Tertiary amines do not react with benzenesulphonyl chloride, providing a basis for distinguishing between primary, secondary, and tertiary amines. This property is employed for the separation of amine mixtures. Nowadays, p-toluenesulphonyl chloride is commonly used in place of benzenesulphonyl chloride.

The reaction of benzenesulphonyl chloride with secondary amines yields N,N-diethylbenzenesulphonamide, which lacks acidic hydrogen and is insoluble in alkali due to the absence of a hydrogen atom attached to the nitrogen.

Nitrogen orbitals in amines are sp³ hybridized, leading to a pyramidal geometry. The fourth orbital of nitrogen contains an unshared pair of electrons.

Amines are derived from ammonia by replacing hydrogen atoms with alkyl and/or aryl groups. Examples include CH₃-NH₂, CH₃-NH-CH₃, and C₆H₅-NH₂.

They find application in the dye and pigment industries and are used to produce dyed fabrics. They are useful in the synthesis of a large variety of organic compounds, especially aryl derivatives.