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278 Chapter 8
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b.
It is not optically active, because it is a racemic mixture.
(Identical amounts of the enantiomers will be obtained.)
Cl
Cl
Cl
Cl
+
47.
a.
+
C
C
H C
H H
N
e.
+
C
C
H CH
H CH
O
O
d.
+
O
f.
+
C
C
H COH
HOC H
O
O
b.
c.
+
C
C
COCH
3
COCH
3
O
O
O
+
C
C
H
H
48.
None are aromatic.
c
is not aromatic, because it has two pairs of
p
electrons.
a
,
b
,
d
, and
e
are not aromatic, because each compound has two pairs of
p
electrons and every atom in the
ring does not have a
p
orbital.
f
is not aromatic, because it is not cyclic.
49.
a.
In the case of 9 pairs of
p
electrons, there are 18 electrons. Therefore, 4
n
+
2
=
18 where
n
=
4.
b.
Because it has an odd number of pairs of
p
electrons, it will be aromatic if it is cyclic and planar and if
every atom in the ring has a
p
orbital.
50.
a.
+
This is the only one that is aromatic; it is cyclic, it is planar, every ring atom has a
p
orbital, and it has one pair of
p
electrons.
The first compound is not aromatic, because one of the atoms is
sp
3
hybridized and, there-
fore, does not have a
p
orbital.
The third compound is not aromatic, because it has two pairs of
p
electrons.