Carbohydrates – polyhydroxyaldehydes or polyhydroxyketones 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
sunlight
(+)-glucose
C6H12O6 + 6 O2
(+)-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
glyceraldehyde
an aldotriose
CHO
H
OH
CH2OH
D-(+)-glyceraldehyde
*
CH2CHCH O
OH OH
CHO
HO
H
CH2OH
L-(-)-glyceraldehyde
D & L are used to relate configuration of the chiral center
most removed from the reducing group ( C=O ). If the -OH
is on the right in the Fischer projection, then it is D, if the -OH
is on the left, then it is L
aldotetroses
* *
CH2CHCHCH O
OH OHOH
CHO
H
OH
H
OH
CH2OH
CHO
H
HO
HO
H
CH2OH
D-erythrose
L-erythrose
CHO
H
OH
HO
H
CH2OH
CHO
H
HO
H
OH
CH2OH
L-threose
D-threose
(+)-glucose? An aldohexose
Emil Fischer (1902)
* * * *
CH2CHCHCHCHCH O
OH OHOHOHOH
Four chiral centers, 24 = 16 stereoisomers
CHO
OH?
CH2OH
H
H
H
H
CHO
OH
OH
OH
OH
CH2OH
HO
HO
H
H
CHO
H
H
OH
OH
CH2OH
H
HO
HO
H
CHO
OH
H
H
OH
CH2OH
HO
HO
HO
HO
CHO
H
H
H
H
CH2OH
H
H
HO
HO
CHO
OH
OH
H
H
CH2OH
HO
H
H
HO
CHO
H
OH
OH
H
CH2OH
HO
H
H
H
CHO
H
OH
OH
OH
CH2OH
H
H
HO
H
CHO
OH
OH
H
OH
CH2OH
HO
HO
HO
H
CHO
H
H
H
OH
CH2OH
H
HO
HO
HO
CHO
OH
H
H
H
CH2OH
HO
HO
H
HO
CHO
H
H
OH
H
CH2OH
H
H
H
HO
CHO
OH
OH
OH
H
CH2OH
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
HO
H
HO
H
CHO
H
OH
H
OH
CH2OH
HO
H
HO
HO
CHO
H
OH
H
H
CH2OH
H
HO
H
HO
CHO
OH
H
OH
H
CH2OH
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.
CHO
H
OH
H
OH
CH2OH
Br2
H2O
CO2H
H
OH
H
OH
CH2OH
Ca2+
CHO
H
OH
CH2OH
D-(+)-glyceraldehyde
H2O2
Fe3+
CO2
H
OH
H
OH
CH2OH
Kiliani-Fischer synthesis. A series of reactions that extends the
carbon chain in a carbohydrate by one carbon and one chiral
center.
CHO
HCN
H
OH
CH2OH
C N
C N
COOH
COOH
HO
H
H
OH
H+,H2O H
OH HO
H
+ H
OH
H
OH
H
OH H
OH
CH2OH
CH2OH
CH2OH
CH2OH
CHO
H
OH
H
OH
CH2OH
diastereomers
separable
Na(Hg)
O C
H
OH
H
OH
H2C
O
lactone
-H2O
Epimers – stereoisomers that differ only in configuration about
one chiral center.
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
D-glucose
HO
HO
H
H
CHO
H
H
OH
OH
CH2OH
D-mannose
epimers
H
HO
H
H
CHO
OH
H
OH
OH
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)
H OH
H
HO
H
H
HO
HO
HO
H
H
H
OH
OH
CHO
OH
H
OH
OH
CH2OH
H OH
HO
HO
H
H
H
OH
OH
H
OH
H
beta-(+)-glucose
CH2OH
O
OH
H
H
alpha-(+)-glucose
H
HO
OH
CH2OH
O
OH
OH
H
H
OH
H
OH
OH
Addition of alcohols to aldehydes/ketones:
R
O
C
H
+ R'OH
OH
R C H
OR'
hemiacetal
geminal
ether/alcohol
reducing!
OR'
R C H
OR'
acetal
geminal
diether
non-reducing!
H OH
HO
HO
HO
H
H
OH
H
OH
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
H OH
HO
HO
HO
H
H
H
OH
OH
nucleophilic addition of -OH on carbon 5 to the aldehyde functional group
H OH
H
HO
H
H
CHO
OH
H
OH
OH
CH2OH
H
HO
H
HOH2C
CH O
OH
H
OH
H
OH
rotate C-5 OH to rear
HO
HO
HO
H
H
H
OH
OH
α
H OH
HO
HO
HO
H
H
OH
H
OH β
H OH
H OH
HO
HO
HO
H
H
alpha
O
4H-Pyran
H
OH
OH
HO
HO
HO
H
H
hemiacetal
OH
H
beta
D-glucopyranoses
OH
H
H
H
HOHO
O
H
HO
H
OH
OH
H
HOHO
O
H
HO
H
H
OH
H
alpha furanose form
beta furanose form
D-glucofuranoses
O
furan
OH
H OH
H OH
HO
HO
HO
H
H
H
OH
OH
HO
HO
HO
alpha
H
H
OH
H
OH
beta
anomers - epimers at C-1
chair conformations - alpha has one group axial
beta has all groups equatorial
mutarotation in solution to 63.6% beta/36.4% alpha
CH2OHO
H
H
OH
CH2OH
OH
H
OH
alpha-D-fructofuranose
CH2OH
O
HO
H
H
OH
H
OH
CH2OH
D-fructose
CH2OHO
H
H
OH
OH
OH
H
CH2OH
beta-D-fructofuranose
acetal
H OH
H OH
HO
HO
HO
H
H
OH
H
CH3OH
OH
HCl
HO
HO
HO
H
H
OH
H
OCH3
methyl beta-D-glucoside
(glucoside - glucose acetal)
non-reducing, does not mutarotate
Disaccharides:
(+)-maltose
“malt sugar”
two glucose units (alpha)
(+)-cellobiose
two glucose units (beta)
(+)-lactose
“milk sugar”
galactose & glucose
(+)-sucrose
“table sugar”
glucose & fructose
H OH
HO
HO
HO
H
OH
H
H OH
HO
H
O
HO
HO
HO
HO
H
H
H
H
(+)-maltose
H OH
two glucose units
alpha C-1 to C-4
OH
H
OH
reducing sugar
H OH
O
OH HO
H
HO
H
H
(+)-cellobiose
OH
H
OH
two glucose units
beta C-1 to C-4
reducing sugar
HO OH
H OH
HO
H
HO
H
H
O
OH HO
H
galactose beta C-1
to C-4 glucose
HO
H
H
OH
H
OH
reducing sugar
(+)-lactose
HO
HO
HO
H
OH
H
acetal
non-reducing
H
CH2OH
H OH
OH
O
H OH
CH2OH
HO
H
(+)-sucrose
glucose alpha C-1
to beta C1 fructose
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
Amylopectin + H2O  (+)-maltose
(+)-maltose + H2O  (+)-glucose
Also a polyglucose, but branched every 20-25 units:
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
CH2
O
O
O
O
O
O
O
O
O
Cellulose is a polyglucose with a beta-linkage:
O O
O O
O O
O O
O O
O O
O O
O O