Principle of Lassaigne's test for nitrogen

In Lassaigne's test, the organic compound is fused with sodium. If nitrogen is present along with carbon, sodium converts them into sodium cyanide: $\text{Na} + \text{C} + \text{N} \rightarrow \text{NaCN}$ Then cyanide ion is detected through Prussian blue formation.

So, for a nitrogen-containing compound to give a positive Lassaigne's test for nitrogen, it must generally contain both carbon and nitrogen.

Check each option

A: Glycine Formula: $\mathrm{NH_2CH_2COOH}$ It contains carbon and nitrogen, so on sodium fusion it can form $\mathrm{NaCN}$. Hence, glycine gives Lassaigne's test.

B: Phenyl hydrazine Formula: $\mathrm{C_6H_5NHNH_2}$ It contains carbon and nitrogen, so it gives Lassaigne's test.

C: Urea Formula: $\mathrm{NH_2CONH_2}$ It contains carbon and nitrogen, so it gives Lassaigne's test.

D: Hydrazine Formula: $\mathrm{N_2H_4}$ It contains nitrogen but no carbon. Therefore, during sodium fusion, $\mathrm{NaCN}$ cannot be formed. Hence, hydrazine does not give Lassaigne's test.

Conclusion

The compound that does not give Lassaigne's test is: $\boxed{\text{D: Hydrazine}}$

Comparison with stored correct answer

Stored correct answer: D

My derived answer: D

Therefore, the derived answer agrees with the stored correct answer.