Post on 04-Apr-2018
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Greek sakcharon= sugar
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Carbohydratespolyhydroxyaldehydes or polyhydroxy-
ketones of formula (CH2O)n, or compounds that can behydrolyzed to them. (aka sugars or saccharides)
Monosaccharidescarbohydrates that cannot be hydrolyzed
to simpler carbohydrates; eg. Glucose or fructose.
Disaccharidescarbohydrates that can be hydrolyzed intotwo monosaccharide units; eg. Sucrose, which is hydrolyzed
into glucose and fructose.
Oligosaccharidescarbohydrates that can be hydrolyzed into
a few monosaccharide units.
Polysaccharidescarbohydrates that are are polymeric
sugars; eg Starch or cellulose.
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Aldosepolyhydroxyaldehyde, eg glucose
Ketosepolyhydroxyketone, eg fructose
Triose, tetrose, pentose, hexose, etc.carbohydrates that
contain three, four, five, six, etc. carbons per molecule(usually five or six); eg. Aldohexose, ketopentose, etc.
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Reducing sugara carbohydrate that is oxidized by Tollens,
Fehlings or Benedicts solution.
Tollens: Ag+ Ag (silver mirror)
Fehlings or Benedicts: Cu3+ (blue) Cu2+ (red ppt)
These are reactions of aldehydes and alpha-hydroxyketones.
Allmonosaccharides (both aldoses and ketoses) and most*
disaccharides are reducing sugars.
*Sucrose (table sugar), a disaccharide, is not a reducing sugar.
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Glucose (a monosaccharide)
Plants:photosynthesis
chlorophyll
6 CO2 + 6 H2O C6H12O6 + 6 O2
sunlight (+)-glucose
(+)-glucose starch or cellulose
respiration
C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy
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Animalsplant starch (+)-glucose
(+)-glucose glycogen
glycogen (+)-glucose(+)-glucose fats or aminoacids
respiration
(+)-glucose + 6 O2 6 CO2 + 6 H2O + energy
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OH
CHO
H
CH2OH
H
CHO
HO
CH2OH
D-(+)-glyceraldehyde L-(-)-glyceraldehyde
glyceraldehyde
an aldotriose
CH2CHCH O
OH OH
*
D & L are used to relate configuration of the chiral center
most removed from the reducing group ( C=O ). If the -OHis on the right in the Fischer projection, then it is D, if the -OHis on the left, then it is L
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CHO
H OH
CH2OH
H OH
aldotetrosesCH2CHCHCH O
OH OHOH
* *
CHO
HO H
CH2OH
HO H
CHO
H OH
CH2OH
HO H
CHO
HO H
CH2OH
H OH
D-erythrose L-erythrose
L-threose D-threose
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(+)-glucose? An aldohexose
Emil Fischer (1902)Four chiral centers, 24 = 16 stereoisomers
CHO
CH2OH
OH?
CH2CHCHCHCHCH O
OH OHOHOHOH
* * * *
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CHO
OHH
OHH
OHH
OHH
CH2OH
CHO
HHO
OHH
OHH
OHH
CH2OH
CHO
OHH
HHO
OHH
OHH
CH2OH
CHO
HHO
HHO
OHH
OHH
CH2OH
CHO
OHH
OHH
HHO
OHH
CH2OH
CHO
HHO
OHH
HHO
OHH
CH2OH
CHO
OHHHHO
HHO
OHH
CH2OH
CHO
HHOHHO
HHO
OHH
CH2OH
CHO
HO H
HO H
HO H
HO H
CH2OH
CHO
H OH
HO H
HO H
HO H
CH2OH
CHO
HO H
H OH
HO H
HO H
CH2OH
CHO
H OH
H OH
HO H
HO H
CH2OH
CHO
HO H
HO H
H OH
HO H
CH2OH
CHO
H OH
HO H
H OH
HO H
CH2OH
CHO
HO HH OH
H OH
HO H
CH2OH
CHO
H OHH OH
H OH
HO H
CH2OH
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Ruff degradationa series of reactions that removes the
reducing carbon ( C=O ) from a sugar and decreases the
number of chiral centers by one; used to relate configuration.
CHO
H OH
CH2OH
H OH
CO2H
H OH
CH2OH
H OH
Br2
H2O
CO2
H OH
CH2OH
H OH
Ca2+
H2O2
Fe3+
CHO
CH2OH
H OH
D-(+)-glyceraldehyde
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Kiliani-Fischer synthesis. A series of reactions that extends the
carbon chain in a carbohydrate by one carbon and one chiral
center.
