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642 Chapter 18
Copyright © 2017 Pearson Education, Inc.
94.
The configuration of the asymmetric center in the reactant will be retained only if the asymmetric cen-
ter undergoes two successive S
N
2 reactions. In the first step of the reaction, the NH
2
group is converted
to a good leaving group. The first S
N
2 reaction involves the carboxylate ion that is closest to the carbon
attached to the leaving group. The product of the reaction is a strained three-membered ring that reacts
with the other carboxylate ion in a second S
N
2 reaction, forming a more stable five-membered ring.
−
OCCH
2
CH
2
O
C
C
H
NH
2
O
O
NaNO
2
HCl
−
OCCH
2
CH
2
O
C
C
H
N
O
O
+
N
O
O
H
COO
−
−
−
S
N
2
S
N
2
C
C
O
O
H
CH
2
CH
2
C
O O
+
N
2
−
95.
a.
+
O
NO
2
OH
CH
2
O
NO
2
O
NO
2
OH
Br
CH
2
+ HB
+
O
H
+
B
NO
2
O
O
b.
O
S
NO
2
O O
NO
2
H
H
3
C
CH
3
O
−
H
3
C
O
S
O
−
O
H
3
C
O
S
NO
2
NO
2
O O
−
NO
2
NO
2