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.
How is the reactivity of tertiary amines towards benzenesulphonyl chloride different from primary and secondary amines, and how is this property utilized in amine distinction and separation?
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Tertiary amines do not react with benzenesulfonyl chloride (Hinsberg’s reagent) under mild conditions, making them unresponsive to this reagent. This contrasts with primary and secondary amines, which undergo substitution reactions. The unreactivity of tertiary amines with Hinsberg’s reagent is utilized for amine distinction and separation. In a mixture of primary, secondary, and tertiary amines, treatment with benzenesulfonyl chloride allows selective identification and isolation of tertiary amines based on their lack of reactivity. This property aids in the stepwise differentiation and characterization of various amine functionalities in organic synthesis and analysis.