Jean-Louis Luche and the Interpretation of Sonochemical Reaction Mechanisms

Abstract

Sonochemistry can be broadly defined as the science of chemical and physical transformations produced under the influence of sound. The use of sound energy is rather a young branch of chemistry and does not have the clear definitive rules of other, more established, divisions such as those in cycloaddition reactions or photochemistry. Nevertheless, there are a few guidelines which can help to predict what is going to happen when a reaction mixture is submitted to ultrasonic irradiation. Jean-Louis Luche, formulated some ideas of the mechanistic pathways involved in sonochemistry more than 30 years ago. He introduced the idea of “true” and “false” sonochemical reactions both of which are the result of acoustic cavitation. The difference was that the former involved a free radical component whereas only mechanical effects played a role the latter. The authors of this paper were scientific collaborators and friends of Jean-Louis Luche during those early years and had the chance to discuss and work with him on the mechanisms of sonochemistry. In this paper we will review the original rules (laws) as predicted by Jean-Louis Luche and how they have been further developed and extended in recent years.

Sonochemical Reaction of Bifunctional Molecules on Silicon (111) Hydride Surface

“…The notion that a sonochemical-based reaction is merely a mechanistic rather than a chemical operation was also discussed by Kegelaers et al [77] who, after repeating the same series of experiments as described by Ando et al [75], came to the different conclusion that sonochemical reaction served as a mechanistic approach akin to those from extensive stirring that shortens the reaction time [78] but by itself did not induce a chemical change. Despite various examples of 'true' [79][80][81] and 'false' [82,83] sonochemical reactions in literature, which so far remain as the most common explanations, it is necessary to acknowledge that the exact mechanism of sonication chemistry has not yet been clearly elucidated [84].…”

Greener organic synthetic methods: Sonochemistry and heterogeneous catalysis promoted multicomponent reactions

“…At this point, the extremes of temperature and pressure provide an unusual environment or high energy microreactors that allow molecular fragmentation of the gases trapped in the collapsing cavities [14] . However, some chemical transformations have been observed that cannot be explained by the effect of cavitation [65] , [66] ; in these cases, the need for a broader investigation of the aspects that make possible the occurrence of chemical reactions by irradiation of ultrasonic waves is implicit .…”

“…In the 1980′s, the Luche group began the investigations into the effects of ultrasound on chemical reactions and the mechanistic pathways involved in sonochemistry [66] . In this regard, in a seminal paper published in 1996, Luche and col. categorize sonochemical reactions into three groups [66] : homogeneous sonochemistry: reactions that fall into this category are governed by a radical route, in which the intermediates (radicals or radical ions) are generated by cavitation in homogeneous media. In this case, sonication would be able to promote reactions by means of radicals and ionic reactions could not be modified by such irradiation; this would be the “real” sonochemistry.…”

Influence of 1-Hydroxyethylidene-1,1-Diphosphonic Acid on the Soft Tissue-Dissolving and Gelatinolytic Effect of Ultrasonically Activated Sodium Hypochlorite in Simulated Endodontic Environments

“…However, ultrasonic activation invariably results in an increased temperature of the irrigant in the root canal [ 21 ] and may also be hampered by the altered physical features of a combined NaOCl & HEDP solution [ 14 , 17 ]. Moreover, the so-called “sonochemical” effects of NaOCl, i.e., the expediting of chemical reactions in aqueous solution by ultrasound, albeit somewhat enigmatic [ 22 , 23 ], may be linked to increased local temperature in cavitation bubbles [ 24 ]. This may accelerate the chemical interaction between NaOCl and HEDP even more, thus leading to a quicker loss in available chlorine [ 12 , 16 ].…”