Chemistry · Qualitative analysis: Detection of nitrogen, sulphur, phosphorus and halogens
The covalent compound which does not give a positive test in Lassaigne's test is
The covalent compound which does not give a positive test in Lassaigne's test is:
- A. 1,3-dinitrobenzene
- B. glycine
- C. urea
- D. hydrazine
Step-by-step solution
Lassaigne's test detects nitrogen only if it is covalently bonded to carbon, forming cyanide upon fusion with sodium. Hydrazine (N2H4) lacks carbon-nitrogen bonds, so it does not produce cyanide, resulting in a negative test. In contrast, 1,3-dinitrobenzene, glycine, and urea all contain C-N bonds and give positive tests.
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