Environmentally Responsible Redox Chemistry: An Example of Convenient Oxidation Methodology without Chromium Waste

Author Contact: r.crumbie@uws.edu.au

Summary

Oxidations and reductions are among the most commonly performed reactions in organic chemistry. Consequently, it is vital that redox chemistry is taught in our undergraduate chemistry courses. Unfortunately many oxidations are classically and currently performed with toxic, carcinogenic chromium (VI) metals and require time-consuming and wasteful aqueous work-ups.

All of these abovementioned concerns are avoided in this laboratory exercise. By using Magtrieve, a magnetically retrievably oxidant, students can safely oxidize benzoin to benzil while also learning important principles of green chemistry and gaining valuable laboratory experience. Magtrieve, CrO₂, is a heterogeneous oxidant that can be retrieved by holding a magnet to the reaction flask and simply pouring the reaction mixture off, or by filtration.

This experiment has two parts; the first is the oxidation of benzoin by Magtrieve, the second is the reduction of benzil to hydrobenzoin. Combining these two experiments allows students to learn about green chemistry, oxidation and reduction chemistry, carbonyl chemistry, thin-layer chromatography, vacuum filtrations, rotary evaporation, recrystallization, melting point determination and IR spectroscopy.

Supplemental materials include background information and procedures for students, post-lab questions, an equipment list and instructor notes.

Summary prepared December 2008 by Douglas M. Young at the University of Oregon.

Category Descriptors

Chemistry Concepts

• Addition Rxn
• Aldehydes/Ketones
• Carbonyl Chemistry
• Chirality
• Oxidation/Reduction Chemistry
• Preparation of Alcohols
• Reactions of Alcohols
• Stereochemistry

Laboratory Techniques

• Heating and Cooling Methods
• IR Spectroscopy
• Rotary Evaporation
• Thin-layer Chromatography
• Vacuum Filtration

Green Chemistry Principles

• Design Less Hazardous Chemical Syntheses
• Prevent Waste
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Organic Chemistry

Target Audience

• Colleges/Universities

Source

• Journal Articles