Question

Consider the reactions: Y \(\xrightarrow{i.\ LiAlH_4,\ ii.\ H_2O}\) X; \(CONH_2 \xrightarrow{Br_2/OH^-}\) X. Statements: I. \(pK_b\) of X \(>\) Y; II. Both form stable diazonium salts with \(NaNO_2/HCl\); III. Both prepared by ammonolysis.

• A. I, II only
• B. II, III only
• C. I only
• D. I, III only

Hint:

Hofmann bromamide degradation decreases the carbon chain length by one carbon atom while converting amides into primary amines.

Answer 1

The Correct Option is D

Concept: Hofmann bromamide degradation converts amides into primary amines.

Step 1: Identify X and Y.
\[ CONH_2 \xrightarrow{Br_2/OH^-} \text{Primary amine} \] Reduction of nitro compounds using \(LiAlH_4\) also gives primary amines. Thus: \[ X = \text{amine} \] \[ Y = \text{nitro compound} \]

Step 2: Evaluate statement I.
Amines are basic, while nitro compounds are far less basic. Hence statement I is considered correct.

Step 3: Evaluate statement II.
Only primary aromatic amines form stable diazonium salts. Nitro compounds do not form diazonium salts. Hence statement II is incorrect.

Step 4: Evaluate statement III.
Primary amines can be prepared by ammonolysis of alkyl halides. Thus statement III is correct. Hence: \[ \boxed{I,\ III\ only} \]