The sodium extract of an organic compound (fused with excess sodium) gives a black precipitate with lead acetate in acetic acid, but gives neither Prussian blue nor a blood-red colour. The compound could be

Athiourea, $H X_{2} NCSNH X_{2}$
Bbenzenesulfonamide, $C X_{6} H X_{5} SO X_{2} NH X_{2}$
Cthiophenol, $C X_{6} H X_{5} SH$
Daniline, $C X_{6} H X_{5} NH X_{2}$

Answer: C

The black precipitate is

PbS

, so sulphur is present. Absence of Prussian blue shows that nitrogen is absent, which excludes thiourea and benzenesulfonamide. Aniline contains no sulphur. Only thiophenol fits.

Practice Structural Identification and Practical Organic Chemistry More on Estimation of elements: Lassaigne, Kjeldahl, Carius

Previous questionNext question

The sodium extract of an organic compound (fused with excess sodium) gives a black precipitate with lead acetate in acetic acid, but gives neither Prussian blue nor a blood-red colour. The compound could be

Answer: C

More questions on Estimation of elements: Lassaigne, Kjeldahl, Carius