Introducing\nColumn Chromatography through Colorful\nReactions of Guaiazulene

We report two related experiments\nto introduce column chromatography\nin the context of a second-year organic chemistry lab course or an\nupper-division advanced organic chemistry lab course. Both experiments\ninvolve functionalization of guaiazulene via electrophilic aromatic\nsubstitution, and the highly colored starting material and products\nserve as clear visual indicators of reaction progress and of the purification.\nThe longer version of the experiment scaffolds the chromatography\nprocess by guiding students to develop conditions to purify their\nown unique compound. The products are amenable to a wide variety of\ncharacterization techniques, including UV–visible absorbance\nspectroscopy and 2D NMR spectroscopy. These experiments are highly\nflexible and have been implemented in a second-year course as an activity\ntaking a single lab period and in an upper-division course as an activity\ntaking three full lab periods. As judged by the results and discussion\nfrom their lab reports, students in both classes were largely successful\nat meeting the learning objectives for these experiments, including\nmonitoring reaction progress using thin-layer chromatography, separating\ncompound mixtures using column chromatography, and assessing the success\nof a reaction based on experimental data.