with the
peroxide the beta --CHOH-- group is converted into carbonyl at the same
time that the terminal COOH [alpha] is oxidised to CO_{2}. The yields of
the resulting pentose are large. Simultaneously there is formed an
oxygluconic acid, which appears to be a ketonic acid of formula
--CH_{2}OH.CO.(CHOH)_{3}.COOH--.
From these results we see a further range of physiological
probabilities; and with the concurrent actions of oxygen in the forms of
or related to hydrogen peroxide on the one side, and ozone on the other,
we are able to account in a simple way for the relationships of the
'furfuroid' group, which may include a number of intermediate terms in
the hexose-pentose series.
Following in this direction of development of the subject is a study of
the action of persulphuric acid upon furfural.
EINWIRKUNG DES CARO'SCHEN REAGENS AUF FURFURAL.
C. F. CROSS, E. J. BEVAN, and J. F. BRIGGS (Berl. Ber., 1900, 3132).
Regarding this reagent as another form of 'active oxygen,' it is
important to contrast its actions with those of the hydrogen peroxide.
Instead of the beta-hydroxyfurfural (_ante_, 115) we obtain the
delta-aldehyde as the first product. The aldehydic group is then
oxidised, and as a result of attendant hydrolysis the ring is broken
down and succinic acid is formed, the original aldehydic group of the
furfural being split off in the form of formic acid. The reactions take
place at the ordinary temperature and with the dilute form of the
reagent described by Baeyer and Villiger (Ber. 32, 3625). These results
have some special features of interest. The alpha delta-hydroxyfurfural
has similar colour reactions to those of the alpha beta-derivative, and
may also therefore be present as a constituent of the lignocelluloses.
The tendency to attack in the 1.4 position in relation to an aldehydic
group further widens the capabilities of 'active oxygen' in the plant
cell. Lastly, this is the simplest transition yet disclosed from the
succinyl to furfural grouping, being effected by a regulated proportion
of oxygen, and under conditions of reaction which may be described as of
the mildest. In regard to the wide-reaching functions of asparagin in
plant life, we have a new suggestion of genetic connections with the
furfuroids.
VERGLEICH DER PENTOSEN-BESTIMMUNGSMETHODEN VERMITTELST PHENYLHYDRAZIN
UND PHLOROGLUCIN.
M. KRUeGER (Inaug.-Diss., Goettingen, 1895).
~COMPARISON OF METHODS OF ESTIMATING FURFURAL AS HYDRAZONE AND
PHLOROGLUCIDE.~
The author traces the development of processes of estimating furfural
(1) by precipitation with ammonia (furfuramide), (2) by volumetric
estimation with standardised phenylhydrazine, (3) by weighing the
hydrazone.
In 1893 (Chem. Ztg. 17, 1745) Hotter described a method of quantitative
condensation with pyrogallol requiring a temperature of 100 deg.-110 deg. for
two hours. The insoluble product collected, washed, dried at 103 deg., and
weighed, gives a weight of 1.974 grm. per 1 grm. furfural.
Councler substitutes phloroglucinol for pyrogallol, with the advantage
of doing away with the digestion at high temperature. (_Ibid._ 18, 966.)
This process, requiring the presence of strong HCl, has the advantage of
being applied directly to the acid distillate, in which form furfural is
obtained as a product of condensation of pentoses, &c. A comparative
investigation was made, precipitating furfural (a) as hydrazone in
presence of acetic acid, and (b) as phloroglucide in presence of HCl
(12 p.ct). In (a) by varying the weights of known quantities of
furfural, and using the factor, hydrazone x 0.516 [+ 0.0104] in
calculating from the weights of precipitates obtained, the maximum
variations from the theoretical number were +1.71 and -1.74. In (b) it
was found necessary to vary the factor from 0.52 to 0.55 in calculating
from phloroglucide to furfural. The greatest _total_ range of variation
was found to be 2.5 p.ct. The phenol process is therefore equally
accurate, has the advantages above noted, and, in addition, is less
liable to error from the pressure in the distillates obtained from
vegetable substances of volatile products, e.g. ketonic compounds,
accompanying the furfural.
