S TEREOCHEM S OLUTIONS
1. When 350 mg of sample is dissolved in 5.00 mL of alcohol solvent, an optical rotation of
-0.456

is measured in a cell with a path length of 2.00 cm. Calculate [

]
D
and include its units.
 
D

 c
 l

 
D

( 0 .
07 g /

0 mL
.
456
)


( 0 .
200 dm )


32 .
6
  mL g
 dm c = 350 mg

(1g/10 3 mg) = 0.350 g in 5 mL

(1mL/5mL) = 0.070 g/mL l = 2.00 cm

(1 dm/10 cm) = 0.200 dm
2. State the relationship between the optical rotation of: a) (2S,3S)-dibromobutane and (2R,3R)-dibromobutane equal in magnitude but opposite in direction b) (2S,3S)-dibromobutane and (2R,3S)-dibromobutane no relationship
3. Circle all chiral atoms in the structure shown below. Do not guess – ½ mark is deducted for each incorrect answer.
H
+
N
Cl
O
4. For a molecule with 4 chiral centers, state: a) the maximum possible number of stereoisomers 2 4 = 16 b) the maximum possible number of pairs of enantiomers 2 4-1 = 8
5. Draw a tetrahedral representation (wedge projection) of (S)-2-chloropentane with H on top.
H
H
H
3
C
Cl
C
C
3
H
7
C
3
H
7
C
Cl
CH
3
(R) (S)
CH 526 Page 1

S TEREOCHEM S OLUTIONS
O
6. For the structure shown, draw any structure of its a) enantiomer
Cl
O
Cl
O
H b) positional isomer
H
This mirror image is the enantiomer
H
Cl or simply interchange any two groups on the chiral carbon to produce the enantiomer
O
Cl c) functional isomer
H
C
4
H
5
OCl
OH
Note: isomers have the same
Cl and others chemical formula.
7. Assign (R) or (S) configuration to all chiral centers. Caution: ½ mark will be deducted for
3 each incorrect answer. Do not guess.
3
2
H
3
C
OH
1
Cl
H
CH
3
Br
1
(R)
H
3
H
3
C
H
(S)
C
2
H
5
2
H
NH
2
(S)
2
8. Redraw these wedge projections as Fischer projections with H in the top position.
H H
H Br
Br Cl or Cl CH
3 or H
3
C
H
3
C Cl
CH
3
Br
I
H
H H
Br
Cl
H
I
Br
Cl or
Br
Cl
I or Cl
I
H
Cl
Br
Br
CH 526 Page 2

S TEREOCHEM S OLUTIONS
9. Assign (R) or (S) configuration to all chiral centers. Also identify any meso compounds.
One mark will be subtracted for each wrong answer. Do not guess.
OH
Br
CH CH
2
H CHO (R)
H CH
3
(R)
H CHO
H
3
C OH (S)
OHC H (R)
CH
3
H
Br
(R)
H
H
3
H
1
3
OHC Br
1
(R)
1 2 CH
3
OH (R) 2
2
OHC CH=CH
2
2
3
H
3
C
2
1
OH (S)
1 Br CHO
3
(R)
CH
3
H
3
H
10. Assign (R) or (S) configuration to all chiral carbons in this compound. Do not guess.
One mark will be subtracted for each incorrect answer. Also give three correct IUPAC names using cis/trans, (E)/(Z), and (R)/(S) formats.
H
3
Cl
1
(R) (1R,2R)-1-bromo-2-chlorocyclopentane
(E)-1-bromo-2-chlorocyclopentane trans-1-bromo-2-chlorocyclopentane
3
2
2
Br
H
(R)
1
11. Circle all stereogenic centers in the compound shown below. Do not guess. Wrong answers will be subtracted from correct ones.
HO
O
CH
3
Si
H
CH
2
CH
3
CH 526 Page 3

S TEREOCHEM S OLUTIONS
12. Using tetrahedral representations (wedged, solid and dashed lines) draw 2 enantiomers of 2-bromo-1-propanol and label them as R and S. Do not guess. Wrong answers will be subtracted from correct ones.
H H
3
H
3
C
Br
C 2
CH
2
OH
2
CH
2
OH
C
Br
3
CH
3
1
(R) (S)
1
13. Circle any meso compounds. . Do not guess. Wrong answers will be subtracted from correct ones.
HO
H
OH
H
2,3-dichloro-1,4-butanediol
HOH
2
C
Cl
C
H
Cl
C
H
CH
2
OH
14. Assign R and S configuration to the stereogenic centers in the following compounds. Do not guess. Wrong answers will be subtracted from correct ones
F
Cl
H H
COOH
NH
2
HO
3
CH
2
CH
3
CHO
1 2
Br
H
OH
H
CH
3
4
(S)
(R)
(R)
Cl
2
Br
1
F
3
NH
2
2
OH
1
COOH
3
Note: The lowest priority group is already on the bottom, so rearrangement is unnecessary.
CH 526 Page 4