Interface cavity effect

In this form of catalysis, inclusion of the substrate in the CD cavity provides an environment for the reaction that is different from that of the bulk, normally aqueous, medium. In the traditional view, the catalytic effect arises from the less polar nature of the cavity (a microdielectric effect) and/or from the conformational restraints imposed on the substrate by the geometry of inclusion (Bender and Komiyama, 1978). However, catalysis may also arise as a result of differential solvation effects at the interface of the CD cavity with the exterior aqueous environment (Tee and Bennett, 1988a,b Tee, 1989). 

Any system involving a homogeneous liquid in which bubbles are produced is not strictly homogeneous however in sonochemistry it is normal to consider the state of the system to which the ultrasound is applied. Sonochemical effects generally occur either inside the collapsing bubble where extreme conditions are produced, at the interface between the cavity and the bulk liquid where the conditions are far less extreme or in the bulk liquid immediately surrounding the bubble where the predominant effects will be mechanical (Fig. 3.2). 

Influence of the Additives. Complexing agents like Kryptofix 222 and Kro-nenether are known to effect a dramatic change in the interactions of cations with their counter ions. The addition of these macrocycle compounds to a micellar Na(AOT) solution is supposed to gather alkaline cations (Na+) within macrocycle cavities near the interface. 

A quantitative model for repulsion and dispersion interactions has been derived by Amovilli and Mennucci [21] based on the theory of weak interactions [22], Cavitation is strictly empirical in this context since it does not depend on the molecule but only on the cavity shape and on the environment it will have an indirect effect on properties only by contributing to the determination of the preferred molecule-interface orientation. 

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