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Reactions related to class

Another characteristic experimental observation which should be associated with Type la effects would be that even upon switching off the acoustic energy the reaction would continue for a while. Indeed, the sonochemically created intermediates would perpetuate the reaction (think of a match igniting a bunsen burner). [Pg.378]

Keeping the parallel with photochemistry where the notion of dark reactions follows the photochemical step, one would have a set of silent reactions after the sonochemical step. In contrast, for Type lb reactions, switching off the acoustic wave would immediately stop or drastically decrease the production of the compounds specific to the sonochemical activation. [Pg.379]

Several examples of Type la sonochemical activation are found in the literature. It should be clear that the main advantage of the present classification is to open the route to a multitude of experiments within the application of the approximative correspondence principles . The heuristic richness of these principles precisely originates in their looseness. This looseness has several origins, but the practical application is that a reaction recognized as a photochemically or electrochemically induced chain reaction may lead to far better yields of products under sonication. This bonus may be again amplified by the fact that industrial scaling-up of reactions seems better mastered in sonochemistry than in photochemistry or electrochemistry. To find a reservoir of reactions where sonochemical activation could possibly lead to ameliorations, one may consult a number of reviews.  [Pg.379]

A second example of a Type la sonochemical effect is provided by chain reactions proceeding without initiator when sonication is applied. This seems to be the case for several addition reactions to multiple bonds (p. 70). Sonochemical activation permits this type of chain reaction to occur at lower macroscopic temperatures without pollution of the medium by an added initiator. This is an advantage imder study in the chemistry of free-radical polymerization.  [Pg.380]

The third example corresponds to the case where sonochemistry is able to generate active species which catalyze the formation of the product(s). The catalyst may be an adventitious impurity sonochemically created as shown for the acid-catalyzed inversion of saccharose. Such an indirect, more or less hidden mechanism can be operative in the sonochemical addition of tin hydrides to olefins and alk5mes.i5 In this reaction, it was suggested that some radical species produced by solvent [Pg.380]


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