Carbohydrates

Question 1

What is the most abundant molecule?

Answer 1

Carbs

Question 2

List 3 features of monosaccharides

Answer 2

H2O soluble
insoluble in organic solvents (esters)
1+ chiral carbons

Question 3

Formula for carbs

Answer 3

(CH2O)n

Question 4

Draw Aldose vs ketone

Answer 4

Refer to notes

Question 5

Difference between D and L sugar

Answer 5

D = last chiral H on the left
R = last chiral H on the right

Question 6

What is an enantiomer?

Answer 6

mirror images

Question 7

What is a diastereomer?

Answer 7

chiral C that differs at some but not others

Question 8

What are epimers?

Answer 8

identical except 1 chiral carbon

Question 9

How do you calculate stereoisomers?

Answer 9

2^n (half are D and half are L) - every C added doubles isomers

Question 10

Draw the cyclization of glucose

Answer 10

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

Question 11

What ring does the cyclization of glucose form?

Answer 11

pyranose (6C) - bcs aldehyde
aka hemiacetal

Question 12

Draw the cyclization of fructose?

Answer 12

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

Question 13

What ring does the cyclization of fructose form?

Answer 13

furanose (5C) - bcs ketose
aka hemiketal

Question 14

What is Mutarotation? How much of a, B and linear?

Answer 14

When the solid form of glucose is dissolved in H2O it slowly converts into equilibrium.
1/3 a, 2/3B, and trace amounts linear

Question 15

What are reducing sugars?

Answer 15

Carbonyl sugars can be oxidized to a carboxyl group by oxidizing agents

Question 16

Reducing sugars - the ability to reduce cupric ions (Cu+2) to cuprous ions (Cu+) is the basis for the reducing sugar test…

Answer 16

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)

Question 17

What is a glycosidic bond?

Answer 17

Condensation of anomeric carbon with the nucleophile OH

Question 18

What happens when both anomeric carbons are in the glycosidic bond?

Answer 18

It becomes a non reducing sugar because it can no longer undergo mutarotation (linear form)

Question 19

What is the nucelophile?

Answer 19

does the attacking (O of OH group)

Question 20

What is electrophile?

Answer 20

Gets attacked (anomeric carbon)

Question 21

What is a disaccharide and how does it form?

Answer 21

2 monosaccharides
when the anomeric carbon reacts with the hydroxyl group of the other