O-Demethylation of biobased anisole-like derivatives induced by acoustic energy: role of the cavitation bubble–water interface

Abstract

Using the O-demethylation of syringol as a model reaction, we investigated and clarified the reaction mechanism occurring at the cavitation bubble–water interface. By combining kinetic data, experimental tests, and product analysis, we demonstrated that water at this interface reaches a supercritical state, with a roughly estimated temperature of around 400° ± 35 °C. Under these conditions, syringol mainly undergoes thermal cracking, predominantly forming 3-methoxycatechol. By controlling the solution temperature and the nature of the gaseous atmosphere, we were able to modulate the energy released at the bubble collapse time, thereby minimizing over-cracking reactions and enhancing the selectivity toward 3-methoxycatechol (up to 88%). With these findings, we assessed the potential of this catalyst-free technology for a possible implementation in the field of chemistry. In this context, we identified avenues for improvement, particularly in terms of reactor productivity and energy efficiency to better align with industrial standards of the field.