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

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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.