Jones oxidation of glycerol catalysed by small gold clusters

Abstract

We present here a joint theoretical and experimental study on the oxidation reactivity of glycerol catalysed by chemically pure small Au clusters in the absence and presence of H₂O₂. From high-resolution mass spectrometry, fruitful products of glyceraldehyde, glyceric acid, tartronic acid, mesoxalic acid and glycolic acid are observed pertaining to the successive Jones oxidation process associated with C–O and C–H bond activation. We then fully demonstrate the reaction pathways on the basis of a complementary-active-sites mechanism, revealing the favourable dehydration of glycerol followed by oxidation to form glyceraldehyde and carboxylic acids in the presence of small Au clusters and H₂O₂. It is found that the Au_n/H₂O₂ system undertakes a heterolytic mechanism by firstly transferring an O-atom from H₂O₂ to the Au cluster forming an active intermediate, on which hydride abstraction and subsequent oxygen rebound become thermodynamically possible, promoting the C–H insertion reaction and further oxidation of aldehyde to carboxylic acids.