Question

An organic compound ‘A’ contains nitrogen and chlorine. It dissolves readily in water to give a solution that turns litmus red. Titration of compound ‘A’ with standard base indicates that the molecular weight of ‘A’ IS 131±2. When a sample of ‘A’ is treated with aq. NaOH, a liquid separates which contains N but not Cl. Treatment of the obtained liquid with nitrous acid followed by phenol gives orange precipitate. The compound A is :

• A.
• B.
• C.
• D.

Answer 1

The Correct Option is D

To solve this problem, we need to identify the organic compound 'A' based on the given properties and reactions it undergoes. Let's analyze the details step-by-step: 

• Compound Properties: The compound 'A' contains nitrogen and chlorine and is acidic in nature, as it turns litmus red.
• Molecular Weight: The given molecular weight of 'A' is around 131±2.
• Reaction with NaOH: When treated with aqueous NaOH, a liquid separates that contains nitrogen but not chlorine. This suggests the formation of a compound that has nitrogen but has removed the chlorine, likely as a gaseous product like HCl.
• Diazotization: The liquid obtained after treatment with NaOH, when reacted with nitrous acid and phenol, gives an orange precipitate. This indicates the presence of a primary aromatic amine, as diazotization followed by coupling with phenol yields azo dyes.

Based on these observations, the compound 'A' is likely to be an aromatic amine with a hydrochloride form, as aromatic amines can undergo diazotization and azo coupling reactions.

Let's consider the options provided and their structures:

The compound depicted in the image corresponds to a hydrochloride salt of an aromatic amine. It fits all the conditions:

• Dissolves in water to form an acidic solution (due to HCl present).
• Has a molecular weight close to 131 g/mol.
• Reacts with NaOH to release HCl and form a free amine.
• Undergoes diazotization and coupling with phenol to form an azo dye, indicating it is a primary aromatic amine.