Chemistry Reference
In-Depth Information
O
O
O
O
-
+ H
+
H
O
O
O
O
CH
3
CH
3
O
O
O
-
O
-
O
O
O
O
CH
3
CH
3
Figure 3.7
The ionisation of warfarin.
Warfarin is an interesting compound in that, in addition to ionising,
it exhibits keto-enol
tautomerism
. This means that warfarin exists in two
constitutional isomeric forms (tautomers) that are in equilibrium with each
other, although one of the forms is usually present to a much higher degree
than the other. See Figure 3.8.
O
O
O
O
H
OH
O
H
H
O
CH
3
O
CH
3
Enol form
Keto form
Figure 3.8
The tautomerism of warfarin.
It is important not to confuse the properties of tautomerism and reson-
ance. They are quite different effects and the differences between them are
summarised in Table 3.1. Although the enol form of warfarin is present to
