CHEM 2222: Chapter 24
Terms in this set (35)
molecular formula of carbohydrates
What are the methods of classifying carbohydrates?
# of carbohydrate units
position at carbonyl group
number of carbons
How do you classify carbohydrates by number of carbohydrate units?
How do you classify carbohydrates by position of carbonyl group?
At C1, carbonyl is aldehyde => aldose
At any other carbon, carbonyl is ketone => ketose
How do you classify carbohydrates by number of carbons?
3 = triose
4 = tetrose
5 = pentose
6 = hexose
7 = heptose
How do you classify carbohydrates in cyclic form?
furanose = 5 membered ring
pyranose = 6 membered ring
D notation of carbohydrates from Fischer projection?
D-carbohydrates => -OH of highest number chiral carbon pointing to the right
L notation of carbohydrates from Fischer projection?
L-carbohydrates => -OH of highest number chiral carbon pointing to the left
How do aldoses form cyclic hemiacetals?
alcohol reacts with aldehyde to form ring
substituents that are right in Fischer projection are ____ in Haworth
How do you draw from Fischer to Haworth?
rotate bottom carbon so nucleophilic hydroxyl group is at the vertical position
only rotate the bottom carbon - leave the rest in place
How do you assign alpha and beta to anomeric carbon?
alpha if -OH is trans to the last group on the ring
beta if -OH is cis to the last group on the ring
anomeric hydroxyl group is replaced by another group
Fischer glycosidation: carbohydrates react with an alcohol in presence o acid catalyst
carbon-homologation = killani Fischer synthesis
carbohydrate is treated with:
1) HCl / NaCN
2) H₂, Pd, BaSO₄
1) cyanohydrin formation
2) reduction w/ poisoned catalyst
3) hydrolysis to aldehyde
2) acid anhydride
C1 oxidized to carboxylic acid
C1 and last carbon oxidized to carboxylic acid
last carbon oxidized to carboxylic acid
How do you make aldonic acid?
treat aldose with Br₂ or AgCl
How do you make aldaric acid?
treat aldose with HNO₃
How do you make uronic acid?
What is a disaccharide?
is comprised of two monomers connected at anomeric position
What is the general synthesis strategy of oligosaccharides?
1. prepare glycosyl donor and glycosyl acceptor
-donor: has leaving group at anomeric carbon
-acceptor: one nucleophilic -OH
-the rest of the -OHs are protected
2. formation of glycosidic C-O bond by nucleophilic substitution
3. removal of protecting groups
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