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Chapter 26 813
Copyright © 2017 Pearson Education, Inc.
4.
If the bases existed in the enol form, no hydrogen bonds could form between the bases unless one of the
bases were shifted vertically.
N
sugar
thymine
A
D
N
N
N N
sugar
H
3
C O H
H
H
D
A
adenine
N
sugar
OH
N H
H
D
A
D
OH
D
cytosine
N
N
O N
sugar
H
D
A
guanine
NH
H
D
N
N
N
N
N
sugar
uracil
A
D
O H
OH
D
N
5.
a.
3
¬
C
¬
C
¬
T
¬
G
¬
T
¬
T
¬
A
¬
G
¬
A
¬
C
¬
G
¬
5
b.
guanine
6.
Notice that when a nucleophile attacks the phosphorus of a diester, the
p
bond breaks. However, when a
nucleophile attacks the phosphorus of an anhydride, a
s
bond breaks instead of the
p
bond.
O O
−
O O
O OH
P O O
−
H B
+
OH
HO
O
b
a
O
P
−
O O
OH
O
O
P
H
H B
O
O
O O
P
−
O OH
H B
+
H B
b
a
+
HO
O
O
O
O