Which of the following compounds CANNOT be analyzed for its nitrogen content using Kjeldahl's method — Practical Organic Chemistry and Purification Chemistry Question

💡 Solution & Explanation

Kjeldahl's method cannot be used for the estimation of compounds containing nitrogen in a ring structure (like pyridine and quinoline), nitro compounds ($-NO_2$), or azo compounds ($-N=N-$). This is because the nitrogen in these specific groups cannot be quantitatively converted into ammonium sulphate during digestion with $H_2SO_4$.