Microscale Catalytic and Chemoselective TPAP Oxidation of Geraniol

The mild, room-temperature oxidation of a primary alcohol catalyzed by tetrapropylammonium perruthenate (TPAP) is presented for the undergraduate organic laboratory. In this experiment, geraniol is oxidized to form geranial, a liquid product that is easily characterized via IR and proton NMR spectroscopy. Both substrate and product have very distinct and pleasant odours, so their respective reactivity and formation generates class interest. Comparison between this synthesis and other alcohol oxidation procedures affords discussion of catalytic behaviour apparent in the former method. Although catalysis is favourable in terms of green chemistry, certain improvements can be made from a sustainability perspective, which is an important focal point for student discourse. The reaction also provides an opportunity to perform a reaction under dry conditions, and to investigate a detailed autocatalytic mechanism of TPAP oxidation.