CHO
H OH
CH2OH
HCN
C
H OH
CH2OH
H OH
C
HO H
CH2OH
H OH+
N N
H+,H2O
COOH
H OH
CH2OHH OH
COOH
HO H
CH2OHH OH
diastereomersseparable
C
H OH
H2C
H OH
O
O
lactone
Na(Hg)
CHO
H OH
CH2OH
H OH
-H2O
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Epimersstereoisomers that differ only in configuration about
one chiral center.
CHO
OHH
HHOOHH
OHH
CH2OH
D-glucose
CHO
HHO
HHOOHH
OHH
CH2OH
D-mannoseepimers
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CHO
OHH
HHO
OHH
OHH
CH2OH
(+)-glucose
Exists only in solution. There are two
solids:
-glucose m 146o [] = +112.2
-glucose m 150o [] = +17.5
In water each mutarotates to an
equilibrium with [] = +52.7
(63.6% / 36.4% )
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CHO
OHHHHO
OHH
OHH
CH2OH
OH
HO
H
HO
H
OHOHH
H
OH
OH
HO
H
HO
H
HOHH
OH
OH
alpha-(+)-glucose beta-(+)-glucose
OH
OH
OH
HH
OHH
OH
CH2OHOH
OH
H
OH
H
OHH
OH
CH2OH
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RC
H
O
+ R'OH R C H
OH
OR'
R C H
OR'
OR'
hemiacetalgeminalether/alcoholreducing!
acetalgeminaldiethernon-reducing!
Addition of alcohols to aldehydes/ketones:
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CHO
OHH
HHO
OHHOHH
CH2OH
O
H
HO
HHO
H
OHOHH H
OH
O
H
HO
HHO
H
HOHH OH
OH
nucleophilic addition of -OH on carbon 5 to the aldehyde functional group
CHO
OHH
HHO
OHHOHH
CH2OH
CH
OHH
HHO
OHH
HHOH2C
OH
O
H
HO
H
HO
H
OHOHH
H
OH
O
O
H
HO
H
HO
H
HOHH
OH
OH
rotate C-5 OH to rear
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O
H
HO
H
HO
H
HOHH
OH
OH
O
H
HO
H
HO
H
OHOHH
H
OH
hemiacetal
4H-Pyran
OD-glucopyranoses
alpha beta
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OH
H
HH OH
HO HO
H
HOHO
H
OH
HH OH
HO HO
H
HOHO
O
furan
alpha furanose form beta furanose form
D-glucofuranoses
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O
H
HO
H
HO
H
HOHH
OH
OH
O
H
HO
H
HOH
OHOHH
H
OH
alpha beta
anomers - epimers at C-1
chair conformations - alpha has one group axialbeta has all groups equatorialmutarotation in solution to 63.6% beta/36.4% alpha
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CH2OH
O
HHO
OHH
OHH
CH2OH
D-fructose
CH2OH
OH
H
CH2OH
OH H
H OHO
beta-D-fructofuranose
OH
CH2OH
H
CH2OH
OH H
H OHO
alpha-D-fructofuranose
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O
H
HO
H
HO
H
HOHH
OH
OH
CH3OH
HCl
OH
HO
H
HO
H
HOHH
OCH3
OH
acetal
(glucoside - glucose acetal)non-reducing, does not muta-rotate
methyl beta-D-glucoside
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Disaccharides:
(+)-maltose malt sugar
two glucose units (alpha)
(+)-cellobiose
two glucose units (beta)
(+)-lactose milk sugar
galactose & glucose
(+)-sucrose table sugar
glucose & fructose
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(+)-maltose
O
H
H
HO
H
HOHH
OH
OH
O
H
HO
H
HO
H
OHHH
OH
O
two glucose unitsalpha C-1 to C-4
reducing sugar
O
H
HO
H
HO
H
HOHH
OH
O
H
O
H
HO
H
HOHH OH
OH
(+)-cellobiose
two glucose units
beta C-1 to C-4
reducing sugar
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O
H
HO
H
HO
H
OHHH
OH
glucose alpha C-1
to beta C1 fructose
O
HO
H
H
HO
H
HOHH
OH
O
H
O
H
HO
H
HOHH
OH
OH galactose beta C-1to C-4 glucose
reducing sugar(+)-lactose
OO
CH
2OH
CH2OH
H
H
OH
HO
H
(+)-sucrose
acetalnon-reducing
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Polysaccharides
starch
cellulose
Starch 20% amylose (water soluble)
80% amylopectin (water insoluble)
amylose + H2O (+)-maltose
(+)-maltose + H2O (+)-glucose
starch is a poly glucose (alpha-glucoside to C-4)
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
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O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
CH2
O
Amylopectin + H2O (+)-maltose
(+)-maltose + H2O (+)-glucose
Also a polyglucose, but branched every 20-25 units:
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Cellulose is a polyglucose with a beta-linkage:
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O