Chemistry Reference
In-Depth Information
4.44
a.
The nitro substituent must be introduced first, to block the
para
position from
the chlorination.
CH
3
CH
3
CH
3
Cl
Cl
2Cl
2
FeCl
3
HONO
2
H
+
NO
2
NO
2
+some
ortho
isomer
b.
The nitration must be performed first. The nitro group is a
m
-director while a
chloro group is an
o
,
p
-director.
c.
If the chlorination were performed first, a considerable portion of product
would have the chlorine
para
to the methyl group. Also, note that in the
second step, both substituents direct the chlorine to the desired position
(
−
CH
3
is
o
,
p
-directing,
−
NO
2
is
m
-directing).
d.
If the bromination were performed first, the Friedel-Crafts acylation would
occur at the 2 and 4 positions.
4.45
3-Nitrobenzoic acid is better because both substituents are
meta
-directing:
