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200 THE CARBOHYDRATES.
In order to explain multirotation Hupson ’ believes that the aldoses exist in
two isomeric forms having different rotation, which on being dissolved pass
into each other by means of a reversible reaction. The two forms can be derived
because a lactone-like binding exists between the end carbon atom in the alde-
hyde group and the y-carbon atom ae to the formula
CH:GHCHOH. a .CHOH.CHOH. CHORE, . In this way the end carbon becomes
asymmetric and Roane to whether the position of the atoms that are combined
with this carbon atom are:
C OH
aya eA
C or C
YUN F°y
O H
we obtain the two forms. TANRET 2? has obtained two isomeric forms of glucose,
galactose, arabinose and lactose which pass from one form to the other. The
two forms of glucose correspond according to E. H. Armstrone # to the syntheti-
cally prepared a- and B-methyl glucosides prepared by E. Fiscuer (see pages
61-62).
Like the ordinary aldehydes and ketones, the sugars may be made to
take up hydrocyanic acid. Cyanhydrins are thus formed. These addi-
tion products are of special interest in that they make possible the arti-
ficial preparation of sugars rich in carbon from sugars poor in carbon.
As an example, if we start from glucose we obtain glucocyanhydrin
on the addition of hydrocyanic acid:
CH2.(OH).[CH(OH)]4.COH+HCN = CH2(OH).[CH(OH)]4.CH(OH).CN.
On the saponification of glucocyanhydrin the corresponding oxyacid is
formed.
CH2(OH).[CH(OH)]4.CH(OH).CN +2H20
= CH2(OH).[CH(OH)]4.CH(OH).COOH+NHs3.
By the action of nascent hydrogen on the lactone of this acid we obtain
glucoheptose, C7H1407 and according to this principle the construction
of sugars up to nine carbon atoms has been accomplished.
The monosaccharides give the corresponding oximes with hydroxyl-
amine; thus glucose yields glucosoxime, CH2(OH).{CH(OH)|4.CH:N.OH.
These compounds are of importance on account of the fact, as found by
Wout that they are the starting-point in the formation of one class
1 Journ. Amer. Chem. Soc., 31, 61, 955 (1909).
2 Bull. soc. chim., 18, 728 (1895), 15, 195, 349 (1896).
3 Journ. Chem. Soc., 88, 1305 (1903).
4 Ber. d. d. chem. Gesellsch., 26, p. 730.
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