For which of the following classes of compounds will Kjeldahl's method fail to estimate the nitrogen — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Kjeldahl's method relies on converting nitrogen to $(NH_4)_2SO_4$. This conversion fails for nitrogen atoms within an aromatic ring (like pyridine or quinoline), nitro groups, and azo groups because they do not quantitatively yield ammonium sulphate upon digestion. Primary aliphatic amines pose no such issue.