Water-assisted sonochemically-induced demethylenation of benzyl alcohol to phenol over a structurally stable cupric oxide catalyst

Novel catalytic chemistry of demethylenation of benzyl alcohol to phenol is presented here using the synergy between an earth-abundant transition metal oxide (CuO) catalyst and high frequency ultrasound (HFUS). This chemistry is achieved in water and at room temperature. Using a combination of catalyst characterization, chemical and acoustic analysis, isotope labelling and density functional theory computations, we reveal the molecular reaction mechanism, involving benzaldehyde as an intermediate. Water is not just a benign solvation medium, but it directly participates in the chemistry by getting dissociated due to sonolysis. The adsorption of the OH from water on the catalyst surface inhibits its recombination. The surface adsorbed OH from water also activates the C-H bond in benzyl alcohol to form benzaldehyde and later incorporates itself into the phenyl ring to form phenol.

Automated summary

This study presents a novel catalytic chemistry for the demethylenation of benzyl alcohol to phenol using a combination of an earth-abundant transition metal oxide (CuO) catalyst and high frequency ultrasound (HFUS). The reaction takes place in water and at room temperature. By characterizing the catalyst, analyzing the chemistry and acoustics, using isotope labelling and density functional theory computations, the researchers unveil the molecular reaction mechanism, which involves benzaldehyde as an intermediate. Water is not only a benign solvation medium, but also directly participates in the reaction by undergoing dissociation due to sonolysis. The adsorption of the OH from water on the catalyst surface inhibits recombination and activates the C-H bond in benzyl alcohol, leading to the formation of benzaldehyde and its incorporation into the phenyl ring to form phenol.