Chemistry Reference
In-Depth Information
[O], -H
2
O
[O]
[O]
R
NH
2
R
NHOH
R
NO
R
NO
2
primary amine
hydroxylamine
nitroso
nitro
coupling:
O
[O]
R
N
R
N
N
R
N
R
Fig. 11.36
Azo and azoxy compounds
in peroxide reactions.
azo
azoxy
CO
2
H
CO
2
H
H
2
O
2
N
H
2
O
3
P
N
catalyst
O
H
2
O
3
P
CO
2
H
CO
2
H
catalyst
N
H
2
O
3
P
CO
2
H
glyphosate
Fig. 11.37
Peroxide process to
glyphosate.
An important industrial application of C-N cleav-
age has been 'dealkylation' of
N
-phosphonomethyl
iminodiacetic acid used during production of the
pesticide glyphosate (
N
-phosphonomethyl glycine)
[274] (Fig. 11.37). Hydrogen peroxide oxidation
remains significant, although some methods based
on oxygen also now are available.
Reports of new chemistry arise from time to time,
such as the recent cyanation reaction of
N
,
N
-
dimethylaniline catalysed by Ru
III
[267] (Fig. 11.38)
and the aromatisation of 2,3-dihydropyridazines
[268] (Fig. 11.39).
N
N
CN
H
2
O
2
/ CN
-
Ru
III
Fig. 11.3
8
Cyanation of
N
,
N
-dimethylaniline.
Sulfide oxidations
4.3 Oxidations at sulfur
Organic sulfides can be oxidised to sulfoxides and
further to sulfones, both steps involving single
oxygen transfer (Fig. 11.40). The first oxidation is
essentially electrophilic, but the second is nucle-
ophilic and this, along with control of stoichiometry,
permits selective preparation of either product.
Many systems for this are long established: as noted
for nitrogen chemistry, it is not the purpose of this
chapter to catalogue all the available chemistry.
The analogue of ammonia oxidation in sulfur chem-
istry would be the oxidation of H
2
S. However, this
oxidation does not add value and the corresponding
use of H
2
O
2
is confined to the abatement of H
2
S in
gaseous and liquid effluents, in which it performs
extremely well. At acidic to neutral pH the product
is sulfur, whereas in alkaline solution oxidation can
proceed through to sulfate.
