1. Ch 21 Carbohydrates
1. Draw Fischer projections of all the aldotetrose stereoisomers. Name and label D & L and indicate enantiomers.

2. Ch 21 Carbohydrates 2. One form of galactose is drawn below.
Describe the sugar in all possible terms
How many stereocenters does it have?
How many stereoisomers does it have?
Is this D or L form?

3. Ch 21 Carbohydrates 3. Comparing these to galactose from last problem…
a. Which is a ketose?
b. Which is L-galactose?
c. Which is a C-3 epimer of D-galactose?

4. Ch 21 Carbohydrates
4. Complete the following reactions: a. b.

5. Ch 21 Carbohydrates
5. Answer the following: a.Which aldohexoses will form an optically inactive aldaric acid? b. Which sugar, when reduced with NaBH4, will form D-glucitol and D-mannitol?

6. Ch 21 Carbohydrates
6. Identify unknown sugars X, Y and Z from the following info: i)
ii)
iii)

7. Ch 21 Carbohydrates
…(#6 cont’d) X is one of the following:

8. Ch 21 Carbohydrates
7. Draw the Haworth projections and chair conformers (if possible) for the following:
β–D-glucopyranose
α-L-mannopyranose
methyl β–D-galactopyranoside
α -D-ribofuranose
8. Which of these are reducing sugars?

9. Ch 21 Carbohydrates
9. Give the major product for the following: a. c. b.

10. Ch 21 Carbohydrates
10. An unknown disaccharide gives a positive Tollen’s test. A glycosidase hydrolyzes it to D-galactose and D-mannose. When the disaccharide is treated with methyl iodide and Ag2O and then hydrolyzed with dilute HCl, the products are 2,3,4,6-tetra-O-methylgalactose and 2,3,4-tri-O-methylmannose. Propose a structure for the dissacharide.

11. Ch 21 Carbohydrates
11. What’s the primary structural difference between:
maltose and lactose
lactose and sucrose
amylose and amylopectin
amylose and cellulose