Exercício de Química Sintética e Organica Mista (715)

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Two moles of periodic acid per mole of glycoside are required. One mole of formic acid is
produced.
(d ) There are two independent vicinal diol functions in this glycoside. Two moles of periodic acid
are required per mole of substrate.
25.18 (a) The structure shown in Figure 25.2 is D-(�)-xylose; therefore (�)-xylose must be its mirror
image and has the L-configuration at C-4.
(b) Alditols are the reduction products of carbohydrates; D-xylitol is derived from D-xylose by
conversion of the terminal GCHO to GCH2OH.
(c) Redraw the Fischer projection of D-xylose in its eclipsed conformation.
HO H
H OH
CHO
H OH
CH2OH
d-Xylose Eclipsed conformation
of d-xylose
Haworth formula of
�-d-xylopyranose
redrawn as
H
H
HO
OH
H
H
OH
H
HO
OH
H
H
H
OH
OH
CH2O
CHO
O
d-Xylitol
H OH
HO H
CH2OH
CH2OH
H OH
d-(�)-Xylose
H OH
HO H
CHO
CH2OH
H OH
l-(�)-Xylose
HO H
H OH
CHO
CH2OH
HO H
2HIO4
H
CH
CH HC
O
O
OCH3
HCH
H
O
O
�
O
H
CH2OH
OCH3
HOH
HHO
H
H OH
O
710 CARBOHYDRATES