Formation and cleavage of carbon-heteroelement bonds

Mechanistically, additions of this type lead either to imstable transitory species, as in the first step of ester hydrolyses, or to new isolable compounds. In both cases, a polar mechanism is probable, and no sonochemical effect is expected in solution. 

In an acidic medium, the formation and hydrolysis of esters proceed via a series of ionic intermediates. Even if only a few studies have been published in this domain, it seems that sonication is of little help in improving the rates of these 

19°C AcOEt + H3O AcOH + EtOH Conditions Rate constants (x 10 min ) 

The acid-catalyzed hydrolysis of ethyl acetate was studied at three frequencies, 400, 700, and 1500 kHz, and various energy levels. Differences in rate between the sonicated and non-sonicated reactions fall for most of them within the experimental error. In a weakly basic medium, the rate increase of the sonicated hydrolysis of 4-nitrophenyl esters is a modest 15%. On the other hand, the 

Ambiguous results were obtained in the hydrolysis-oxidation of ketals using the Jones reagent (Eq. 17). Sonication seems to substantially accelerate the process, a result apparently due to the increased rate of the hydrolysis step. This hypothesis was tested using a ketal known to be slowly hydrolyzed (Eq. 18). Unfortunately, the conditions of the latter reaction are clearly heterogeneous (p. 133), making the comparison invalid. 

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