Chemistry Reference
In-Depth Information
6.3.2 Reactivity of Ferrate(V) and Ferrate(VI)
The reactivity of ferrate(VI) with a number of inorganic compounds has been
performed to seek application of ferrate(VI) to remediate pollutants and to
understand the mechanism of oxidation reactions [17, 19]. The correlations of
the rate constants with one-electron and two-electron thermodynamic reduc-
tion potentials were able to distinguish one- and two-electron transfer steps
[19]. A linear relationship was found between log
k
and the one-electron
reduction potentials for iodide, cyanides, and superoxide, while oxy-compounds
of nitrogen, sulfur, selenium, arsenic showed a linear relationship for two-
electron reduction potentials [19]. Stoichiometric and products observed of
oxidation reactions were consistent with steps obtained from the correlations
[17]. Similar correlations were also performed with organosulfur compounds
(sulfur-containing amino acids, aliphatic and aromatic thiols, and mercaptans)
to understand oxygen transfer in oxidized products [20]. The ratios of
ferrate(VI) to the various organosulfur compounds for the one-oxygen-atom
transfer were 0.50 and 0.67 for Fe(II) and Fe(III) as final products, respectively.
The oxidation of the compounds involved a 1 − e
−
transfer step from Fe(VI)
to Fe(V), followed by 2 − e
−
transfer to Fe(III) as the reduced product
(Fe(VI) → Fe(V) → Fe(III)). The 2 − e
−
transfer steps resulted in the formation
of Fe(II) (Fe(VI) → Fe(IV) → Fe(II)). The schemes for oxygen transfer are
presented in Equations (6.111)-(6.116):
Scheme 1
RS O H formation
(
)
HFeO RSH HFeO
−
+
→
2
−
+
RS H
•+
(6.111a)
4
4
HFeO RS H OH
−
+
•+
+
2
−
→
HFeO
2
−
+
RS O H H O
(
)
+
(6.111b)
4
4
2
2
HFeO
2
−
+
2
RSH H O
+
4
→
2
Fe OH
(
)
+
2
RS O H OH
(
)
+
4
−
(6.111c)
4
2
3
RS O H formation
(
)
2
HFeO RS O H HFeO
−
+
(
)
→
2
−
+
RS O H
•+
(
)
(6.112a)
4
4
HFeO RS O H OH
−
+
•+
(
)
+
2
−
→
HFeO
2
−
+
RS O H
(
)
(6.112b)
4
4
2
2
HFeO
2
−
+
2
RS O H H O
(
)
+
4
→
2
Fe OH
(
)
+
2
RS O H OH
(
)
+
4
−
(6.112c)
4
2
3
2
RS O H formation
(
)
3
HFeO RS O H HFeO
−
+
(
)
→
2
−
+
RS O H
•+
(
)
(6.113a)
4
2
4
2
HFeO RS O H OH
−
+
•+
(
)
+
2
−
→
HFeO
2
−
+
RS O H
(
)
(6.113b)
4
2
4
3
2
HFeO
2
−
+
2
RS O H H O
(
)
+
4
→
2
Fe OH
(
)
+
2
RS O H OH
(
)
+
4
−
(6.113c)
4
2
2
3
3
2
HFeO
−
+
3
RNHCSO H OH
+
4
−
→→→
2
Fe OH
(
)
+
3
SO
2
−
+
3
RCONH
4
3
3
4
2
(6.114)
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