Power ultrasound in organic synthesis: moving cavitational chemistry from academia to innovative and large-scale applications

Abstract

Ultrasound, an efficient and virtually innocuous means of activation in synthetic chemistry, has been employed for decades with varied success. Not only can this high-energy input enhance mechanical effects in heterogeneous processes, but it is also known to induce new reactivities leading to the formation of unexpected chemical species. What makes sonochemistry unique is the remarkable phenomenon of cavitation, currently the subject of intense research which has already yielded thought-provoking results. This critical review is aimed at discussing the present status of cavitational chemistry and some of the underlying phenomena, and to highlight some recent applications and trends in organic sonochemistry, especially in combination with other sustainable technologies. (151 references.).

Interplay Between Mechanochemistry and Sonochemistry

“…This chapter aims to describe the mechanical bias of cavitational effects and how they are related to conventional mechanochemistry and force-induced physical fields in general. This subject has been well documented over the last decade [5][6][7][8][9], and particular attention has been paid to scenarios such as mechanically responsive polymers [10][11][12], micro-and nano-structured materials [13][14][15], and sonocrystallization [16], which are all expected to have a major impact on the fabrication of novel and smart materials as well as the pharmaceutical industry. Although we shall briefly mention these past achievements, our goal is to focus on the aspects of sono-mechanochemistry that have been overlooked in recent thematic issues.…”

Efficient H2O2/CH3COOH oxidative desulfurization/denitrification of liquid fuels in sonochemical flow-reactors

“…Economics, industrial competitiveness, demand and regulatory constraints have driven the development of greener reaction paths and the intensification of chemical processes to the point where it has become a key research area and one that has widely exploited non-conventional energy sources such as power ultrasound (US) [1,2]. The collapse of cavitation bubbles generates a host of physical and chemical phenomena which are particularly evident in heterogeneous systems in which liquid microjets disperse and break up particles and droplets.…”

A facile and environmentally benign polyethylene glycol 600-mediated method for the synthesis of densely functionalized 2-aminothiophene derivatives under ultrasonication

“…In order to describe the regions where sonochemical reactions occur, a three-site model was introduced. According to this model, the reaction can occur either in the bubble's hot interior gas phase where the temperature is about 5000 K, in the liquid shell surrounding the bubble which can be as high as 1900K, or in the liquid-phase from the injection of liquid droplets into the hot zone during the asymmetric collapse of the bubble as well as the bulk solvent (39).…”

“…Therefore, development of ecofriendly protocols using more efficient and safer conditions for the Gewald MCRs is still in high demand. Furthermore, the application of ultrasound irradiation in synthetic organic chemistry has received considerable attention recently (38,39).…”