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Chem 241
Chpt 5: Stereochemistry
1.
Name_________________
(2 pts) Draw the structure for (2R,3S)-2,3-dichloropentane clearly
showing stereochemistry around the tetrahedral carbons:
(1 pt) Is the circled H in the following structure
pro-R or pro-S?
O
CH3
C
CH3
C
H H
2.
For the following molecules of blood sugar: -D-glucose and -D-glucose:
A. (6 pts) Label each of the indicated chiral centers as R or S.
H
4
H
OH
6
5
HO
HO
H
3
H O
2
4
1
HO
HO
H
OH
3
OH
H
OH
6
5
H O
H
2
1
H
-D-glucose
OH
OH
H
-D-glucose
B. (1 pt) What is the relationship between the 2 above structures of glucose?
Circle one: identical, enantiomers, diasteriomers, other __________
C. (2 pts) Circle the above structures of glucose that is the most stable? Show why.
3.
Ketones react with sodium acetylide (H-C C-Na+) to give alcohols as in the following reaction.
O
CH3
C
1) Na
CH2 CH3
+
2) H3O
C
CH
HO
CH3
C
C
CH
CH2 CH3
A. (2 pts) Would the product of the above reaction be optically active? (Would it rotate a plane of
polarized light?)
Circle one: Yes or
No
Explain why:
B. (1 pt) Draw the correct stereochemistry of the product that would occur from attack of the
acetylide ion from the Si face of the starting ketone.