Explain: Diethyl aniline is more basic than Aniline?

Diethylaniline: C₆H₅(C₂H₅)₂N + H⁺ ⇌ C₆H₅(C₂H₅)₂NH⁺
Aniline: C₆H₅N + H⁺ ⇌ C₆H₅NH⁺

The two ethyl group are electron releasing which would increase the stability of the C₆H₅(C₂H₅)₂NH⁺ ion by inductive effect. Hence, C₆H₅(C₂H₅)₂NH⁺ is more stable than C₆H₅NH⁺. In other words, C₆H₅(C₂H₅)₂N accept a proton more readily than C₆H₅N, and thus C₆H₅(C₂H₅)₂N is more basic.

The above inductive effect overweighs the increase in steric hindrance of the two ethyl groups in C₆H₅(C₂H₅)₂N. This is because the steric hindrance of the two ethyl groups is much weaker than that of the phenyl group (C₆H₅-) as the phenyl group is very bulky.