Principle of column chromatography on silica gel

• Silica gel is a polar stationary phase.
• Hence, less polar compounds move faster and elute earlier.
• More polar compounds interact more strongly with silica and elute later.

Compare the polarity of the given compounds

We must arrange:

• (A) benzanilide
• (B) aniline
• (C) acetophenone

(i) Acetophenone (C)

• Contains one carbonyl group: $\mathrm{C_6H_5COCH_3}$
• It is polar, but it has no N-H group to form very strong hydrogen-bonding interaction with silica.
• So its adsorption is moderate.

(ii) Benzanilide (A)

• It is an amide: $\mathrm{C_6H_5CONHC_6H_5}$
• Amides are quite polar because of the $-CONH-$ group.
• It can interact strongly with silica by dipole interaction and hydrogen bonding.
• Hence it should be retained more than acetophenone.

(iii) Aniline (B)

• Structure: $\mathrm{C_6H_5NH_2}$
• The amino group is basic and strongly interacts with the acidic silanol groups of silica gel.
• Therefore, aniline is usually strongly retained on silica and elutes last among these.

Order of elution

Since the least strongly adsorbed compound comes out first: $\text{acetophenone} < \text{benzanilide} < \text{aniline} \quad \text{(in retention strength)}$

Therefore, the sequence of compounds obtained is: $(C), (A), (B)$

Match with options

• Option A: $(A), (B), (C)$ ❌
• Option B: $(B), (A), (C)$ ❌
• Option C: $(C), (A), (B)$ ✅
• Option D: $(B), (C), (A)$ ❌

Final answer

The correct sequence is: $\boxed{(C), (A), (B)}$ So the correct option is C.