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146 Chapter 3
Copyright © 2017 Pearson Education, Inc.
Because the 1,3-diaxial interaction between a methyl group and a hydrogen causes a strain energy of
0.9 kcal
>
mol, the chair conformer with both substituents in axial positions is
4
*
0.9
=
3.6 kcal
>
mol
less stable than the chair conformer with both substituents in equatorial positions.
CH
3
CH
3
CH
3
H
H
H
H
a 1,3-diaxial
interaction
CH
3
b.
Each of the chair conformers of
cis
-1,4-dimethylcyclohexane has one substituent in an equatorial posi-
tion and one in an axial position. Therefore, the two conformers are equally stable.
55.
Both condensed and skeletal structures are shown.
a.
CH
3
CH
2
CHOCCH
3
CH
3
CH
3
CH
3
O
d.
Br
CH
3
CHCH
2
CH
2
Br
CH
3
b.
CH
3
CHCH
2
CH
2
CH
2
CH
2
OH
CH
3
OH
e.
CH
3
CH
CH
3
3
CHCH
2
CH
2
CH
2
CHCH
2
CH
2
CH
2
CH
3
c.
CH
3
CH
2
CHNH
2
CH
3
NH
2
f.
CH
3
CH
2
N
N
CH
2
CH
3
CH
2
CH
3