Imidazole is over a million times more basic than pyrrole because the sp2 nitrogen that is part of one double bond is structurally similar to pyridine, and has a comparable basicity.
Is pyrrole more acidic than imidazole?
The pKa of imidazole itself is 14.2, about three order of magnitude lower than the pKa of pyrrole (pKa = 17.5). This is due to the extra N atom in imidazole which is electron- withdrawing and thus stabilizes the negative charge in the conjugate base.
Which is more basic imidazole or pyrazole?
Pyrazole is a weaker base than Imidazole. This is due to the sp2 orbital of nitrogen is the site of protonation in both pyrazole and imidazole. The nitrogen atom bonded to hydrogen is not basic because its lone pair of electrons is part of the aromatic ring system.
