Teaching Atom Economy and E-Factor Concepts through a Green Laboratory Experiment: Aerobic Oxidative Cleavage of meso-Hydrobenzoin to Benzaldehyde Using a Heterogeneous Catalyst

We herein report an efficient aerobic oxidative cleavage of meso-hydrobenzoin to benzaldehyde using a heterogeneous earth-abundant metal oxide catalyst. The reaction can be carried out at 70 °C in ethanol and uses a balloon filled with O₂ as oxidant. Reagents are simple and have long shelf lives, and the whole laboratory exercise can be done in 120 min, which makes it highly implementable to standard undergraduate organic curriculum. meso-Hydrobenzoin cleaves exclusively to benzaldehyde, which gives off a nice almond smell, and generates water as the only byproduct. The exercise also compares the present methodology with two other conventional diol oxidative cleavage protocols to illustrate the use of atom economy and E-factor. This laboratory exercise is suitable for second-year undergraduates because it does not require any prerequisites while demonstrating the concepts of catalysis, ease of separation, atom economy, E-factor, earth-abundant material utilization, and biomass transformation.