Question

Lassaigne's test for the detection of nitrogen
fails in

• A. NH${}_2$CONHNH${}_2$ . HCI
• B. NH${}_{2}N{H}_2$ . HCI
• C. $N{H}_{2}CON{H}_2$
• D. $C_6{H}_{5}NHN{H}_2.HCI$

Answer 1

Answer: (B)

Lassaigne's test is given by only those compounds which contain both carbon and nitrogen. When compounds containing C and N heated with sodium, then it form NaCN which is easily detected by FeCl${}_3$ $Or$ Some compounds live hydrazine (NH${}_2$ . NH${}_2$) although contain nitrogen but they do not respond Lassaigne's test because they do not have any carbon and hence, NaCN is not formed.