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  Home > JCE Print > Journal of Chemical Education > Issues > 2004  > July  >
In the Laboratory
Thin–Layer Chromatography: The "Eyes" of the Organic Chemist
Hamilton Dickson, Kevin W. Kittredge, and Arlyne M. Sarquis
Department of Chemistry and Biochemistry, Miami University–Middletown, Middletown, OH 45042
Cover
July 2004
Vol. 81 No. 7
p. 1023
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 utilized by solving a simulated application where students run a reaction and monitor its progress by TLC. When TLC analysis shows all of the starting material is consumed and only product is present in the reaction mixture, the reaction should be stopped and the product isolated.
Supplement
Student and instructor notes are available.
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*  Citation
 Dickson, Hamilton; Kittredge, Kevin W.; Sarquis, Arlyne M. J. Chem. Educ. 2004 81 1023.
*  Keywords
 Chromatography; General Chemistry; Inquiry-Based / Discovery Method; Introductory / High School Chemistry; Laboratory Instruction; Organic Chemistry
*  History
 Created:
Last Updated:		 May 27, 2004
January 19, 2005
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