CARBOHYDRATES SOLUTIONS
1. Label the chiral centers as ‘R’ or ‘S’ in each of the following molecules. Do not guess as
wrong answers will be subtracted from the correct answers.
4 CH3
HO
1
1 OH
4 CH3
NH2
2
OHC
3
3 CHO
H3C
4
OH
1
2. Draw the following structures
a) D-arabinose (Fischer)
4 CH3
(R)
c) the C-4 epimer of D-glucose
(Fischer) and give its name
O
HO
CHO
3
(S)
(R)
NH2
HO
1
NH2
2
3 CHO
2 NH2
(R)
2
O
H
H
O
OH
H
OH
HO
H
OH
H
OH
H
OH
H
H
4
OH
HO
H
HO
H
H
OH
OH
OH
OH
D-glucose
D-galactose
d) -D-mannopyranose (Haworth)
b) L-talose (Fischer)
O
O
OH
O
HO
HO
HO
H
H
H
H
HO
H
H
H
OH
OH
OH
OH
H
HO
HO
H
H
H
H
OH
OH
OH
OH
OH
L-talose
D-talose
D-mannose
O OH
H
OH OH
HO
H
H
H
H
 -D-mannopyranose
3. Draw the Haworth projection of -D-xylofuranose.
O
HO
H
HO
H
OH
H
OH
OH
D-xylose
H
O
OH H
H
OH
OH
H
 -D-xylofuranose
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CARBOHYDRATES SOLUTIONS
4. Draw the structures of the products you would expect to obtain from the following reactions.
Name the products where required.
a) -D-ribofuranose + CH3I, Ag2O  ..................................................... (no name required)
O
permethylation
OH
H
H
H
OH
OH
OH
H
O
OH
CH 3I
H
H
OH
OH
OH
H
H
O
H
H
Ag2O
D-ribofuranose
D-ribose
OCH 3
H
OCH 3
OCH 3OCH 3
D-ribofuranose tetramethyl ether
b) D-threose + Tollens reagent (Ag+ in NH3)  .............................................. (name)
O
O
-
O Na
+
+
HO
H
H
OH
Ag in NH 3
HO
H
OH
H
OH
OH
D-threonic acid sodium salt
D-threose
i.e., sodium D-threonate
c) -D-altrofuranose + isopropyl alcohol, HCl  ....................................................... (name)
O
HO
H
H
H
H
HO
H
H
H
H
OH
OH
OH
OH
D-altrose
OH
H O
OH
(CH 3)2CHOH, HCl
OH
OH
H
O
H HO
H
O
OH H
OH
CH 2OH
CH3
CH3
isopropyl  D-altrofuranoside
D-altrofuranose
d) -D-arabinofuranose + acetic anhydride (CH3CO)2O in pyridine solvent  (no name)
(H 3 C)OCO
O
HO
H
H
H
OH
OH
OH
D-arabinose
H
HO
H
H
OH
H O
OH
CH2OH
D-arabinofuranose
HO
OCO(CH 3 )
H
O
C5 H5 N
H
O
H
H HO
H
OCO(CH 3 )
H
OH
(CH 3CO) 2O
H
OH H
OCO(CH 3 )
 D-arabinofuranose
tetraester
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CARBOHYDRATES SOLUTIONS
e) D-idose + NaBH4, then H2O  .............................................................. (name required)
O
HO
H
HO
H
OH
H
OH
H
OH
1. NaBH 4
2. H2O
HO
H
HO
H
H
OH
H
OH
OH
OH
D-iditol
D-idose
f) D-lyxose in Kiliani Fischer Synthesis  ...........................................(name both products)
O
O
HO
HO
H
1. NaCN, HCN
H
H
OH
2. H3O
+

H
HO
HO
H
O
OH
H
H
OH
OH
HO
HO
HO
H
+
OH
D-lyxose
H
H
H
OH
OH
D-talose
D-galactose
g) D-glucose in Wohl Degradation  ............................................................ (name product)
O
H
HO
H
H
O
1. NH 2OH
OH
H
OH
OH
HO
H
H
2. (CH 3CO) 2O
NaAc
3.
NaOCH 3
OH
OH
D-arabinose
D-glucose
5. Draw the following structures ...
a) cellobiose
CH2OH
4'

CH2OH
..
O
..
b) any deoxyribose
c) any amino sugar
O
O
..
O
..
OH
C
OH
H
OH
C
H
H
OH
H
OH
H
OH
H
NH2
H
H
H
OH
1
OH
OH
O
H
OH
OH
CH2OH
OH
D-deoxyribose
CH2OH
an amino sugar of
D-ribose
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CARBOHYDRATES SOLUTIONS
6. Write the correct name of each of the following ...
a) polysaccharide in potatoes and digestible by humans ..........starch.....
b) polysaccharide stored in the liver and muscles of humans ........... glycogen...................
c) polysaccharides in grass …………………………………… cellulose………………
d) the disaccharide produced when starch is metabolized ……… maltose……………..
e) water soluble form of starch ......................................... amylose..................................
f) pulverized with hot water ............................................. tritutated................................
g) the 2 monosaccharides which make up sucrose ........ glucose + fructose.....
h) the polysaccharide imparting strength and rigidity to plants ..... cellulose........
i)
textile fiber made from wood pulp, CS2, and NaOH ....... viscose rayon............
j)
milk sugar
.................................................... lactose.........................
k) carbohydrate which yields 3 to 10 monosaccharides on hydrolysis .. oligosaccharides...
l)
general name for a 5 carbon aldehydic monosaccharide ........ aldopentose......
m) general name for a 7 carbon ketonic monosaccharide ........ ketoheptose.............
n) general name for the 2 diastereomers produced when an open chain monosaccharide
cyclicizes to its hemiacetal form ....................... anomers.......................
o) Name the 2 reagents, which are combined to produce ‘acetate rayon’.
………………………… cellulose + acetic anhydride…………………………
p) Explain the difference between an epimer and an anomer. ……………………………..
… anomers have cis- or trans-stereochemistry at the #1 Carbon in the cyclic sugar……..
… epimers (also diastereomers) have opposite configuration at any one of their chiral carbons……
7. Identify all chiral centers as (R) or (S) in the following and give their IUPAC and common
names
D-xylose
(3S,4R,5R)-1,3,4,5,6-pentahydroxy-2-hexanone
a)
OH
(S) HO
H
(R)
H
(R)
O
H
OH
OH
OH
D-fructose
O
b)
H
HO
H
OH (R)
H (S)
OH (R)
OH
(2R,3S,4R)-2,3,4,5-tetrahydroxypentanal
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CARBOHYDRATES SOLUTIONS
8. Explain in words or by a drawing, the structural difference between cellobiose and maltose.
Be sure to identify which is which
Maltose is a 1,4’---D-glycoside of D-glucose , whereas Cellobiose is a 1,4’---D-glycoside of D-glucose.
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