Which compounds generally have the highest Rf values on silica gel TLC?

Which compounds generally have the highest Rf values on silica gel TLC?

• A. The least polar compounds
• B. The most polar compounds
• C. Aromatic compounds
• D. Large molecules

Answer: (A)

On a polar stationary phase like silica gel, how far a compound travels depends on how strongly it sticks to the surface versus how well it dissolves in the mobile phase. The least polar compounds interact weakly with the silica, so they are carried farther by the solvent and end up with larger Rf values. In contrast, the most polar compounds form stronger interactions with the silica, are retained longer, and move more slowly, giving smaller Rf values. So, the highest Rf values are observed for the least polar compounds. Aromaticity or molecular size alone don’t determine Rf as reliably; polarity relative to the silica governs the extent of retention.

On a polar stationary phase like silica gel, how far a compound travels depends on how strongly it sticks to the surface versus how well it dissolves in the mobile phase. The least polar compounds interact weakly with the silica, so they are carried farther by the solvent and end up with larger Rf values. In contrast, the most polar compounds form stronger interactions with the silica, are retained longer, and move more slowly, giving smaller Rf values. So, the highest Rf values are observed for the least polar compounds. Aromaticity or molecular size alone don’t determine Rf as reliably; polarity relative to the silica governs the extent of retention.