Chemistry Reference
In-Depth Information
2.41
In each case, the formula at the left is named; the right-hand structure shows the
other isomer.
a.
cis
-1,3-dichlorocyclohexane
b.
trans
-1-bromo-2-methylcyclohexane
2.42
cis
-1,3-Dimethylcyclohexane can exist in a conformation in which both methyl
substituents are equatorial:
CH
3
CH
3
H
H
In the
trans
isomer, one methyl group must be axial. On the other hand, in 1,2- or
1,4-dimethylcyclohexane, only the
trans
isomer can have both methyls equatorial.
H
H
CH
CH
3
3
CH
3
CH
3
H
H
2.43
We can have 1,1- or 1,2- or 1,3-dimethylcyclobutanes. Of these, the last two can
exist as
cis-trans
isomers.
1,1-dimethylcyclobutane
cis
-1,2-
dimethylcyclobutane
trans
-1,2-
dimethylcyclobutane
CH
3
CH
3
H
3
C
H
3
C
cis
-1,3-dimethylcyclobutane
trans
-1,3-
dimethylcyclobutane
2.44
The
trans
isomer is very much more stable than the
cis
isomer because both
t
-butyl
groups, which are
huge
, can be equatorial.
axial
H
C(
CH
3
)
3
C(
CH
3
)
3
H
CH
3
(
)
3
C
CH
3
(
)
3
C
H
H
trans
(
e,e
)
cis
(
e,a
)
