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HYDRAZONES AND OSAZOXES. 203
The reaction takes place with the aldoses as follows:
<a)XH2 (OH).[CH(OH)]3 .CH(OH).CHO+H2 X.XH.C6 H5 =
CH2 (OH).[CH(OH)]3 .CH(OH)CH:X.NH.C6H5 +H20.
Phenylglucosehydrazone
(b) CH,(OH)[CH(OH)]3.CH(OH).CH:X.NH.C6 H5 +H2 N.NH.C8 H5 =
CH2 (OH).[CH(OH)]3 .C.CH:X.XH.C«H5
N.XH.C6H6 +H2 0+H2 .
Phenylglucosazone
and with the keteoses:
CH,fOH)[CH(OH)]3 CO.CH2 (OH)+H2 N.NH.C8 H5 =
CH2 (OH)[CH(OH)]3 C.CH2 OH
X.XH.C6 H5 +H20,
and CH2 (OH)[CH(OH)];.C.CH,(OH)
X.XH.C6 H5 +H2 X.XH.C6 H5 =
CH2 (OH)[CH(OH)]3 .C.CH :X.XH.C6 H5 +H2 0+H2 .
X.XH.C6 H3
The hydrogen is not evolved, but acts on a second molecule of phenylhy-
drazine and splits it into aniline and ammonia
:
H2 X.H.C6 H3 +H2 =H2 X.C6 H5 +XH3 .
As seen from the above equations the aldoses and ketoses yield the
same osazones, while the hydrazones are different.
The osazones, which are more important than the hydrazones, are
generally yellow crystalline compounds which differ from each other in
melting-point, solubility, and optical properties, and hence have been of
great importance in the characterization of certain sugars. They have
also become of extraordinarily great interest in the study of the carbo-
hydrates for other reasons. Thus they are a very good means of pre-
cipitating sugars from solution in which they occur mixed with other
bodies, and they are of the greatest importance in the artificial prepara-
tion of sugars. On cleavage, by the brief action of gentle heat and fum-
ing hydrochloric acid (for disaccharides still better with benzaldehyde), 1
the osazones yield so-called osones, which on reduction yield aldoses or
more often ketoses. The hydrazones can be much more readily retrans-
formed into the corresponding sugar, especially by decomposition with
benzaldehyde (Herzfeld) or with formaldehyde (Ruff and Ollen-
dorff 2
), whereby the sugar is replaced by the aldehyde used.
An important property, although not applicable to all sugars, is their
ability to undergo fermentation, especially their ability to undergo
alcoholic fermentation with alcohol-yeast. We must state, however,
that the power of fermentation with pure yeast has been shown only for
1
E. Fischer and Armstrong, Ber. d. d. chem. Gesellsch., 35.
2
Herzfeld, ibid., 2S; Ruff and Ollendorff, ibid., 32.
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