Σακχαρων Greek “ sakcharon” = sugar. Carbohydrates – polyhydroxyaldehydes or...
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σακχαρων Greek “sakcharon” = sugar
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Aldose – polyhydroxyaldehyde, eg glucose Ketose – polyhydroxyketone, 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.
Transcript of Σακχαρων Greek “ sakcharon” = sugar. Carbohydrates – polyhydroxyaldehydes or...
σακχαρωνGreek “sakcharon” = sugar
Carbohydrates – polyhydroxyaldehydes or polyhydroxy-ketones of formula (CH2O)n, or compounds that can be hydrolyzed to them. (aka sugars or saccharides)
Monosaccharides – carbohydrates that cannot be hydrolyzed to simpler carbohydrates; eg. Glucose or fructose.
Disaccharides – carbohydrates that can be hydrolyzed into two monosaccharide units; eg. Sucrose, which is hydrolyzed into glucose and fructose.
Oligosaccharides – carbohydrates that can be hydrolyzed into a few monosaccharide units.
Polysaccharides – carbohydrates that are are polymeric sugars; eg Starch or cellulose.
Aldose – polyhydroxyaldehyde, eg glucose
Ketose – polyhydroxyketone, 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.
Reducing sugar – a carbohydrate that is oxidized by Tollen’s, Fehling’s or Benedict’s solution.
Tollen’s: Ag+ Ag (silver mirror)
Fehling’s or Benedict’s: Cu3+ (blue) Cu2+ (red ppt)
These are reactions of aldehydes and alpha-hydroxyketones.
All monosaccharides (both aldoses and ketoses) and most* disaccharides are reducing sugars.*Sucrose (table sugar), a disaccharide, is not a reducing sugar.
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
Animals
plant starch (+)-glucose
(+)-glucose glycogen
glycogen (+)-glucose
(+)-glucose fats or aminoacids
respiration
(+)-glucose + 6 O2 6 CO2 + 6 H2O + energy
OHCHO
HCH2OH
HCHO
HOCH2OH
D-(+)-glyceraldehyde L-(-)-glyceraldehyde
glyceraldehyde
an aldotrioseCH2CHCH OOH OH
*
D & L are used to relate configuration of the chiral centermost 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
CHOH OH
CH2OHH OH
aldotetroses CH2CHCHCH OOH OHOH
* *
CHOHO H
CH2OHHO H
CHOH OH
CH2OHHO H
CHOHO H
CH2OHH OH
D-erythrose L-erythrose
L-threose D-threose
(+)-glucose? An aldohexose
Emil Fischer (1902)
Four chiral centers, 24 = 16 stereoisomers
CHO
CH2OH
OH?
CH2CHCHCHCHCH OOH OHOHOHOH
* * * *
CHOOHHOHHOHHOHH
CH2OH
CHOHHOOHHOHHOHH
CH2OH
CHOOHHHHOOHHOHH
CH2OH
CHOHHOHHOOHHOHH
CH2OH
CHOOHHOHHHHOOHH
CH2OH
CHOHHOOHHHHOOHH
CH2OH
CHOOHHHHOHHOOHH
CH2OH
CHOHHOHHOHHOOHH
CH2OH
CHOHO HHO HHO HHO H
CH2OH
CHOH OH
HO HHO HHO H
CH2OH
CHOHO H
H OHHO HHO H
CH2OH
CHOH OHH OH
HO HHO H
CH2OH
CHOHO HHO H
H OHHO H
CH2OH
CHOH OH
HO HH OH
HO HCH2OH
CHOHO H
H OHH OH
HO HCH2OH
CHOH OHH OHH OH
HO HCH2OH
Ruff degradation – a 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.
CHOH OH
CH2OHH OH
CO2HH OH
CH2OHH OH
Br2
H2O
CO2H OH
CH2OHH OH
Ca2+
H2O2
Fe3+
CHO
CH2OHH OH
D-(+)-glyceraldehyde
Kiliani-Fischer synthesis. A series of reactions that extends the carbon chain in a carbohydrate by one carbon and one chiral center.
CHOH OH
CH2OH
HCN
CH OH
CH2OHH OH
CHO H
CH2OHH OH+
N N
H+,H2OCOOH
H OH
CH2OHH OH
COOHHO H
CH2OHH OH
diastereomersseparable
CH OH
H2CH OH
O
O
lactone
Na(Hg)CHO
H OH
CH2OHH OH
-H2O
Epimers – stereoisomers that differ only in configuration about one chiral center.
CHOOHHHHOOHHOHH
CH2OH
D-glucose
CHOHHOHHOOHHOHH
CH2OH
D-mannose
epimers
CHOOHHHHOOHHOHH
CH2OH
(+)-glucose
Exists only in solution. There are two solids:
α-glucose m 146o [α] = +112.2
β-glucose m 150o [α] = +17.5
In water each mutarotates to an equilibrium with [α] = +52.7
(63.6% β / 36.4% α)
CHOOHHHHOOHHOHH
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
OHH
OHH
OH
CH2OH
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:
CHOOHHHHOOHHOHH
CH2OH
OH
HO
H
HO
H
OHOHH H
OH
OH
HO
H
HO
H
HOHH OH
OH
nucleophilic addition of -OH on carbon 5 to the aldehyde functional group
CHOOHHHHOOHHOHH
CH2OH
CHOHHHHOOHHHHOH2C
OH
OH
HO
H
HO
H
OHOHH H
OH
O
OH
HO
H
HO
H
HOHH OH
OH
rotate C-5 OH to rear
OH
HO
H
HO
H
HOHH OH
OHO
H
HO
H
HO
H
OHOHH H
OH
hemiacetal
4H-Pyran
OD-glucopyranoses
alpha beta
OH
H
HH OH
HO HO
HHOHO
H
OH
HH OH
HO HO
HHOHO
O
furan
alpha furanose form beta furanose form
D-glucofuranoses
OH
HO
H
HO
H
HOHH OH
OHO
H
HO
H
HO
H
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
CH2OHOHHOOHHOHH
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
OH
HO
H
HO
H
HOHH OH
OH
CH3OH
HCl
OH
HO
H
HO
H
HOHH OCH3
OHacetal
(glucoside - glucose acetal)non-reducing, does not muta-rotate
methyl beta-D-glucoside
Disaccharides:
(+)-maltose “malt sugar”
two glucose units (alpha)
(+)-cellobiose
two glucose units (beta)
(+)-lactose “milk sugar”
galactose & glucose
(+)-sucrose “table sugar”
glucose & fructose
(+)-maltose
OH
H
HO
H
HOHH OH
OH
OH
HO
H
HO
H
OHH H
OH
O
two glucose unitsalpha C-1 to C-4
reducing sugar
OH
HO
H
HO
H
HOHH
OH
OH
O
H
HO
H
HOHH OH
OH
(+)-cellobiose
two glucose unitsbeta C-1 to C-4
reducing sugar
OH
HO
H
HO
H
OHH H
OH
glucose alpha C-1to beta C1 fructose
OHO
H
H
HO
H
HOHH
OH
OH
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
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
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:
Cellulose is a polyglucose with a beta-linkage:
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
