Chemistry Reference
In-Depth Information
-
OH
O
O
OH
-
-e
Easily oxidised
Phenol
Phenoxide ion
Phenoxy radical
H
O
H
H
O
O
O
H
-2H
Tautomerism
O
O
HO
OH
A quinone
(coloured oxidation product)
Further oxidation
Figure 8.8
Oxidation of the phenoxide ion.
(Figure 8.10), which, in aqueous solution, gives a pH of approximately 3. It
is called the acid tartrate since only one carboxylic acid group of tartaric
acid is used up in salt formation with adrenaline. This leaves the remaining
carboxylic group to function as an acid.
Cleavage of the nitrogen-hydrogen bond in aromatic amines occurs in
a similar manner to that described for phenols, to give a complex mixture
of products due to coupling reactions of the type shown in Figure 8.11.
Prevention of oxidative deterioration
A number of steps can be taken to minimise oxidative decomposition in
drugs and medicines. These can be summarised as follows.
Exclusion of oxygen
This is pretty obvious; if oxygen in the air is causing the oxidation, then
exclusion of
oxygen from the formulation will minimise oxidative
