Reduction of Acetylferrocene to 1-(Ferrocenyl)ethanol Using Ammonia-Borane (NH3·BH3) in Water Medium: A Green Laboratory Experiment

Abstract

In this submission, we report a green laboratory experiment involving the reduction of acetylferrocene to 1-(ferrocenyl)ethanol using ammonia borane as the reductant and water as the green solvent. We found this as an interesting, educative, and inexpensive experiment that was easily conducted within a laboratory slot of 4 h. It is also a cost-cutting experiment as the reactants needed for the experiment can be obtained as compounds prepared by students from laboratory experiments that are carried out earlier, thus saving expenses on costly starting materials and reducing chemical wastage. The reduction of acetyl ferrocene in water medium occurs at a moderate temperature (80 °C) and is completed within 2 h, while the product purification, crystallization, and spectral characterization have been completed within another hour. The progress and completion of the reaction were monitored by thin-layer chromatography, and a crystalline product was obtained by ethyl acetate and hexane extraction followed by open evaporation of the hexane extract. The final product was characterized using spectroscopic methods (IR, ¹H NMR), and melting point determination. The safe and environmentally friendly conditions of the reaction and the use of reactants prepared from previously conducted experiments make this experiment accessible to undergraduate- and graduate-level synthetic laboratories across the world. This experiment helps to teach students the principles of green chemistry and how reactions that were traditionally carried out in organic solvents can be conducted in a water medium. The procedure also teaches how upcycling products from a previous experiment can be carried out, thus preventing chemical wastage. The students also learn the green principle of replacing traditional chromatographic workup with less solvent-intensive approaches. The spectral analysis part helps students understand how functional group interconversions from ketones to alcohols can be monitored by using spectroscopic techniques.