Chemistry Reference
In-Depth Information
The
keto
tautomer of phenol does not retain any of the resonance energy associated
with the aromatic ring, while the
keto
tautomer of 2-hydroxypyridine does (compare
with amide resonance).
13.29
Tautomerization of both amide groups gives:
O
N
H
N
The hydroxyl groups are activating, and thus, nitration occurs at the indicated
position,
ortho
to one hydroxyl group and
para
to the other. The product is 5-
nitrouracil (the amide form of uracil is more stable than the
enol
tautomer).
O
H
N
2
N
5-nitrouracil
5
O
N
H
13.30
Two resonance contributors to the structure of uric acid are shown below:
-
O
O
H
H
H
H
+
N
N
N
N
O
O
+
N
N
-
O
O
N
N
H
H
H
H
The hydrogens in the pyrimidine ring are expected to be the most acidic due to
contribution from an aromatic resonance structure that places positive charge on the
pyrimidine ring nitrogens.
13.31
a.
Br
C
H
b.
O
H
2
CCH
2
(see Sec. 8.8)
(CH
3
)
2
NH
+
(CH
3
)
2
NCH
2
CH
2
OH
c.
The first step is a free-radical halogenation (see Sec. 2.13).
