Question

Hexylamine, aniline and methylamine mein increasing pka ka kya order hoga? Aniline toh last hoga, how to compare between the first two?

Answer 1

Aniline < Methylamine < Hexylamine

Answer 2

Solution Explanation:
Aniline’s nitrogen is attached to an aromatic ring, which delocalizes its lone pair, decreasing its basicity (lower pKa of its conjugate acid). Both methylamine and hexylamine are aliphatic amines, but the hexyl group exerts a stronger electron-donating inductive effect than the methyl group, making hexylamine slightly more basic (i.e., its conjugate acid has a higher pKa).

Answer:
Increasing order of pKa:

$$\text{Aniline} < \text{Methylamine} < \text{Hexylamine}$$