Question:

Which of the following compounds is not expected to show Lassaignes' test for nitrogen ?

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In Lassaigne's test nitrogen is detected as NaCN, which needs carbon in the compound to form.
Updated On: Oct 31, 2026
  • Propanenitrile
  • Hydroxylamine hydrochloride
  • Nitromethane
  • Ethanamine
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The Correct Option is B

Solution and Explanation

Lassaigne's test: the organic compound is fused with sodium metal; carbon and nitrogen combine to form sodium cyanide: \(\mathrm{Na + C + N \rightarrow NaCN}\). NaCN is then tested with \(\mathrm{FeSO_4}\), \(\mathrm{FeCl_3}\) (Prussian blue).
Propanenitrile (\(\mathrm{C_2H_5CN}\)), nitromethane (\(\mathrm{CH_3NO_2}\)) and ethanamine (\(\mathrm{C_2H_5NH_2}\)) all contain both C and N, so they give NaCN.
Hydroxylamine hydrochloride (\(\mathrm{NH_2OH\cdot HCl}\)) contains N but no carbon, so no NaCN can form and the test fails.
Answer: (2) Hydroxylamine hydrochloride
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