Question

Which compound does not give positive test in Lassaigne's test for nitrogen?

• A. Urea
• B. Hydrazine
• C. Azobenzene
• D. Phenyl hydrazine

Answer 1

Answer: (B)

In Lassaigne's test, the organic compound is fused with sodium.

Carbon and nitrogen present in the organic compound gives sodium cyanide ($NaCN$).

This is further used in the test for nitrogen.
Hydrazine $(H_{2}N-N{H}_2)$ do not contain carbon. It cannot form $NaCN$ on fusion with sodium.
Hence, hydrazine cannot give Lassaigne's test for nitrogen.