Chemistry Reference
In-Depth Information
Table17.1
TheoxidationpotentialsvsNHEfortheredox
couplesR
2
N
+
O/R
2
NO
•
andX
•
/X
−
=
E
1
/
2
oxd
E
◦
(mv)
(mv)
740,
64
722,
46
719
68
TEMPO
805
20
4-COOH-TEMPO
4-COO
−
-TEMPO
771
20,68
825,
64
810,
46
808
68
TEMPOL
817,
20
826,
46
851
68
4-amino-TEMPO
4-N(CH
3
)
3
+
-TEMPO
940
20
913,
46
918
20
TEMPONE
795
20
TEMPENE
870
20
3-COOH-proxyl
3-COO
−
-proxyl
792,
46
772
69
853
46
3-AP
861,
46
872
69
3-CP
955
20
TCPO
900
46
CHDO
915
15
PTIO
936
15
carboxy-PTIO
HOO
•
750
70
CH
3
OO
•
770
71
t-BuOO
•
710
39
CO
3
•
−
1590
70
•
NO
2
1040
70
at low concentrations of oxygen, some of the reactions proceed via the formation of stable adducts and
others via electron transfer mechanism.
40-44
The reactivity of the nitroxides towards
•
NO
2
and CO
•
3
radicals is almost the same for piperidine,
pyrrolidine, and oxazolidine nitroxides, and does not depend on the pH or buffer concentration, namely
k
o
=
10
8
M
−
1
s
−
1
(Table 17.2).
20,22
k
1
k
2
/(
k
−
1
+
k
2
)
=
(2.5
−
8.7)
×
Table17.2
Therateconstantk
o
(M
−1
s
−1
) ofthereactionbetween
nitroxideand
•
NO
2
orCO
3
•
−
asdeterminedbypulseradiolysis
15,20,22
•
NO
2
CO
3
•
−
Nitroxide
10
8
10
8
TEMPO
(7
.
1
±
0
.
2)
×
(4
.
0
±
0
.
1)
×
10
8
10
8
TEMPOL
(8
.
7
±
0
.
2)
×
(4
.
0
±
0
.
1)
×
10
8
10
8
4-amino-TEMPO
(5
.
5
±
0
.
2)
×
(3
.
9
±
0
.
1)
×
10
8
10
8
TEMPONE
(7
.
1
±
0
.
2)
×
(4.0
−
4.8)
×
4-N(CH
3
)
3
+
-TEMPO
10
8
10
8
(4
.
0
±
0
.
1)
×
(6
.
3
±
0
.
1)
×
10
8
10
8
3-CP
(7
.
1
±
0
.
2)
×
(4
.
0
±
0
.
1)
×
10
8
10
8
3-carboxy-proxyl
(4
.
9
±
0
.
2)
×
(2
.
4
±
0
.
1)
×
10
8
10
8
TCPO
(3
.
2
±
0
.
1)
×
(2
.
7
±
0
.
1)
×
10
8
10
8
CHDO
(2
.
5
±
0
.
1)
×
(2
.
6
±
0
.
1)
×
10
7
PTIO
(2
.
0
±
0
.
1)
×
ND
10
7
carboxy-PTIO
(1
.
5
±
0
.
1)
×
ND
ND - not determined.
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