Carbohydrates Flashcards
What is the most abundant molecule?
Carbs
List 3 features of monosaccharides
H2O soluble
insoluble in organic solvents (esters)
1+ chiral carbons
Formula for carbs
(CH2O)n
Draw Aldose vs ketone
Refer to notes
Difference between D and L sugar
D = last chiral H on the left
R = last chiral H on the right
What is an enantiomer?
mirror images
What is a diastereomer?
chiral C that differs at some but not others
What are epimers?
identical except 1 chiral carbon
How do you calculate stereoisomers?
2^n (half are D and half are L) - every C added doubles isomers
Draw the cyclization of glucose
Refer to notes
Hints:
- aldose
- carbonyl C is the electrophile/anomeric C (last C)
- the OH of the electrophile attacks is the nucleophile
- on the left side from top to bottom = H (up), OH (up), H (up), H
- B = up and a = down for carbonyl C
- when labeling carbonyl carbon is 1
What ring does the cyclization of glucose form?
pyranose (6C) - bcs aldehyde
aka hemiacetal
Draw the cyclization of fructose?
Refer to notes
Hints:
- ketose
- carbonyl C is the electrophile/anomeric C (last C)
- the OH the electrophile attacks is the nucleophile
- on the left side from top to bottom = H (up), OH (up)
- B = up and a = down for carbonyl C
- when labeling carbonyl carbon is 1
What ring does the cyclization of fructose form?
furanose (5C) - bcs ketose
aka hemiketal
What is Mutarotation? How much of a, B and linear?
When the solid form of glucose is dissolved in H2O it slowly converts into equilibrium.
1/3 a, 2/3B, and trace amounts linear
What are reducing sugars?
Carbonyl sugars can be oxidized to a carboxyl group by oxidizing agents
Reducing sugars - the ability to reduce cupric ions (Cu+2) to cuprous ions (Cu+) is the basis for the reducing sugar test…
Condensation of the anomeric C of a sugar with an alcohol renders the sugar a non reducing sugar - a red precipitate forms only when in presence of the sugar in linear form (reducing)
What is a glycosidic bond?
Condensation of anomeric carbon with the nucleophile OH
What happens when both anomeric carbons are in the glycosidic bond?
It becomes a non reducing sugar because it can no longer undergo mutarotation (linear form)
What is the nucelophile?
does the attacking (O of OH group)
What is electrophile?
Gets attacked (anomeric carbon)
What is a disaccharide and how does it form?
2 monosaccharides
when the anomeric carbon reacts with the hydroxyl group of the other
