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Chapter 3 153
Copyright © 2017 Pearson Education, Inc.
77.
The more stable isomer is the one that has a conformer with both substituents in equatorial positions.
Using the following structure, you can determine easily the isomer that has both substituents in
axial positions. That will be the more stable isomer because it will have a conformer with both groups in
equatorial positions.
a.
The cis isomer of a 1,3-disubstituted compound is the more stable isomer, because it has a conformer with
both substituents in axial positions. Therefore, its other conformer has both groups in equatorial positions.
b.
The trans isomer of a 1,4-disubstituted compound is the more stable isomer, because it has a conformer with
both substituents in axial positions. Therefore, its other conformer has both groups in equatorial positions.
c.
The trans isomer of a 1,2-disubstituted compound is the more stable isomer, because has a conformer with
both substituents in axial positions. Therefore, its other conformer has both groups in equatorial positions.
78.
Six ethers have a molecular
formula of C
5
H
12
O.
O
CH
3
OCH
2
CH
2
CH
2
CH
3
O
CH
3
CHCH
2
CH
3
OCH
3
O
CH
3
CH
2
OCH
2
CH
2
CH
3
1-methoxybutane
2-methoxybutane
1-ethoxypropane
butyl methyl ether
sec
-butyl methyl ether
ethyl propyl ether
O
CH
3
CHCH
3
OCH
2
CH
3
O
CH
3
COCH
3
CH
3
CH
3
O
CH
3
CHCH
2
OCH
3
CH
3
2-ethoxypropane
2-methoxy-2-methylpropane 1-methoxy-2-methylpropane
ethyl isopropyl ether
tert
-butyl methyl ether
isobutyl methyl ether
79.
The most stable conformer has two
CH
3
groups in equatorial positions and one in an axial position.
(The other conformer would have two
CH
3
groups in axial positions and one in an equatorial position.)
CH
3
CH
3
CH
3
80.
a.
N
,6-dimethyl-3-heptanamine
b.
3-ethyl-2,5-dimethylheptane
c.
1,2-dichloro-3-methylpentane
d.
2,3-dimethylpentane
e.
5-butyl-3,4-dimethylnonane
f.
5-butyl-3,3,9-trimethylundecane (undecane
is an 11 carbon straight-chain hydrocarbon;
Table 3.1 on page 89 of the text).