Jones oxidation of glycerol catalysed by small gold clusters

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.