Sonochemistry of volatile and nonvolatile solutes in aqueous solutions: A spin trapping study

The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions exposed to ultrasound lead to the thermal dissociation of water vapor into H atoms and OH radicals. Their formation has been confirmed by spin trapping for continuous wave and pulsed ultrasound. Sonochemical reactions occur in the gas‐phase (pyrolysis reactions), in the gas‐liquid interface, and in the bulk of the solution (radiation‐chemistry reactions). The high‐temperature gradients in the interfacial regions lead to pyrolysis products from nonvolatile solutes present at sufficiently high concentrations. The sonochemically generated radicals from carboxylic acids, amino acids, dipeptides, sugars, pyrimidine bases, nucleosides, and nucleotides were identified by spin trapping with a nonvolatile nitroso spin trap. At low concentrations of nonvolatile solutes, the spin trapped radicals produced by sonolysis are due to H atom and OH radical reactions. At higher concentrations of these nonv...