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Carbohydrates – polyhydroxyaldehydes or polyhydroxy-
ketones of formula (CH 2 O) 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.
Glucose (a monosaccharide)
Plants:
photosynthesis
chlorophyll
6 CO
+ 6 H
O C
H
O
+ 6 O
sunlight (+)-glucose
(+)-glucose starch or cellulose
respiration
C
H
O
+ 6 O
6 CO
+ 6 H
O + energy
Animals
plant starch (+)-glucose
(+)-glucose glycogen
glycogen (+)-glucose
(+)-glucose fats or aminoacids
respiration
(+)-glucose + 6 O
6 CO
+ 6 H
O + energy
CHO H OH CH 2 OH H OH aldotetroses CH 2 CHCHCH O OH OHOH
CHO HO H CH 2 OH HO H CHO H OH CH 2 OH HO H CHO HO H CH 2 OH H OH D-erythrose L-erythrose L-threose D-threose
(+)-glucose? An aldohexose
Emil Fischer (1902)
Four chiral centers, 2
= 16 stereoisomers
CHO
CH
OH
OH?
CH
CHCHCHCHCH O
OH OHOHOHOH
* * *^ *
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 CH 2 OH H OH CO 2 H H OH CH 2 OH H OH Br 2 H 2 O CO 2 H OH CH 2 OH H OH Ca
H 2 O 2 Fe 3
CHO CH 2 OH H 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.
CHO H OH CH 2 OH HCN C H OH CH 2 OH H OH C HO H CH 2 OH H OH
N N H
,H 2 O COOH H OH CH 2 OH H OH COOH HO H CH 2 OH H OH diastereomers separable C H OH H 2 C H OH O O lactone Na(Hg) CHO H OH CH 2 OH H OH -H 2 O
CHO H OH HO H H OH H OH CH 2 OH (+)-glucose
Exists only in solution. There are two
solids:
α-glucose m 146
o
[α] = +112.
β-glucose m 150
o
[α] = +17.
In water each mutarotates to an
equilibrium with [α] = +52.
CHO H OH HO H H OH H OH CH 2 OH O H HO H HO H OH H (^) OH H OH O H HO H HO H H H (^) OH OH OH alpha-(+)-glucose beta-(+)-glucose H^ O OH OH H H H OH OH CH 2 OH H^ O OH H OH H H OH OH CH 2 OH
CHO
H OH
HO H
H OH
H OH
CH 2 OH
O
H
HO
H
HO
H
OH
H OH
H
OH
O
H
HO
H
HO
H
H
H OH
OH
OH
nucleophilic addition of -OH on carbon 5 to the aldehyde functional group
CHO
H OH
HO H
H OH
H OH
CH 2 OH
CH
H OH
HO H
H OH
HOH 2 C H
OH
O
H
HO
H
HO
H
OH
H OH
H
OH
O
O
H
HO
H
HO
H
H
H OH
OH
OH
α β
rotate C-5 OH to rear
O
H
HO
H
HO
H
H
H OH
OH
OH
O
H
HO
H
HO
H
OH
H OH
H
OH
hemiacetal
4 H -Pyran
O
D-glucopyranoses
alpha beta
O H HO H HO H H H (^) OH OH OH O H HO H HO H OH H (^) OH H OH alpha (^) beta anomers - epimers at C- chair conformations - alpha has one group axial beta has all groups equatorial mutarotation in solution to 63.6% beta/36.4% alpha
CH 2 OH O HO H H OH H OH CH 2 OH D-fructose CH 2 OH OH H CH 2 OH OH H H OH O beta-D-fructofuranose OH CH 2 OH H CH 2 OH OH H H OH O alpha-D-fructofuranose
