In HantzschâÂÂWidman nomenclature, an azine is an heterocyclic compound containing a 6-membered aromatic ring. It is an analog of a benzene ring in which one or more of the carbon atoms has been replaced by a nitrogen atom, and thus is also called an azabenzene. In both cases, the prefix aza- refers to the presence of one or more nitrogen atoms as replacement for carbon in a parent structure. The nitrogen has a lone pair of electrons instead of the hydrogen or substituent on the carbonâÂÂthe overall replacement is isolobal.