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Amines — Chemistry STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceChemistryAmines1 Mark
MCQ
Which compound does not give positive test in Lassaigne's test for nitrogen?
  • A
    Urea
  • ✓
    Hydrazine
  • C
    Azobenzene
  • D
    Phenyl hydrazine
✓

Answer

Correct option: B.
Hydrazine
In Lassaigne's test, the organic compound is fused with sodium.
Carbon and nitrogen present in the organic compound gives sodium cyanide $\text{(NaCN)}.$
This is further used in the test for nitrogen.
Hydrazine $\left(\mathrm{H}_2 \mathrm{N}-\mathrm{NH}_2\right)$ do not contain carbon. It cannot form $\text{NaCN}$ on fusion with sodium.
Hence, hydrazine cannot give Lassaigne's test for nitrogen.

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