Key Concept: Haloform Reaction

The haloform reaction occurs when a compound containing the group:

–CO–CH₃ (methyl ketone)

is treated with halogen in the presence of base (Br₂/NaOH).

General Reaction

R–CO–CH₃  →  Br₂/NaOH  →  R–COO⁻ + CHBr₃

After acidification, the carboxylate ion converts into a carboxylic acid:

R–COO⁻  →  H⁺  →  R–COOH

👉 Only methyl ketones give carboxylic acids in this reaction.

Analysis of the Given Options

Option (A)

Structure: Bicyclic ketone (no –CO–CH₃ group)

• ❌ Does not contain a methyl ketone
• ❌ Haloform reaction does not occur
• ❌ No carboxylic acid formed

Option (B)

Structure: Benzophenone (Ph–CO–Ph)

• ❌ Carbonyl carbon attached to two phenyl groups
• ❌ No methyl group next to the carbonyl
• ❌ Does not undergo haloform reaction

Option (C)

Structure: Acetophenone (Ph–CO–CH₃)

• ✅ Contains the methyl ketone group (–CO–CH₃)
• ✅ Undergoes haloform reaction with Br₂/NaOH
• ✅ Produces benzoate ion, which on acidification gives
  Benzoic Acid (C₆H₅COOH)
• ✅ Exactly matches the reaction requirement

Option (D)

Structure: tert-Butyl phenyl ketone

• ❌ Adjacent carbon has a tert-butyl group, not a methyl
• ❌ Lacks –CO–CH₃ functionality
• ❌ Haloform reaction does not occur

Final Answer

✅ Correct Answer: Option (C)

Acetophenone gives a carboxylic acid (benzoic acid) upon treatment
with Br₂/NaOH followed by acidification, due to the haloform reaction.

Quick Exam Tip

👉 Remember: Only compounds with –CO–CH₃ (methyl ketone)
or those oxidizable to it give a positive haloform reaction and form a carboxylic acid.

Key Takeaways

• Br₂/NaOH is a test for methyl ketones
• Formation of CHBr₃ confirms the haloform reaction
• Acidification converts carboxylate into carboxylic acid
• Acetophenone is a classic example