561 / 912
Chapter 16 553
Copyright © 2017 Pearson Education, Inc.
98.
Notice that in the mechanism in part
a
, there is an equilibrium between a protonated intermediate, a neu-
tral intermediate, and a second protonated intermediate, just as we saw in many previous acid-catalyzed
mechanisms in this chapter and in Chapter 15.
a.
O O
O O
H
H B
+
+
O
HO
+
H
2
O
O
HO
O
H
+
B
O
HO
HO
H B
+
O
HO
O H
+
H
CH
HO
OH
O
+
B
CH
HO
OH
O
HB
+
H
H
b.
B
O
O
CH
3
CH
2
SH
O
OH
H
SCH
2
CH
3
B
OH
OH
SCH
2
CH
3
O
OH
SCH
2
CH
3
H B
+
H B
+
–