ULTRASOUND AND POLAR HOMOGENEOUS REACTIONS

The effect of ultrasound on the rates of homogeneous heterolytic react ions not switched to a free radical pathway can be explained by the pe rturbation of the molecular organization of or the solvation in the re acting system. A quantitative analysis of the sonochemical acceleratio n on the basis of the microreactor concept was carried out. It was fou nd that (1) the Diels-Alder reaction cannot be accelerated by ultrasou nd except when SET or free radical processes are promoted, (2) the rec tified diffusion during cavitation cannot be responsible for the accel eration of reactions, and (3) the sonochemical acceleration of polar h omogeneous reactions takes place in the bulk reaction medium. This imp lies the presence of a 'sound-field' sonochemistry besides the 'hot-sp ot' sonochemistry. The occurrence of a sonochemical deceleration effec t can be predicted. (C) 1997 Elsevier Science B.V.