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612 Chapter 18
Copyright © 2017 Pearson Education, Inc.
32.
Because the para position is occupied, the electrophile adds to the ortho position. (Attack at the ortho posi-
tion is slower than attack at the para position because of steric hindrance, but since the para position is not
available, the slower reaction prevails.)
+
Cl
−
OH
CH
3
+
N N
OH
CH
3
NN
33.
You can see why nucleophilic attack occurs on the neutral nitrogen if you compare the products of
nucleophilic attack on the two nitrogens. Nucleophilic attack on the neutral nitrogen forms a stable product,
whereas nucleophilic attack on the positively charged nitrogen would form an unstable compound with
two charged nitrogen atoms.
+ Nu
_
N
N Nu
compared to
N
N
Nu
_
+
+
N
N
+ Nu
_
+
N
N
The terminal nitrogen is electrophilic because of electron withdrawal by the positively charged nitrogen. If
you draw the resonance contributors, you can see that the “neutral” nitrogen is electron deficient.
+
N
N
+
N
N
34.
+
N
a.
SO
3
−
+
N
b.
activated ring
diazonium ion
activated ring
diazonium ion
N
N
+
N
N
+