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Chapter 21 707
Copyright © 2017 Pearson Education, Inc.
3.
Solved in the text.
4.
Isoleucine is the only other amino acid that has more than one asymmetric center. Like threonine, it has
two asymmetric centers.
isoleucine
CH CH * *
O
−
CH
3
CH
2
NH
3
+
C
O
CH
3
5.
Alanine exists predominately as a zwitterion in an aqueous solution with pH
7
2.34 and pH
6
9.69.
6.
The electron-withdrawing
+
NH
3
substituent on the
a
-carbon increases the acidity of the carboxyl group.
7.
a.
Solved in the text.
b.
N NH
CH
2
CH
NH
3
+
O
−
C
O
c.
CH
2
CH
2
CH O
−
H
2
N
NH
3
+
C
O
C
O
d.
H
3
NCH
2
CH
2
CH
2
CH
2
CH
NH
3
+
+
O
−
C
O
e.
NHCH
2
CH
2
CH
2
CH
H
2
N
NH
2
NH
3
+
+
O
−
C
O
C
f.
HO
CH
2
CH O
−
C
O
NH
3
+
8.
a.
+
HO CH
2
CH
2
CH OH
NH
3
C
O
C
O
b.
HO CH
2
CH
2
CH O
C
O
C
O
+
NH
3
−
c.
O CH
2
CH
2
CH O
C
O
C
O
+
NH
3
−
−
d.
−
O CH
2
CH
2
CH O
−
C
O
C
O
NH
2