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Chapter 6 221
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d.
Only syn addition occurs. Because the reactant is cis, the product is the pair of enantiomers with the
hydrogens on the same side of the ring.
CH
3
CH
2
CH
3
CH
3
CH
2
CH
3
H
H
H
H
50.
a.
CH
3
CHCH
2
Br
Cl
b.
Equal amounts of the
R
and
S
enantiomers are formed (a racemic mixture)
because a reactant without an asymmetric center forms a product with one
asymmetric center.
CH
2
Br
C
H
Cl
+
CH
2
Br
C
CH
3
H
Cl
or
CH
2
Br
Cl
CH
3
H
+
CH
2
Br
H
CH
3
Cl
S
R
S
R
CH
3
51.
a.
A racemic mixture of
1
R
2
-malate and
1
S
2
-malate. (A product with one asymmetric center is formed
from a reactant with no asymmetric centers.)
b.
A racemic mixture of
1
R
)-malate and
1
S
2
-malate. In the absence of an enzyme, the reactions are nei-
ther stereoselective (part
a
) nor stereospecific (part
b
).
52.
Solved in the text.
53.
a.
CH
3
CH CH
2
CH
3
CHCH
3
H
2
SO
4
CH
3
OH
OCH
3
b.
Br
Br
Br
+
c.
1. R
2
BH/THF
2. HO
−
, H
2
O
2
, H
2
O
CH
2
CH
2
OH
d.
CH
2
or
CH
3
CH
3
OH
H
2
SO
4
OCH
3
CH
3
This is the better option because the reaction is more highly regioselective.
e.
or
HBr
CH
2
CH
3
Br
CH
3
This is the better option because the reaction is more highly regioselective.
f.
H
2
SO
4
+
CH
3
CH
2
CH
2
OH
OCH
2
CH
2
CH
3