Which of the following has the highest solubility in water?
Solubility depends on hydrogen bonding with water. CH₃NH₂ (primary amine) forms more hydrogen bonds than (CH₃)₂NH (secondary) or (CH₃)₃N (tertiary), and C₆H₅NH₂ has lower solubility due to the hydrophobic benzene ring.
Ref: NCERT Class 12 Chemistry > Chapter 13: Amines > Topic: Reaction with Nitrous Acid and Diazonium Salts - Part 1