Between hexane and acetone under the same conditions, which tends to have a higher Rf on a normal-phase plate?

Between hexane and acetone under the same conditions, which tends to have a higher Rf on a normal-phase plate?

• A. Acetone
• B. Water
• C. Dichloromethane
• D. Hexane

Answer: (D)

On a normal-phase TLC plate the stationary phase is polar, so compounds that are more polar interact more strongly with it and move more slowly, resulting in a smaller Rf. Less polar compounds interact weakly with the surface and ride along with the mobile phase, giving a larger Rf. Hexane is nonpolar, so it has the weakest interaction with the polar surface and tends to travel the farthest under the same conditions. Acetone, being polar, sticks to the surface more and thus moves less, yielding a lower Rf. So, hexane tends to have the higher Rf in a normal-phase setup. Water would be very polar and largely stay put, while dichloromethane is moderately polar and would also show a lower Rf than hexane under the same conditions.

On a normal-phase TLC plate the stationary phase is polar, so compounds that are more polar interact more strongly with it and move more slowly, resulting in a smaller Rf. Less polar compounds interact weakly with the surface and ride along with the mobile phase, giving a larger Rf. Hexane is nonpolar, so it has the weakest interaction with the polar surface and tends to travel the farthest under the same conditions. Acetone, being polar, sticks to the surface more and thus moves less, yielding a lower Rf. So, hexane tends to have the higher Rf in a normal-phase setup. Water would be very polar and largely stay put, while dichloromethane is moderately polar and would also show a lower Rf than hexane under the same conditions.