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Ch 6 Principles of Stereochemistry Test Practice
Organic Chemistry
1. Label each molecule as chiral, achiral, or achiral/meso.
O
OH
NH2
O
HO
CH3
H
H3C
Br
O
OH
2. Indicate if the pair of molecules are enantiomers, diastereomers, or the same molecule. Label each
asymmetric carbon as R or S configuration.
a.
CH3
H
H3C
OH
HO
H
CH2OH
HO
H
H
OH
CH2OH
HO
H
b.
HO
c.
H
Br
H
CH3
H
COOH
Br
Br
H
CH3
Br
COOH
H
3. Which of the following have an achiral stereoisomer? (There could be more than one.)
a. 2,3-dichlorobutane
b. 2,3-dichloropentane
c. 2,3-dichloro-2,3-dimethylbutane
d. 2,4-dibromopentane
4. Compound A has two stereoisomers, but compounds B and C exist as single compounds. Explain.
CH
+
H3C
CH2
HC
CH2
••
+
N
H
CH2 CH3
Cl-
H3C
A
N
H
CH3
B
N
Cl
-
H3C
H
CH CH2
C
5. Mevacor is used clinically to lower serum cholesterol levels. How many asymmetric carbons does Mevacor
have? HO
O
O
O
O
Mevacor
2 6. Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane.
a.
b.
c.
d.
Cl
Cl
C
CH3CH2
CH3
H
Cl
H
CH3
Cl
CH3
H
H
7. Indicate the relationship between all pairs (enantiomers, diasteromers, same). How will the R/S configurations at asymmetric carbons of enantiomers relate?
a.
b.
c.
CH3
H
CH3
H
Br
Br
CH3
CH3
CH3
H
H
CH3
H
Br
Br
H
Br
Br
8. Name the following compound following the IUPAC, Cahn-Ingold-Prelog rules.
9. Polarimeters for measuring optical rotation are so sensitive that they can measure rotations to 0.001º, an
important fact when only small amounts of sample are available. Ecdysone, for example, is an insect
hormone that controls molting in the silk-warm moth. When 7.00-mg ecdysone was dissolved in 1.00 mL
chloroform and the solution was placed in a cell with a 2.00-cm pathlength, an observed rotation of 0.087º
was found. Calculate [a]D for acdysone.
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