Question

Why does hydrazine not give test for Lassaigne’s extract?

Answer 1

For an organic compound to show positive result for Lassaigne's test it must be composed of carbon. If carbon is absent in an organic compound it does not show positive result for Lassaigne's test.

Hydrazine is an organic compound composed of elements nitrogen and hydrogen. When this compound is treated with Lassaigne's reagent due to absence of carbon it does not leads to the formation of NaCN, the primary driver of the test.