Chemistry Reference
In-Depth Information
Oxidation
Coordination
NO
+
NO
2
−
+ H
+
−
e
−
L
n
MNO
−
L
n
M
e
−
, HO
−
[NO]
2
2 NO
O
−
+ 2e
−
, 2H
+
Nu
−
N
N
N
2
O + H
2
O
Nu
O
Reduction
Nucleophilic
addition
Figure4.7
Generalreactionsofnitricoxideanditsdimer.
removed from the other products. In addition to one-electron oxidation, nitric oxide is readily oxidized by
halogens and pseudohalogens to give X-N
=
O type molecular compounds.
145
4.9.2 Reduction
The reduction of nitric oxide to give the nitroxyl anion
NO
−
)
, has been studied by a number of high
energy methods, including pulse radiolysis and laser flash photolysis.
146 - 150
(
Nitroxyl is often proposed to
result from the hydrolysis of Angeli's salt (Na
2
N
2
O
3
)
or Piloty's acid (PhSO
2
NHOH) and these putative
sources of nitroxyl have been intensively investigated. As with almost all reactions which are thought
to generate nitroxyl, these two reagents generate primarily nitrous oxide (Equation 4.20) as the ultimate
product. Care needs to be taken when using these reagents and interpreting results from their use: in
acid conditions nitric oxide is a known product of Angeli's salt hydrolysis,
151 - 154
and Bonner has found
that the putative NO
−
generating step in Piloty's acid decomposition is reversible.
155
Perhaps the single
exception to the general observation that nitroxyl dimerization
156
leads to nitrous oxide is the reduction
of nitrite by a sodium/mercury amalgam, which gives some
trans
-hyponitrite
157
as well as nitrous oxide
(Equation 4.21). However in this case there may very well be other key steps which lead to the N-N bond
formation aside from nitroxyl dimerization.
PhSO
2
NHOH
pH > 7
∗
H
2
O
2
−
NO
−
N
2
O+2OH
−
O
(4.20)
N
N
pH ~ 7
O
O
∗
Proposed intermediate
2
−
O
Na/Hg
(4.21)
+
N
2
O
+
2OH
−
NO
2
−
aq
N
N
O
Search WWH ::
Custom Search