Each of the heterocyclopentadienes in the margin contains more than one heteroatom. For each one, identify the

Question:

Each of the heterocyclopentadienes in the margin contains more than one heteroatom. For each one, identify the orbitals occupied by all lone electron pairs on the heteroatoms and determine whether the molecule qualifies as aromatic. Are any of these heterocycles a stronger base than pyrrole?

-N `N' H H Pyrazole Imidazole N S. Thiazole Isoxazole