Question

A chromatography column, packed with silica gel as stationary phase, was used to separate a mixture of compounds consisting of acetanilide (X), aniline (Y) and acetophenone (Z). When the column is eluted with a mixture of solvents, hexane & ethylacelate in 20:80, the sequence of obtained compounds is:

• A. (X), (Y) and (Z)
• B. (Y), (X) and (Z)
• C. (Z), (X) and (Y)
• D. (Y), (Z) and (X)

Answer 1

The correct option is C (Z), (X) and (Y)

The component which is more strongly adsorbed will be obtained later upon elution.
It also depends upon the strength of interaction between compound and mobile phase.

The solvent used for elution is hexane and ethylacetate in the ratio 20:80. Ethylacetate is polar in nature and it is in higher concentration. Since, the solvent is polar , compound which is highly polar in nature will elute first.

Among the compounds in mixture aniline is least polar.
Comparing acetanalide and acetophenone, acetanilide is less polar because the lone pair at N in acetalinide involve in resonance and reduce the polarity of the $C=O$.


Hence, acetophenone is highly polar and it elute first followed by acetanilide and aniline.
Thus, option (c) is correct.