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Chapter 4 179
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90.
a.
and
b.
CH
3
CH
3
CH
2
CH
3
CH
3
CH
3
CH
3
CH
3
ethylcyclobutane
1,1-dimethylcyclobutane
cis
-1,2-dimethylcyclobutane
trans
-1,2-dimethylcyclobutane
CH
3
CH
3
cis
-1,3-dimethylcyclobutane
trans
-1,3-dimethylcyclobutane
CH
3
CH
3
CH
3
CH
3
c. 1.
ethylcyclobutane
1,1-dimethylcyclobutane
1,2-dimethylcyclobutane
1,3-dimethylcyclobutane
2.
the three isomers of 1,2-dimethylcyclobutane
the two isomers of 1,3-dimethylcyclobutane
3.
cis
- and
trans
-1,2-dimethylcyclobutane
cis
- and
trans
-1,3-dimethylcyclobutane
4.
the two stereoisomers of
trans
-1,2-dimethylcyclobutane
5.
all the isomers except the two stereoisomers of
trans
-1,2-dimethylcyclobutane
6.
cis
-1,2-dimethylcyclobutane
(Note:
cis
-1,3-dimethylcyclobutane is not a meso compound because it does not have any
asymmetric centers.)
7.
the two stereoisomers of
trans
-1,2-dimethylcyclobutane
8.
cis
-1,3-dimethylcyclobutane and
trans
-1,3-dimethylcyclobutane
cis
-1,2-dimethylcyclobutane and either of the enantiomers of
trans-
1,2-dimethylcyclobutane