CHAPTER 28: CARBOHYDRATES - CHEM 22, O-Chem II · Page 1 CHAPTER 28: CARBOHYDRATES GENERAL INFO...
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Page 1 C HAPTER 28: C ARBOHYDRATES GENERAL INFO FUNCTIONS OF CARBOHYDRATES (“SUGARS”) Glycocalyx on bacterial cell Structural Material of Plants (cellulose) Energy (starch, sugar) Cell Signaling Cellulose Starch Streptomycin (antibiotic) Complex carbohydrates (starch, cellulose) are polymers of simple sugars.
Transcript of CHAPTER 28: CARBOHYDRATES - CHEM 22, O-Chem II · Page 1 CHAPTER 28: CARBOHYDRATES GENERAL INFO...
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CHAPTER 28: CARBOHYDRATES
GENERAL INFO
FUNCTIONS OF CARBOHYDRATES (“SUGARS”)
Glycocalyx on bacterial cell
Structural Material of Plants (cellulose) Energy (starch, sugar) Cell Signaling
Cellulose
Starch
Streptomycin (antibiotic)
Complex carbohydrates (starch, cellulose) are polymers of simple sugars.
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SIMPLE SUGARS
ALDOSES + KETOSES
D+L VERSIONS
Simplest aldose = glyceraldehyde
ENANTIOMERS + DIASTEREOMERS
H OH
O
OHn
HOOH
O
OH
n
HOH
O
OH
OH
HOH
O
OH
OH
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FAMILY OF SIMPLE SUGARS (MONOSACCHARIDES)
D-Glucose D-Fructose
Most fruits have a roughly equal ratio of fructose and glucose as their source of sweetness. Pears are unusual as they have a higher amount of fructose (3:1 ratio of fructose:glucose).1
1 Gray, T., Molecules, The Elements and the Architecture of Everything, 2014, p 158.
H OHCH2OH
O HH OH
O H
H OHCH2OH
HO H
O H
H OHCH2OH
H OH
O H
H OHH OH
CH2OH
HO H
O H
H OHH OH
CH2OH
H OH
O H
HO HH OH
CH2OH
HO H
O H
HO HH OH
CH2OH
H OH
O H
H OHH OHH OH
CH2OH
HO H
O H
H OHH OHH OH
CH2OH
H OH
O H
HO HH OHH OH
CH2OH
HO H
O H
HO HH OHH OH
CH2OH
H OH
O H
H OHHO HH OH
CH2OH
HO H
O H
H OHHO HH OH
CH2OH
H OH
O H
HO HHO HH OH
CH2OH
HO H
O H
HO HHO HH OH
CH2OH
CH2OHO
CH2OH
CH2OHO
H OHCH2OH
CH2OHO
H OHH OH
CH2OH
CH2OHO
HO HH OH
CH2OH
CH2OHO
H OHH OHH OH
CH2OH
CH2OHO
HO HH OHH OH
CH2OH
CH2OHO
H OHHO HH OH
CH2OH
CH2OHO
HO HHO HH OH
CH2OH
D-Glyceraldehyde D-Erythrose D-Threose D-Ribose D-Arabinose D-Xylose D-Lyxose
D-Allose D-Altrose D-Glucose D-Gulose D-Mannose D-Idose D-TaloseD-Galactose
1,3-dihydroxypropanoneD-Erythrulose D-Ribulose D-Xylulose D-Psicose D-Fructose D-TagatoseD-Sorbose
H
O
OH
OH
OH
OH
OH
HO
O
OH
OH
OH
OH
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CYCLIC FORMS
CYCLIZATION MECHANISM + EQUILIBRIUM QUANTITIES
HAWORTH PROJECTIONS
5 OR 6 MEMBERED RINGS
To a 5-membered ring (furanose):
To a 6-membered ring (pyranose):
H
O+ MeOH
H+
HO H
O
OH
H
O
OHO
OH
OOPyran Furan
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Aldohexose Pyranose (6) Furanose (5) Aldohexose Pyranose (6) Furanose (5) D-Allose 92% 8% D-Gulose 97% 3% D-Altrose 70% 30% D-Idose 75% 25% D-Glucose ~100% <1% D-Galactose 93% 7% D-Mannose ~100% <1% D-Talose 69% 31%
ALPHA + BETA ANOMERS
DRAWING PYRANOSES
Draw D-Gulose in a 6-membered ring Haworth projection.
H OH
O H
H OHHO HH OH
CH2OH
D-Gulose
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DRAWING FURANOSES
Draw D-Fructose in a 5-membered ring Haworth projection.
RIBOSE IN ATP, NADH, DNA, + RNA
Draw D-ribose as both a pyranose and furanose.
Adenosine Triphosphate (ATP) Nicotinamide Adenine Dinucleotide (NAD+)
CH2OHO
HO HH OHH OH
CH2OHD-Fructose
H OH
O H
H OHH OH
CH2OH
D-Ribose
O P
O
O
O P
O
O
OO
OH OH
N
N
N
N
H2N
P
O
O
O
H
HH
H
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RNA + DNA Polymers:
MONOSACCHARIDE REACTIONS
MUTAROTATION
Forms of D-glucose:
a-D-glucopyranose b-D-glucopyranose
Over time, an aqueous solution of either anomer degrades to: [a] =
[a] = +112.2 ˚ [a] =
O
HO
OH
OH
OHOH
OOH
HO
OH
OH
OH
OOH
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Draw b-D-allopyranose in a chair conformation.
TOLLENS REACTION
Sugars in equilibrium with their open forms are called “reducing sugars.” (Note: aldose or ketoses)
H OH
O H
H OHH OHH OH
CH2OH
D-Allose
O
H
Ag(NH3)2+
NaOH
O
CH2OH
OH
OH
OHOH
Ag(NH3)2+
NaOH
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NITRIC ACID OXIDATION
How can this reaction be used to tell the difference between these aldoses?
HYDRIDE REDUCTION
D-Glucose
H OH
H OH
CH2OH
O H
HNO3
0 ˚C
H OH
H OH
CH2OH
O H
HO H
H OH
CH2OH
O H
H OH
O H
HO HH OH
CH2OH
D-Xylose
HO H
H OH
O H
H OH
HO H
CH3Fucose
Sugar Free Items
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Two aldoses can be reduced to make the same first product. Which two?
ACETAL (GLYCOSIDE) FORMATION
REACTION + MECHANISM
Draw the two possible furanoglycosides from this reaction:
H OH
O H
H OHCH2OH
HO H
O H
H OHCH2OH
D-Erythrose D-Threose
O
CH2OH
OH
OH
OHOH
H+
ROH
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POLYSACCHARIDE FORMATION
Lactose is roughly half the dry weight of human milk (5% wet weight).2
2 Gray, T., Molecules, The Elements and the Architecture of Everything, 2014, p 162.
D-Glucose
D-Galactose
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ribose ATP
GLYCOSIDES DON’T MUTAROTATE (DON’T “OPEN”)
ACETAL (GLYCOSIDE) HYDROLYSIS
REACTION + MECHANISM
OH
OH OH
OHO H H
HH
O P
O
O
O P
O
O
OO
OH OH
N
N
N
N
H2N
P
O
O
O
H
HH
H
OOH
OOCH3 NaBH4
EtOH
O
CH2OH
OH
OH
OHOR
H+
H2O
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OEtO
OCH3H+
H2O
