Visually Tracking Acid-Base Extractions Using Colorful Compounds

Acid-base extraction is an important concept in organic chemistry that beginning students often find challenging to comprehend. Herein, we describe the use of a simple demonstration suitable for lecture that allows students to visually track the chemical events that take place in a separatory funnel. The demonstration involves the use of two safe and available dyes with different acid-base properties, phenolphthalein and neutral red. The dyes present distinct colors in their ionic and nonionic forms. With a change in the pH of the media in the separatory funnel, the colors of the solutions change according to the compounds' ionic states and their solubilities in either the aqueous or the organic layers. This provides a visual record of chemical concepts, which helps students to better understand the partition of different molecules between the organic and aqueous layers in an extraction process. In addition, we provide resources describing how to use this demonstration in class aiming to enhance students' engagement and comprehension of the topic.