Chem 109 C
Fall 2014
Armen Zakarian
Office: Chemistry Bldn 2217!
http://web.chem.ucsb.edu/~zakariangroup/courses.html!
update
sections covered: see syllabus
in Ch 21:
all except 21.13 - the anomeric effect
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
K-F synthesis
arabinose
glucose + mannose
conclusion
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
K-F synthesis
arabinose
glucose HNO3, heat
mannose
glucose + mannose
aldaric acid
optically active!
conclusion
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
K-F synthesis
arabinose
glucose HNO3, heat
mannose
glucose + mannose
aldaric acid
optically active!
H
HO
HO
H
CO2H
OH
H
H
OH
CO2H
conclusion
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
K-F synthesis
arabinose
glucose + mannose
glucose HNO3, heat
mannose
arabinose
HNO3, heat
aldaric acid
optically active!
aldaric acid
optically active!
H
HO
HO
H
CO2H
OH
H
H
OH
CO2H
conclusion
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
K-F synthesis
arabinose
glucose + mannose
glucose HNO3, heat
mannose
arabinose
HNO3, heat
3 or 4
aldaric acid
optically active!
aldaric acid
optically active!
H
HO
HO
H
CO2H
OH
H
H
OH
CO2H
conclusion
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
3 or 4
conclusion
Carbohydrates: Stereochemistry of Glucose
known: an aldohexose
experiment
3 or 4
conclusion
Carbohydrates: Shortening the Chain
PROBLEM
What two monosaccharides can be degraded to
a.  D-ribose
H
H
H
O
OH
OH
OH
OH
HO
H
H
O
H
OH
OH
OH
b.  D-arabinose
Carbohydrates: Shortening the Chain
PROBLEM
What two monosaccharides can be degraded to
a.  D-ribose
H
H
H
O
OH
OH
OH
OH
HO
H
H
O
H
OH
OH
OH
b.  D-arabinose
Carbohydrates: Cyclic Hemiacetals
OH
36%
HO
HO
O
HO OH
OH
α-D-glucopyranoside
HO
HO
OH
HO O
acyclic glucose
OH
64%
HO
HO
O
OH
HO
β-D-glucopyranoside
in aqueous solution
0.02%
Carbohydrates: Haworth projections
fundamental reactivity!
H+
R
R
+
O
HO R
R
section 17.12
HO
O+
R
R
R H
HO
-H+
O
R
R
hemiacetal
anomeric
hydroxyl
group
Carbohydrates: More Classification
O
O
pyran
furan
O
HO
OH
O
OH
HO
HO
OH
OH
pyranose
HO
OH
furanose
Carbohydrates: Cyclic Hemiacetals
fundamental reactivity!
H+
R
R
+
O
HO R
HO
R
section 17.10
forms furanose
O+
R
R
R H
HO
-H+
O
R
R
hemiacetal
Carbohydrates: Cyclic Hemiacetals
PROBLEM
Draw the following sugars using the Haworth projections:
α.  β-D-galactopyranose
β.  α-L-glucopyranose
Carbohydrates: Cyclic Hemiacetals
Glucose - most stable aldohexose:
HO
HO
HO
O
OH
HO
HO
HO
HO
OH
O
mannose
OH
HO OH
O
HO
HO
galactose
OH
Carbohydrates: Glycosides
Formation of glycosides:
cis
trans
HO
O
HO
O
OR
OR
cis
trans
HO
HO
O
O
OR
OR
α-glycoside
β-glycoside
Carbohydrates: Glycosides
mechanism for glycoside formation:
HO
HO
HO
H+
O
HO
HO
HO
OH
HO
HO
HO R
HO
HO
HO
O
HO
HO
HO
O+
B
O+
H
- H2O
H
HO
HO
HO
O
HO O+ -HB+
H R
O
HO OR
an !-glycoside
HO
oxycarbenium
cation
HO R
HO
HO
HO
HO
R
HO
O+
HO
+
H -HB
O
HO
B
O
OR
HO
a "-glycoside
Carbohydrates: Glycosides
N-glycoside formation:
HO
O+
HO OH
oxycarbenium
cation
Carbohydrates: Reducing and Non-reducing
OH
HO
HO
HO
O
OH
HO
OH
HO
HO
HO O
reducing sugar: aldehyde reactivity
is accessible
HO
HO
HO
O
OCH2CH3
HO
non-reducing sugar: stable acetal
Tollens reagent:
Ag+, HO–
Carbohydrates: Disaccharides
HO
HO
HO
6
O
HO
OH
1
4'
O
O
HO
OH
1'
HO
an !-1,4'-glycosidic linkage
HO OH
O
HO
HO
OH
O
O
HO
HO
an !-1,4'-glycosidic linkage
lactose
HO
HO
HO
O
HO
O
O
HO
HO
OH
OH
an !-linkage at glucose
a "-linkage at fructose
sucrose - table sugar
OH
Carbohydrates: Cyclic Hemiacetals
anomeric
hydroxyl
group
Carbohydrates: Disaccharides
HO
HO
HO
6
O
HO
OH
1
4'
O
O
HO
OH
1'
HO
an !-1,4'-glycosidic linkage
HO OH
O
HO
HO
OH
O
O
HO
OH
HO
an !-1,4'-glycosidic linkage
lactose
HO
HO
HO
O
HO
O
O
HO
HO
OH
OH
an !-linkage at glucose
a "-linkage at fructose
sucrose - table sugar
PROBLEM X
which ones are reducing
sugars ?
Carbohydrates: Disaccharides
Disaccharide identification, similar to PROBLEM 63
disaccharide X
fully
O-methylated
disaccharide X
H+
CH3I
Ag2O
R
R
OH
R
OCH3
R
Carbohydrates: Disaccharides
Disaccharide identification, similar to PROBLEM 63
disaccharide X
fully
O-methylated
disaccharide X
H+
CH3I
Ag2O
R
R
OH
R
OCH3
R
Carbohydrates: Disaccharides
Disaccharide identification, similar to PROBLEM 63
disaccharide X
H+
CH3I
Ag2O
R
R
OH
R
OCH3
R
Carbohydrates: Disaccharides
Disaccharide identification, similar to PROBLEM 63
H+
CH3I
Ag2O
R
R
OH
R
OCH3
R
Carbohydrates: Common Polysaccharides
starch:
20%
80%
Carbohydrates: Common Polysaccharides
starch:
20%
80%
Carbohydrates: Common Polysaccharides
starch:
20%
80%
Carbohydrates: Common Polysaccharides
cellulose: 90% of cotton, 50% of wood
Carbohydrates: Common Polysaccharides
cellulose: 90% of cotton, 50% of wood
Carbohydrates: Common Polysaccharides
cellulose: 90% of cotton, 50% of wood
Carbohydrates: Common Polysaccharides