The number of compounds from the following which can undergo reaction with Br ₂ /KOH (alcoholic) to give respective products and these respective products can also be obtained separately by Gabriel phthalimide reaction is :

Step-by-step solution

The reaction of an amide with Br ₂/ KOH (alcoholic) is the Hoffmann bromamide degradation reaction. This reaction is specific to primary amides ( R- CONH ₂ ) and produces primary amines ( R- NH ₂ ) with one less carbon atom. Among the given compounds, the primary amides are: 1. Benzamide ( C ₆ H ₅ CONH ₂ ) 2. 2-Phenylacetamide ( C ₆ H ₅ CH ₂ CONH ₂ ) 3. Acetamide ( CH ₃ CONH ₂ ) 4. Cyclohexanecarboxamide ( C ₆ H ₁₁ CONH ₂ ) The other two compounds (N-ethylcyclohexanecarboxamide and N-methylpivalamide) are secondary