Which of the following compound gives blood red colouration when its Lassigne's extract is treated with alkali and ferric chloride ?

Options

A. Benzamide
B. Thiourea
C. Diphenyl sulphide
D. Phenylhydrazine

Answer

B

Explanation

Blood red coloration appears due to the formation of ferric thiocyanate, `Fe(SCN)_(3)`, provided the organic compound contains both `N` and `S`. Thiourea (thiocarbamide) is `H_(2)N-overset(S)overset(||)(C)-NH_(2)` . Benzamid, `C_(6)H_(5)CONH_(2) (S` is absent), dipheylsulphide, `C_(6)H_(5)-S-C_(6)H_(5) (N` is absent), phenyl-hydrazine, `C_(6) H_(5)NHNH_(2) (S` is absent).