Question

In Lassaigne’s extract of an organic compound, both nitrogen and sulphur are present, which gives blood red colour with Fe²⁺ due to the formation of;

Options

• NaSCN

• [Fe(CN)₅NOS]⁴⁻

• [Fe(SCN)]²⁺

• Fe₄[Fe(CN₆)]₃xH₂O

Answer 1

[Fe(SCN)]²⁺

Explanation:

In case nitrogen and sulphur both are present in an organic compound, sodium thiocyanate is formed, it give blood red colour and no prussian blue since there are no free cyanide ions.

\[\ce{Na + C + N + S -> NaSCN}\]

\[\ce{Fe^{+3} + SCN -> \underset{Blood red}{[Fe(SCN)]^{2+}}}\]