This property of amines reacting with benzenesulphonyl chloride
in a different manner is used for the distinction of primary,
secondary and tertiary amines and also for the separation of a
mixture of amines However, these days benzenesulphonyl
chloride is replaced by p-toluenesulphonyl chloride 7 Electrophilic substitution
You have read earlier that aniline is a resonance hybrid of five
structures