Visually following the hydrogenation of curcumin to tetrahydrocurcumin in a natural product experiment that enhances student understanding of nmr spectroscopy

This laboratory experiment was developed to provide two safe and effective ways to instruct undergraduate organic chemistry students about the catalytic palladium hydrogenation reaction. Students hydrogenate curcumin either by refluxing it as a suspension in methanol with 10% Pd/C and a transfer hydrogenation chemical, such as cyclohexene, or by using a hydrogenation flow reactor, an H-Cube, a type of instrument that is rapidly becoming an industry standard. Students develop chromatography and spectroscopy skills by performing thin-layer chromatographic analysis, and if necessary, running a silica gel column on the crude material, followed by acquiring a proton NMR spectrum of the product. Approximately 101 undergraduate students performed this experiment, and the experiment's effectiveness was assessed by two methods: a qualitative postlab student self-assessment and identical quantitative pre-and postlab tests. The tests indicated that the students showed significant improvement in their understanding of NMR spectroscopy after performing the experiment.