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662 Chapter 19
Copyright © 2017 Pearson Education, Inc.
28.
The electrophile adds preferentially to the 2-position.
N
H
N
HC
O
CH
3
CH
3
H B
+
N C
OH
H
N
CH
3
CH
3
H
H
+
B
N C
OH
H
N
CH
3
CH
3
H
H B
+
N C
OH
H
N
CH
3
CH
3
H
H
+
N C
H
N
CH
3
CH
3
H
+
+
H
2
O
Repeat the
previous series
of reactions
adding to the
5-position of
the pyrrole ring.
N C
C
H
H
N
H
3
C
H
3
C
N
CH
3
CH
3
HO
−
HO
−
+
H
+
colored compound
pyrrole
para
-(
N,N
-dimethylamino)-
benzaldehyde
N
CH
3
CH
3
HC
O
29.
Oxygen is the negative end of the dipole in both compounds. Tetrahydrofuran has the greater dipole
moment because the effect of the electron-withdrawing oxygen in furan is decreased by the ability of
oxygen to donate electrons by resonance into the ring.
O
O
tetrahydrofuran
1.73 D
furan
0.70 D