Practicing Success

Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Amines

Question:

An aromatic compound (A) on treatment with aqueous ammonia and heating forms compound (B) which on heating with Br2 and KOH forms a compound (C) of molecular formula C6H7N. 

Identify (A) from the given data.

Options:

Benzaldehyde 

Benzoic acid 

Acetophenone 

None of the above 

Correct Answer:

Benzoic acid 

Explanation:

The correct answer is option 2. Benzoic acid.

Step 1:  To find out the structures of compound (B) and (C)

(i)Since compound (C) with molecular formula C6H7N is formed from compound (B) on treatment with Br2 + KOH (i.e., Hofmann Bromamide reaction), therefore, compound (B) must be an amide and (C) must be an amine. The only amine having molecular formula C7H7NO is C6H5NH2 (aniline).

(ii) Since (C) is aniline, therefore, the amide from which it is formed must be benzamide (C6H5CONH2). Thus, compound ‘B’ is benzamide.

The chemical equation showing the conversion of (B) to (C) is

Step2: To find out the structure of compound (A)

Since compound (B) is formed from compound (A) with aqueous ammonia and heating, therefore, compound (A) must be benzoic acid or benzenecarboxylic acid.