Question

Which of the following compounds gives blood red coloration when its Lassaigne's extract is treated with ferric chloride?

• A. Thiourea $\left(C{H}_4{N}_{2}S\right)$
• B. Diphenyl sulphide $\left(C_{12}{H}_{10}S\right)$
• C. Phenyl hydrazine $\left(C_6{H}_8{N}_2\right)$
• D. Benzamide $\left(C_7{H}_{7}NO\right)$

Answer 1

The correct option is A Thiourea $\left(C{H}_4{N}_{2}S\right)$

Thiourea is a compound which has got sulfur, carbon, and nitrogen.
The sodium fusion extract of the compound will have thiocyanate ions resulting red colour of ferric ions.
$NaSCN+FeC{l}_3\to \underset{BloodRed}{\left[Fe\right(SCN){]}^{2+}}$
Hence answer is option a.