Question

Which compounds do not give Lassaigne test for nitrogen?

• A. $C_6{H}_5{N}_{2}Cl$
• B. ${NH}_2-{CH}_2-COOH$
• C. ${NH}_{2}OH$
• D. ${CH}_{3}CO{NH}_2$

Answer 1

The correct option is A $C_6{H}_5{N}_{2}Cl$

Lassigne’s test is used for detection of Nitrogen, halogens, Sulphur and Phosphorous. The elements present in the compound are converted from covalent into ionic form by fusing the compound with sodium metal. Following reactions take place:

$NaCN+C+N\stackrel{\Delta }{\to }NaCN$

$2Na+S\stackrel{\Delta }{\to }N{a}_{2}S$

$Na+X\stackrel{\Delta }{\to }NaX(X=Cl,Br,I)$

Carbon and nitrogen present in the compound gives NaCN. Benzene diazonium chloride on fusion loses N, hence can’t form NaCN on fusion with Na.

Hence,(a) is the correct answer.