An Undergraduate Organic Chemistry Laboratory Experiment: The Use of Thin Layer Chromatography to Monitor the Hydrogenation of Unsaturated Esters

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 18 (2013) pp 255-258
DOI 10.1007/s00897132509

An Undergraduate Organic Chemistry Laboratory Experiment: The Use of Thin Layer Chromatography to Monitor the Hydrogenation of Unsaturated Esters

Kenneth O’Connor

Department of Chemistry, Marshall University, One John Marshall Drive, Huntington, WV 25755, oconnor9@marshall.edu
Received June 19, 2013. Accepted July 18, 2013.

Published: 23 September 2013

Abstract. Thin layer chromatography (TLC) represents a simple yet valuable technique employed by chemists for monitoring the progress of a chemical reaction. In most undergraduate organic lab courses, students conduct an experiment using TLC. For example, the reduction of benzophenone with NaBH₄ can be easily monitored by TLC in order to determine when the reaction has gone to completion. Unfortunately, virtually all of the experiments published in organic chemistry laboratory textbooks that incorporate TLC involve reactions that are conducted in an open atmosphere. Consequently, students do not learn how to use TLC to determine when a reaction has gone to completion for reactions that take place under an inert or gaseous atmosphere. A micro-scale hydrogenation experiment of unsaturated esters using 5% Pd/C has been developed to address this void in organic chemistry lab courses. This experiment enables students to master the use of thin layer chromatography to monitor the progress of a reaction conducted under a gaseous atmosphere. During pre-lab, a guided inquiry approach was used to teach students how to sample the reaction by using a 16 gauge (G) needle and a 30 µL micropipette. Methyl trans-cinnamate and dimethyl fumarate were chosen as representative alkenes. Student yields were between 50-90% with an average yield of approximately 70–75%.

Key Words: Laboratories and Demonstrations; organic chemistry; undergraduate; laboratory; experiment; hydrogenation; thin layer chromatography; catalyst; palladium; alkene; ester; critical thinking

(*) Corresponding author. (E-mail: oconnor9@marshall.edu )

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Supporting Materials:

The proton NMR and IR spectra of methyl 3-phenyl propionate, a student handout and instructor notes are included in the supporting materials (298 KB).