Why Pyridine is basic while pyrrol is slightly acidic?

Answer 1

Pyrrol is a weak acid as the pair of electrons found on the nitrogen atom are delocalised into the five membered ring thus making the electrons unavailable for donation. In addition, the hydrogen that is bonded with the nitrogen atom can be removed without causing disruption to the aromatic sextet.

Pyridine is basic as the lone pair on nitrogen is not involved in the delocalised system and thus can be donated.

Answer 2

Pyridine is basic because its nitrogen lone pair can accept a proton, forming a stable conjugate acid. On the other hand, in pyrrole, the nitrogen lone pair is part of the aromatic system, making it less available to accept a proton, resulting in weakly acidic properties.