The Sonochemical Activation of Solids

Compound LiAlH4 KMn04 KCN NaBH4 NH4HF2 KO2 NaN3 NaCN 

Compound NaOAc NaH KF CaC2 Mn02 Si02 AI2O3 

This classification, even if not valid in every case, has some predictability, which is useful when attempting a reaction. However, the limit between the reactive and unreactive compounds should be considered with care, since it can be anticipated that its position will depend on the cavitational energy (p. 56), then on the ultrasound intensity and the medium in which it is produced. 

In a series of experiments, the same authors studied the influence of small amounts of water in solid-liquid reactions. The result of this presence also consists of the destruction of the lattice by local partial dissolution. Due to the acceleration of mass transfer by ultrasonic microstreaming, it is reasonable to interpret the overall increased effectiveness of the reactions by an improved transfer from the solid to the solution, and to consider water and sonication as physical PTCs, which in a number of cases can be used in conjunction. 

A last point to question is the inertness of the support in solid-supported reactions. This assumption should be examined, at least in some cases, in light of the tribochemical effect, and it is not established that some commonly used supports, e.g., silica or alumina, remain chemically neutral. 

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With respect to processes in which a metal dissolves, tribochemists have established that the removal of an ion from the lattice proceeds more readily at imperfection sites, in agreement with the discussion above. All these arguments converge towards a novel vision of the sonochemical activation of solids in general, and metals in particular 39... 

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