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Kinetics and mechanism of oxidation of S(IV) by the ethylenebisbiguanide Ag(III) ion
Weak intermediate are involved in the oxidation of SO 2 (aq) to SO 4 2 - by [ethylenebis(biguanide)]silver(II) in the acidic medium by successive one-electron transfer. The reaction, first-order both in Ag(H 2L) 3+ and S(IV), is not affected by dissolved oxygen and the rate is retarded by the hydrog...
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| Published in: | Polyhedron 2007-10, Vol.26 (17), p.4809-4817 |
|---|---|
| Main Authors: | , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | Weak intermediate are involved in the oxidation of
SO
2
(aq) to
SO
4
2
-
by [ethylenebis(biguanide)]silver(II) in the acidic medium by successive one-electron transfer.
The reaction, first-order both in Ag(H
2L)
3+ and S(IV), is not affected by dissolved oxygen and the rate is retarded by the hydrogen ion. The rate law in Eq.
(i) is deduced from the mechanism given below where
k
obs is the pseudo first-order rate constant ([S(IV)]
≫
[Ag(H
2L)]
3+), and
k
1 and
k
2 are composite rate constants.
(i)
k
obs
=
(
k
1
+
k
2
[
H
+
]
-
1
)
[
S
(
IV
)
]
(ii)
SO
2
(
aq
)
⇌
K
a
1
HSO
3
-
+
H
+
(iii)
Ag
(
H
2
L
)
3
+
+
SO
2
(
aq
)
⇌
K
1
Ag
(
H
2
L
)
SO
2
3
+
(iv)
Ag
(
H
2
L
)
3
+
+
HSO
3
-
⇌
K
2
Ag
(
H
2
L
)
HSO
3
2
+
(v)
Ag
(
H
2
L
)
SO
2
3
+
→
k
′
HSO
3
+
Ag
(
H
2
L
)
2
+
+
H
+
(vi)
Ag
(
H
2
L
)
HSO
3
2
+
→
k
″
HSO
3
+
Ag
(
H
2
L
)
2
+
(vii)
Ag
(
H
2
L
)
2
+
+
HSO
3
+
H
2
O
→
fast
Ag
(
H
2
L
)
+
+
HSO
4
-
+
2
H
+
where
k
1
=
k
′
K
1
and
k
2
=
k
″
K
1
K
2
in Eq.
(i). The inner-sphere mechanism is supported by similar activation parameters reported in other oxidations for similar reaction pathways. |
|---|---|
| ISSN: | 0277-5387 |
| DOI: | 10.1016/j.poly.2007.06.020 |