Tuning synthesis and sonochemistry forges learning and enhances educational training: Protection of 1,3-diols under heterogeneous catalysis as sustainable case study

Abstract

This research article describes the thermal and sonochemical enhancements of 1,3-diol protection, via acetal formation, catalyzed by a biomass-derived heterogeneous catalyst. This investigation was also conducted under the framework of a postgraduate program in green chemistry, and the application of ultrasonic activation represented an opportunity to expose the field to junior colleagues unaware of sonochemistry. Accordingly, we show not only a facile and high-yielding synthetic transformation, but also the pluses of performing a parallel protocol using low-frequency ultrasound, which provided new learning tools and skills in context. The main role of sound waves can be associated to enhanced mass transfer of the heterogeneous reaction (false sonochemistry). Acoustic energy was delivered into the reagents and solvent using so-called cavitation intensifying bags (CIB). The micropitted polymeric material enabled a greater focused radiation that proved to be highly reproducible at 25 °C and led to reaction completion much faster than the conventional external heating. Furthermore, sonication fine-tunes selectivity in ketal formation, as witnessed by a facile synthesis of solketal, a green solvent obtained by acetalization of glycerol. The pedagogical benefits of conveying education in sonochemistry are outlined, alongside the catalyst characterization of the ultrasound-driven reaction. Our ambition is to stimulate similar pursuits in synthesis and catalysis at other laboratories and educational institutions.