The number of isomers of C₃H₉N that liberate nitrogen gas with nitrous acid is:
C₃H₉N has four isomers: propan-1-amine, propan-2-amine, ethylmethylamine, and trimethylamine. Only primary amines (propan-1-amine and propan-2-amine) react with HNO₂ to liberate N₂, so the number is 2.
Ref: NCERT Class 12 Chemistry > Chapter 13: Amines > Topic: Preparation - Hoffmann Bromamide and Reduction of Nitro Compounds
