Selective Activation of Methyl C–H Bonds of Toluene by Oxygen on Metallic Gold

Abstract: In accord with its gas phase acidity, toluene is activated by atomic oxygen adsorbed on Au(111) at the methyl C–H bonds. Titration of this species from the surface with HCOOD yields C₆H₅CHD₂, indicating that much of the toluene has been doubly deprotonated at the methyl carbon. Even at low surface coverages of atomic oxygen the thusly-activated species yields only CO, CO₂ and water as gas phase products when heated above room temperature, indicating the facile formation of an adsorbed benzoate, not simple oxygen insertion into the carbene to form benzyl benzyloxy. At higher O pre-coverages benzoic acid forms between 400 and 500 K. Graphical Abstract: [Figure not available: see fulltext.]