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294 Chapter 8
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b.
Addition of an electrophile to C-1 forms a carbocation with two resonance contributors; both are
tertiary allylic
cations. Addition of an electrophile to C-4 forms a carbocation with two resonance
contributors, a
secondary allylic
cation and a
primary allylic
cation. Therefore, addition to C-1 results
in formation of the more stable carbocation. Only one product is formed, because the carbocation is
symmetrical.
+
+
−
−
HCl
94.
a
and
d.
OH
Free energy
OH
O
−
O
−
Progress of the reaction
b.
OH
OH
OH
OH
OH
+
+
+
_
_
_
c.
..
O
O
O
O
O
_
_
_
_
_