This method has been criticised by Helbel and Zeisel [Sitz.-ber, Wiener
Akad. 1895, 104, ii. p. 335] on two grounds of error, viz. (1) the
presence of diresorcinol in all ordinary preparations of phloroglucinol,
and (2) changes in weight of the precipitate of phloroglucide on drying.
The process was carried out comparatively with ordinary preparations,
and with specially pure preparations of the phenol. The quantitative
results were identical. The criticisms in question are therefore
dismissed. Although the process is to be recommended for its simplicity
and the satisfactory concordance of results it is to be noted that it
rests upon an empirical basis, since the phloroglucide is not formed by
the simple reaction 2 [C_{5}H_{4}O_{2} + C_{6}H_{6}O_{3}] - H_{2}O =
C_{22}H_{18}O_{9}, but appears to have the composition
C_{16}H_{12}O_{6}.
In part ii. of this paper the author discusses the question of the
probable extent in the sense of diversity of constitution of
furfural-yielding constituents of plant-tissues. Glucoson was isolated
from glucosazon, and found to yield 2.9-3.6 p.ct. furfural. Gluconic
acid distilled with hydrochloric acid gave traces of furfural; so also
with sulphuric acid and manganic oxide.
Starch was oxidised with permanganate, and a mixture of products
obtained of which one gave a characteristic violet colouration with
phloroglucol, with an absorption-band at the D line. On distilling with
HCl furfural was obtained in some quantity. The product in question was
found to be very sensitive to the action of bases, and was destroyed by
the incidental operation of neutralising the mixture of oxidised
products with calcium carbonate. It was found impossible to isolate the
compound.
UNTERSUCHUNGEN UEBER DIE PENTOSANBESTIMMUNG MITTELST DER
SALZSAeURE-PHLORO-GLUCIN-METHODE.[8]
E. KROeBER (Journ. f. Landwirthschaft, 1901, 357).
~INVESTIGATION OF THE HYDROCHLORIC ACID-PHLOROGLUCINOL METHOD OF
DETERMINING PENTOSANES.~
This paper is the most complete investigation yet published of the now
well-known method of precipitating and estimating furfural in acid
solution by means of the trihydric phenol. In the last section of the
paper is contained the most important result, the proof that the
insoluble phloroglucide is formed according to the reaction
C_{5}H_{4}O_{2} + C_{6}H_{6}O_{3} - 2H_{2}O = C_{11}H_{6}O_{3},
also, by varying the proportions of the pure reagents interacting, that
the condensation takes place invariably according to this equation.
Incidentally the following points were also established:--The solubility
of the phloroglucide, under the conditions of finally separating in a
condition for drying and weighing, is 1 mgr. per 100 c.c. of total
solution, made up of the original acid solution, in which the
precipitation takes place, and the wash-water required to purify from
the acid. The phloroglucide is hygroscopic, and must be weighed out of
contact with the air. The presence of diresorcinol is without influence
on the result, provided a sufficient excess of actual phloroglucinol is
employed. Thus even with a preparation containing 30 p.ct. of its weight
of diresorcinol the influence of the latter is eliminated, provided a
weight be taken equal to twice that of the furfural to be precipitated.
The phenol must be perfectly dissolved by warming with dilute HCl (1.06
sp.gr.) before adding to the furfural solution. For collecting the
precipitate of phloroglucide the author employs the Gooch crucible.
The paper contains a large number of quantitative results in proof of
the various points established, and concludes with elaborate tables,
giving the equivalents in the known pentoses and their anhydrides for
any given weight of phloroglucide from 0.050 to 0.300 grm.
UEBER DEN PENTOSAN-GEHALT VERSCHIEDENER MATERIALIEN.
B. TOLLENS and H. GLAUBITZ (J. fuer Landwirthschaft, 1897, 97).
~ON THE PENTOSANE CONSTITUENTS OF FODDER-PLANTS AND MALT.~
(p. 171) (a) The authors have re-determined the yield of furfural from
a large range of plant-products, using the phloroglucol method. The
numbers approximate closely to those obtained by the hydrazone method.
The following may be cited as typical:
Substance Furfural p.ct.
