A Multioutcome, Guided Inquiry-Based Liquid–Liquid Extraction Laboratory for Introductory Organic Chemistry

摘要

A multioutcome, guided inquiry-based liquid–liquid extraction (LLE) experiment has been designed for introductory organic chemistry. Multiple outcomes were established by identifying a series of red and blue dyes that are (1) soluble in organic solvent, (2) soluble in aqueous solution, or (3) soluble in either the organic or aqueous layers by tuning the pH of the aqueous solution. This series of dyes led to the development of 10 different dye mixtures that can be separated using LLE. In this experiment, students first evaluate the individual solubilities of three assigned dyes under neutral, acidic, and basic biphasic conditions. The colored nature of these dyes allows students to visually follow their solubilities and thus make connections between solubility and the molecular structure, ionization, and acid/base properties of these compounds. Then, students develop a two-step LLE procedure to separate a three-component mixture of their dyes using the observations from their solubility study, and they perform their separation to verify its effectiveness. Student feedback has shown that the visual nature of this lab permitted >90 of students to prepare a successful separation procedure and that students left this lab feeling more confident about LLE. Further, students felt that this guided inquiry-based experiment allowed them to develop laboratory skills, while also improving their understanding of LLE, enhancing their problem-solving and critical thinking abilities, and increasing their engagement and enjoyment in the lab. The ability to diversify the inquiry problem ensures that all students performing this experiment gain the full benefits of conducting inquiry-based learning.