_⇒ The structure of ethylamine is CH₃CH₂NH₂

⇒ The structure of aniline is:

Ethylamine form H-bonds with water. It dissolves in water due to intermolecular H-bonding as shown below:

Thus, ethylamine is soluble in water.

However, in aniline, due to the larger hydrophobic part, i.e., hydrocarbon part (C₆H₅ group), which tends to retard the formation of H-bonds. The extent of H-bonding decreases and hence aniline is insoluble in water.