Basicity. Unlike most amines, indole is not basic: just like pyrrole, the aromatic character of the ring means that the lone pair of electrons on the nitrogen atom is not available for protonation. ... The sensitivity of many indolic compounds (e.g., tryptamines) under acidic conditions is caused by this protonation.

Is indole non polar?

7-(2′-Pyridyl)indole is practically nonfluorescent at room temperature, in nonpolar and polar aprotic solvents.

What is the position of highest electron density in indole?

Indole is a planar molecule with 10 electrons. It's resonance energy is 47-49 K cal/mole. It is a very weak base with pKa value 3.63. The electrophilic attack results at 3rd position because Presence of high electron density at 3rd position.