Kjeldahl's method cannot be used to estimate nitrogen for which of the following compounds?

Question

Canvas Classes · Accepted Answer

Step 1: Recall Kjeldahl's Limitations

Kjeldahl's method converts N to  using conc. . It FAILS for:
- Nitro groups (): N in high oxidation state, not reduced to 
- Azo groups (): N-N bonds not cleaved under Kjeldahl conditions
- Nitriles (): C≡N triple bond → some sources say nitriles CAN be estimated; depends on the question
- Heteroaromatic N (pyridine): aromatic C-N bonds too stable

Step 2: Evaluate Each Option

(a) Urea  — Contains  (amide-like N) → Kjeldahl WORKS ✅

(b) Aniline  — Contains

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