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182 Chapter 4
Copyright © 2017 Pearson Education, Inc.
c.
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl Cl
Cl
Cl
=
This is the most stable stereoisomer. Because the
chloro substituents are all trans to each other, they
can all be in the more stable equatorial position.
(Recall that there is less steric strain when a sub-
stituent is in the equatorial position.)
99.
a.
O
CH
3
CH
2
CH
3
R
b.
O
CH
3
S
c.
OH
Br
R
R
100.
O
O
O
H
2
N
O
HN
R
R
S
101.
Yes, as long as the Fischer projection is drawn with the #1 carbon at the top of the chain of carbons.
102.
The trans compound exits as a pair of enantiomers.
C(CH
3
)
3
(CH
3
)
3
C
CH
3
CH
3
As a result of ring flip, each enantiomer has two chair conformers. In each case, the more stable conformer
is the one with the larger group (the
tert
-butyl group) in the equatorial position.
H
C(CH
3
)
3
more stable
H C(CH
3
)
3
CH
3
H
H
3
C
H
(CH
3
)
3
C H
H
CH
3
H
(CH
3
)
3
C
CH
3
H
more stable