Ionic liquids and green chemistry : a lab experiment

Although ionic liquids have been investigated as solvents for many applications and are starting to be used in industrial processes, only a few lab experiments are available to introduce students to these materials. Ionic liquids have been discussed in the context of green chemistry, but few investigations have actually assessed the degree of their greenness. This experiment combines two research areas, ionic liquids and ecological assessment, in an advanced undergraduate lab course. The modular combination of these two research areas allows for the adaptation of the timetable and content. Two ionic liquids are synthesized, and the method of heating (microwave-assisted vs convective), temperature, time, and alkylating agent are varied. In addition to the yield, simple metrics (atom economy, reaction mass efficiency, E-factor) in combination with energy efficiency, prices of chemicals, and ecological impacts of the materials are considered. It is the goal of this experiment to help students realize that a synthetic method leading to quantitative yields is not a priori green: other factors (nature of reactants, energy consumption, etc.) must be assessed as well.