In the organic teaching lab, students often struggle to determine where their desired compound is between two colorless solvents during extractions. We have developed a series of demonstrations and a lab to visualize the partition equilibrium during the extraction process. These experiments make use of the fact that the water solubility of some polycyclic aromatic hydrocarbon (PAH) derivatives is pH-dependent. Specifically, we have examined the fluorescence and solvatochromism of anthracene (a PAH) and various anthracene derivatives under UV light to visually monitor their partition equilibrium. Additionally, we use UV-Vis to quantify the partitioning of these compounds. This work serves as a tool for students to see the conditions under which compounds move from one phase to another. In particular, by using acid-base extraction conditions these experiments facilitate students' ability to understand and apply the concepts of pH and pKa.

Visualization of the partition equilibrium of polycyclic aromatic hydrocarbons

245th National Meeting (2013)

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