Separation of primary , secondary and tertiary amines by Hoffmann's method

The mixture of three amines is treated with diethyl oxalate. The primary amine forms a solid oxamide, a secondary amine gives a liquid oxamic ester while tertiary amine does not react.

Hofmann method of separation of amines.JPG

Primary amine is recovered when solid oxamide is heated with caustic potash solution and collected as distillate on distilling the reaction mixture.


Hofmann method of separation of amines1.JPG

The liquid (mixture of oxamic ester+ tertiary amine) is subjected to fractional distillation when tertiary amine distils over.

The remaining liquid is distilled with KOH to recover secondary amine.

Hofmann method of separation of amines2.JPG

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