Question

Diazo compounds, sometimes do not respond Lassaigne’s test for nitrogen because
(a) these are quite stable compounds and do not decompose to elemental nitrogen
(b) these contain very little carbon
(c) these form organometallic compounds with sodium
(d) their nitrogen contents is removed, during heating, in the form of nitrogen gas

Answer 1

As diazonium salts are unstable and lose nitrogen as N2 gas on heating. hence during fusion, no NACN is formed in lassaigne's extract due to the loss of nitrogen.

hence (d) is the correct answer

Answer 2

Diazo compounds do not respond to Lassaigne's test due to loss of nitrogen:

• Lassaigne's test is usually carried out to detect the presence of N, S, and X(halogens) in an unknown chemical compound.
• To test for presence of nitrogen, the sodium fusion extract that is formed is heated at a high temperature with FeSO₄ after which the addition of H₂SO₄ is done for acidification.
• Acidification oxidizes ferrous to ferric ions resulting in the formation of ferriferous cyanide and production of a Prussian blue coloration indicating the presence of nitrogen.
• Diazo compounds when exposed to higher temperature decompose and results in the formation of elemental nitrogen which escapes as a gas. Due to this NaCN cannot be formed, and a positive test for nitrogen is not obtained.
• Thus, diazo compounds do not respond to  Lassaigne's test for nitrogen because (Option d) their nitrogen contents are removed during heating, in the form of nitrogen gas.