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.

Benzenesulphonyl chloride reacts with primary amines to form sulphonamides, such as N-ethylbenzenesulphonyl amide. The sulphonyl group imparts acidity to the hydrogen attached to nitrogen, making it soluble in alkali.

Aromatic amines react with nitrous acid at low temperatures to form diazonium salts, a crucial class of compounds employed in the synthesis of various aromatic compounds. Secondary and tertiary amines exhibit different reactions with nitrous acid.

Primary aliphatic amines, when treated with nitrous acid, form unstable aliphatic diazonium salts that quantitatively release nitrogen gas and alcohols. The quantitative evolution of nitrogen is used for the estimation of amino acids and proteins.

Aliphatic and aromatic primary amines undergo the carbylamine reaction, producing foul-smelling isocyanides, when heated with chloroform and ethanolic potassium hydroxide. This reaction, known as the carbylamine reaction or isocyanide test, is utilized as a test for primary amines.

Steric hindrance to hydrogen bonding occurs when the alkyl group is larger than -CH₃, affecting the order of basic strength. The nature of the alkyl group, changing from -CH₃ to -C₂H₅, leads to a shift in the order of basic ...

The order of basicity for aliphatic amines, determined by the stability of substituted ammonium cations, is primary > secondary > tertiary, contrary to the inductive effect-based order.

The basicity of amines is related to their structure, and it depends on the ease of cation formation by accepting a proton. The more stable the cation relative to the amine, the stronger the amine’s basic character.