Rye (Goettingen) 6.03
Wheat (square head) 4.75
Barley (peacock) 4.33
Oats (Goettingen) 7.72
Maize (American) 3.17
Meadow hay 11.63
Bran (wheat) 13.06
Malt 6.07
Malt-sprouts 8.56
Sugar-beet (exhausted) 14.95
(b) A comparison of wheat with wheat bran, &c. was made by grinding in
a mortar and 'bolting' the flour through a fine silk sieve. The results
showed:
Furfural p.ct.
Original wheat 4.75
Fine flour 1.73
Bran (24 p.ct. of wheat) 11.25
Wheat-bran of commerce 13.06
It is evident that the pentosanes of wheat are localised in the more
resistant tissues of the grain.
(c) An investigation of the products obtained in the analytical
process for 'crude fibre' gave the following:
(1) In the case of brewers' grains:
100 grms. grains gave furfural = 29.43 pentosane
---------------
20 " crude fibre " = 2.52
Acid extract " = 22.76
Alkali " " = 1.20
Deficiency from total of original grains 2.95
-----
29.43
(2) In the case of meadow hay:
The crude fibre (30 p.ct.) obtained retained about one fourth (23.63
p.ct.) of the total original pentosanes.
(d) An investigation of barley-malt, malt-extract or wort, and
finished beer showed the following: An increase of furfuroids in the
process of malting, 100 pts. barley with 7.97 of 'pentosane' yielding 82
of malt with 11.18 p.ct. 'pentosane'; confirming the observations of
Cross and Bevan (Ber. 28, 2604). Of the total furfuroids of malt about
1/4 are dissolved in the mashing process. In a fermentation for lager
beer it was found that about /10 of the total furfuroids of the malt
finally survive in the beer; the yield of furfural being 2.92 p.ct. of
the 'total solids' of the beer. In a 'Schlempe' or 'pot ale,' from a
distillery using to 1 part malt 4 parts raw grain (rye), yield of
furfural was 9 p.ct. of the total solids.
In a general review of the relationships of this group of plant-products
it is pointed out that they are largely digested by animals, and
probably have an equal 'assimilation' value to starch. They resist
alcoholic fermentation, and must consequently be taken into account as
constituents of beers and wines.
UEBER DAS VERHALTEN DER PENTOSANE DER SAMEN BEIM KEIMEN.[9]
A. SCHOeNE and B. TOLLENS (Jour. f. Landwirthschaft, 1901, 349).
~BEHAVIOUR OF PENTOSANES OF SEEDS IN GERMINATION.~
The authors have investigated the germination of barley, wheat, and
peas, in absence of light, and generally with exclusion of assimilating
activity, to determine whether the oxidation with attendant loss of
weight, which is the main chemical feature of the germination proper,
affects the pentosanes of the seeds. The following are typical of the
quantitative results obtained, which are stated in absolute weights, and
not percentages.
_____________________________________________________________
| | | | |
| | Original seed | Malt or | Pentosane in |
| | | germinated product | |
| | | |_______________|
| | | | | |
| | A | B | A | B |
|________|_______________|____________________|_______|_______|
| | | | | |
| Barley | 500.00 | 434.88 | 39.58 | 40.38 |
| " | 500.00 | 442.26 | 40.52 | 41.17 |
| Peas | 300.00 | 286.60 | 15.25 | 15.97 |
|________|_______________|____________________|_______|_______|
The authors conclude generally that there is a slight absolute increase
in the pentosanes, and that the pentosanes do not belong to those
reserve materials which undergo destructive oxidation during
germination.
In this they confirm the previously published results of De Chalmot,
Cross and Bevan, and Gotze and Pfeiffer.
UEBER DEN GEHALT DER BAUMWOLLE AN PENTOSAN.
H. SURINGAR and B. TOLLENS (Ztschr. angew. Chem., 1897, I).
~PENTOSANE CONSTITUENTS OF COTTON.~
(p. 290) It has been stated by Link and Voswinkel (Pharm. Centralhalle,
1893, 253), that raw cotton yields 'wood gum' as a product of
hydrolysis. The authors were unable to obtain any pentoses as products
of acid hydrolysis of raw cotton, and traces only of furfural-yielding
carbohydrates. They conclude that raw cotton contains no appreciable
quantity of pentosane.
FOOTNOTES:
[8] This paper appears during the printing of the author's original MS.
[9] This paper appears during the printing of the author's original MS.