Colorful Chemical Demonstrations on the Extraction of Anionic Species from Water into Ether Mediated by Tricaprylylmethylammonium Chloride (Aliquat 336), a Liquid–Liquid Phase-Transfer Agent

Abstract

Liquid–liquid phase transfer catalysis (LLPTC) plays an ever-increasing role in academic research and in the large scale industrial production of chemicals. This method involves a biphasic medium composed of water and an organic solvent in which the LLPT-catalyst plays a critical role in the transport of some water-soluble reagents (e.g., nucleophiles or bases) from water into the organic layer. This article provides a list of easy to perform and relatively safe experiments that may be used to demonstrate the extraction of some colorful water-soluble reagents by Aliquat 336 into ether. This demonstrative process serves to simulate the preliminary extractive step of an ionic species in LLPT-catalyzed reactions and introduce various undergraduate chemistry concepts and principles to students.

Visually Tracking Acid–Base Extractions Using Colorful Compounds

“…This enables students to visually follow the solubility change and partition between the two immiscible layers after shaking the separatory funnel. Dyes have been widely used to illustrate a variety of chemical properties and concepts such as solubility, acid–base chemistry, chromatographic separation, distillation, and LLE. ,,,− ,− In previous work describing laboratory experiments on LLE, authors employed these colored compounds as a visual aid to help students determine the partitioning of molecules into different layers as a function of pH. Sudan Blue and Congo Red, or Nile Blue and 2,6-dichloroindophenol, are among the most common dyes utilized for this purpose.…”

“…Classroom demonstrations are a valuable tool that instructors can take advantage of in order to help students be more involved with chemical concepts and develop a connection between them . In class demonstrations involving liquid–liquid extraction (LLE) have been previously reported. − However, they utilize hazardous materials that are not safe to be handled in a classroom environment. Herein, we describe a visual demonstration utilizing commercially available colorful compounds that can be employed to enhance students’ overall comprehension of acid–base LLE.…”

Colorful Approach to Teaching Extraction Using Azo Dyes and Comparison of Hands-On vs Distance Learning Assessment

“…Colored indicator materials have long been used to help students visualize acid/base theory during titrations, − but instructional use of the dye structures themselves have only recently been published. − Food dyes, natural pigments, and biological stains have also been explored with TLC, , paper chromatography, , column chromatography, − and liquid–liquid extraction, − though these have focused on learning laboratory technique, without relating reactivity to structure. We have chosen conjugated azo dyes (Table ) to demonstrate their acid/base properties using extraction, as they are inexpensive, stable solids that come in a variety of colors.…”

“…Students can compare functional groups to directly connect the acid/base properties with the structure of the dyes. We chose to focus on simple azo dyes rather than previously published indicators like phenolphthalene, Nile blue, and larger azo dyes like congo red. , By using the same general structure, we believe the identification of the functional groups is easier for students just beginning organic chemistry. As an added benefit, many dyes can be synthesized by students using diazo coupling (Figure ) as part of an experiment on the reactivity of nitrogen compounds or dyeing .…”

ÊA simple approach for THE DETERMINATION AND CHARACTERIZATION OF TERNARY PHASE DIAGRAMS of aqueous two-phase systems composed of water, poly(ethylene) glycol and sodium carbonate

“…The determination of ternary phase diagrams of ATPS composed of water, sodium carbonate and PEG of different molecular weights is proposed. Several laboratory experiments aimed at teaching liquid-liquid extraction have been reported, [7][8][9][10][11][12][13][14] yet few involve the determination of the ternary liquid-liquid phase diagrams. [15][16][17][18][19] Since ATPS are here proposed, this work also provides the opportunity to discuss the environmental advantages associated to water-rich systems.…”