Separation and identification of primary and secondary aliphatic amines as p-(N,N-dimethylamino)-benzene-p′-azobenzamides by paper and thin-layer chromatography

The benzoylating agent p-(N,N-dimethylamino)-benzene-p′-azobenzoyl chloride, which is used for the identification of alcohols, also reacts readily with primary and secondary amines. A series of p-(N,N-dimethylamino)-benzene-p′-azobenzamides of primary and secondary amines were prepared and optimum conditions for their synthesis were found. The chromatographic separation of amides is very good, amides of secondary amines, in particular, exhibiting extraordinarily good chromatographic properties, so that the above mentioned method of analysis is considered to be one of the best in use at present. Their derivatives are orange-red and scarlet substances and, therefore, no method of detection is necessary in their identification. This property could also be made use of in their photometric determination. The sensitivity of detection is very good, and spraying the chromatogram with 0.01 N sulphuric acid can prove the presence of less than 0.3 μg of amide in the spot.