Thin-Layer Chromatography: The "Eyes" of the Organic Chemist

Abstract

Thin-layer chromatography (TLC) is a versatile, inexpensive, and rapid analytical separation technique available to the organic chemist. This inquiry-based experiment investigates the governing principles as to why and how the technique works. Students are led into expressing the position a sample travels in a systematic manner, the retention factor, Rf. It is found that compounds that are hydrogen bond acceptors (ethers and esters) are less strongly absorbed by the silica surface and possess larger Rf values. Compounds such as alcohols and carboxylic acids which are strong hydrogen bond donors and acceptors are more strongly absorbed by the surface and have smaller Rf values. A qualitative TLC study is also performed on compounds possessing different functional groups. The order of increasing functional group polarity is observed to be: ether < ester < ketone < aldehyde < amine < alcohol < carboxylic acid and directly corresponds to their observed Rf values. Knowledge gained in earlier sections is utiliz...