Question

Following is a confirmatory test for aromatic primary amines. Identify reagent (A) and (B)

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The Correct Option is D

The given reaction is a confirmatory test for aromatic primary amines, which typically involves converting the amine into a diazonium salt followed by reaction with a phenol derivative to produce a dye. Here is a step-by-step explanation:

1. Formation of Diazonium Salt: The aromatic primary amine reacts with nitrous acid, generated in situ from sodium nitrite (NaNO₂) and hydrochloric acid (HCl), to form a diazonium salt. Therefore, reagent (A) is NaNO₂/HCl.
2. Coupling Reaction: The diazonium salt then undergoes a coupling reaction with a phenol compound. In this case, the reaction occurs in the presence of sodium hydroxide (NaOH), leading to the formation of a scarlet red dye. Hence, reagent (B) is a phenol derivative, often with NaOH present to facilitate the reaction.

Given this understanding, the correct reagents for (A) and (B) should correspond to the diazonium formation and coupling reaction as explained.

Therefore, the correct answer is the option where (A) is NaNO₂/HCl and (B) is a suitable phenol derivative in NaOH solution, forming the scarlet red dye.