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Chapter 9 325
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b.
OCH
2
CH
3
CH
3
CH
2
CH H
CC
CH
3
H
CH
3
CH
2
CH CHCHCH
3
OCH
2
CH
3
45.
Conjugated double bonds are more stable and, therefore, are easier to form than isolated double bonds.
a.
b.
CH CHCH
3
c.
CH
2
CHCH CCH
3
CH
3
46.
a.
c.
CH
2
CHCH CCH
3
CH
3
CH
3
CH CHC CH
2
CH
3
+
b.
The secondary alkyl halide does not undergo an El reaction.
47.
a.
CH O
3
CH OH Br
−
3
CH
3
CH CH
2
C
CH
3
Br
CH
CH
3
CH C
2
CH
2
+
+
+
−
b.
CH
3
CH CH
2
C
CH
3
Br
CH
CH
3
CH C
3
CH
2
CH OH
3
+
CH
CH
3
CH C
2
CH
2
CH OH
3
+
+
CH
CH
3
CH
Br
–
+
HBr
C
3
CH
2
+
Only one elimination product is formed because elimination from the other resonance contributor would form
a cumulated diene, which is much less stable and, therefore, much harder to form than a conjugated diene.
48.
a.
Br
An aryl halide cannot
undergo an
S
N
1
reaction
because an aryl cation is
too unstable to form.
49.
a.
Br
An aryl halide cannot
undergo an
S
N
2
reaction
because it cannot
undergo back-side
attack.
b.
Br
A vinyl halide cannot
undergo an
S
N
1
reaction
because an vinyl cation is
too unstable to form.
b.
Br
A vinyl halide cannot
undergo an
S
N
2
reaction
because it cannot undergo
back-side attack.