Question

An organic compound containing nitrogen, sulphur, and oxygen as extra elements is fused with metallic sodium and then extracted with distilled water.
Which of the following species is/are present in the Lassaigne’s extract?

• A. $C{N}^{-}$
• B. $N{O}_3^{-}$
• C. $[SCN{]}^{-}$
• D. $S^{2-}$

Answer 1

Answer: (A), (C), (D)

$S^{2-}$

Given, the organic compound has $C,H,N,S\text{and}O$
In Lassaigne's test, the elements present in a compound are converted from covalent to ionic form by fusing the organic compound with Sodium $\left(Na\right)$ metal because ionic forms are more reactive.
Thus, carbon and nitrogen will form cyanide ion and $N{a}_{2}S$ will be formed from sulphide ion.
Since, both nitrogen and sulphur are present in the organic compound, sodium thiocyanate is formed.
$Na+C+N\stackrel{\Delta }{⟶}NaCN2Na+S\stackrel{\Delta }{⟶}N{a}_{2}SNa+C+N+S\stackrel{\Delta }{⟶}NaSCN$

Cyanides, sulphides and thiocyanate of sodium formed on sodium fusion are extracted from the fused mass by boiling with water.
This extract is known as Sodium Fusion Extract (Lassaigne Extract).
Thus, $N{O}_3^{-}$ is not present in the Lassaigne's Extract.
Therefore, the correct options are (b), (c) and (d).