**2.1 Structure**

The pyrazole structure exists as two tautomers due to the movement of the C-N double bond (**Figure 1**). When both nitrogens are unsubstituted, each has a similar reactivity. However, when any carbon or nitrogen atom is substituted, the substitution(s) influences the reactivity of the other positions of the ring. This in turn may lead to several regioisomers of the substitituted pyrazole.
