Which of the following compounds cannot be analysed correctly for nitrogen by the Kjeldahl method?

Anitrobenzene, $C X_{6} H X_{5} NO X_{2}$
Bazobenzene, $C X_{6} H X_{5} N = NC X_{6} H X_{5}$
Cethanamide, $CH X_{3} CONH X_{2}$
Dpyridine, $C X_{5} H X_{5} N$

Answer: A, B, D

Kjeldahl digestion converts amino and amide nitrogen to ammonium sulphate. Nitro compounds, azo compounds and compounds with nitrogen in the ring (pyridine) do not give all their nitrogen as ammonium sulphate, so (A), (B) and (D) fail. Ethanamide works.

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