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202 THE CARBOHYDRATES.
CH3
I
zol, C—NHV ,
from glucose by the action of ammonium-zinc hydroxide
CH—N^
at ordinary temperatures. This formation can be conceived as follows:
First methyl glyoxal is formed from the sugar, and then from this, or
from the sugar, formaldehyde is produced, which reacts with the meth\ 1
glyoxal with the formation of methylimidazole according to the following
equation:
CH3CO NH3 Hx H3C.C—NHX
I
+ + >CH= ||
>CH+3H2
COH NH3 0* CH—1ST
Methylglyoxal Formaldehyde Methylimidazole
A genetic relationship of the carbohydrates to histidine and the purine
bodies is thus made probable by the imidazole formation.
As the sugars are derivatives of polyhydric alcohols, they also form
esters, among which the benzoyl ester is of special interest because it is
used in the detection and isolation of the sugars and also of other car-
bohydrates. The nucleic acids probably also belong to the acid esters
of the sugars, and thus may be considered as complex phosphoric acid
esters, and perhaps the chondroitin sulphuric acid and the glucothionic
acid are sulphuric acid esters. The nature of these two groups of
sulphuric acid esters is not yet thoroughly understood.
The sugars can also combine with other bodies and with each other,
forming ether-like combinations. By the action of hydrochloric acid
as catalyst, as shown by Fischer and collaborators, the sugars split off
water and unite with "other bodies, producing lactone-like combinations,
which have been called glucosides (see pages 61 and 200). These glucosides,
which are generally compounds with aromatic groups, occur widely dis-
tributed in the vegetable kingdom. The more complex carbohydrates
may be considered, according to Fischer, as glucosides of the sugars.
Thus maltose, for example, is the glucoside and lactose the galactoside
of glucose. The glucosides can be split into their components by chem-
ical agents, boiling with dilute mineral acids, as well as by the action
of enzymes. The complex sugars hereby yield simple sugars and the other
glucosides yield compounds which belong either to the aromatic or the
aliphatic series besides the sugar. A long-knoAvn example of a decom-
position of this kind is the splitting of amygdalin by the enzyme emulsin
(see page 60).
With phenylhydrazine or substituted phenylhydrazines, the sugars
first yield hydrazones with the elimination of water, and then on the fur-
ther action of hydrazine on warming in an acetic-acid solution we obtain
osazones.
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