Question

Phenols do not respond to which of these tests?

• A. Ferric chloride test
• B. Litmus test
• C. Bromine test
• D. Nessler's reagent test

Answer 1

The correct option is D

Nessler's reagent test

Explanation for the correct option:

Option (D): Nessler reagent test

• Nessler's reagent is used to test ammonia, which gives a brown color precipitate with Nessler reagent
• Nessler's reagent reacts with Ammonia in the presence of $\mathrm{KOH}$ to produce a brown color complex.
• $\underset{\mathrm{Nessler}\text{'}\mathrm{s}\mathrm{reagent}}{2{\mathrm{K}}_2\left[{\mathrm{HgI}}_4\right]}+3\mathrm{KOH}+{\mathrm{NH}}_3\to \underset{\mathrm{Brown}\mathrm{ppt}.}{[{\mathrm{OHg}}_2.{\mathrm{NH}}_2]\mathrm{I}}+7\mathrm{KI}+2{\mathrm{H}}_2\mathrm{O}$

Explanation for the incorrect options:

Option (A): Ferric chloride test

• This test is used to check the presence of phenol.
• In addition to ferric chloride, a Compound with a phenol group forms a blue, violet, or purple colour compound.

Option (B): Litmus test

Phenol is acidic in nature, so it will give a litmus test. Phenol turn blue litmus solution to red.

Option (C): Bromine test

• The $(-\mathrm{OH})$ group in phenol is an electron-withdrawing group making the ring highly reactive.
• When Bromine water is added to the phenol solution, the solution is decolorized, and a white precipitate of $2,4,6-\mathrm{tribromophenol}$ is formed.

Hence, Option (D) is correct.